All posts by Lisa Dermer

Growing Rhubarb from Seed

by Ira Wallace

Many gardeners are familiar with growing rhubarb from divisions or crowns, but if you want to start a large rhubarb patch quickly, without spending a lot, growing rhubarb from seed is the answer. The stems of rhubarb grown from seed will not all have that intense red color you might be used to. Some stems will be red, some green, and some in between. But they will all taste the same, perfect for your home-cooked pie. If you want all red stalks, get divisions from a friend or neighbor or buy crowns from your local nursery.

When starting your seeds, remember that rhubarb is a cool-weather crop.

  • In climate zones 6 and cooler, it’s an easy-to-grow perennial (traditionally planted where there used to be an outdoor privy). The stalks and leaves die back with first frost in the fall, but the plants will come right back in early spring.
  • In zones 7 to 8, growing rhubarb is tricky. but it can be grown as a short lived perennial. You will need to be careful to shelter your rhubarb plants from extreme summer heat. Choose a location with afternoon shade in the summer. The north side of a grape arbor, raspberry patch, or asparagus ferns would work well.
  • In areas with very hot summers, where winters are mild (zones 9 to 10), rhubarb can be grown from seed as a winter annual. ECHO ("Educational Concerns for Hunger Organization") in Florida has had good luck with planting rhubarb seed in August and harvesting in March-May. The variety Victoria is noted as a productive late summer/early fall started annual from almost subtropical Florida to semi-arid northeast Texas. Read how to do this in “Growing Rhubarb from Seed as an Annual” below.

Starting Rhubarb Seeds

Rhubarb seeds are encased in a large paper-like shell. To speed germination, soak your seeds in water for 1-2 hours before planting. If you’re starting indoors, plant the seeds in screened compost or other suitable organic planting mixture, 2 seeds per 2 to 3 inch pot. Using peat pots or cow pots makes transplanting easier. For spring plantings a heating cable or mat will speed the germination if the room temperature is below 70°F. Rhubarb seeds germinate quickly when planted in the warmth of late August or early September. Keep your seedlings evenly moist but don’t over-water (the seedlings can die from root rot if the ground is too wet).

Growing Rhubarb from Seed as a Perennial

To start rhubarb in the spring (zones 8 and lower), sow seed in pots or flats under cover 8-10 weeks before your average last frost. Transplant the young plants out into the garden about two weeks before your average last frost, into an area amended with compost or well rotted manure and plenty of organic matter. The plants should be about 4 inches tall. Mulch your seedlings to maintain even soil moisture and keep the roots cool. Harden plants off before transplanting or protect the new transplants with row cover until danger of frost has passed.

Choose a location protected from the heat. The warmer your climate, the more important it is to provide afternoon shade (on the west and south) during the hottest months. A row of tall annual plants (your late summer tomatoes or pole lima beans), shade cloth, or a temporary structure can provide adequate shade that you can remove when the weather cools. Always remember to maintain even moisture. Letting your young rhubarb plants dry out in hot weather is the kiss of death.

Growing Rhubarb from Seed as an Annual

To grow rhubarb as an annual in the fall and winter (zones 9 and higher), start the seeds in a cool location (a bright indoor spot or a shady outdoor place) from late August to early October. Transplant into the garden when the seedlings reach about 4 inches tall. The plants will be ready for harvest in March through early May. Intense summer heat will kill the plants, so harvest all the leaves in late spring. This technique only works where winters are very mild, or if you can protect the plants from damaging frost with a cold frame or row cover.

Harvesting Rhubarb

Harvest rhubarb either by cutting or pulling off the leaf stalks at soil level. When your plants have 10 stalks you can harvest 3 or 4 stems at a time per plant.  If you are growing your rhubarb as an annual harvest the entire plant. Harvest stalks only! DO NOT eat the rhubarb leaves as they contain high levels of toxic oxalic acid.

For perennial plantings let some leaves remain on the plants during summer to generate energy and reserves for the following year. We recommend harvesting a few stems at a time, in spring and fall only. It’s best not to stress the plants during the summer, so avoid harvesting at this time. Frost will kill all the leaves, so harvest all the leaves when frost threatens in the fall.

Break off and discard any flowering stalks at ground level. (The flowering stalks don’t make good eating, and breaking them off prevents the plant from putting energy into flowers and seeds.)

It’s best not to harvest during the first year if you are establishing a perennial bed. For annual beds, harvest all remaining stalks when the weather begins to get too hot in the summer.

Ira Wallace lives and gardens at Acorn Community Farm, home of Southern Exposure Seed Exchange, where she coordinates variety selection and seed growers. Southern Exposure offers 700+ varieties of non-GMO, open-pollinated, and organic seeds. Ira is a co-organizer of the Heritage Harvest Festival at Monticello. She serves on the board of the Organic Seed Alliance and is a frequent presenter at the Mother Earth News Fairs and many other events throughout the Southeast. Her first book, “The Timber Press Guide to Vegetable Gardening in the Southeast,” is available online and at booksellers everywhere.

