When to Plant and Harvest Rhubarb

While we wait until summer to enjoy juicy peaches and plump blueberries, rhubarb plants help us fulfill our spring cravings for homegrown fruits. This leafy green is technically a vegetable, but its tart flavor is at home in pies and jams, where it pairs wonderfully with just-picked strawberries.

Since rhubarb returns year after year and requires little maintenance, many people consider it an easy addition to their gardens. If you want to add this interesting plant to your homestead or garden, learning when to plant it is key. Knowing when to harvest will give you the best-tasting stalks and allow the plant to return the following year.

Where Can You Grow Rhubarb?

Before you plant rhubarb in your garden, make sure you live in an area that supports its growth! This leafy green not only thrives in cool climates but actually requires an extended period of temperatures below 40°F (4°C) to stimulate growth. The plants also prefer summer temperatures below 75°F (24°C) but can tolerate warmer periods.

Considering this information, you should only grow rhubarb if you live in zones 3-7.

When to Plant Rhubarb

You have three choices for planting rhubarb: seeds, crowns, and transplants.

Seeds

Growing from seed is the best option if you want to save money, plant a large number of plants, and harvest a ton of rhubarb. However, since rhubarb seeds don’t breed true, plants grown from seed often produce red, green, and white stalks. Although these stalks look different, they have the same tart rhubarb flavor.

If you’re growing rhubarb as a perennial, aim to start seeds indoors about two months before your predicted last spring frost date. The seeds germinate within a week if you plant them in warm soil and keep them around 70°F (21°C).

Once the seeds sprout, place them under bright grow lights and keep the seedlings somewhere between 60-75°F (16-24°C). After six to eight weeks, the seedlings should be about four inches tall. Begin moving them outdoors for a few hours each day to help them acclimate to their new outdoor home. Gradually increase the amount of time they spend outdoors until the potted plants stay outdoors for an entire day and night. At this point, you can plant them in your garden!

The ideal time to transplant rhubarb seedlings into your garden is one to two weeks before the last spring frost. This will protect them from intensely cold temperatures but allow them to acclimate to their new environment before the summer heat arrives.

Crowns

Crowns, also known as bare-root rhubarb plants, are a popular option if you aren’t super concerned about cost and only want to plant a few rhubarb plants. The crown is a piece of a mature rhubarb plant that contains both roots and buds. This means it is “true to type” and will grow identically to the mother plant cultivar, which is typically labeled on the crown box. When the dormant crown is planted in the right environment, it will resume growth and send out healthy stalks.

Early spring is the best time to plant rhubarb crowns. Whether you purchase a crown online or receive one from a neighbor, aim to plant it while it’s still dormant. If you notice the plants putting on new growth, get them in the ground ASAP. You shouldn’t plant the crowns into frozen ground, but you can plant them before the last spring frost arrives.

Another option is to plant rhubarb crowns in the fall. If you choose this option, make sure to wait until the crowns go dormant. Your goal is to get the plants in the ground so they have enough time to establish roots before the ground freezes but late enough to avoid warm temperatures that promote leaf growth. In most areas, mid-September to mid-October is ideal.

Divisions

If you have rhubarb growing in your garden (or know a friend who does), you can divide mature plants in the early spring right before they break dormancy. This provides you with new rhubarb plants to harvest and prevents mature plants from becoming overcrowded and unproductive.

So, when do you know you can divide a plant? Most gardeners find they need to divide their rhubarb plants about once every five to ten years. If you’re not sure how old your plant is, you can look for signs of slowed growth. Overcrowded plants often produce few or small stalks in the center of the plant.

To divide a rhubarb plant, dig up the entire root ball. Then, use your hands to remove any excess soil. Once you have a better view of the plant, it’s time to divide it into multiple sections. Each division should contain at least one bud and a healthy section of roots.

It’s best to plant your rhubarb divisions as soon as possible after dividing. If you need to wait a few days before planting, place the divisions in a plastic bag or container and store them somewhere cool.

When to Harvest Rhubarb

When determining when to harvest rhubarb, consider the plant’s age, the size of the stalks, and the time of year.

Since rhubarb takes a few years to reach maturity, you should avoid harvesting the same year you added the plant to your garden. If you planted rhubarb from crowns or seedlings, the plants should be large enough to harvest during their second year in your garden. However, if you grew rhubarb from seed, you should wait until the third year.

Once your plants are old enough to stand up to harvesting, wait until the right time of year. Rhubarb leaves and stems die back each winter and regrow the following spring. Since the stalks are sweeter and more tender when they’re young, the spring and early summer are the best times to harvest. Additionally, letting the plants keep their stalks throughout the summer allows them to conserve energy for the following year.

When spring arrives, keep an eye on your rhubarb plants. You’ll use the size of the stalks to determine when they’re ready for harvest. Stalk size varies between varieties, so it’s helpful to know which variety you’re growing. If you’re not sure, wait until the stalks are at least a foot long before harvesting.

The morning is the best time to harvest since the stalks will be full of water and cool from the previous night. However, you can also pick the stalks in the evening. 

When you harvest rhubarb, remember that the leaves and roots are toxic! Make sure to trim off any leaves and roots before consuming. Another helpful hint is to harvest the large outer stalks and leave the inner stalks. These smaller stalks will keep growing and allow you to harvest continually.