We are still in the dormant period for most fruits, but in March, we get to appreciate and enjoy rhubarb! In case you didn’t already know, RHUBARB LEAVES ARE POISONOUS – don’t eat them!
I have a funny story related to this (no one died): One year a novice cook baked us a fine looking pie. She scrupulously cut off every scrap of leaf and put it in the compost bucket. She chopped the stems, added plenty of sugar, and baked the pie. The gardeners among the diners were surprised to get a rhubarb pie so late in the spring. Ah! She had used Ruby chard (sometimes even called Rhubarb chard). The pie was OK, but we were sad not to get to eat he leaves! The non-gardeners ate the pie and found nothing odd about it.
Rhubarb is the Focus Fruit for March: Weed, compost around the plants, or where you think the plants are! Mulch if not already done in the fall. Divide & replant if needed.
The information below first appeared in an article I wrote for Growing for Market magazine in October 2009. I have revised it slightly for this post.
This is a good time of year to plan and make preparations for planting new perennial crops. As well as the better known fruits, options include rhubarb, (also known as pie plant), and asparagus. Both are early harvesting crops, so can provide fresh crops to start your CSA season, or enhance your market booth or your offerings for restaurants. Rhubarb can also be used in jam-making, for growers looking for value-added products to extend the market season. Rhubarb is better known among older people, so supplying recipe cards and samples of baked goods or jam may be a good idea to help boost sales. As rhubarb is very tart and rarely eaten raw, you cannot offer raw samples. It needs cooking to bring out the aromatic mellow flavor.
Rhubarb will be in the ground for up to 20 years, so it is important to incorporate it into your field plans after a bit of long-term thinking. This article covers what you need to know to establish the crops, including a look ahead to what you might expect in the future.
Crop Requirements of Rhubarb
Rhubarb appreciates deep soil with high organic matter, and as with all long term crops, it pays to remove perennial weeds before planting. Moderate to high levels of phosphorus and potassium are desirable, and a pH of 6.2-6.8. This is a very easy care crop, with few pests or diseases, requiring little attention.
Rhubarb is a cool climate crop – the north of England is “Rhubarb Central” – the area where rhubarb grows best. I have visited the UK National Rhubarb Collection within Harlow Carr Gardens , near Harrogate in Yorkshire. It’s a collection of different rhubarb varieties, a kind of growing gene bank. Rhubarb does require a winter chill period to break the heat-induced dormancy and start spring growth. Varieties vary in their chill requirements, from about 500 hours at between 28°F (-2°C) and 49°F (9°C). We successfully grow rhubarb in central Virginia, USDA cold hardiness zone 7 and also National Horticultural Society zone 7 for summer temperatures. I was told by a plant nursery in Tennessee that rhubarb would not grow in such a warm place, but our experience says otherwise. Ideal summer temperatures for this crop average around 75°F (24°C). Our summer temperatures include many days above 90°F (32°C). To protect the rhubarb from the heat, we planted it in a single north-south row, directly west of our asparagus and east of our grapevines. In summer it is shaded on both sides. Choose a microclimate to protect from extreme temperatures, and from drying out. It is hardy down to –20°F (-29°C). Early season open sun exposure is valuable.
Ensure a good regular supply of water from spring when growth starts, until fall frosts. On the other hand, avoid water-logged sites, as Crown Rot is one of the few diseases rhubarb can suffer from. Very sandy soils aren’t good for rhubarb, unless you can make heavy additions of organic matter. To test drainage at a potential site, dig a 12” (30 cm) hole, fill with water. If the water has all percolated within 3 hours the site is suitable.
Choosing Rhubarb Varieties and Buying Plants
Although rhubarb can be grown from seed, it is much more usually grown from “crowns” (young plants), or from pieces of crowns divided from established plants. Plants started from seed will be two years old before harvest can start. Our plants at Twin Oaks are of unknown parentage, having been divided and moved around the farm a few times. Many people don’t even realize that rhubarb has distinct varieties, and many nurseries only offer one or two. Growers may wish to select either red or green stalks (green can be more flavorful), yield, disease resistance or winter chilling requirement. Try to get recommendations from other local growers, or buy several and see which does best. Here’s some information I’ve found, although there may be duplication of names for the same variety:
- Macdonald: pinky-red, thin tender, upright stalks, some resistance to crown rot.
