GROW: Rhubarb - The Vegetable That Became a Fruit
Several years ago, I was out on a seldom-used dusty logging road picking St. John’s Wort flower buds to use in a healing salve I make when a neighbor came bouncing down the road in her pick-up. She stopped and asked if I wanted to go pick rhubarb at a friend’s cabin down the road. Though I had one rhubarb plant in the garden, how could I say no to free food?
Apparently, the cabin does not have many visitors: the driveway was hard to find and the overgrowth of trees and shrubs prevented us from driving on it so we hopped out and headed down what was mostly a path. An old wooden structure, slumped a bit on one side, came into view but it, too, was gradually being reclaimed by the plant world, slowly hiding any trace of human activity. Our arms served as dull machetes as we cleared the path to the back of the cabin.
And there was the largest rhubarb plant I had ever seen: the enormous, glossy leaves were easily extended 2 feet from their red stems. We pulled (not cut) out the crimson stems and cut off the toxic leaves, and filled our two baskets to the top. My imagination wandered as I thought about the old cabin as someone’s permanent home at one time who intentionally planted rhubarb as part of their vegetable garden. I wanted to explore the property a bit more - looking for more evidence of a garden - but it was June and the pollen from the jungle-like setting had me sneezing non-stop, eyes watering and an increasing awareness that I was going to be congested, itchy and drippy the rest of the day. I knew that I needed to get out of all that pollen ASAP.
Old homestead and farm gardens, sometimes called legacy gardens, often hosted two perennial vegetables whose early buds were the harbingers of spring: rhubarb and asparagus. Back then, after a winter of stored root crops and no grocery store fresh produce (now flown into US markets from Mexico and South America), what excitement there must have been to see fresh vegetables budding out as the snow started to melt.
THE BENEFITS OF PERENNIAL VEGETABLES
Perennial vegetables - plants that grow back each year - make a lot of sense in the vegetable garden. Because you only plant them once, they save money, time and energy and will provide an reliable harvest of vegetables for 10 to 20 years...or longer as in the case of the abandoned rhubarb plant mentioned above.
As we learn more about the many forms of life that form the complex soil food web and its importance in growing healthy plants, we now know that the typical garden actions of tilling, digging and shoveling disturbs the microscopic soil infrastructure. Once planted, perennial plants are not moved or pulled from the soil (except to divide every 5 years or so) so the soil web stays intact. Many perennial plants have deeper root systems so they can tap into water and nutrient resources, offering another benefit for the gardener: less irrigation and less fertilizing. Unlike many annual vegetables that offer a one-time reward, most perennials continue to produce for weeks allowing for multiple harvests. At the end of the season, perennials are cleaned up a bit and then mulched for winter. It doesn't get much easier!
A member of the Polygonaceae (buckwheat) family, the genus, Rheum, contains more than 50 species including R. officinale, a medicinal rhubarb used for 2700 years in (TCM). Rhubarb originated in northern China and eastern Siberia and was introduced to Europe in the 14th century. Marco Polo wrote of its medicinal properties and it became a highly regarded plant, valuable enough to be included in the Spice and Silk trade economies. The Russians controlled the profitable medicinal rhubarb trade and used Instanbul as a thoroughfare for their trade routes. Rheum palmatum, commonly called Turkey Rhubarb, was cultivated there and the common name reflects that geography.
In the early 1700s, the English began to propagate the plant eventually creating a hybrid that found its way into the kitchen as a fruit substitute in the 19th century. The cheap abundance of slave-grown sugar in the 1800s in the western markets made rhubarb pie a possibility. Some wise and entrepreneurial gardeners began to sell the stems with the leaves attached that, in due course, led to an awareness and chemical analysis of the oxalic acid's toxic effects on some people.
