Growing Rhubarb
Many of us enjoy strawberry and rhubarb pie. I number among those who enjoy this dessert. Both of those main ingredients will soon be available fresh from gardens. In this article, we'll concentrate on growing rhubarb, also called pieplant. Next week – strawberries.
Rosie Lerner, Purdue Extension consumer horticulture specialist (retired), said rhubarb harvest can begin as soon as the stalks are large enough to cut and continues on through late spring.
Rhubarb is harvested for its leaf stalks, or petioles. “The leaf blades of the rhubarb plant contain oxalic acid and, therefore, are not edible, either raw or cooked,” said Lerner. “Poisoning has been reported from eating the leaf blades of the rhubarb plant.”
Once growth starts in the spring, which it recently has, the weather will influence the color of the leaf stalks. The cooler it is, the stalks may appear pinker or red. The warmer it is, the more those colors will fade, and green colors will tend to dominate. The cultivar will also influence color.
Rhubarb crowns, rather than seeds, are generally planted in well-drained, tilled soil. A balanced fertilizer should be worked in. Crowns should be spaced 3 feet apart in rows that are spaced 5-6 feet apart. Remember, this is a perennial plant, so choose your site well, as rhubarb will be growing there during the next several years.
If you have recently planted rhubarb, it is best to allow two full years of growth before harvesting. This allows all growth energy manufactured by the leaves through photosynthesis to be stored and utilized by the crown and roots for a healthier plant over time.
If your rhubarb is in its third year of growth, you can harvest rhubarb stalks when they have elongated 10-15 inches. Lerner said, "You can cut the stalks with a sharp knife, but be careful not to injure any new stalks that are just beginning to poke through the ground." She said a simple harvesting technique is to grasp the stalk near its base and pull it down and slightly to one side. The stalk should snap and separate fairly easily. 3-year-old rhubarb can be harvested for 4 weeks, while older rhubarb harvest may continue for as much as 8-10 weeks.
Do not remove more than two-thirds of the developed stalks at any one time. Trim off all leaf blades. Stalks may be stored in plastic bags in the refrigerator up to 4 weeks.
“Gardeners frequently ask why their rhubarb is bolting,” said Lerner. “Well, if you think of it from the plant’s perspective, it is just a part of the plant’s natural life cycle.” Flowering is part of the reproductive phase that leads to the production of fruit and seed.
These seed stalks should be removed. Allowing seed stalks to remain and mature steals growth energy from the plant and reduces its overall vigor. Certain rhubarb cultivars tend to bolt more than others. Lerner said if bolting persists, you might consider replacing with improved cultivars.
“Another question that sometimes comes up is whether the flowering makes the leaf stalks poisonous,” said Lerner. “The answer is no, the leaf stalks remain edible, regardless of whether flower stalks are present.” She emphasized, however, that the leafy blade portion is always poisonous.
Keep rhubarb beds well cultivated and weed-free. Allow leaves to remain past the harvest season to enable carbohydrates to be continually manufactured for storage and growth the following year.
Lerner said plants should be divided and reset every 8-10 years. Use a sharp spade to divide the crown, leaving 3-4 buds undisturbed in the old location. “Old plants which become thick only produce inferior, slender stems,” she said.
For additional ideas on using rhubarb, access Purdue Extension’s FoodLinkSM fact sheet on rhubarb.
Find Lerner’s publication on rhubarb, which she co-authored with Michael Dana, at Purdue Extension’s Education Store, or request a copy from your local Purdue Extension office.