By Kathleen Cue, Nebraska Extension Horticulture Educator (5/26/2020)
Rhubarb, Rheum rhabarbarum, is an easy-to-grow perennial that lends a delightfully tart taste to pies, crisps and jams. The fact it is a perennial means there’s no extra labor to grow plants annually from seed like you do for the vegetable garden. The edible part of rhubarb, the petiole (also called a stalk), is technically not a fruit, but its size relative to fruit trees makes rhubarb a nice fit for a smaller space. The robust leaves, though poisonous, are eye-pleasing and make an unexpected addition into landscape plantings.
Depending on the variety, the stalks of rhubarb range in color from light green to hints of red to strongly red. Varieties like ‘Canada Red’ and ‘Crimson Red’ have bright red stalks while ‘Victoria’ has green stalks. Rhubarb performs robustly in a location where it gets sun all day but will still do OK in a location where it gets a minimum of 6 hours of direct sunlight each day. Crown rot can be a big problem in dense soils, so amend the site liberally with well-rotted manure or compost. Spring is a good time to add rhubarb plants to the garden as well as dividing clumps that have been in place for four or more years.
During its first growing season, none of the stalks of rhubarb should be harvested, allowing time for the crown and roots to establish. In the second year, a few stalks can be harvested. From the third growing season on, stalks can be harvested starting in May and continue through mid-June. Stalks should never be cut from plants because the stubs left behind are entrance points for pathogens. Instead, firmly grasp each stalk and give a slight twist while pulling. The stalk will disengage from the crown.
The toxins produced in rhubarb leaves do not transfer into the stalks if leaves wilt. It’s still best, however, to prepare only firm, fresh stalks for baking. As the growing season progresses, rhubarb stalks get progressively tougher and stringier. If a special occasion calls for rhubarb later in the season, a few of the newer stalks can be pulled with no detrimental effects to the health of the plant.
Because rhubarb is a heavy user of soil nutrients, dig and divide plants every fourth year or so, moving plants to new locations and amending the soil with well-rotted manure. Divide plants with a sharp spade to ensure clean, not jagged, edges. Plant the crown even with the surface of the soil. Water plants thoroughly and maintain about an inch of water per week, precipitation and irrigation combined, to foster good growth. Healthy plants growing in a well-prepared location have few insect and disease problems. Occasionally, rhubarb sends out flower stalks. These should be clipped away so the plant does not expend energy to develop seed. 