Rheum rhaponticum, Rheum x hybridum, Rheum rhubarbarum, Rheum x cultorum - Rhubarb, Garden Rhubarb, Bastard Rhubarb, Sweet Round-Leaved Dock, English Rhubarb, Wine Plant
According to Grieves’ A Modern Herbal, our modern garden rhubarb (R. rhubarbarum) is derived from Rheum rhaponticum and Rheum officinale. The many other species are mostly used ornamentally though some cultures use their native rhubarb for edible and medicinal purposes. Cultivars are cultivated varieties that have been created by plant breeders for many different reasons. As a result, there are ornamental rhubarbs with beautiful leaf structures and there are edible stems that range in color from light green to pink to crimson red. While red is the most common variety, green stalks are actually the most productive. The green stalks are also reported to be sweeter than the red stalks. Regional adaptation is usually the best way to select vegetables for your garden so check with your state’s Extension Service to see what varieties do well in your region.
FRUIT OR VEGETABLE?
Let’s get the biology right on this: botanically speaking, rhubarb is a vegetable but horticulturally, we use it as a fruit - after we add copious amounts of sugar to offset its tart /sour taste! Rhubarb is one of the few plants grown for its edible leaf stalks, botanically called petioles. Celery and asparagus is another petiole we eat.
Alas, rhubarb is mostly (95%) water. Nutritionally, the stems are high in vitamin C and dietary fiber so there certainly are more nutrient dense vegetables to eat. Rhubarb is the first “fruit” of the gardening season so just pretend that you don’t have access to imported fruit and jump for joy when you harvest your first stalks of the season.
THOSE GORGEOUS LEAVES
Those humongous green leaves start as little crinkled leaf buds and they look delicious but we can’t eat them because they contain high concentrations of oxalic acid and anthraquinones. In permaculture, the leaves are removed from the stalk and laid around the plant to serve as a soft mulch. Folklore hints that the oxalic acid kills weeds but there is no scientific evidence to support that claim.
Rhubarb’s (R. officinale) long history of medicinal use is what made it a valuable trade item and is still considered one of Chinese Medicine’s more powerful herbs. The roots of six year old rhubarb are harvested in the fall, dried and sometimes ground into powder. Rhubarb roots contain anthraquinones which have a purgative effect and are used to help with constipation that is associated with specific health conditions. Note: Avoid using rhubarb root medicinally without consulting someone trained in Traditional Chinese Medicine. Pregnant and nursing mothers should avoid rhubarb root.
PERENNIAL RULES OF ENGAGEMENT
Starting rhubarb by seed is the second most economical way to propagate the species and delays harvest by a year in some species. The cheapest way to is acquire roots by dividing a five year old plant and remove the many new roots - called crowns - that formed on the root system. If you know someone with a mature rhubarb plant, ask about dividing for new crowns.
The best time to divide is in early spring (Zones 7 and under), when the first few sprouts are peeking out of the soil. Carefully dig a circle around the plant, lift it out with a shovel and look for new growth of crowns with developing buds - buds are necessary so that the transplanted crown has a way to produce food. Separate the newer crowns with buds from the original crown. Replant the older crown and and plant the new crowns in your designated rhubarb bed. If you don’t know anyone with a rhubarb plant, you can order rhubarb crowns here and here.
Perennials need several years to mature to their full size and rhubarb is no exception. After planting the new crowns, you will need to practice patience and not harvest for two seasons. This allows for the plant to develop a healthy root system. Another rule is to never remove all of the leaves at one harvest; they feed the plant through the process of photosynthesis and need those leaves throughout the growing season. Remember that a perennial needs to store energy to return the following year.
Since the plant will live in the same spot for at least several years, the perennial plant bed must be located and prepared to best serve the needs of the plant. I discuss this in the How To Grow section below.
IN THE GARDEN: HOW TO GROW RHUBARB
Rhubarb is a hardy, vigorous perennial plant that will grow beautifully in hardiness zones 3-9 with full sun and cool/cold winters with little to no care, producing fresh stalks of lemon-sour “fruit” from mid-spring to mid-summer. Once established, they are drought tolerant and are considered deer resistant (remember that not all deer read the Rules of the Garden).
- Rhubarb needs 500 hours of cold temperatures between 28°- 40° to form new leaf buds.
- Rhubarb likes full sun unless there are hot afternoons; then just like humans, it prefers a bit of shade.
- Each rhubarb plant needs space to mature; it will eventually grow to 3ft wide. Allow 3 ft of space on both sides of each crown.
- The ideal soil for rhubarb is rich, well-drained sandy loam with a pH of 6.0 to 6.8.
