Rhubarb (Rheum rhabarbarum) is a tasty, low-maintenance plant that you can use in cooked desserts, jams, syrups, and drinks. It's a perennial in USDA zones 3-8 but can be treated like an annual in warmer climates. Only the stalks are usable, but you can still compost the non-edible leaves.
Want to grow a plant in your garden that will keep coming back year after year and provide you with some of the best pie filling ever? Rhubarb (Rheum rhabarbarum) requires little maintenance, and in areas where it grows as a perennial, you can keep one plant going for typically five to 10 years, if not longer. It doesn't take long to learn how to grow rhubarb, and even better: This is a no-waste plant. There are parts you can't eat, but you won't have to trash them because you can compost them.
How and When to Plant Rhubarb
When you plant rhubarb, assuming you're planting a division or crown and not a seed, plant in late autumn in a well-prepared site. This can be in a garden bed or a container; while rhubarb generally does better in a garden bed, it will grow well in a container with good care and a careful eye on when to divide the plant.
Where Can I Find Rhubarb Plants?
You have a couple of options if you want a new rhubarb plant. One is to get a division from someone else. Rhubarb plants need to be divided every few years – you'll eventually have to divide yours – and that means people eventually end up with several divisions that have to go somewhere. It may as well be in your yard, right?
The other option is to buy a rhubarb crown from a plant nursery or garden supply company. These crowns are root divisions that have at least one bud on them, and when you plant them, the entire thing will be covered with soil.
Technically you can plant a rhubarb seed and get a plant that way. However, it will take longer for the plant to grow and become established, which means you'll have to wait longer to harvest. Seed-grown plants can look a lot different from what you'd expected, and they can also be weaker. You'd spend year after year coaxing stronger plants along while thinning out weaker ones. It's a lot more convenient to simply plant a division or crown.
Where to Plant Rhubarb
Rhubarb doesn't have many growing or site requirements, but what it does require are things you should do your best to provide. That means preparing the planting site well and ensuring the division or crown is planted correctly with some compost and water to start it off.
Choosing and Preparing the Planting Site
Wherever you plant rhubarb, make sure the site gets the right amount of sunlight throughout the growing season. You don't want to plant in a site that gets full sun in early spring but is thoroughly shaded in mid-summer. In colder climates, southern exposure is a good idea.
Make sure the site is free of weeds. You may need to spend a season doing lasagna composting, or remove the topsoil and replace it with weed-free topsoil.
The hole for the crown or division should be relatively large. You're not planting seeds, remember; you're planting a chunk of what's basically a plant root that will become established and then increase in size. A hole that's about 1 1/2 feet wide and up to 2 feet deep is a good size. The hole should be 3 or 4 feet away from other plants, structures, or other planting sites. Mix compost in with the soil that's in the hole. You can add fertilizer, too, if you want – use 10-10-10 – and then add the crown or division. Cover with soil; the crown or division should be covered by a couple of inches of soil. Water well.
If you plant rhubarb in a container, assume that you won't be doing any transplanting – that rhubarb will stay there until it's time to divide the root. The container should be larger than the hole needed for the rhubarb crown, so keep that in mind when choosing a container.
How to Care for Rhubarb
Rhubarb has a reputation as indestructible, and while that's not really true, it is a hardy plant that can take a lot. When you have the right cultivar for your area, that plant can keep going for years with just a little standard fertilizer and regular water.
In general, water the crown and soil well when first planting, and keep watering the soil whenever the top inch of soil is dry. Mulch is extremely helpful for conserving moisture in the soil, especially in hot weather; adding a couple of inches of mulch around the base of the plant in summer is recommended. Don't let the mulch give you a false sense of security, though – keep checking the moisture levels and watering down near the base of the plant. Try to keep the leaves dry. Straw is a good mulch for summer; aged compost is great for the over-winter mulch.
Sunlight needs vary, but most cultivars want either full sun or a partial sun/shade mix, with full sun more common. Never block rhubarb from getting any sun; ensure that wherever you plant it, it will not be lost in total shade due to tall trees or crowded plant beds.
Soil and Fertilizer Needs
Rhubarb varieties differ in their soil and fertilizer needs, so it's difficult to give exact instructions. Most varieties demand well-draining soil; moist soil that doesn't drain well can be a disease vector. Many rhubarb types do well in several soils, from sandy to clay. When you first plant rhubarb, adding lots of compost or manure to the soil is a good idea; if you have a countertop composting unit, such as Lomi, you can use the final product from there.
Adding a little bit of complete (10-10-10) fertilizer each spring just after the last frost is generally a good idea, especially if the rhubarb is in a container and not in a garden bed. At the end of each growing season, when you've removed all the stalks, covering the remaining base of rubarb with compost as a form of mulch is a very good way to both protect the base from freezing and to give the base and soil a good source of nitrogen.
For completely new plantings, amend the soil with manure or compost before planting the rhubarb crown.
