Here is a table of vegetable seed germination temperatures. These apply to soil temperatures when you sow directly in the ground, and to air temperatures when you sow indoors in small containers. If your indoor air temperature is not warm enough when you want to sow your chosen crop (watermelons, anyone?) you can make a small warm place, or use a professional heat mat, or, for a small scale, germinate seeds in an instant pot! If you have one of these handy cooking devices, check the lowest setting. Perhaps labeled for making yogurt, it might be 91°F (33°C). Look at my chart below and see if your seeds will germinate at that temperature. You’ll have to experiment for the seeds which germinate well at 86°F (30°C) but not at 95°F (35°C). Don’t try this with spinach or lettuce! You might be surprised to see that some cool weather crops, like broccoli and cabbage, can germinate just fine at high temperatures!
You can see my chart is a work in progress, so if you can add any info, please leave a comment on this post. Bold type indicates the best temperature for that vegetable seed. The numbers indicate how many days it takes that seed to germinate at the temperature at the head of the column. Where I don’t know the number of days, I have put “Yes” if it does germinate at that temperature, “no” if I think it doesn’t and a question mark where I plain don’t know. I would love to know, so if you can resolve the uncertainties, please speak up! I’ve also used the words “best’, “min” and “max” which I hope are self-evident.
To measure the temperature of the soil outdoors, I recommend a dial-type soil thermometer. Ignore the vague guidelines on Min/Optimal/Max and use the table above. The usual practice is to check the temperature at 9am each day, and if you are unsure, check again the next day. In some cases it is best to get 4 consecutive days of suitable temperatures, or even (in spring!) a few days of rising temperatures.
Harbinger weeds of spring and fall
The progress of emergence of different weeds in the spring shows us how quickly the soil is warming up. I wrote about that here. In that post you can see photos of flowering chickweed, purple dead nettle, and henbit.
In the fall we will be waiting for the soil to cool enough to sow spinach. I have a blog post about thishere, and also photos of those three weeds as seedlings, which is what we are looking for in the fall, as an indication that the soil has cooled down enough for them (and spinach!) to germinate.
I have a post about phenology here.You can read some of the details of when to plant by natural signs. For instance, we sow sweet corn when white oak leaves are the size of a squirrel’s ear. I got excited this past weekend (April 10) when I saw wind-driven twigs on the ground with oak leaves definitely bigger than squirrels’ ears. But they were Red Oak, not White Oak.
The chart in that 2013 post has now got corrupted (at least it has on my screen), so here is a pdf
Phenology records are a useful guide to when to plant certain crops, and a way to track how fast the season is progressing right where you are. Phenology involves recording when certain wild and cultivated flowers bloom, seedlings emerge, or various insects are first seen. These natural events can substitute for Growing Degree Day calculations. Certain natural phenomena are related to the accumulated warmth of the season (rather than, say, the day-length), and by paying attention to nature’s timetable you will be in accord with actual conditions, which vary from year to year, and are changing over a longer time-scale.
Keeping your own phenology record will help build resilience in the face of climate change. Ours might be interesting to you, but unless you live in central Virginia, you can’t use our dates. You do need to make your own. This can be a great home-schooling project, or a crew I-Spy competition, or a calming end-of-day walk around your gardens.
After all this time, my website was due for some spring cleaning. In particular, the old format didn’t work well on smart phones, and this new one does. So I hope that makes life easier for lots of you! I’ve also moved the Categories and Recent Comments so they are easier to find. Let me know if you have ideas for improvements.
It’s cold and rainy here as I write this (almost sleeting). I will need to plug in the heat mats under the pepper, eggplant, cucumber and squash seedlings, cover the tender potted tomatoes and peppers in the greenhouse with rowcover, and pull rowcover over the newly transplanted beds of tomatoes and squash in the hoophouse. I’m expecting a third night with temperatures around 25F (-4C). Hence I’m in the mode of staying indoors and doing some reading. Here’s a big round up of good stuff.
