Why Is My Rhubarb Crown Rotting at the Base?

A rhubarb plant that collapses suddenly — with wilting stems that pull away from the crown easily, and the crown tissue proving brown, soft and foul-smelling when exposed — has crown rot. This is one of the most serious rhubarb problems and is often fatal to the affected crown. The condition is typically caused by a combination of waterlogged soil, which creates the anaerobic conditions that favour rot pathogens, and in some cases by fungal pathogens such as Phytophthora or bacterial soft rot organisms that enter through wounds or stressed tissue.

Can a rotting crown be saved?

If only part of the crown is affected, cut away all soft, discoloured tissue back to firm, white or pink flesh. Dust the cut surfaces with powdered sulphur (a natural fungicide) and allow the cut surface to dry in the air for a day before replanting in improved, well-drained soil. Success is possible when the rot is caught early and a significant healthy portion of the crown survives. If the entire crown is soft and brown, it cannot be saved — remove it and improve the site before replanting.

Conditions that cause crown rot

The primary driver is persistent waterlogging — soil that sits wet for extended periods after rain. Heavy clay soils, low-lying sites, and beds with poor structure that compact and hold water all predispose rhubarb to crown rot. Planting too deeply (buds more than 3cm below the surface) also keeps the crown in a perpetually moist environment. Frost damage to crowns in spring, followed by warm wet conditions, can also open the door to rot organisms.

Prevention

Plant rhubarb only on freely-draining or raised sites. Test drainage before planting. Avoid planting in depressions where water collects. Keep the crown top at or just below the soil surface, not buried deep. Do not mulch directly onto the crown with wet organic material.