One specific growing technique can give you sweeter rhubarb, but it takes some planning. This is called forcing, and it's when the rhubarb is grown in a way that redirects its sugars to make stalks sweeter. When you force rhubarb, you grow it in the dark; this can be in a dark (meaning completely dark) greenhouse or by covering the plant with special forcing pots. Any light save for maybe a little candlelight will stop the forcing process.
Rhubarb plants that are one or two years old are covered early in the season with these pots; you don't have to use a forcing pot, but they are built to provide the best conditions for forcing, so they may be worth looking into. No gaps should be open, and the base of the pot should be covered with a layer of straw. Leave it this way for a couple of months. You can still water the soil around the pot's base. Uncover and harvest. Don't force the same plant for a couple of years after that, although by then, you'll be dividing the plant anyway, giving you nice new divisions to plant and force in a year or two.
When your rhubarb plant is a few years old, take a good look at the stalks. They're a mass of stalks sprouting out of the same small spot of land, right? When the rhubarb plant reaches that point, the root is getting older and less able to produce good stalks. You might not have seen a decline in quality yet, but if you wait a couple of years, you'll eventually see the stalks looking not so good.
Divide rhubarb in early spring, before any growth. Dig up the plant and cut between buds, giving every division at least one and up to three buds. Each division should have some roots as well. Plant the divisions immediately. If you miscalculated and ended up with more divisions than you have ready planting sites, wrap the unused divisions in a plastic bag in the fridge. They may dry out a little in there, so give them some water just before you plant them.
Troubleshooting Weak Rhubarb Stalks
Weak or scraggly stalks are usually due to poor planting and care. Sometimes the age of the plant is the issue; if the plant is only one or two years old, then the stalks are going to be short and thin, for the most part. In that case, delay your harvest until the next year.
Check the distance between plants and look back at the care you gave the plant. A lack of water and space will result in weak plants. The solution there is to remove and replant some of the rhubarb so that each plant has adequate space, and remember to give it enough water throughout the season.
If the rhubarb is old enough to be harvested and all other factors seem normal, you could be overharvesting. Taking too many stalks off one plant can weaken the plant and lead to thin stalks the next year. Stalk removal is a form of stress for rhubarb, so leave at least one-third to one-half of each plant if you're harvesting a lot of stalks. This is also a good reason to plant more than one rhubarb crown if you're really into rhubarb. You'll be able to harvest more without stressing out the plants.
Excessive heat is a problem, too. Rhubarb does better when kept in temperatures under 90 degrees Fahrenheit. If you're in a hot climate and growing this as an annual, you need to plant and harvest before temperatures reach that point. If you have a container plant, bring it inside during the heat of the day (and be sure the interior temperature is moderate, too). Placing containers on sturdy wheeled platforms makes moving them simple. Note: Be sure the wheeled platform can carry the weight of the container, soil, water, and mature plant. Otherwise, it will break under the weight.
If your area experiences a heat wave, you may need to build a temporary shelter to shade the plants if they are in a garden bed. Keep watering well, and hope that the heat wave is short.
A source of trouble that people sometimes overlook is the seed stalk or flower stalk. When the plant produces flowers, it looks very pretty, but those flowers divert nutrients away from the edible stalks into the flowering stalk. The plant wants to reproduce, which means it wants those flowers to grow for pollination and for seeds to form for dispersal.
You need to remove the flower or seed stalk. Without that, the plant will send nutrients into the edible stalks. It may try to form another flower stalk, so be on the lookout.
When the plant produces flowers, this is called bolting or going to seed. It sounds terrible, but it's what the plant is supposed to do in a "normal" life cycle. Be aware that some varieties produce more flowers than others, and some of these varieties are among the more common that you can find. If you're not thrilled about flowering rhubarb, look for cultivars that do not produce as many flowers. If you end up with a prolific flowering plant anyway, take a picture of the plant in bloom (they do look kind of neat, coming in white, pink, and red) and then chop off the flower stalks.
Note that the older the rhubarb plant, the more likely it is to flower or produce lots of flowers. This is a sign that it's time to divide the root. Division will actually help reduce the flowering, at least until that division becomes older and you have to divide again.
How to Harvest Rhubarb
You need to know five things about harvesting rhubarb. One is that you shouldn't harvest stalks from rhubarb grown as a perennial during the first year of growth; let the plant become established. Even the second year isn't ideal; it's in the third year that rhubarb really produces stalks you want to eat.
The second thing is that annual rhubarb, such as what you'd grow in hot climates, needs to be harvested all at once. You can certainly try removing flowers and seeing how long you can prolong the harvest, but in general, this plant isn't doing anything after the harvest season ends. You may as well take the entire thing out as you'll have to do that eventually anyway.