- Victoria: green tall stalks, good vigor, tart flavor, makes many seed stalks.
- Tilden: Good red color, thick stalks.
- Valentine: Good red color, medium vigor, few seed stalks.
- Crimson: Thick red stalks.
- Canada Red: for cooler regions. Red stalks, high in sugars.
- Red Cherry: for low winter chill areas. Grown in California.
- Allport Giant rhubarb (found growing in woodland in Chenango County, NY), now for sale as seeds.
Propagation of Rhubarb
Once you have some established rhubarb it is very easy to propagate and have more. The roots of rhubarb become enormous, and even small broken pieces will grow. To divide the crowns, use a sharp shovel or spade to chop through an unearthed crown, creating pieces with 2 or 3 buds on each. This can be done very early in the spring, before growth has started, or late in the fall. If fall is the recommended time for planting other fruits in your area, it will also work as a time for dividing rhubarb. After dividing, let the cut surfaces air dry for a day or two before replanting.
It is generally recommended to renovate rhubarb plantings every 5-10 years, by digging up and dividing the roots. This gives the opportunity to move or to increase the planting. If your stalks have become thin, brittle and hollow, it’s time to divide and renovate your planting.
Plant in very early spring (or late fall). If you buy crowns and cannot plant them when they arrive, store them in a refrigerator, and check to prevent mold growing during storage. After preparing your site and removing perennial weeds, incorporate about 15 tons of compost per acre (34 metric ton per hectare). On a smaller scale, this translates to one or two shovelfuls of compost per plant. Crowns should be planted 2-3 ft (0.6-1 m) apart, with the bud about an inch (2.5 cm) below the soil surface. Make trenches or holes 6” (15 cm) deep. Fill in the holes or trenches, pack firmly (except directly over the bud), and water well. For multiple rows, space the rows 3-4ft (1 m or so) apart. Rhubarb is a large plant and will easily use this amount of space. To combat over-wet soils, use raised beds. Organic mulch will help prevent weeds and keep the soil cool and moist.
Rhubarb grows actively in the spring, and then in most climates, goes dormant for the summer. Once fall frosts arrive, the leaves and stems will die back to the ground and you can do the annual maintenance.
Give an annual application of compost in the fall when the plant goes dormant, and mulch around the plants with straw or spoiled hay. In early spring come back to your plants, weed, and add more mulch and perhaps more compost if needed as soon as you see the big pink buds emerging from the soil. Provide 1-2” (0.5-1 cm) of water per week.
The warmer your climate, the more flower stalks you will see. Unlike the squarish leaf stalks, flower stalks are round. They quickly grow tall, above the leaves, and have big buds at the top. For maximum rhubarb yield, remove these flower stems as soon as you see them, by cutting them low down, or at least by cutting off the flower buds as you go by. We harvest stalks twice a week in April and May, and cut the flower stems out at the same time.
In the Rhubarb triangle in Yorkshire, England, there are farms with dark forcing sheds, where pale pink rhubarb grows. It is harvested by candlelight. Click the link for the audio slideshow.
Rhubarb emerges from hibernation once temperatures have reached the upper 40°F (5°C) range for several weeks. Do not harvest stalks the first year after planting, as it is important to help the plant get well established.
Most people harvest by grasping a thick stem near the base, and twisting and pulling. We like to pull 1/3 of the stalks available and leave at least 2/3 of them growing, but with big plants you can remove half of the stalks, provided you leave at least 10 stalks per plant. I believe it is possible to cut all the stems at ground level, if you have a big commercial planting and need a fast harvesting technique. This may only apply to those growing rhubarb as an annual, setting new plants each year.
The leaves (and any frosted stalks) of rhubarb are poisonous, as noted above. This is due to the presence of oxalic acid, so play it safe and cut the leaves off in the field, bringing only the stalks to the shed. We like to stand the stalks upright in buckets and add an inch (2.5 cm) of water to keep them crisp.
