Question: I have been growing Rhubarb for eight years and last year the plants leaves and stalks were much smaller. Do you know what could be causing this?
Answer: Rhubarb grows very well in New Jersey. They require winter temperatures below 40 degrees to go from dormancy to growth in the spring. The tops are killed in the first heavy freeze in the fall but roots survive and produce new tops in spring.
Rhubarb plants produce well for several years, but after five or six years you may notice a decrease in vigor. This could be the result of crowding or low soil fertility. Over time your plant has produced so many growing points at its base that the only way the stalks can continue to grow, is to shrink in diameter.
Rhubarb is a very hardy plant affected by few insects. The leaf stalks grow directly from the crown and are harvested in late spring or early summer. Only the stalk is edible. The leaf blades contain toxins which can be harmful or deadly if ingested in large quantities. The stalk contains large amounts of Vitamin A and C, as well as smaller amounts of calcium and potassium.
Since your plants have been in the same location for many years they most likely need to be divided. This is best done in early spring before the plants have a chance to begin to grow. Carefully dig up your plants and divide them into pieces that contain at least two or three buds. Leave as many roots as possible with each division. Place the plants three to four feet apart in each direction. Cover the crowns with one inch of soil and water deeply and slowly.
Don't harvest your new plants the first year after planting. Each plant needs time to build up its energy reserves to produce roots and thick robust stems. During the second year begin to harvest the older stems first. Harvesting can be done with a knife or by grasping the stalk close to the base, pulling down to one side, and snapping off the stalk. Never harvest all the leaves off one plant.
If you notice that your plants are producing seed stalks early in the spring, remove them immediately. They may rapidly reappear, but continue cutting them and they will stop after a few weeks. Seed stalks reduce the vigor of the plant by using up energy that should go into developing larger crowns. Older plants tend to send up seed stalks more than younger plants. If you would like to start growing Rhubarb, the recommended varieties for our area are MacDonald, Canada Red, and Victoria.
Mona Bawgus is a certified master gardener with Rutgers Cooperative Extension of Atlantic County. Write to her c/o Rutgers Cooperative Extension, 6260 Old Harding Highway, Mays Landing, NJ 08330. Email: firstname.lastname@example.org