Days to germination: Started from crowns not seed
Days to harvest: Lightly in 1 year, fully in 3
Light requirements: Light shading
Water requirements: Regular watering
Soil: Rich loose soil
Container: Reasonably suitable for large pots
Rhubarb is a hardy perennial that will keep growing for a decade or more once established. Though it grows more like a vegetable, it’s used mainly in sweet dishes (along with a generous helping of sugar to balance the tart flavor). Rhubarb stalks are high in fiber, potassium and calcium.
Your plants can survive cold winters, and grow between zones 3 and 8. The plants are very large and leafy, and come in either red stalk or green stalk varieties. It’s a popular plant for many gardeners because you will start to get a harvest from it much earlier in the spring than most other plants.
Starting from Seed
You don’t usually start your rhubarb plants with seed, but rather with small plants called crowns. Crowns are actually dormant pieces of a mature plant, rather than a newly growing seedling so they are quite hardy.
Before your plant your crowns, loosen up the soil and add a generous helping of rich organic matter such as compost to the soil. The base of the crown should be about 3 inches under the soil, and you should allow for 2 to 3 feet of space on either side of the plant.
A location with good drainage is essential, so don’t plant rhubarb any place where you often see water accumulation after a rain. You may even want to build up a raised bed to help the water drain, or add a bit of sand to the soil.
You can put your crowns in the garden as soon as the weather warms enough that you can dig.
You may want to use mulch around your plants for weed control, as the shallow roots of the rhubarb can easily be damaged by hoes or other cultivators.
A dose of fertilizer, compost or aged manure twice a year will keep your plants at their peak. Apply first in early spring and then again in late summer.
After around 4 to 5 years, your plants will start to get very large and can start to crowd each other or the rest of your garden. Very gently, dig up the plant and split it into several smaller crowns to be replanted. Once you do that, treat as any new crown and allow at least a year before you do any more harvesting again. Ideally though, you will have enough space to leave your plants unmoved. They will thrive better if left alone.
If your plants start to go to seed, clip off the flowering stems right away to keep your rhubarb producing stalks and leaves.
Overall, rhubarb is a very easy to care for plant. Many people plant it, take their spring harvest and then just leave it alone for the rest of the year. It does not need to be fussed over.
When winter comes, you can add a layer of mulch to help it overwinter though not all gardeners feel it necessary. Pull back the mulch in the next spring to allow the new shoots to come up unrestricted. Clean away any dead leaves in the spring as well. They are very large and can block new growth.
With fairly shallow roots, rhubarb is actually well-suited to container life providing the pot is large enough. For each plant, you should have a pot at least the size of a half barrel. It may seem like a lot of room for a little crown, but after a few years, your rhubarb will definitely fill it. If your plant does grow out of the pot, you can always break it up just like with a garden plant (mentioned in the Growing Instructions section).
Fertilizing is important with potted rhubarb, and you may want to add a third feeding to your annual routine to keep it growing well.
Pests and Diseases
Though the leaves are toxic to us, rhubarb still gets its share of insect pests that chew on the leaves. Slugs and snails in particular, because they like to hide under the large leaves. Check your plants regularly, and pick off any that you see. Use some snail traps or diatomaceous earth to control them if you find it’s a regular problem.
The broad leaves can also attract some various fungus issues if they are left wet too frequently. Make sure to gently lift them aside and water the soil directly to help keep the moisture down. Downy fungus in particular can be a problem, and it looks like fuzzy white patches underneath the leaves. Patches of reddish-brown rust will also be a leaf fungus. Trim off any leaves that have mildew or fungus, and treat the plant with a natural fungicide.
Harvest and Storage
Only harvest and use the rhubarb stalks. The leaves and roots are actually poisonous, due to the oxalic acid they contain. If you are particularly industrious, you can boil the leaves in water and make a home-made insect repellent that you can use to keep the pests away from some of your other plants. Of course, it’s still toxic and should be used with care.
Leave your plants for the first year to develop a strong root system. During the second year, do only a light picking of a few stalks from each plant. By the third year, you should be able to harvest normally and enjoy your crop of rhubarb.
Harvesting is usually done in early summer rather than at the end of the season, to get the most tender stalks. Right when the leaves are fully opened is the ideal time, and you should never take more than half the stalks on a plant if you want it to produce another harvest the next year. You can harvest for several weeks once you’re into the third year.
Grip each stalk near the bottom, and gently twist it off the plant.
Wrapped in plastic wrap, you can store whole fresh stalks in the refrigerator for up to 3 weeks. If you have more rhubarb than you can use, chop it up and freeze it. It will last 6 months and will retain much of its texture when thawed.