As well as the 6-8 weeks of spring harvest, it is also possible to take one or two harvests in September, in most regions. Some people “force” rhubarb for an earlier spring yield, using rowcovers or field houses, or digging up the roots in late fall and replanting them in a heated greenhouse. Forced plants can be harvested twice a week for 4-6 weeks, but then they are fairly exhausted.
A respectable yield is 2-3 pounds (1-1.5 k) of stalks per mature plant per year, or 15 tons per acre (34 metric tons per hectare).
It’s not just pies and crumbles (similar to cobblers). I recently saw a recipe for mackerel with rhubarb. Roasted rhubarb, topped with mackerel fillets, broiled (that’s “Grilled” in the UK), and served with watercress. Back in the dessert realm there are cold summer dishes like rhubarb fool, a kind of fluffy soufflé.
More Rhubarb Information
Iowa Extension has a free 2-page online publication Rhubarb in the Home Garden
University of Minnesota Extension has a web page with a lot of pop-out info sections: Growing Rhubarb in Home Gardens
GrowVeg has a YouTube Rhubarb from Planting to Harvest
The wonderful website, The Rhubarb Compendium includes planting information, propagation, history, lots of recipes, photos, everything you need to know, in a dozen Informational pages.
Virginia Tech Extension Service has a good Specialty Crop Profile on Rhubarb by Tony Bratsch, covering large commercial production as well as information for small growers.
Some other university extension sites also have good information on rhubarb, particularly Oregon State, Kansas State, Purdue and the University of Kentucky.
Special Topic for March: Nutrition facts on rhubarb.
Sources include: USDA
26 Calories –
|Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.
Other small fruits still available in March
Dried and frozen fruits, jams, jellies, chutneys, other preserves, or even stored apples and pears are all we are likely to have, apart from buying imports. Remember that vegetables are at least as nutritious as fruit, but simply have fewer sugars. The vitamin C content of green leafy vegetables is as good as oranges. Even potatoes have a fair amount of vitamin C, as Carol Deppe points out in a very interesting article The 20 Potato a Day Diet versus the Nearly All Potato Winter about the nutritional and gastronomic wonders of potatoes. It will inspire you to grow and eat more potatoes! (if you can find it. I can’t now.) Try https://www.resilience.org/resilience-author/carol-deppe/
The vitamin C is concentrated just under the skin, so hopefully you have grown organic potatoes and will eat the skins too.
Other fruit care in March in the mid-Atlantic
Complete any weeding, fertilizing, mulching, and planting new plants early in March! Mow aisles (a regular task from now on.)
Blueberries: Plant new bushes now, before buds break. Weed, and restore mulch if it is thin. Set up irrigation – we’ve often been surprised how early in the year we need to start irrigating.
Summer-fruiting raspberries: Mulch, water. Weed shallowly. Set up ropes or wires to hold the canes in check.
Fall raspberries: Weed and water all raspberries. Plant new canes if needed, keep the roots damp during planting. Once the beds are all prepared, go ahead and set T-posts and ropes or wires to corral the newly emerging canes. We like to use T-pots so we can remove them at the end of the season and mow right over the beds. Fall raspberries start from scratch growing new canes each year. It’s a great help with weeding!
Strawberries: Weed this month, before the winter annual weeds seed all over the place. Water new beds if they need it. Get rowcover out once you see flowers. That’s not till April here, but if you are in a warmer climate you need to know to cover any flowers on frosty nights. The leaves will be fine, so if your rowcover is skimpy, it’s OK if leaves are exposed for the night. Keep deer off (electric fence?) Set up drip irrigation and water twice a week from now till November, unless it rains enough. Top up wood chip path mulch. Fill any gaps using runners.
Grapes: Mow if needed. Water if there is a spring drought. Weed, top up mulch if needed. This is the last chance this year to plant new vines. Prune them after planting, and tie them to a sturdy cane or the low wire of the trellis. If using the Geneva Double Curtain method, note that vines are trained to alternate sides of the bottom wire and then to alternate sides of top wires, where they will have space to spread.
Random fruits: Depending on your climate, you could still plant new fruit bushes and canes, and there may still be pruning to take care of. This is a good time to repair or replace broken support frameworks.