Root Crops and Storage Crops
In A Way to Garden Margaret Roach interviews Daniel Yoder of Johnny’s Seeds on Mastering Root Vegetables. Read, or listen to her podcasthow to grow root crops: Carrots, beets, radishes, parsnips. Lots of tips, and links to more articles/interviews
An earlier article discusses how to store garden vegetables for winter. Margaret covers the basics of temperature and humidity, along with details of some crops and ideas for preserving crops that don’t store well.
Ticks and Tasks in Virginia
The Garden Shed is a monthly online newsletter published by the Piedmont Master Gardeners. It provides all gardeners in Charlottesville-Albemarle County area of Virginia with a science-based, reliable source of gardening information, monthly tasks and tips, and other gardening related features. Here are a couple of the most recent ones:
Note that the link in this article to VCE Publication 246-480 “Vegetables Recommended for Virginia,” does not work. It looks like the Extension has taken the publication down. Ralph Morini suggests that the next best reference is 426-331 Vegetable Planting Guide and Recommended Planting Dates
This post by Craig Wallin for the Profitable Plants Digest gives info on lavender, gourmet mushrooms, woody ornamentals, landscaping trees and shrubs, bonsai plants, Japanese maples, willows, garlic, bamboo and herbs. I’ll add a big caution about bamboo, as we have found many bamboo varieties very invasive and hard to control. Links on the site provide info on ginseng, microgreens and more.
Urban Gardening 101: How to Deal with Contaminated Soil It’s hard to find much information on this topic for organic gardeners, although Leah Penniman does also offer help in her book Farming While Black
Al Jazeera, in their Witness series, has a 25 minute film The Seed Queen of Palestine Can one woman’s mission to revive ancient heirloom seeds inspire a celebration of traditional Palestinian food? Vivien Sansour is distributing rare, ancient heirloom seeds to Palestinian farmers. Click hereand search for The Seed Queen of Palestine
Join more than 6,000 other naturalists across the nation in taking the pulse of our planet. You’ll use scientifically-vetted observation guidelines, developed for over 900 species, to ensure data are useful to researchers and decision-makers. On their website, learn about the National Phenology Network Pest Patrol which is seeking observers to report their sightings of insect pest species that cause harm to forest and agricultural trees. Your observations as part of this campaign will help validate and improve the USA-NPN’s Pheno Forecasts, which help managers know when these species are active and susceptible to treatment.
Heed the Warnings for Agriculture from the Fourth National Climate Assessment
The U.S. Global Change Research Program has released the Fourth National Climate Assessment, an examination of the effects of climate change on the United States. Chapter 10 of the Assessment is on “Agriculture and Rural Communities.” This chapter contains four key messages regarding productivity decline, resource degradation, livestock health, and rural-community capacity to respond.
The Texas High Plains and Southern Plains continue to experience reductions in irrigation water from the Ogallala Aquifer as water levels decline, and producers need some way to improve their revenue from their farming systems. They have the potential to get a pretty good return and be able to take better advantage of the water they do have, using high tunnels to grow regular vegetable crops and also use them for seed production, cut flowers, small fruit.
Bug Tracks Charley Eiseman Life in a Cubic Foot of My Lawn. This inspiring article is one of many by this expert in leaf miners as well as other insects. It’s such fascinating stuff! And his photos are exquisite. There are over 40 in this post!
Learn about Vegetable Grafting
Members of a Specialty Crops Research Initiative Grafting Project Team have organized a grafting webinar series. The webinars each cover a different topic about the science and technology of vegetable grafting. While not specifically about organic production, upcoming topics that could be of interest to organic growers include Grafting to Increase Production for Small-acreage and High Tunnel Tomato Growers, by Cary Rivard of K-State University; past topics include Making Grafting Affordable and Beneficial to US Growers by Richard Hassell of Clemson University. Past presentations in the series were recorded and archived. Find the recordings on the project YouTube channel here, and learn more about upcoming webinars here.
See Enhancing the Utility of Grafting in US Vegetable Production, by Matthew Kleinhenz of the Ohio State University, below.
