Why Are the Leaves on My Rhubarb Plants Turning Bright Red?

Red Leaf Disease

• Affecting rhubarb plantings in Western Canada, Montana and other western areas, red leaf disease attacks the roots and crown areas of the plant, though the first obvious symptom is sudden change of leaf color. Bright red leaves soon wilt and shrivel, new leaves fail to appear and both plant roots and crown start to rot. The cause is the bacterium Erwinia rhapontici, easily transmitted when infected rhubarb crowns are divided. It is also transmitted to disease-free crowns if they are planted in soil where diseased rhubarb has grown

Control

• There is no cure for red leaf disease, and no easy way to control it other than removing and destroying infected plants. Don't plant disease-free rhubarb crowns where the disease has occurred. According to the University of Montana Extension website, insects that feed on roots and foliage can transmit bacteria from infected to uninfected plants -- thus infecting them. Preventing insect infestations will help limit local and regional spread of red leaf disease. Shallow planting and providing adequate soil moisture may also reduce red leaf disease infection, according to University of Saskatchewan Extension website.

Prevention

• Rhubarb is usually purchased as crowns or divisions, not propagated from seed. Purchase disease-free rhubarb crowns from local nurseries, garden centers or seed catalogs. As tempting as it may be to start a rhubarb patch from a friend or relative's plant divisions, don't do it. Plant crowns as soon as you can in early spring -- when plants are dormant or just starting to leaf out -- and keep them evenly moist to reduce stress. When plants are well-started mulch them with 3 to 4 inches of compost, shredded leaves, pesticide-free lawn clippings or straw to keep soil cool, conserve moisture and discourage weeds.

Healthy Plants

• Rhubarb needs winter temperatures below 40 degrees Fahrenheit to stimulate later spring growth and prefers summer temperatures lower than 75 degrees. Clay loam high in organic matter is ideal. Don't fertilize or harvest plants during their first year, but do water them consistently. Avoid harvest during the second year, too, to allow roots and crowns to get well established. Full harvest can begin the third year after planting. Don't remove more than two-thirds of a plant's larger stalks -- and stop harvesting altogether by July, so plant energy reserves can be replenished for next year's production. Prevent plants from producing seed -- remove flower heads in spring -- to direct plant energy to stalk production instead. Continue watering rhubarb until late fall.