Rhubarb is a cold-hardy perennial vegetable often mistaken for a fruit due to its culinary use in desserts. While traditionally grown directly in the ground where its large root system can spread, growing this plant in a container is possible for gardeners with limited space. Success depends on providing the right environment to accommodate its substantial growth habits and specialized care needs.
Container Requirements and Preparation
The primary constraint for container-grown rhubarb is the size of its root system, which needs significant room to develop and support large foliage. Select a container that holds at least 15 to 20 gallons of volume, typically a pot with a 20-inch diameter or larger. Half whiskey barrels are often ideal, providing the necessary depth and width for a healthy root mass.
Pot material impacts moisture retention; porous terracotta dries out faster than plastic or glazed ceramic. The container must have multiple, unobstructed drainage holes to prevent the roots from sitting in saturated conditions and rotting. Rhubarb requires a rich, well-draining substrate, so use a high-quality, peat-based potting mix instead of heavy garden soil, which compacts easily.
Planting and Siting
The ideal time to plant rhubarb crowns is in early spring as soon as the soil is workable. Crowns are preferred over seeds because they establish faster and allow for earlier harvesting. Position the crown (the dormant root section) so the visible growth bud sits just below the surface of the potting mix, allowing new shoots to emerge unobstructed.
After planting, situate the container in a location that maximizes the plant’s growth potential. Rhubarb thrives in full sun to partial afternoon shade. When container growing, afternoon shade is beneficial, as intense sunlight can cause the limited soil volume to overheat and dry out quickly. This placement helps mitigate the increased watering demands.
Ongoing Care and Maintenance
Successful container gardening requires meticulous attention to moisture and nutrient levels throughout the growing season. Unlike in-ground plants, container roots cannot seek distant moisture sources, so the potting mix must be kept consistently moist but never waterlogged. Check the soil daily, especially during warm weather, to prevent moisture stress and stunted growth.
Rhubarb is a heavy feeder, rapidly depleting the limited nutrient supply within the container soil. To sustain vigorous stalk production, incorporate a balanced, slow-release granular fertilizer at planting. Supplement this initial feed with a liquid feed every four to six weeks during the active growing season.
Applying a liquid fertilizer high in nitrogen supports the development of large leaves, which drive root and stalk growth. Monitor regularly for common pests, such as slugs or aphids. Container plants generally suffer less from soil-borne diseases than in-ground counterparts, but ensuring good air circulation helps mitigate potential fungal issues that thrive in high humidity.
Managing Dormancy and Overwintering
As a perennial, rhubarb requires a mandatory cold period (dormancy) to rejuvenate and produce healthy stalks the following spring. Without this chill, the plant will not properly establish or yield a harvest. Containerized plants are susceptible to winter damage because the soil mass freezes solid faster and deeper than the surrounding garden ground.
Once the foliage dies back in late autumn, trim the old stalks down to the soil surface. Move the pot to an unheated garage, shed, or cold frame to protect the roots from extreme temperature fluctuations. Alternatively, insulate the container outdoors by wrapping it in bubble wrap or burlap and grouping it with other pots. Reduce watering significantly, providing just enough moisture to prevent the crown from desiccating until spring.