If you are a gardener, you may be interested in another webinar by Cary Rivard about grafting for home gardeners: Demystifying Grafted Tomatoes: The Why & How for Gardeners, which is part of the 2019 series of Advanced Training Webinars for Master Gardeners sponsored by Oregon State University Extension. Find out more informationhere.
Read up on New Research
eOrganic recorded presentations on current organic research from the Organic Research Forum organized by the Organic Farming Research Foundation at Organicology. The following presentations are freely available now and more will be added to their playlist on the eOrganic YouTube channel and mentioned in upcoming newsletters. Find the program here and click here to find the recordings on a YouTube playlist.
Our hoophouse is bursting with winter greens. We just decided to hold back on harvesting our outdoor Vates kale and focus on the greens which are starting to bolt in the hoophouse. That includes the last turnips (Hakurei, Red Round and White Egg), Senposai, tatsoi, Yukina Savoy, mizuna, Ruby Streaks, Scarlet Frill and Golden Frills mustards. Big but happily not yet bolting are the spinach, Rainbow chard and Russian kales. A row of snap peas has emerged. Time to stake and string-weave them!
The lettuce situation is changing as we are eating up more of the overwintered leaf lettuce in the hoophouse. The lettuces in the greenhouse have all gone, to make way for the flats of seedlings. Plus, we needed the compost they were growing in, to fill the flats. More about lettuce in February next week.
We have also cleared the overwintered spinach in one of our coldframes, so we can deal with the voles and get them to relocate before we put flats of vulnerable seedlings out there. The voles eat the spinach plants from below, starting with the roots. We had one terrible spring when they moved on to eat the baby seedlings when we put those out there. After trial and error a couple of years ago, we now clear all the spinach from one frame, then line the cold frame with landscape fabric (going up the walls a way too), wait two weeks, then put the seedlings out on top of the landscape fabric. The voles by then have decided nothing tasty is going to appear there, so they move on.
Outdoors, we have just started transplanting new spinach. We have four beds to plant, a total of 3600 plants, so we have to keep moving on that! We are trialing several varieties again, as we did in the fall. We have the last Tyee, alongside Reflect and Avon this spring. Inevitably things are not going perfectly according to plan. Yesterday I forgot to follow the plan, and we started with Avon and Tyee at opposite ends of a bed we had planned to grow Reflect in! Anyway, we are labeling everything and hoping to learn which have best bolt resistance. Watch this space.
We have grown our spinach transplants (as well as kale and collards) in the soil in our hoophouse, sowing them in late January. I wrote about bare root transplants in early January this year. You can find more links and info in that post. Growing bare root transplants saves a lot of work and a lot of greenhouse space.
For those relatively new to this blog but living in a similar climate zone, I want to point you to The Complete Twin Oaks Garden Task List Month-by-Month. It includes a link for each month’s task list. I notice from the site stats that some of you are finding your way there, but now there are so many years’ worth of posts it’s perhaps harder to find. Happy browsing!
The post has lots of other interesting weather info too. Thanks Anne!
I remembered another of the items lost in the hacked post a few weeks ago: My Mother Earth News Organic Gardening Blogpost on Heat Tolerant Eggplant Varieties made it into their 30 Most Viewed blogposts for 2016. I’ll be writing up more about those varieties, linking the 2016 results to the weather each week (especially the temperatures) and adding what I learn in 2017.
I’ve just got back from the Carolina Farm Stewardship Sustainable Agriculture Conference in Durham, NC. There were about 1200 people, five workshop slots, 12 tracks, lots of good, locally grown food, a whole pre-conference day of bus tours and intensive workshops, a courageous and inspiring keynote address from Clara Coleman on the joys and challenges of family and farm life. She and her two young sons are now living and working alongside Eliot Coleman (her dad) and Barbara Damrosch at Four Seasons Farm in Maine.
My sweet potato slideshow from my first workshop at CFSA is viewable above. Just click on the forward arrow. To see it full screen, click on the link below the image and then click the diagonal arrows when the new page opens. About 70 very engaged people attended that workshop. My other workshop was Sustainable Farming Practices for Vegetable Growers, which I’ll include next week.
