Sunflowers: Which, How & When
Spring is always too short. The wildflowers, the longer days, the pleasant temperatures for working outside—it never lasts long enough. For gardeners, putting seeds or plants into fresh soil is the very image of hope. April's combination of warming temperatures and more daylight stimulates growth.
But spring isn't summer. Those plants that need warm soil for their seeds and warm air for their tender leaves don't belong in the garden until night temperatures are in the 50's and frost is over. Zinnias, marigolds, and other summer flowers are usually planted indoors, or direct-sown after the last frost.
Sunflowers are summer flowers that like spring planting. They are native to North America, not to the tropics like other summer flowers. They do best with April to May planting. They are bushier and more vigorous when the seeds can sprout and root in cold soil, about a month before the last frost date. Strangely enough, sunflower seedlings lose their frost-hardiness when they are about a foot high. After that, frost will kill them—and usually does at the end of the summer.
You'll have flowers for a lot longer if you start planting early, and then make two or three succession-sowings, ending in July. That will give you flowers through summer into fall. See the choices here.
Quinoa is another summer crop that likes to start in cool spring soil and should be planted during April. Others are echinacea, calendula, mache, love-in-a-mist, milkweed, poppies, and cilantro. Calendula and mache, may not sprout at all in warm soil. If you plant too late, the seeds will just sit there until fall, and sprout when the fall rains come. Sunflowers are more forgiving; they will still give you flowers from a July planting—just not so many.
Sunflowers are fun and easy to plant. You can start them indoors or out, direct-sown or transplanted. (The main reason for transplants is to evade birds and slugs that can decimate outdoor plantings.) They are big plants with a big appetite, so work in a lot of compost or manure before planting. Rake to an even surface and texture. Then plant your seeds about an inch deep and water well. Or plant 1/2" deep and put down an inch of mulch. (not more, yet.) When the little plants are a foot high, you can put more mulch if needed to control weeds and keep the soil moist.
If sunflower seeds are your goal, plant your entire crop early, so they can mature seeds before fall. If what you really want in flowers, you should succession-sow for a longer season of bloom. Even though the earliest plants may be bushier, those later plants will still give you flowers after the others have stopped or slowed down. The sunflowers in my pictures were planted July 1, because that's when I had time and space to do it. So don't feel that spring planting is an absolute necessity. I recommend you start planting in April, and then make a few more plantings until mid-summer so you always have blooms, and you learn what works best in your garden.
Some varieties, bred for the cut-flower trade, have no pollen, and are useless to bees and butterflies. Stick with heirloom pollen-bearing types to feed garden pollinators and make seeds for you or the birds (That's what we carry.)
The biggest decision is whether you want primarily flowers or primarily seeds for food. Most purely ornamental types have many small-to-medium flowers on long stems, and very small seeds.
Oilseed types have medium-sized black seeds and bear a large flower on top, followed by 1-2 dozen smaller (but still substantial) flowers. They are prized for birdseed and for making high-quality oil. This type is also used for microgreens. Birds (including chickens) love the seeds, which are featured in the more expensive birdseed mixes. Thousands of acres of these are grown in Ukraine.
The largest flowers and seeds come from the confectionery type. These make the seeds used for snacks. The biggest seeds come from a variety called Humongous. It is easy to grow and the seeds are easy to shell with just your fingers. To ripen those big seeds, confectionery varieties stop blooming after making a handful of truly immense flowers.
Hopi Black Dye is one of the parents of oilseed sunflowers, and its black seeds are similar in size and can be used for oil or food. However, they have an additional use.
The hulls of the seeds make a beautiful purple-black dye, used traditionally by the Hopi for dyeing basketry materials to make woven patterns. It can be used as a food coloring as well as a general-purpose dye. When we do germination tests, it dyes the lab papers! If your hair is dark, you might want to try boiling up a tea of the seeds for a hair rinse. It will add deep color and luster to dark hair in the same way that chamomile adds gold highlights to blonde hair.
These beautiful plants bear many large flowers and have a strong constitution.
If you just want lots of flowers all season, we offer the China Cat Ornamental Sunflower Mix. It features lots of bright golden blooms, as well as some with russet, rose, orange, maroon or yellow tones.
The China Cat Mix also plays a part in a fun new seed collection where each variety is named for a Grateful Dead tune. The others are Sugar Magnolia Pea, Stella Blue Squash, and Dark Star Zucchini, bred by organic farmers (and music fans) Bill Reynolds and Alan Kapular.
One of the great things about gardens is that they are at once silly and serious, personal and universal. So whether it is sunflowers, salad, strawberries or musical zucchini, go plant yourself some joy. After all, it's spring.
4/9/2022 04:38:20 pm
Love your well written website. It is not only interesting but light hearted and cheerful. Just what I need as I impatiently await a bit warmer weather to direct sow anything. Here at 4500' elevation we're still having freezing nights. But soon I will be practically living in my garden.
4/9/2022 11:27:32 pm
Thank you! Those of us in the mountains definitely need patience as far as planting goes! We got frost the second week of June here last year. I really depend on those shoulder-season crops that can live with sunny hot days and freezing nights.
4/10/2022 03:23:45 am
I feed the birds in my yard sunflower seeds and after reading a bit I hoed in a lot of wasted seeds and shells under a feeder. It is in the sun in a good spot and I hope they do well. I never bothered before but thought it might be a good idea.
4/10/2022 09:50:00 am
Great idea. Then the sunflower plants become bird feeders themselves. Sunflower seed hulls have a natural inhibitor compound in them, which can prevent weeds from sprouting until after the sunflowers are up. This can also yellow lawngrass somewhat.. A nice patch of sunflowers is a great alternative to some yellowing grass under your feeder. (People who don't want either a patch of sunflowers or yellowing grass under their feeder might put the feeder above some low shrubs, which should be deep-rooted enough not to be bothered.)
4/14/2022 08:25:07 pm
I live in western Washington state, and our soil temperature now in mid April is 41 degrees. By our last frost date, April 21st, the soil temperature is likely only 2 degrees warmer-maybe. What is the best soil temperature for sowing sunflowers outside?
4/14/2022 09:33:51 pm
Good question. This is a confusing topic. The gardening books, catalogs, and websites mostly say to plant after frost is over and the soil is 70 degrees. I always thought that too, but got interested in the question after I read Will Bonsall's great book about his farm in Maine. He plants in April. Then I remembered that the best local gardener I know planted hers in April, and they were so much happier than mine. Thinking about their life cycle in the wild, on the American plains and prairies, I realized that the seeds would overwinter on the ground and sprout when the soil first started to warm. Sure enough, when I looked on university websites, it turns out they are frost-hardy as sprouts but not as adults. They do need some heat though--Purdue University says germination is sometimes possible at 39 degrees, but good normal germination is at 46 to 50 degrees. The plants can grow and mature at 64 to 91 degrees, with optimum temps in the high seventies. Soil temperature is a funny thing; we are still getting frost at night and will be for another month and a half, but plants are growing vigorously, so the soil is not as cold as night time air temperature. If you want to test your soil temperature, use something like a meat thermometer, and bury it down a couple of inches, where temperatures are more stable. I'd love to hear what you find out. Have fun!
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Jamie Chevalier lives and gardens on a river in the Coast Range of Northern California. She has gardened professionally in Alaska and California, as well as living in a remote cabin, commercial fishing, and working with seeds. She is the proprietor of Quail Seeds.