Fall rhubarb care

Are you one of those people who loves rhubarb pie, cake, sauce and even preserving rhubarb for off-season use?

Although not everyone enjoys eating rhubarb, few dispute its majestic beauty. Whether grown for aesthetics or food, this hardy perennial can be a long-lived addition to the gardening landscape.

A thin layer of mulch or compost can be added once rhubarb goes dormant in the fall. Photo by Joyce Amsden
A thin layer of mulch or compost can be added once rhubarb goes dormant in the fall. Photo by Joyce Amsden.

Every five to 10 years you need to divide your rhubarb plants to prevent the roots from becoming too dense. Signs of this are smaller, more plentiful stalks and failure to produce stalks at the center of the plant.

While most gardening experts recommend dividing the roots in the spring, it can be done successfully in the fall, if timed carefully.

Dividing and planting needs to be done early enough for the roots to become established but late enough that the newly transplanted root does not push up leaves instead of going dormant. Think mid to late September.

If you decide to wait until spring to plant rhubarb, you can prepare your bed now and be prepared for early spring planting. Rhubarb needs good drainage, plenty of water and fertilizer or compost.

To prepare the bed, you will need to dig out a three- to four-foot-wide by two-foot-deep area for each plant. If your soil has poor drainage, consider creating a raised bed. An undersized bed may discourage optimal root growth and hold water leading to root rot.

Work three to four inches of compost or composted manure into the soil. If not planting until spring, cover the bed with an inch of straw mulch, and add an additional two inches after the ground freezes.

For fall division, dig up your existing plant and divide at the natural weak points between buds with at least one or two buds per division. Plant your division in the new location one to two inches deep with the bud on top.

Cover with soil and press down to eliminate air pockets. Be careful not to damage the buds. Add an inch of straw mulch.

If you are not dividing your rhubarb plants this fall, you can remove the stalks and leaves after the first killing frost. While fine for the compost heap, do not eat the stalks at this time. The oxalic acid, a powerful toxin in rhubarb leaves, moves into the stalks when the leaves are damaged.

Remove grass and weeds, as they crowd the plants and can harbor insects that damage rhubarb. You can add a little compost or composted manure once the plant is fully dormant. Adding too much in the fall can delay dormancy needed for winter hardiness.

After the ground freezes, add about three inches of mulch to your existing rhubarb plants or new transplants. Waiting for the freeze helps the plant become fully dormant and discourages rodents from establishing routes under the mulch and snacking on your plant’s roots over winter.

As winter waxes long, look for new rhubarb recipes to try so you will be ready for spring with a shovel in one hand and a spoon in the other!

Joyce Amsden is a UVM Extension Master Gardener Intern from Sharon.