Late Blight – Sustainable Market Farming

Potato pests and diseases

These potatoes were almost killed by frost two weeks previously, and have now recovered.
Photo Pam Dawling

This is part of a monthly series on growing potatoes, a dietary staple.

PART ONE: Planting potatoes (April)

PART TWO: Growing potatoes (May)

PART THREE: Potato pests and diseases (this one, June)

PART FOUR: Harvesting potatoes (July)

PART FIVE: Storing potatoes (August)

PART SIX: Planning to grow potatoes again (September)

I have a whole chapter about potatoes in Sustainable Market Farming, where most of this information can be found.

See Root Crops in June for info on digging up new potatoes, if you can’t wait for them to mature!

See The Potato Association of America, Commercial Potato Production in North America 2010 for lots of interesting info, including planting in hot weather. (But hurry up, you need to have enough growing days left in the season to get them to maturity.)

Organic Integrated Pest Management involves tackling pest problems one step at a time with ecologically-based practices, starting with actions to reduce the chances of the pest ever getting a grip on your crops. I recommend the ATTRA online publication Organic Integrated Pest Management. Each of the 22 pages is a poster, complete with good photos and concise clear info. Because nightshades have a lot of fungal, bacterial and viral diseases, it pays to take action to minimize the chance of diseases attacking your plants.

June-planted potatoes in early September
Photo Kathryn Simmons

Integrated Pest Management in Organic Field Crops Webinar from eOrganic

https://www.youtube.com/watch?v=nQXC8SElTMk

Biological IPM disease and pest reduction strategies for potatoes

Cultivate strong crops and provide healthy soil, sufficient space, nutrients and water, suitable temperature, and soil pH.

Choose varieties that resist the pests and diseases you most expect. Improve the soil tilth, drainage and aeration. Chisel plow or broadfork to break hardpan, or grow deep-rooting cover crops ahead of your potatoes. Maximize air circulation around the plants. Choose a bright, breezy location (avoid frost pockets as they also collect dew), orient the rows parallel to prevailing winds and give the plants plenty of space.
Add compost and cover crops to build fertile soil to support strong plant growth and help increase the diversity of soil microorganisms, building naturally disease-suppressing soil. Use foliar sprays of seaweed extract, microbial inoculants or compost tea to boost general disease resistance. Consult ATTRA for compost tea Brew one part of compost to 5 parts water by volume for 14 days before spraying.
Practice crop rotation to reduce the chances of pests and diseases carrying over from one crop to the next. For potatoes, it’s best to rotate away from nightshade crops for at least three years. We don’t manage this ideal of one year in four. In our ten-year rotation, three of our ten years are nightshades (one paste tomatoes and peppers, two plantings of potatoes).
Practice good sanitation. Clear old crops promptly, so they don’t act as a breeding ground for pests or diseases. Avoid smoking, especially near nightshades, and have smokers wash their hands with soap or milk before working with potatoes. Tobacco can spread tobacco mosaic virus (TMV) to nightshade plants. Avoid working potato plants while the leaves are wet. Remove and destroy diseased plants, especially for late blight. Clean tools in between use in one field and another. When the harvest is finished, till the tops into the soil to speed decomposition, or remove and compost or burn them if growing on a small scale.
Remove nightshade weeds (e.g., horsenettle, jimsonweed and black nightshade), which can be alternate hosts for pests and diseases.

Potatoes, weeds and standing water. Don’t let this happen to you! Provide good drainage, remove weeds especially nightshade weeds.
Photo Bridget Aleshire

Prevent soil splash-back onto leaves, to reduce outbreaks of soil-borne diseases. Use drip irrigation rather than overhead sprinklers.