I enjoyed meeting old friends, making new friends, learning some good tips about different drip irrigation parts, how to sharpen and use a scythe, how many years half the henbit seeds are viable for (23 years!!), and picking up literature from the trade booths to digest later.
Save the date: 2017’s CFSA SAC will be November 3-5 (Fri-Sun)
The November/December issue of Growing for Market is out, including my article about phenology. Phenology is the study of recurring animal and plant life cycle changes in relation to the weather. Some changes are temperature-dependent, rather than (daylength-) calendar-dependent. The opening of some buds and the emergence of some
insects from the ground are related to the accumulated warmth of that season. Observations of certain changes can be used to help growers decide when to expect outbreaks of certain insect pests and when to plant certain crops. For instance, we look to the leaves of the white oaks to decide when it is warm enough to plant sweet corn. The oak leaves should be as big as squirrel’s ears. We have plenty of squirrels! Phenology is especially useful when the weather is extremely variable, which we can expect more of as climate change gets us further in its grip.
Also in this bumper edition of Growing for Market are articles on growing heading chicories (Josh Volk), milling your own logs on your farm (Mark Lieberth), online weather tools for farmers (Eric and Joanna Reuter), a review of The Farmers Market Cookbook by Julia Shanks and Brett Grohsgal (Andrew Mefferd), and favorite perennials for flower growers (Jane Tanner). There are also two pages of cameos of books available from GfM. A seasonal tip about gift giving, I think.
I am working on a review of Soil Sisters by Lisa Kivirist, which I will tidy up and post soon.
Young turnip and radish plants.
Credit Kathryn Simmons
We’re in cold-hardiness zone 7, and our average first frost date of October 14. This makes the first half of August our last chance to sow several vegetables and get crops from them before winter. In 2012 I wrote Last Chance Sowings. Depending on your climate zone, your dates might need to be earlier or later than ours. Fall vegetable growing provides fresh harvests, storage crops and possibly some crops to overwinter.
There are three categories of vegetable crops to consider planting at this time of year:
Warm weather crops that die with frost.
Cool weather crops that grow well in spring and fall, but don’t thrive in the summer.
Cold-hardy crops to grow over winter and get off to a fast start in early spring.
Planning and timing are crucial – if germination fails, you may not get a second chance with that vegetable. The twin challenges of fall crops are sowing in hot weather, followed by keeping the crop happy in cold weather.
Warm weather crops
Don’t stop too soon! But don’t plant too late to have a reasonable chance of success. For crops to be harvested before killing frosts arrive, the formula to find the last sowing date for frost-tender crops is:
Number of days from outdoor planting to harvest (read the seed packet or catalog)
+ Number of days from seed to transplant if growing your own starts
+ Average number of days of harvest period
+ 14 days “Fall Factor” to allow for the slowing rate of growth as the weather cools
+ 14 days from your average first fall frost date (in case of an early frost)
= Days to count back from your average first fall frost date
For example, yellow squash takes 50 days from sowing to harvest, and our last planting is 8/5, a whole month later than we could risk without rowcover to throw over on chilly nights. Don’t worry that rowcover prevents pollination – you don’t need to get every flower pollinated, just keep the developing fruits growing. In many parts of the country, a frost or two will be followed by a few more weeks of warm weather, so getting past the first few frosts is worth the effort. (Unless you’ve reached the exhaustion point we call “Praying for a Killing Frost.”) It’s easy to get harvests for an extra month from mature plants you already have.
Cool weather spring and fall crops
Beets, carrots, chard, spinach, lettuce, scallions, peas, potatoes, Asian greens and other leafy brassicas, turnips, rutabagas and radishes all fall in this group. Fall gives you a second chance to enjoy these crops. The flavor of crops produced during warm sunny days and cool nights can be a delightful combination of sweetness and crunchy succulence.
