Rhubarb is easy to grow in containers—if you have enough space for the leaves to spread out. You’ll need a sunny spot for it to sit in during the growing season, and a cool basement, garage, or barn for it to ride out the off-season from first frost to last.
The container should be big: about 18 to 22 inches wide and deep. Rhubarb has a big root system, and you don’t want to crowd it.
Make sure your soil is clean, weed-free, and nutrient-rich. Don’t reuse last season’s soil. It will be so much better for your rhubarb if you start with fresh gardening soil; there’s even soil formulated especially for container gardening. And make sure your containers have good drainage; soggy soil can lead to root rot—which can spell disaster for your rhubarb plants.
Rhubarb needs at least six hours of sunlight each day to flourish; more is better. It can tolerate some shade, but only if necessary in the event of high temperatures. Putting your container on wheels is one way to help your rhubarb get the sunlight it needs. Just move the container when you need to.
Water, sunlight, and soil are all essential ingredients for a successful rhubarb harvest. Watering is one of the easiest things to do—and therefore one of the easiest things to overdo. Your rhubarb needs about an inch of water a week. You can supplement whatever nature does not provide. Wherever it’s planted, rhubarb needs soil with good drainage—and that includes containers! You can mulch the soil around your rhubarb to help retain some moisture; but also make sure your container has adequate drainage, and don’t let the mulch touch the stems or crowns of your plants. Don’t kill your crop with kindness—water just enough, but no more. Too much water can invite disease, and you want to keep your rhubarb healthy.
For rhubarb in containers or planters, use a commercial soil mix that’s formulated for vegetables. This gives your plants a healthy head start, and you’re less likely to introduce weeds or soilborne diseases by digging up soil from your garden.
Use fertilizer sparingly. If you’re mulching with compost, you may be providing your plant with sufficient nutrients. But in the spring and fall, it’s OK to add a little balanced 10-10-10 NPK (nitrogen, phosphorus, and potassium) granular fertilizer. Follow the application directions carefully.
Have you grown rhubarb in containers? Please tell us about your successes and challenges growing rhubarb in containers.