July photo of a mulched June-planted potato.
Photo Wren Vile

Cover or protect the plants physically from the pests
- mulches to stop soil-dwelling pests (CPB) moving up into your crops
- netting or rowcover to protect from airborne pests (leaf hoppers, blister beetles)
Provide habitat for natural enemies and other beneficial insects. Farmscaping with sunflowers, peas, vetch, buckwheat or small grains, to encourage ladybugs and lacewings, can make insect control unnecessary in a good year. Ground beetles and bats can consume surface and air attackers before you even need to look.
Monitor your crops regularly at least once a week and identify any pests you see.
Introduce natural enemies of the pest (bacteria, fungi, insect predators or parasites). Try biofungicides for use against some diseases. F-Stop, T-22G Biological Plant Protectant Granules or other forms of Trichoderma can control Rhizoctonia, Fusarium and Sclerotonia. Soil-Gard (Gliocladium virens) can work against Rhizoctonia. Bacillus subtilis works against Rhizoctonia, and Sclerotonia. Mycostop (Streptomyces griseoviridis) can be used against Phytophthora, Alternaria, 35% hydrogen peroxide diluted to a 0.5–1% foliar spray solution may help control early blight. 1% solution = 3.7 oz in 124.3 oz water to make one gallon (1 ml:33 ml). There are commercial products such as Oxidate that are based on hydrogen peroxide, which is corrosive and challenging to handle.
Hand pick (or trap) and kill the pests if the pest population is above the action threshold. Many fruit and root crop plants can take 30% defoliation before suffering any loss of yield. Where the crop is the foliage, this may be too much, but people don’t east potato foliage!
Use biological controls (often derived from natural enemies) if the damage is still economically significant after trying the earlier steps in the process, including Spinosad or Bt.

Colorado potato beetle on an eggplant leaf.
Photo Pam Dawling

Potato Pests

Potatoes can be attacked by more than 150 insect pests. But don’t despair! In each region there are only a few species that could cause unacceptable losses of yield or quality. These losses can result either directly from the insects or indirectly by transmission of diseases.

Colorado potato beetle is the most common pest that potato growers get to deal with. The pink blob-like larvae of this beetle can eat enormous amounts of potato leaves while growing into bigger pink blobs. Left alone they can kill a planting. Acceptable amounts of defoliation without causing loss of yield are surprisingly high: 50%–75% of the top leaves on a young 6″–8″ (15–20 cm) plant, 25% on a 12″–16″ (30–40 cm) plant, a mere 10% at the critical full bloom stage (when the tubers are sizing up), and up to 25% once full grown. As with many pests, having a few of them is not important — it’s all about the numbers. Action to control CPB is only needed if the number of adults or larvae is higher than 1.5 per plant or egg masses exceed one per ten plants.

Crop rotation is effective, because Colorado potato beetles overwinter as an adult in the soil and when they emerge they have to walk around searching for a potato plant. CPB can have 1-3 generations a year. Even where two or three generations are usual, a significant portion of the summer generation adults go directly into the soil and become dormant. Eggs are laid in clusters of 20 or more. They look like ladybug eggs but are a stronger orange color – don’t kill the wrong ones! The beetle can go from egg to adults in as few as 21 days. There are four larval instars, with 75% of the total foliage destruction caused by the final and fattest instar.

Colorado Potato beetle late stage larva or pupa.
Photo Pam Dawling

Mulching with hay or straw can prevent CPB finding your potato plants – we never find them on our summer planting. Our unmulched spring planting is a different matter. I scout that field once a week, counting adults and larvae on a hundred randomly selected plants. As soon as I see more than 50 adults or 150 large larvae or 400 small larvae per 100 plants, I unpack the sprayer. I do a spraying with Spinosad, a fermentation product of a soil bacterium. It kills insects by over-stimulating their nervous systems. Spinosad kills a wide range of helpful and harmful insects too, so spray in the early morning or late evening when bees are not flying. Shake the bottle well, and mix following the instructions. Clean and triple rinse the sprayer. Do not flush in the creek or pond. Repeat in 6 days, but only if needed. Usually one spraying is enough, although I continue weekly checks. In the South, there can be three generations of CPB each year, so stay vigilant.

Prior to using Spinosad, we used Bt. The version of Bt for CPB nowadays is Bacillus thuringiensis var. tenebrionis. The kurstaki strain (such as Crymax) generally available in small quantities previously is genetically modified, so we stopped using it, not wishing to be part of any support for GMOs. Neem and Beauvaria bassiana can also kill CPB larvae.

Flaming when the potatoes are less than 8” (20 cm) tall, is another effective control measure for CPB. Choose a warm sunny day when the pests are at the top of the plants. Flaming can kill 90% of the CPB adults and 30% of the egg masses, according to Colorado Potato Beetle: Organic Control Options – ATTRA

Young eggplant struggling against lots of aphids.
Photo Pam Dawling

Insects with piercing-sucking mouthparts damage potatoes by physical injury to the leaves, sucking out phloem, injecting their toxic saliva and possibly transmitting diseases. While potatoes can grow new leaves, there is still damage to plant health. Direct injury by sap-feeding insects can kill the plant. Soil-dwelling insects have only minor effects on yield, generally, but can reduce tuber quality and storage life.

Aphid-transmitted viruses cause greater losses than all other insect-related damage together. There are at least 9 aphid-transmitted potato viruses. Aphids can be reduced by farmscaping, planting flowers which attract ladybugs, lacewings and other aphid-eating insects.