We sowed 60% of our fall carrots last week, along with some “indicator beets,” and I ran overhead irrigation Wednesday, Thursday and Friday nights, on a third of the length each time. The indicator beets started to germinate on Sunday, and so yesterday (Monday) we flame-weeded the beds. Last night we got a little rain. Today there are hazy rows of green – germinated carrots! Maybe you’re wondering why we only sowed 60% of what we wanted. Well, we ran out of seed! Embarrassing and annoying, but oh well. More is on order, and it’s not too late to sow them, although they have less time to grow big. Every day counts in the fall!
The formula for calculating last sowing dates for frost-tender crops can be modified for hardier vegetables. For example, Early White Vienna Kohlrabi takes 58 days from sowing to harvest (line 1). You can direct sow, so line 2 = 0. You can harvest it all at once and store it in your cooler, so line 3 is 1 day. Assuming you don’t want to use rowcover for this, line 4 = 14. Line 5 = 14 also. That all adds up to 87 days. Kohlrabi is hardy to maybe 15°F. The temperature is not likely to drop to 15°F before the beginning of November here, so counting back 31 days in October, plus 30 in September, plus 31 in August – that’s 92 days already, more than enough. We could sow kohlrabi in early August and get a crop at the end of October.
We have made ourselves a chart for fall harvest crops so that we don’t have to calculate each time. It helps us ensure we don’t sow too late to get a decent harvest.
Sowing dates for crops with various days to maturity
We’ve sown two beds of beets, one of kale, some winter radish and fall radish. We’re behind on tilling and prepping beds, or we would have more. We’re experiencing the domino effect of getting late with one task, and then struggling to catch up as more and more tasks get behind-hand. We were late with our potato harvest. And therefore with our broccoli and cabbage transplanting (which uses that plot). Because we are transplanting older plants, we’re removing a couple of the older leaves from each one as we plant, to reduce transpiration losses. We’re late with tilling and bed prep, and therefore with planting. But we do still have hope. One of our mantras (learned from another farm) is “Prioritize planting during the planting season.” Here the planting season extends from early February to November outdoors.
We don’t sow spinach till September, so we’re not behind on that yet! Because spinach germinates so poorly in warm soil, we wait for temperatures to drop. This “summer” has been extremely cool, but we’re in no hurry to start spinach earlier than usual, because of all the other tasks. This year it would probably work. I saw fall dead nettle germinating on 8/4. That’s a phenology sign that the soil is cool enough for spinach.
I’ve been recording phenology data here since 2003. 8/4 is the earliest date I have for dead nettle, by a margin of 11 days! It has been as late as 9/1 (2004).
Cold-hardy crops to grow over winter
I covered this topic in detail in Growing for Marketin September 2010, and in my slideshow Cold-hardy winter vegetables. The gist is “Before taking the plunge, know your climate, know your resources, know your market, know your crops, and when you don’t know, experiment on a small scale.” Useful information includes the winter-kill temperature of your desired crop. Choose hardy varieties, and be clear about whether you intend to harvest outdoors all winter (kale, spinach, leeks, parsnips, collards for us), or whether you want to have small crops going into winter so you can rest during the winter and be first out the gate in early spring, with crops waiting for you.
I wrote about phenology and shared our Twin Oaks phenology chart on 3/28. Since then I’ve read two related blogs I want to tell you about. One is my fellow Twin Oaker Ezra Freeman, whose blog ObserVa A year observing nature in Central Virginia has wonderful photos of plants and animals here at Twin Oaks and wherever he goes. Most recently a hike up Old Rag mountain in the Shenandoahs. The other is Chert Hollow Farm’s Bird list & other natural events. Eric and Joanna Reuter own and operate Chert Hollow Farm, a small, diversified farm featuring certified organic produce near Columbia, MO. They have a great website. Probably a thousand miles from Twin Oaks, so not the same as our backyard. In some ways that makes it all the more interesting. Another natural event I’m keeping tabs on is the emergence of the 17-year cicada. Debbie Roos of the Growing Small Farms site posted a link to a news article about the coming emergence of Brood II of the 17-year periodical cicadas on her Facebook page and sent out a link to the Cooperative Extension’s Growing Small Farms website.