- Dig a trench 6-8 inches deep and fill 4 inches with well-aged manure.*
- Set the crown on top of the manure, 1-2 inches below the soil line and top with soil, pressing the crown firmly into the trench to eliminate any air pockets.
- Make sure the leaf bud is above the soil line.
- Water thoroughly and whenever the top 2 inches of the soil is dried out for the best stalk production. If the leaves are wilting, more moisture is needed.
- Rhubarb is ready to divide when it produces 25-30 thinner and smaller stalks instead of the usual 12 - 18 thicker stalks.
- Rhubarb has no significant pest issues though slugs always appreciate new growth anywhere in the garden.
*Never use fresh manure as it will burn the roots. If you don’t have access to manure that has not been aged for at least one year, then use compost and a small amount of natural fertilizer high in nitrogen.
Harvest begins in late May and depending on variety and environmental conditions, may continue through August.
Do not harvest from the plant during the first season and only a few stalks during the second season should be taken.
Never harvest all of the stalks at once.
Harvest thicker stalks first.
- Pull each stalk from the mother plant by grasping the bottom of the stem and twist slightly and pull sideways. Cutting stalks leaves open tissue that can invite problems.
- Cut leaves off and use as mulch around the plant (or use as a natural dye - see below)
- As the season progresses, the stalks will become thinner and woody. Let them sit on the plant until the first frost. Then, remove them, toss compost and straw to mulch the plant and tuck it in for the winter.
- If the temps are hot or fluctuate between cold and hot rhubarb will bolt - sending up a tall seed stalk which is beautiful but needs to be cut so the energy can be redirected into the roots.
IN THE KITCHEN
Like all vegetables and fruits, rhubarb is best used immediately to maintain taste, texture and optimum nutrition. You can store trimmed rhubarb in a sealed plastic container in the refrigerator for about two weeks but remember that as soon as a vegetable is harvested it begins to decay. Longer storage will result in stalks that are dried out and spongy and are best used in the compost pile.
You can preserve rhubarb by canning or freezing. Blanching the cut fruit for one minute will help with retain its texture and color.
Rhubarb strawberry pie is probably the most well-known recipe for rhubarb and you will find countless recipes to make pies, crisps, upside down cake, muffins and jam. Rhubarb is often combined with strawberries or blueberries; this allows you to reduce the amount of sugar and helps a bit with the texture. Cooked rhubarb can have a texture problem for some people. It becomes mushy and stringy and if someone says they don’t like rhubarb, it’s probably because of the texture problem.
One way to avoid the texture problem is to make a syrup, like a Rhubarb and Rose Syrup (from the Wild Drinks and Cocktails book I reviewed) to mix with carbonated water or perhaps, with some chilled vodka for a Rhubarb Drop on a warm summer evening. Last spring, I had enough rhubarb to explore some new recipes: Rhubarb Viniagrette and Rhubarb Leather. This spring, I plan to experiment using rhubarb in a vinegar-based shrub.
IN THE CRAFT ROOM
Wait - we are not quite done with rhubarb. Those gorgeous glossy leaves that are too toxic to eat? You can use them as a natural dye for wool and as a natural mordant (a substance that helps bind dye to fiber) and the roots have long history as a dye. From the Wild Color book by Jenny Dean:
“In Himalayan regions, species of rhubarb are particularly valued for the contribution in the dye pot. In parts of Tibet and Ladakh, and among the Tibetan refugees in Nepal, rhubarb root is the most common source of yellow dye, and species of rhubarb have long been sought after locally. The roots are dried, chopped up and ground into powder before use and give strong, fast shades of yellow, gold and orange.” (p. 121)
Oregon State Extension Publication - Grow Your Own Rhubarb
The New Oxford Book of Food Plants by J.G. Vaughn and C.A. Geissler
Sunset Western Garden Book
Gaia’s Garden by Toby Hemenway
Botanica: The Illustrated Encyclopedia of 10,000 Plants
"Good Stalk: Rhubarb" by D. Grumdahl in May 2013 issue of Saveur
The Way of Chinese Herbs by Michael Tierra
A Modern Herbal by Mrs. M. Grieve