Clover flowers attract beneficial insects. Red clover in June.
Photo Pam Dawling

Potato leafhoppers are a bad problem in central and eastern North America. They overwinter on the Gulf Coast. In spring, flying adults are transported north on upper level airstreams. Yield loss can occur before visual symptoms are obvious. Leafhoppers can cause leaves to shrivel and die. The initial effects are reversible if leafhoppers are controlled before leaf tissue is destroyed (“hopperburn”). By reducing the green leaf area, hopperburn affects photosynthesis and growth. The most vulnerable stage is when the tubers are bulking up. Leafhoppers can also transmit diseases. Trichogramma wasps parasitize leafhopper eggs. Garlic with insecticidal soap, sprayed early in the morning, especially on the undersides of the leaves, can control hoppers.

Potato psyllid occurs in the western U.S. Damage to the roots and tubers is caused by feeding nymphs, which can cause psyllid yellows. The first symptoms of psyllid yellows include stunting, loss of green color, leaflet distortion, reddish discoloring of new leaves, and the appearance of aerial tubers. Early action can stop and even reverse the damage. Adults cause little to no damage underground.

Wireworms (click beetle larvae) can tunnel through the tubers. Wireworms can live for 1-3 years, so crop rotation is important. Avoid planting potatoes the first year after turning under pasture or lawn. If you expect to have wireworms, plant small whole seed potatoes rather than cut pieces. Cut slices of potato can be used to trap wireworms (dig up the trap pieces each day and kill the wireworms.

Cutworms can eat the leaves from the bottom of the plant up (the opposite approach from CPB larvae). Once the plants are fully grown, up to 75% loss of lower leaves is unimportant. At earlier stages, if any cutworm damage is seen, dig around the stem, find and kill the cutworms.

Blister beetles can cause trouble later in the season, skeletonizing leaves and spreading a wilt. They contain cantharadin, which can cause blisters on the skin of unwary workers. Blister beetles can be trapped in crops of chard or beets next to the potatoes. The beetles are easier to see and catch in the trap crops than in potato foliage. If there aren’t too many it may be worth putting up with them, as their larvae are carnivorous and eat grasshopper eggs.

The potato tuber moth damages both foliage and tubers during growth, but the biggest losses occur in storage. Larvae inside the potatoes can continue their development in storage, filling the tubers with frass and letting in decay organisms. When commercial infestations are high, the crop is not worth harvesting because of labor costs to cull out the infested tubers.

Nematodes can be deterred by choosing appropriate preceding cover crops, or by applying 1-2 tons/ac (2240-4480 kg/ha) of crushed mustard seed meal to the soil before planting. This will also reduce early weeds and act as a fertilizer.

Potato Diseases

Before a plant can become diseased, three conditions must exist: a susceptible host, a disease organism, and a suitable environment for the pathogen. The choice of the disease control method should be based on an accurate identification of the pathogen and the disease.

Late blight on a potato leaf. http://blogs.cornell.edu/livegpath/gallery/potatoes/late-blight/

Late Blight (Phytophthora infestans) is by far the worst disease to afflict potatoes. This is the disease that contributed to the famine in Ireland (caused by the profiteering of the English land-owners, who sold the barley and left the tenant farmers to subsist almost entirely on potatoes). The disease is caused by a species of a fungus-like oomycete or water mold (previously considered a fungus, now reclassified as protozoa) that blows in on the wind. It is worse in warm wet weather with cool nights. Late blight starts as “water-soaked” spots on the leaves. These expand into gray-black “scorched” areas, sometimes with a dotted white mold growth, especially on the underside of the leaves. Cut stems reveal a dark circle of infected tissue. The disease spreads rapidly, turning plants black, as if badly frosted, and can kill an entire planting in ten days unless stopped by hot dry weather.

The best defense is to always remove volunteer nightshades from your fields and compost or bury all crop debris. The disease spreads via cull piles, nightshade plants and petunias — it needs live plant material to survive. If you find volunteer potato plants popping up in early spring, it is best to pull them up! Spores survive winter in warmer climates and then blow north and uphill. Preventive action may be taken with sprays every five days of (toxic) copper products, hydrogen peroxide, Bacillus pumilus or Bacillus subtilis products.

If Late Blight occurs late enough in the season, you can save your crop by mowing off the foliage, raking it off and disposing of it, and leaving the field untouched for two weeks before harvesting whatever potatoes have grown. This prevents the spores getting into the soil and infecting the tubers. Disposing of large amounts of blighted foliage is no easy task. When I had to deal with Late Blight, back in the 70’s, we made a fire and gradually added more tops as the previous ones burned. This was a very smoky fire, polluting, and no doubt contributing to global warming. Digging a big hole and burying it all is probably better.