The third thing is knowing when the rhubarb is ready to be picked. Stalks should be at least 10 inches long, although some varieties may be ready when stalks are only 7 inches long. Color, believe it or not, is not the best indicator of whether you can pick a stalk. You can usually harvest beginning somewhere between April and June, depending on your zone and the cultivar, but stop harvesting before the first frost.
The fourth and fifth things are the two ways to harvest. In rare cases, you can cut the stalk near its base. Use a sharp, clean knife and verify that the cultivar you have is one that you can cut. Cutting usually isn't recommended, however, because the open stalk end that's left on the plant is an entryway for diseases that can kill the rhubarb. (Listen, it's a tough plant, but it's not invincible.)
Or, you can remove the entire thing from the base by pulling and twisting, and this is the recommended way to harvest stalks. Literally grab the stalk near the base and pull, twist, or lean it to one side. Most of the time, a ripe stalk will come away easily. Never harvest more than half to two-thirds of perennial plants at once; otherwise, the plant could die.
Rhubarb Varieties to Grow
Like any plant, rhubarb has several cultivars or varieties that allow you to grow a version of the plant in most climates and zones. These varieties vary by color, size, ripening time, and other factors. You'll also want to see which varieties need full sun versus partial shade.
Rhubarb 'Timperley Early'
Thick red-to-reddish-green stalks with green flesh grow fast and ripen early in the season in moist but well-drained soil. This variety can take a few years to reach its full height, so while you can harvest before that, keep in mind that later years will bring bigger stalks. Give this one full sun; force it if you want better color.
Rhubarb 'Stockbridge Arrow'
This variety has good flavor but ripens late in the season. It can be among the stringier varieties, but that late ripening provides a solution: Force the rhubarb so that you get tender, younger stems that lack those strings. Give this variety full sun and well-draining soil. The leaves are rather small.
Rhubarb 'Cawood Delight'
This is a hardy variety that does well in colder zones. The stems are dark red and produce white flowers. The plant grows to 4 feet tall and wide, although it can sometimes be smaller. Give this variety full sun and well-draining soil, and be prepared to get some beautifully colored jams and jellies.
'Victoria,' named for Queen Victoria, is a reliable cultivar that's nearing 200 years old. It's a classic example of good rhubarb, known for little to no stringiness and good flavor. Thick stalks produce blooms in May and June, which you can cut off to prolong stem production. This is one rhubarb where you should remove the entire stalk from the root, rather than cutting the stalk off partway.
Rhubarb 'Fulton's Strawberry Surprise'
For bright red stalks and excellent flavor, 'Fulton's Strawberry Surprise' is a winner. Deemed to have the best taste in a Royal Horticultural Society trial, this variety does well in a number of different soil types, including clay. It grows to about 4 1/2 feet tall and wide and needs partial shade.
How to Use Rhubarb
Before getting into how to use rhubarb, you need to know that you can use, as food, only the stalks. The leaves and roots are not edible.
The entire rhubarb plant contains something called oxalic acid, or oxalate. This is in a lot of edible plants, including spinach, and in these plants the level of oxalic acid is low enough to be safe to eat for people who haven't had issues with kidney stones (the foods can have a high amount relative to other foods, but they are edible). The same goes for rhubarb stalks; the level of oxalic acid is low enough that having some rhubarb stalk is perfectly fine.
However, the levels of oxalic acid soar in the leaves of rhubarb, to the point where the leaves could be considered toxic (both to humans and animals). Healthline notes that rhubarb can have anywhere from 570 to 1,900 mg of oxalate in every 100 grams, with the leaves at the bigger end of that range. Spinach tends to have about 750 mg per 100 grams. The high concentration of oxalic acid in rhubarb leaves means that you can experience symptoms like vomiting for even mild cases of poisoning.
Using the Stalks
Rhubarb might botanically be a vegetable, but its real-world use is as a fruit. As such, it's a great ingredient for sweet dishes like pies and jams. Probably the best-known use of rhubarb, not to mention one of the easiest, is in strawberry-rhubarb pie. Chopped rhubarb stalks are combined with chopped strawberries, butter, sugar, and a few more ingredients and placed in a double pie crust. Try this recipe from Threadgill's restaurant to see how these tart stalks transform into delicious dessert.
If you're not a fan of pie, rhubarb jelly and jam are simple to make. You can make classic jams and jellies that require a boiling water bath or go the quick route with an easy freezer jam. Use red rhubarb to create a candy-apple-red syrup, or use either color of rhubarb for cakes, crumbles, and custards. And if those hardy rhubarb stalks produce more rhubarb than you can eat? Slice and freeze them.
Rhubarb is one of the easiest plants to grow and one of the hardest to kill. It's perfect for any garden whether you can grow it as a perennial or have to keep it as an annual container plant. Got a friend who wants to know how to grow rhubarb or who has more rhubarb than they know what to do with? Let them know what you learned here. And remember, those parts of the plant that you can't eat can always be composted in a countertop composter like the one from Lomi.