Planning and Planting for an Abundant Fall and Winter Harvest

article by Ira Wallace, with Lisa Dermer, photo by Irena Hollowell

Who wouldn’t want a fall garden abundantly producing cabbages, broccoli, carrots, turnips, parsnips, radishes, bok choi, Brussels sprouts, a wide variety of greens, and even peas? The trick to growing a cool season garden, and setting up the fall garden to continue through winter, is planning and preparation.

Check your understanding of cool-season. When grown for fall, many “cool-season” plants actually need to be sown and transplanted in high summer heat, and some as early as June.

Make room! We start our winter crops in August and September, and those plantings will need to supply us through February! We need lots of space for these plantings, so planning ahead is critical.

Below are our tips for getting the most out of your fall garden.

Choosing the Best Fall Crops for Your Garden

Look for storage varieties: these varieties have been bred to be grown in the fall and harvested for winter storage, or left in the ground to be harvested during thaws. Storage tomatoes can be harvested green to ripen slowly wrapped in newspaper in cardboard boxes; storage beets and radishes grow very large and keep well in the ground or root cellar.

Of course, be sure to choose the crops that you and your family enjoy and that are well-suited to your climate!

Calculating Time to Plant or Sow

Calculate back from your average first fall frost date to determine when to plant fall crops. Add 14 days to the listed days to maturity for your variety to account for the “fall effect” of shortening days and cooler temperatures. For plants with a long harvest period, like a broccoli that will make side shoots for 3 weeks after the central crown is gone, add that time in as well. (This may be as long as a month or more.) Add an additional 14 to 28 days if you will be starting transplants from seed, to account for transplant shock and setback.

For us, this means sowing most broccoli and cabbage in late June, with a second sowing 2 weeks later and often a third that we plan to keep growing under row cover until Thanksgiving or later if the weather is with us.

Sowing seedlings in pots or flats for transplanting out later lets you start your fall garden before space is available in your outdoor garden. Use benches or tables high enough off the ground (at least 3 feet) to deter flea beetles or use an enclosed shade structure.

We sow our fall crops in outdoor seedling beds well-supplied with compost in a location shaded from the harsh afternoon sun. The north side of a stand of corn, caged tomatoes or pole bean trellis makes an excellent choice. Outdoor seedling beds should be covered with thin spun polyester row cover or the newer Protek net row cover to guard against flea beetles and other insects. Summer broccoli and cabbage seedlings are ready to transplant in 4 weeks during the summer. Lettuce and Oriental greens in 2-3 weeks.

Making Space in your Summer Garden

Come summer, it can be tempting to fill every inch of the garden with summer tomatoes, peppers, squash, melons, and more. But even the most densely planted garden will still afford room to plant fall crops. Summer lettuce, green beans, radishes, greens, and root vegetables all yield space by late summer for the fall garden. Beds that were once filled with spring cool-season crops, like peas and fava beans, often rotate best into fall cool-season crops (if they’re not used for late summer successions). Plan for summer cover crops to be ready to turn under in time for fall crops.

When will each spring and early summer crop be finished harvest? You can calculate using the listed days to maturity, but we find that a mid-point check allows us to adjust for weather, later-than-planned planting, early bolting, or unexpectedly extended harvests.

Preparing the Ground for Fall Crops

Caring for the soil is even more important when growing 2 or 3 crops a year in the same area. Generously add compost and any other needed amendments before planting your fall crops. Keep plants growing fast and reduce risk of disease by providing regular and adequate moisture (at least 1 inch each week).

Season Extension

If you’ll be planting in cold frames, under row cover, or in a greenhouse, you can adjust your average last frost date backwards by two weeks or longer when calculating when to plant fall crops.

Tomato Successions: why to sow multiple tomato crops

photo credit: Irena Hollowell

We sow tomato transplants twice here on our farm in central Virginia: once in March, for our earliest crops, and again in mid-April, for a second tomato crop that will start producing in August. Although many heirlooms will produce continuously until frost, we find that production sometimes slows when summer rains or disease-pressure take a toll on our plants. Sowing that second crop gives us the best quality fruit late in the summer and into early fall (and for harvesting underripe fruits to ripen in storage when frost threatens).

Multiple tomato crop successions spaced about a month apart can also help you grow more flavorful tomatoes. We find our tomatoes are sweetest and most flavorful when the weather has been dry when the fruits are ripening. You can get this effect by reducing or stopping irrigation altogether when your tomatoes start to ripen. The fruits will be more intensely flavorful, but the plants will likely stop producing sooner. Time your next succession to start producing just when your parched plants are ready to quit.

We recommend sowing your early-crop tomato transplants 5 to 6 weeks before your average last frost. You can also sow sooner to get a jump on the season, but you may need to pot up into larger containers 2 or more times, instead of just one, to prevent the young plants from becoming leggy and root-bound.