Early Blight (Alternaria solani) is a common fungal disease, which mostly affects stressed or older plants. It starts as small brown spots on the lower leaves, which conglomerate into brown blotches that are restricted by the leaf veins, and so they can be angular in shape. The lesions have a bullseye appearance – concentric circles with a yellow halo around each one. During warm humid conditions, the fungus steadily defoliates the plants, reducing yields. The disease is seed-borne, soil-borne and airborne, surviving on plant debris and nightshade weeds. Early blight (Alternaria solani) can appear late in the season, not just early, despite the name. The manifestation of blight symptoms can be minimized by growing strong healthy plants, supplying sufficient water, and spraying with compost teas. The beneficial fungus Trichoderma harzianum can give good results.

Black Scurf or Stem Canker fungus (Rhizoctonia solani) is worst in cold wet soils. Early in the season it can cause sprout death. On older plants, red-brown stem lesions develop into cankers, and the infection can spread to the tubers, which then become cracked and misshapen, and may have dead tissue at the stem end. There may be firm black sclerotia (small dried reproductive bodies) on the tuber. In future, get disease-free seed potatoes and wait for the soil to warm a bit before planting.

White Mold (Sclerotinia sclerotiorum) on the vines. If you want to prevent this in future, you could dust the seed pieces with the commercially available fungal antagonists Trichoderma viride and Trichoderma virens.

For a chart with about 30 potato diseases, see The Potato Association of America, Commercial Potato Production in North America 2010

A lady bug on a potato leaf, perhaps producing larvae to help control aphids.
Photo Kathryn Simmons

Book Review: The Tao of Vegetable Gardening by Carol Deppe

Book Review

The Tao of Vegetable Gardening: Cultivating Tomatoes, Greens, Peas, Beans, Squash, Joy and Serenity

Carol Deppe, Chelsea Green, 2015

I enjoyed Carol Deppe’s other gardening books, Breed Your Own Vegetable Varieties and The Resilient Gardener. I haven’t read her renditions of Taoist Stories or the Tao Te Ching, but this new book offers entwined wisdom from both aspects of Carol’s life. Something for beginners and experienced growers alike. A combination of Carol’s exquisite attention to detail, solid grounded-in-experience advice and application of Taoist philosophy can help make us better and happier gardeners. Better understanding, more inner harmony. Carol is an independent and iconoclastic gardener, and she introduces each chapter with a passage from her own translation of the 2500 year old Tao Te Ching and intersperses fables from her anthology Taoist Stories.

The Resilient Gardener focused on growing basic food staples – corn, potatoes, dry beans, winter squash and eggs. This new book moves us onward to groups of nutritionally- and economically-valuable vegetables we love to eat (and therefore to grow): tomatoes, summer squash, peas, green beans, greens. Each crop is used as an opportunity to explain a technique or concept. 13 chapters with titles like “Honoring Your Own Essential Nature”, “Non-Doing” and “Joy” lead us into the practicalities of crop requirements, plant genetics, lacto-fermentation and preserving land-races.

The tomato chapter covers how to grow and plant transplants, how to choose the best-tasting varieties, then how to breed late blight resistant tomatoes. The chapters on peas and green beans explain how to direct sow big seeds. That on greens tells how to sow small seeds, and introduces the Eat-All Greens Garden, a new way of growing direct-sown greens, producing high yields from small amounts of work. The final chapter explains why and how to grow your own seeds and prepare them for long-term storage

Carol clearly thinks for herself. I enjoy reading her take on the recent “accepted wisdom” of “imitating nature,” by prioritizing perennials, growing in polycultures (the carrots-love-tomatoes school), increasing diversity – “Ant agriculture violates all these principles.” I have long felt irritated and frustrated by the carrots-love-tomatoes belief, so I got special pleasure from reading Carol’s amusing story of actually trying to make interplanting carrots and tomatoes work, despite different needs for temperature, soil texture, soil fertility, watering, plant spacing, mulch, fencing, and length of time occupying a garden bed. And the competition for sunlight. I am a practitioner of some interplanting (spinach and peas, lettuce and peanuts, cabbage and okra), saving space, work, and in some cases, mulch or rowcover. But the almost religious belief that certain crops “like” each other, despite lack of data and lots of practical impediments, drives me potty. Carol takes the time to explain which pairs of crops stand a chance of complementing each other, and to point us towards a study by R Fred Denison (sorry I can’t find the link) that showed that yields of the best intercrop combos were somewhat better than the lower-yielding of the pair as solo occupant of the space, but less than the higher-yielding of the pair was capable of. So don’t plant crops together hoping for increased yields.

