What’s Wrong With My Rhubarb? Rhubarb Growing Problems

Rhubarb is relatively pest and disease-free, though it sometimes faces problems in poor growing sites. Improper soil, low moisture levels, and pests and diseases can turn a healthy crop into a scraggly, weak one. 

Rather than letting the plants battle alone, protect them from pesky critters! Healthy, vigorous rhubarb is the best defense against pests and diseases. Strong, turgid leaves and stems resist insect bites. They also prevent fungi and bacteria from creeping in. 

If you’re unsure what’s wrong with your rhubarb, this guide will help you identify the issue. Take a close look at your plants and inspect the soil surrounding them. Though pests and diseases seem like likely problems, most rhubarb growing problems stem from improper care or poor site selection. Correct the conditions and you’ll promote a rapid recovery. 

Though root rots stem from fungal and bacterial infections, they start because of improper soil moisture levels. You want rhubarb soil to be well-drained, fertile, and absorbent. Dense clay and loamy clay are tough soil types for this plant.

Rhubarb sprouts rhizomes underground. These tough, knobby roots thicken and swell over time to create large, hardy structures. The rhizomes help rhubarb resist droughts, swampy conditions, and adverse weather. 

When water sits in the soil for long periods, it can cause the fibrous feeder roots to begin rotting. They’ll turn black, mushy, and rotten as time goes on. The rhizomes may sprout new feeder roots if you correct the moisture levels, otherwise, the rot can spread into the crown of the plant.

Crown Rot

Like root rot, crown rot results from excess moisture levels in the soil. Fungi and bacteria thrive in the soggy conditions. They’ll invade the crown of the plant, causing rot to spread upwards into the leaves and downwards into the roots. 

Prevent crown and root rot problems by growing rhubarb in well-drained soil. A loamy mix with equal parts sand, silt, and clay is ideal. Compost is especially beneficial, as it feeds the soil with nutrients while also improving drainage.

If crown rot is already occurring, cutting out the rotten parts and replanting the crown may prevent it from spreading. Check the soil before watering to ensure it’s not already moist, and hold off on watering if it is. If the rot is severe, ditch the plants and plant new ones in a different location for a few years to starve the soil-dwelling disease. 

Red Leaf

Red leaf is a bacterial condition that causes crown rot symptoms. It starts below the buds and spreads throughout the crown, turning it brown, black, and hollow. Leaves may continue sprouting despite the infection, though they quickly rot after sprouting. 

Red leaf is incredibly common in wet and cool areas like the Pacific Northwest. To prevent it, grow rhubarb in free-draining soil with plenty of drainage particles, like pumice, perlite, or vermiculite. Add compost to improve the soil over time. 

Weeds

Weeds crowd the site, pulling nutrients and moisture away from your tender crop. Though they seem harmless, they can cause poor growth and weak stems. Maintain a weed-free garden for the best results.

Weeds are easiest to pull when they’re young—they have small roots that come out of the ground with little effort. Grasp them by their stem, and gently pull until all their roots come out. Some weeds, like dandelions, can resprout from small, leftover root fragments in the soil.

When pulling weeds, take care not to dig into your rhubarb’s crown, as this can cause even more problems. Open wounds make it easier for pests and diseases to move into the plant. 

Limp Leaves

Limp, lifeless leaves occur for several reasons. Most likely, the soil is dry and your plant is thirsty. This vegetable needs consistent moisture to thrive during the growing season. Grant it regular irrigation in spring, summer, and fall. Water less during winter to prevent rot from occurring. 

Limp leaves may also be a sign of red leaf or a similar rotting condition. As the underground portions decay, the leaves aboveground struggle to stay perky and healthy. They can’t thrive without a healthy root system to feed them.

Limp leaves may also occur during late fall and winter when frosty weather returns in temperate climates. This is a normal response the plant has towards cold weather—let them turn limp and fall, then watch for fresh growth in spring. 

Rhubarb Curculio

Rhubarb curculio is a cool name for a dangerous pest! These beetles lay eggs on the plants around rhubarb that hatch into tunneling larvae. The larvae tunnel through the stems and become pupae in the soil. After a few weeks, the pupae hatch into adults that continue feeding on rhubarb and other plants like docks, sunflowers, and thistles.

Cultural control is key in preventing curculios. If you see the brown, elongated beetles, pick them and throw them in a bucket of soapy water. Maintain a weed-free environment to remove the host plants that curculios overwinter and hatch in. This will discourage them from returning and reduce their population the next year. 

Stem Borer

Stem borers, unlike curculios, can tunnel into rhubarb stalks and cause significant problems. They don’t just hurt the leaves! They may tunnel into the crowns and roots of your plants, creating holes for rots and other pests to enter.

Control stem borers with the same methods for controlling curculios. Remove weedy host plants in the garden, and destroy infested leaves. Consider choosing a new growing site for a few years if the infestations are particularly severe. 

Slugs and Snails

These slimy mollusks harm tender seedlings before they mature. They’ll decimate your crop before you can enjoy the sweet-tart stems! Slugs and snails like to hide under boards, beneath rocks, and in cool, dark, and damp locations. 

A few methods may protect your rhubarb from these pesky critters. Copper rings shock these mollusks, encouraging them to turn around when they approach your seedlings. Find them available at nurseries, garden centers, and online.

Rather than preventing damage, you may also try trapping slugs and snails to control their populations. Use beer, a dough slurry, or boards to trap them. Fill a plastic container with beer or dough, then bury it in the soil so its top is exposed. The mollusks will fall into the trap, and you can remove them as they fill it up. 

For board trapping, place a wooden board down near your beds or containers. Lift the board every morning and afternoon—you’ll find dozens of slugs and snails underneath! Place them in a bucket of soapy water, then discard them in the garden for birds and small mammals to eat. 

Deer

If you garden with deer, you know how troublesome they can be! These mammals strip seedlings, saplings, and mature plants of their foliage. They’re especially damaging to young plants with small rhizomes. Mature stands will recover, though seedlings will struggle to survive.

The best way to prevent deer damage is with a tall, impenetrable fence. These smart creatures are high jumpers and clever thinkers; if there’s a way for them to find your rhubarb, they will! You may also place a netted basket, like a critter cage, over your small seedlings to discourage the deer. 

Many gardeners in my area plant their tender crops inside a small, fenced area, and they let the deer browse on their other hardy plants around the yard. Consider placing rhubarb inside a similarly protected site to keep it safe from deer.