Cicada Mania is a great source for all cicada-related information. The blog is amusing and packed with info. Adult cicadas begin to emerge when the soil temperatures reach 64F. (My soil thermometer is monitoring temperature in a carrot bed I plan to flame-weed.) If you haven’t got a soil thermometer, Cicada Mania has an emergence calculator based on air temperature. http://www.cicadamania.com/cicadas/cicada-emergence-formula/ Here is a map of the areas which can expect to see this cicada, for a month or so, starting in May. We’re right in there.Adult female cicadas damage young woody plants by tunneling in thin twigs to lay eggs. I didn’t plant any new fruit bushes this past winter, so don’t really think I have much to worry about. Damage to older bushes and trees is dramatic-looking, but not usually permanently harmful.
For ten years I have been keeping phenology records, as a guide to when to plant certain crops, and as a way of tracking how fast the season is progressing.
Phenology involvestracking when certain wild and cultivated flowers bloom, seedlings emerge, or various insects are first seen. These natural events can substitute for Growing Degree Day calculations. Certain natural phenomena are related to the accumulated warmth of the season (rather than, say, the day-length), and by paying attention to nature’s calendar you will be in sync with actual conditions, which can vary from year to year, and are changing over a longer time-scale..
Many people know to sow sweet corn when oak leaves are the size of a squirrel’s ear. By this point, regardless of date, the season has warmed enough to get oak leaves to that size, which happens to be warm enough for sweet corn seed to germinate and grow well. Some people transplant eggplant, melons and peppers when irises bloom; sow fall brassicas when catalpas and mockoranges bloom; and know to look for squash vine borers laying eggs for the two weeks after chicory flowers. Some transplant tomatoes when the lily of the valley is in full bloom, or the daylilies start to bloom.
Lilac is often used to indicate when conditions are suitable for various plantings:
When lilac leaves first form, plant potatoes
When lilac is in first leaf (expanded), plant carrots, beets, brassicas, spinach, lettuce
When lilac is in early bloom, watch out for crabgrass germinating
When lilac is in full bloom, plant beans, squash, corn. Grasshopper eggs hatch.
When lilac flowers fade, plant cucumbers.
Also, recording the dates of the same biological events each year can show longer term climate changes. In Europe, 500 years of recorded dates of grape harvests provide information about summer temperatures during that time. Project Budburst is a citizen science field campaign to log leafing and flowering of native species of trees and flowers across the US each year. Each participant observes one or more species of plant for the whole season.
The September issue of Growing for Market magazine is out, and with it, my article Building resilience into farm systems. I’ve embarked on a four-part fall and winter series of articles aimed at helping growers thrive under varying situations, some of which we have no control over.
This first article is about being prepared for whatever Nature throws at you, expecting to adapt, and building in options. I’ve sent in the second article, about understanding and predicting conditions,for the October issue. It covers weather forecasting, frost prediction, Growing Degree Days and phenology. The next one after that will include using soil temperatures, scouting and monitoring for problems and something about on-the-spot decision-making. The last one will deal more with decision-making, reviewing results and learning from mistakes.
To read the articles, get a subscription to the magazine.
For those who like inspiring background reading, I recommend Stewart Brand in How Buildings Learn: What Happens After They’re Built(Penguin 1995). He advocates for
constructing buildings that are easy to modify later, in gradual or drastic ways to meet the changing needs of the people inside. Farms can be looked at similarly. Keep as many options as possible (for crops, cover crops, crop layout) open for as long as possible. Brand’s current main activity is through The Long Now Foundation
It can be helpful to do some scenario planning, which I learned about when I read The Art of the Long View, by Peter Schwartz (Doubleday, 1991). Scenario Planning is a method of making flexible long-term plans, using stories (scenarios) to help us visualize different possible futures that include not only factors we don’t control, like the weather or the market’s enthusiasm for bulb fennel, but also intangibles such as our hopes and fears, beliefs and dreams.
No time to read books? Very sad! Maybe see you at the Heritage Harvest Festival at Monticello, near Charlottesville, this Friday and Saturday.