Carol encourages us to look at what actually happens in nature, and in the garden. Is this particular USDA-Organic-approved pesticide actually less damaging to non-target organisms and the general environment than the synthetic alternative? Will planting extra to “share” with pests like gophers still provide enough of a harvest? (“Lots of luck with that,” says Carol.) In the Balance chapter, Carol cautions against unrealistic beliefs about what to always or never do. “Prudence trumps completion when it comes to your health or safety.” “Ultimate Knowing does not create emergencies.”

Carol gives examples of intercropping that work for her. She sometimes plants her Eat-All Greens between alternate rows of corn (not sweet corn, which is quickly over), after the corn is up and has been cultivated twice. I’d guess that’s about 4 weeks after planting, the same age corn would be if sowing pole beans to grow up the corn stalks. The greens can grow fast enough in the shade of the corn to need no weeding, and the corn can be harvested from the alternate aisles without trampling the greens.

Russian Hunger Gap Kale from Adaptive Seeds

Carol names her “Perfect Polyculture” as Russian Hunger Gap kale (a tall, hardy Brassica napus, unlike the Hungry Gap kale I grew in England, which is an oleracea type), and vining winter squash. Initially an accident, the self-sown kale came up after she planted her squash. It grew rapidly, and timely harvesting of the kale nearest the squash was important to maintain enough space for the squash to thrive. Carol recommends her Candystick Dessert Delicata C.pepo fall squash; Sweet meat – Oregon Homestead C. maxima and fast-maturing Lofthouse Landrace Moschata C. moschata winter squashes. The Lofthouse squash is not sweet, so works well for soups and other savory dishes.

Although the USDA doesn’t regard tomatoes as an essential food group, most gardeners act as if tomatoes are fundamental. Indeterminate varieties for full season crops give the highest yields and the best flavors. Determinates provide the earliest harvests and come to an early end. Plenty of large leaves will be more likely to produce lots of sugar and flavor for the fruit, compared to what is possible with less well-endowed plants. (But keep an eye on Craig LeHoullier’s new Dwarf Tomatoes.)

Not simply under-ripe. See http://windowsillarranging.blogspot.com/2012_06_01_archive.html **Nancy Ross Hugo**

I was fascinated to learn that the green shoulders of some heirloom varieties are a cause of good flavor. The extra chlorophyll develops more sugars and flavors. Modern breeders decided to eliminate the undesired green shoulders and got uniform ripening at the expense of good flavor! My respect for Glacier and Stupice grew! Carol’s favorites for her shady Oregon garden include Amish paste – Kapuler, Pruden’s Purple (flavor, size, earliness), Black Krim, Legend (not for flavor, but for earliness, size, dependability, and especially for late blight resistance), Geranium Kiss (late blight resistance, lots of 1 ounce fruit).

Carol explains (Late Blight 101, page 96) why we need to be more careful about Late Blight now. Previously there were several strains of Late Blight, but they were all in the same mating group and could only reproduce asexually (requiring live plant material) – unless we left cull piles of potatoes in our fields, we only got the disease if we were unlucky enough to have spores blow in or be imported on diseased plants. This has now changed and newer strains of Late Blight, from both mating groups, have moved into the US. The disease will be able to evolve more rapidly, and the oogonia (sexually propagated ‘spores’) can persist in the soil. We will need to develop tomatoes and potatoes with stronger resistance. We will need to be more careful and not put any store-bought tomatoes in our compost piles. We will need to get better at recognizing late blight symptoms and acting swiftly. See http://usablight.org/.

Potato late blight lesion. Image courtesy of Jean Ristaino, NC State University.

Legend and other of the more resistant open-pollinated and hybrid varieties are very useful in breeding work to produce more varieties resistant to late blight in future. Carol lists the resistance level of 10 promising hybrids (including Mountain Magic which we grow on our farm, Jasper, Golden Sweet, Juliet, Defiant PhR, Plum Regal, Iron Lady, Mountain Merit, Ferline and Fantasio) and 19 OPs (in order of earliness: Red Pearl, Stupice, Slava, Matt’s Wild Cherry, Yellow Currant, Geranium Kiss, Legend, Pruden’s Purple, Quadro, Black Plum, Red Currant, Tigerella, Old Brooks, Black Krim, Brandywine, West Virginia 63, Aunt Ruby’s German Green, Aunt Ginny’s Purple and Big Rainbow. At the end of the book, Carol tells us how to do this. It’s not that difficult.

