I grew rhubarb from seed for years – here’s exactly how to do it for guaranteed germination and healthy crops of fruit

Rhubarb is a low-maintenance and reliable perennial plant ideal for any productive garden, as you can harvest stems for crumbles, pies, jams, cakes, and more, for many years. There are different ways to start the plant off, which include the option to grow rhubarb from seed.

Propagating from seed is not the most common method to grow rhubarb, nor is it the fastest way to get stems to pick, but it is a cheap and effective way to get crowns. I grew rhubarb plants from seed every year when working in a historic vegetable garden to have a succession of healthy, productive crowns.

Using that experience, this guide looks at how to grow rhubarb from seed both indoors and outdoors to help you get strong germination and ensure your rhubarb plants have a healthy start to life.

Can you grow rhubarb from seed?

You can grow rhubarb from seed, however, there are pros and cons to this method of propagation.

Sowing seeds is budget-friendly, but it is not the easiest method of growing rhubarb, and you must wait several years to start harvesting rhubarb.

The quickest way is to plant rhubarb crowns, which can give you a harvest after only a year, compared to at least three for seed-grown rhubarb. Dividing plants is also a common way to propagate, and is ideal if you want an exact clone of established crowns.

Despite the drawbacks, growing rhubarb from seed can be simple and enjoyable. If you are happy to be patient or want to enjoy a growing experiment, below are my tips to help you get started.

You can sow seeds indoors or outdoors, and the timing can depend on your US hardiness zone, as climates impact how rhubarb is cultivated. Here, we look at how to germinate seeds both indoors and outdoors.

If you live in US hardiness zones 8 and below, rhubarb can grow as a perennial vegetable. The seeds are sown in spring and, after waiting for that first harvest, you can enjoy picking stems for many years.

Growers in US hardiness zones 9 and above grow it as an annual plant and get one harvest, as rhubarb does not like heat. The crop is grown from seeds sown outdoors in late summer in hotter climates.

How to grow rhubarb from seed indoors

Sow seeds indoors in early spring and germinate them in a greenhouse or warm windowsill. If you soak seeds before planting for a few hours, it can benefit germination, though this is not essential.

Fill trays, modules, or small individual pots with a potting mix designed for seeds - this is always the best soil to start seeds in, rather than old potting soil or soil from the garden.

Sow seeds a half-inch deep in the soil and cover with a thin layer of compost or vermiculite, taking care not to plant them too deep, as it will inhibit germination. Moisten the soil and place the container in a warm and bright spot where it can get temperatures of 65-75°F.

Keep the soil moist, but not waterlogged, and the seedlings should appear within a couple of weeks. Pot up seedlings when they have developed true leaves that are large enough to handle, and transplant seedlings out into the kitchen garden after the last frosts.

How to grow rhubarb from seed outdoors

The soil temperature needs to reach at least 60°F to sow seeds outdoors successfully. Sowing into cold and wet soil would be a seed sowing mistake and risks the seeds not germinating or rotting in the ground.

In US hardiness zones 8 and below, wait until the risk of frosts has ended and use a soil thermometer, available at Amazon, to check the time is right for sowing. In US hardiness zones 9 and above, the soil will be more than warm enough when you sow in late summer or early fall.

Prepare the bed by thoroughly weeding it and raking the ground level. Adding organic matter, such as compost or well-rotted manure, will boost the fertility and moisture-holding capacity of the soil to help rhubarb plants as they grow.

Sow seeds a half-inch deep and at least six inches apart in rows that are around five feet apart. Keep the soil moist and thin seedlings to at least two feet apart as they develop.

One of the drawbacks to sowing seeds outdoors is the increased risk of extreme weather and damage from slugs or snails. Covering the area with cloches can retain warmth and protect against heavy rains, while surrounding seedlings with rough surfaces or using beer traps can be effective slug control methods.

FAQs

How long does it take to grow rhubarb from seed?

Rhubarb are quick-developing plants. The seeds will take 1-2 weeks to germinate, and early spring-sown plants can be large enough to go outside, after hardening off, in late spring or early summer.

The plants do not need fertilizer for the first year spent outdoors, but will benefit from fertilizing twice a year from year two onwards. Give rhubarb plants a nitrogen-rich fertilizer in spring and a phosphorus-rich fertilizer in fall for healthy development.

You can harvest the odd few stems in the second year, but it is better to wait until the third year to start picking. From the third season onwards, you can enjoy harvesting rhubarb for a wide variety of sweet or savory dishes.

Once rhubarb crowns are well-established, you can start to grow forced rhubarb for earlier and sweeter stems each year.

Forcing is done by covering the crowns with a forcing pot, bin, bucket or box in late winter to block out any light. It encourages the growth of paler, sweeter stems.

Forcing vegetables like rhubarb is only suitable for strong, healthy, established plants and should not be done every year to the same crown.