How and When to Divide Rhubarb: 9 Pro Tips
Perennial rhubarb thrives year to year without much care. After many years of thriving, it’ll form a large, knobby rhizome below the soil. You can dig the plant out, separate the roots, and plant the new divisions throughout your garden. Learn how to divide your rhubarb with these nine pro tips from seasoned grower Jerad Bryant.
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The best crops to cultivate in the home garden are perennial, easy-growing, and prolific species. They produce ample harvests yearly, and you don’t have to worry about starting them from seeds! Plant them once and you’ll have them for decades.
Rhubarb is a superb perennial vegetable. It sprouts edible, red or green stems with a tart and mild flavor. They work well in pies, sautés, and pickling recipes. No matter how you use them, make sure you only use the stems! The leaves and roots are poisonous, while the stems are edible.
The roots of this perennial grow gigantic over time. The division process may take some time, but it’s easy to do with the right instructions. Follow these nine tips to turn your one plant into many more!
Divide in Fall or Spring
Fall and spring are the ideal seasons to divide and plant rhubarb. The weather is mild, temperatures are cool, and the ground is warm. These conditions lead to healthy root growth after you transplant the separate pieces.
Rhubarb is incredibly frost-hardy, with some varieties tolerating temperatures as low as -40°F (-40°C)! You won’t hurt it by dividing it; rather, you’ll set it up for future success. Divide established clumps a month or more before your last average frost date, or as soon as the ground is workable in the spring.
Avoid divvying up your rhubarb in the summer or winter, as these are the two most inopportune seasons for this process. Summer is too hot and dry, while winter is too cold and frosty.
Dig Up the Entire Plant
Start the division process by uncovering your plant’s entire root system. Dig a few feet from the center of the rhubarb—these specimens have large, woody, and rhizomatous crowns with fibrous roots underneath. You want to avoid slicing prematurely into the roots during the digging process.
After digging down on all sides of the plant, lift the rhubarb out of the ground with your shovel. Stick it under the rhizome, then lift it slowly. The rhubarb may be heavy, but with a slow heave, you should be able to lift it out of the ground.
Take the dug-out rhubarb and place it on a table where you can inspect it and work on its roots. Avoid leaving the plant out of the ground for longer than a day, and mist the fibrous roots often to prevent them from drying out.
Inspect the Roots
A careful inspection before slicing into the roots will help us make smart dividing decisions. Rinse off excess soil and muck, then take a look at the large, woody rhizome. It’ll have thick tendrils near the surface and small, thin feeder roots on its bottom.
Some parts may look shrunken, shriveled, or dead. You can trim these dead parts to make room for healthy new growth.
After cleaning up the roots, it’s time to decide how to divvy up the rhizome. Each portion should have a few buds where new stems will sprout. Three to four buds are ideal per piece.
Use Sharp Tools
A few tools make this an easy process. You’ll need a clean and sharp spade shovel or long knife. Some rhubarbs can reach epic proportions, and you’ll need a strong piece of metal to cut through them. I recommend a spade shovel, as you can step into it and cut through a woody rhubarb in one slice.
Sterility is equally important as sharpness to ensure you avoid spreading diseases onto your new divisions. Use rubbing alcohol or a similar disinfectant to sterilize your tools before using them.
Divide Rhizomes into Pieces
Once you have your tools and have decided how to divide your rhubarb, you’re ready to do the deed! Separate your rhubarb into multiple portions by slicing through it, creating many new pieces. Mist the pieces or keep them in a bucket of water until planting to ensure they don’t dry out.
Extremely thick specimens may require multiple slices to separate. You can get anywhere from two to ten or more pieces from a single rhizome.
Some smaller pieces will be left over that are unsuitable for planting. You can still plant them if you’d like, just know they’ll need a few years of growth before they’re ready for harvesting.
Pot Up Rhizomes
You have two options when potting up the rhizomes: plant them in pots or in the ground. Containers are perfect for potting up divisions in spring, as they’ll have the entire summer to establish themselves before winter frosts return.
When potting up rhubarb, choose containers that are a bit larger than the rhizomes. You want to grant each specimen enough space to thrive for a few years. The division process is tough on the plants, and they need some time before they’re fit for transplanting again.
Rhubarb appreciates moist, fertile, and well-drained soil rich in organic matter. Use a potting mix with plenty of compost mixed in to give your plants a boost.
Plant Rhizomes
Instead of planting rhubarb in containers, you can put the divisions straight into the ground. This vegetable is incredibly ornamental—its lush, green leaves mix well with flowering shrubs, perennials, and trees. Plant it in garden spaces that have full sun, good soil, and regular moisture.
Bury the plants so their buds sit one to two inches underground. They should sit at the same depth that they were before the division process. Cover their roots with the garden’s soil, then water them well. Avoid filling the hole with soil that’s different from the surrounding ground, as it’ll create a pocket where the rhubarb roots constrict themselves.
After filling the holes and watering your plants, cover the area with a layer of compost two to three inches thick. A mulch layer protects, insulates, and feeds the soil. With compost, your rhubarb will stay healthy throughout the year after planting. Instead of compost, you can also use leaf mold, fallen leaves, and straw.
Care for the Transplants
Rhubarb needs a few things to grow well in the home garden. Ensure your specimens have regular water, rich soil, and full sun. Watch for pests and diseases; rhubarb is relatively pest-free, though your divisions are weak in their first year and susceptible to insects, fungi, and bacteria.
Watch for red leaf, root rot, curculios, and stem borers. Prevent pests with row cover in early spring when the shoots emerge. Keep rhubarb pathogens away by keeping your plants as healthy as possible; give them mulch, moisture, and sunlight.
Wait to Divide Again
Dividing rhubarb gives you extra plants! You turn one plant into many with a few seasons of growth. Though you may feel the urge to divide every year, it’s better to give your rhubarb time to establish itself before dividing it again.
Wait three to four years before dividing the clumps again. The pieces will need one to two years after planting to establish themselves before they’re ready for harvesting, and another one to two years before they’re ready for dividing or transplanting.
If you’re unsure how to harvest rhubarb, check out this guide. Rhubarb, like asparagus, has specific harvesting requirements to avoid depleting the vegetable of its energy.