The chapter about the Eat-All Greens garden also has the title “Effortless Effort.” The idea is to broadcast seeds densely enough that no weeding is needed. Harvest when 10-16” tall by cutting the top 7-12” with a serrated knife, leaving the lower 3-4” of tougher stuff. Align the stems in the harvest tote or trug, to make chopping in the kitchen easier. Yields can be as high as 4.5 pounds per square yard (2.45 kg/sq m) in 8 weeks. The patch can be resown as many as three more times in the Willamette Valley climate. This is like a grown-up-tall version of growing baby salads, in that the entire tops of all the plants are harvested together. But salad mixes are cut small and may provide more than one cutting from the same plants. Eat-All Greens are usually harvested just once, then cleared., although it can work to harvest out the biggest plants, leaving others to grow bigger later in the increased space available.

Generally it’s best to grow just one type of Eat-All greens in one patch – mixes don’t do as well, because they grow at different rates to different heights. You can sow different patches right next to each other, and harvest whichever is ready. The Eat-All Greens system is a technique to perfect by practice. Spacing, timing, varieties – all can make or break your success. Timing will depend on your climate. Carol can sow in mid-March, harvest in mid-May and follow with a crop of tomatoes or squash.

Carol Deppe's Eat All Greens. Photo from The Tao of Vegetable Gardening — Carol Deppe’s Eat All Greens. Photo from The Tao of Vegetable Gardening

After years of work, Carol identified about a dozen good Eat-All crops. You can read the qualities of a good Eat-All crop in her book and test others, but I recommend taking advantage of her experience rather than re-inventing the wheel. Suitable greens include Green Wave mustard, Groninger kale, Tokyo Bekana, Spring Raab, several leaf radishes (Shunkyo Semi-Long, Saisai, Four Seasons, Hittorikun and Pearl Leaf) , several Chinese kales/gai lohns (Crispy Blue, South Sea, China Legend, Hybrid Blue Wonder, Hybrid Southern Blue, Green Lance Hybrid), three amaranths (All Red, although a bit slow-growing, Green Calaloo and Burgundy), Indian Spinach – Red Aztec Huauzontle, quinoa (choose a variety expected to grow well locally), pea shoots (Oregon Giant Sugar edible pod peas or Austrian Winter field peas) and shungiku (oh no! Chrysanthemum greens, I just haven’t managed to learn to like those!)

Another garden myth is exploded when Carol points out that we don’t necessarily get maximum nutrition out of greens when we eat them raw. Tables of vitamin C lost when greens are boiled and the water poured away are plain irrelevant if you steam your greens and use the liquid. Assays of nutrients present before and after cooking a food tell us nothing about what we actually absorb. All animals absorb nutrients better from starchy roots and tubers, meat and grains when they are cooked. That has been studied, but there is no information on cooked greens. Clearly raw greens are neither essential nor harmful in themselves. Unclear is whether the claim that raw greens are more nutritious than cooked ones has any basis in fact, or is just plain wrong. Interesting.

Carol wrote about dried beans in The Resilient Gardner. Here she writes about varieties suited for eating fresh. This chapter includes instructions for direct sowing of any large-seeded crop, and explains when trellises or plant supports are needed and what types there are. Edible-podded peas provide much more food from the same space and the same amount of garden labor (and less kitchen labor) than shelling peas do. You need no longer confuse snow peas (flat pods, not sweet, harvested before peas develop much at all), sugar peas (flat pods but sweeter), and snap peas (round cross-section pods harvested after the peas develop full size). Oregon Giant Sugar is a flat sugar type, although it has fleshy succulent pods that can be harvested with fully developed peas. Carol calls this a “flat-snap” type. In England we grew “mangetout” peas, which according to Wikipedia can be either snow or snap peas, but according to the BBC must have flat pods and can be either snow or sugar peas. Thompson & Morgan classifies Oregon Sugar Pod as a mange-tout. Mange-tout is French for “Eat-All”, so they fit right in with Eat-All Greens.

For those hoping to follow the Native American practice of growing pole beans on corn, Carol gives detailed instructions – there are so many ways to go wrong! I don’t grow field corn, so I didn’t take notes, but as always, I was very impressed with the helpful precision of Carol’s instructions. She can save so many of us from making wasteful mistakes.

Carol recommends we all try some seed-saving, in case of hard times, or for the benefits of selecting traits best suited to our climate and soil. She warns against buying a “Survival Kit” of seeds, as these won’t keep forever, and are unlikely to be varieties suited to your farm or garden. We need to pay attention and develop food crops that reliably feed us, not expect a miracle-in-a-can. Carol helps by leading us through a calculation of how much seed of a staple crop we will need, and how much land we will need to grow that amount of seed. She recommends a rotating stockpile of seed: grow and replace some of your seed every year.

At $24.95 this book will pay for itself many times over, and provide enjoyable reading, encouragement and inspiration on the way.

Book Review “Potato: a history of the propitious esculent” John Reader, Yale University Press 2008

I came upon this book by chance. The Economist said “The spud now has the biography it deserves.” I thoroughly enjoyed reading it, and appreciated the way John Reader explores the whole picture – history, farming, politics, science, nutrition, greed, deceit, compassion, generosity, climate change, global food supplies, population growth, land ownership, colonialism and hopes for the future. His style is clear and engaging. Unfortunately the book is out of print (it deserves a reprint!), so try your library or look for a used copy.

This review is long. I used the “Read More” button for the first time. There are also more photos in the second part. While writing this I remembered that Carol Deppe has good things to say about potatoes. Read a post I wrote about her perspective.

This book divides into three parts: the first tells of the potato’s origins in South America; the second the impact of importing the potato to Europe, and the third, how the potato spread throughout the world, finishing with a chapter on China, currently the world’s largest producer and largest consumer of potatoes. Measured in tons per country, not girth. NASA plans to supply astronauts one day, on the three-year trip to Mars with various “home-grown” crops. Potatoes will be the star of the garden, using the astronaut-exhaled carbon dioxide to grow, and providing a fresh supply of oxygen as well as all-they-care-to-eat potatoes.

Back in the Andes, where potato ancestors grow wild, at least 400 varieties are cultivated. They divide into three distinct groups, for growing at different altitudes: 3000-3500 metres, 3500-4000 metres and above 4000 metres. The International Potato Center (CIP), which has headquarters in Lima, is an internationally-funded scientific research organization aiming to increase food security and reduce poverty in the developing world. Their Peruvian station preserves potato genetics.

Chitting seed potatoes ready for planting. Credit Kati Folger — Chitting seed potatoes ready for planting.
Credit Kati Folger

Although potatoes tend to be denigrated as “pure starch’ and “empty calories” in developed country, these opinions are far from the scientific fact. The ratio of carbohydrate to protein in potatoes ensures that anyone eating enough potatoes to fulfil their energy needs will automatically get enough protein too. In addition there are significant amounts of various minerals and vitamins. For example, 100 gm of potato provides half the daily requirement of vitamin C. Potato protein is of high biological value (easily absorbed and retained), second only to that in eggs. The starch provides a steady stream of energy, healthier than the rush from sugars and fats. And compared to many food crops, the percentage of the total biomass that can be eaten is very high, at around 75%. Compare with grains at 33% of the mature plant total. An efficient use of land, water and labor. If needed, people can maintain an active working life for months, eating 2-3 kilos of potatoes a day, with a little fat, and nothing else.

Potatoes have been bred to adapt to many different climates. Today, potatoes are grown in at least 149 countries, from latitude 65°N to 50°S, and from sea level to higher than 4000 metres. Only wheat, maize and rice are globally more important food crops. No, not soy.

Potatoes have changed the course of history and evidence of potatoes has changed the interpretation of history. Around 10,000 years ago, in many parts of the world, agriculture began, perhaps following a period of global warming, glacial melting and sea level rise, itself followed by ten centuries of dry, even arid conditions. We don’t know exactly. We do know that the rise of agriculture went along with development of civilizations fuelled by development and growth of a staple food. Potatoes were that food for Andean civilizations. Contrary to the long-held belief that the Clovis culture of 11,200 years ago was the oldest in the Americas (people having migrated across the Bering land bridge from Asia), the Monte Verde site in Chile has been dated at about 12,500 years old. The artifacts include none of the Clovis spear points, but mastodon bones with cut marks, clay-lined hearths, remains of food plants including potatoes. This site is older than any site in North America, suggesting these people did not reach the Americas by crossing the Bering bridge, and rapidly moving a long way south. The boggy conditions at Monte Verde preserved soft organic matter, not merely bones and stones. Assumptions that the residents were nomadic hunters were disproven. How often have early archeological digs suggested a “Man the Hunter” life, because evidence of agriculture has rotted away?

Newly emerging potato plant in the spring Credit Kathryn Simmons — Newly emerging potato plant in the spring
Credit Kathryn Simmons

Tiwanaku, the first state to be based on raising potatoes, lies in present day Bolivia. The site is 3845 metres above sea level. In its heyday, between 800 AD and 1200 AD, it was a powerful empire. Llama herds provided meat, transportation and fuel. The author is careful to avoid the Man the Hunter mindset. Plant foods enabled the people to settle and thrive. Potatoes, quinoa and kañihua were important crops. Agriculture was undertaken judiciously, using ridged fields to keep the land frost-free. (The ditches held water which moderated the soil temperature on cold nights by as much as 6-9 Celsius degrees.)

It isn’t known exactly when potatoes were first introduced to Europe, perhaps 1588 in Belgium, perhaps 1586 in England, certainly by the early 1600s. A poster from 1664 recommended planting potatoes to feed the family, or to sell. However, not all market farmers jumped at the chance. Some thought radishes or turnips a more worthwhile crop. It took a couple of centuries before the potato became Europe’s most widely consumed, cheap, nutritious food. This wasn’t simple prejudice about new foods – the first potatoes to reach Europe were not adapted to the growing conditions, where the day length varies much more than in the equatorial Andes. The plants produced lots of stems and leaves all summer, then struggled to grow tubers in the falling temperatures of late September. Word spread of disappointing yields. But the Spaniards in the Canary Islands had been developing adapted varieties, and this lead to better results. Continue reading “Book Review “Potato: a history of the propitious esculent” John Reader, Yale University Press 2008”

Summer reading

The August issue of Growing for Market magazine is out (the June-July issue was the most recent previous one). This one includes my article on Last Chance Sowings.

In line with my advice, at home we are busy preparing beds and sowing beans, bulb fennel, cucumbers and squash. As well as being our last chance with these warm weather crops, it’s now our first chance to start again with the spring and fall crops such as carrots, beets, kale, scallions, turnips (no rutabagas for us these days – it needs extra time to grow to a good size, and we’re never ready soon enough). It’s too soon for us to sow spinach (although the weather is surprisingly cool for August!) – we wait till the fall chickweed, dead nettle and henbit germinate before sowing spinach. we’re also out in the garden every evening transplanting broccoli and cabbage. We’re over half way, and the mild weather is really helping.

Cutting Zephyr yellow summer squash. Credit Brittany Lewis — Cutting Zephyr yellow summer squash.
Credit Brittany Lewis

Also in this Growing for Market issue are valuable articles by other growers, such as Ben Hartman on arranging their farm’s CSA into two separate seasons, spring and fall, with a two week gap in the middle. What a great idea. I got a two week gap myself, thanks to our stalwart crew keeping the crops happy while I was gone.

There’s encouragement from Lynn Byczynski, the editor, to comment to the FDA on the proposed food safety rules for produce. Jonathan Magee (author of the book Small Farm Equipment) writes about irrigation pumps, which will likely be a big stress-saver for anyone who has stood in exasperation over a non-working pump. Andrew Mefford writes about useful tools for the hoophouse, including some nifty little Harvest Scissors, worn like a ring, freeing up the hands to alternate with other tasks while working.Erin Benzakein, the regular writer on cut flowers, covers ideas for early spring blooms, and, as always, has some beautiful photos.

For the next issue I am writing on strawberry production systems, including our latest method – using landscape fabric with holes burned in it.

My presentation on Planning Fall Crops at the Virginia State University Commercial Berry and Vegetable Field Day on June 27 is now a full blown video. you can view it at their website, along with those of the other presenters; Reza Rafie on specialty crops such as baby ginger, Steven Pao on food safety and Debra Deis from Seedway Seeds on their variety trials.

I’ve recently found a website I think will be very useful for help in predicting pest outbreaks, as well as counting accumulated Growing Degree Days and recording the weather. It’s called My Pest Page. It’s for the technically minded. To modify our page for your area, start with the map and zoom out then in again on your area, using your nearest weather station. Then you can choose which pieces of information to have displayed, by clicking on the plus button by each topic to expand the list of options. Then click on the big Refresh button and bookmark the site. I see we’re now at the point when Late Blight infection is possible. . . , so I’ll keep my eyes open.A few years ago when we thought we had Late Blight on our tomatoes we spent a lot of time removing infected leaves into trash bags. When we sent a sample to the plant diagnostic clinic they said we didn’t have Late Blight. I think it was a heat stress condition caused by us using the wrong kind of drip tape. (We had too much on at once, so not all the plants were actually getting the irrigation we thought they were.)

Talking of irrigation, It’s time I left my desk and went to switch over to today’s fourth sub-system.