Days to germination: 10 to 14 days
Days to harvest: 75 to 100 days
Light requirements: Full sun
Water requirements: Only when plants are dry
Soil: Fertile and draining
Container: Dwarf is ideal but standard flowers can be potted
Sunflowers are a beautiful addition to the flower garden, and will reward you with a head full of tasty seeds at the end of the summer. They are very easy-to-grow annuals, and with all those seeds, it’s a simple matter to replant them each year.
Not all sunflowers will produce an edible seed, so decide what variety you want before buying seeds or new plants. The gray striped seeds are the best for snacking, but the smaller black seeds are grown more for bird food or for their oil.
Though you may think of sunflowers as huge towering plants, you can actually get dwarf varieties that will grow less than two feet high. Most have bright yellow flowers with large dark centers, but there are some varieties with deep red petals instead. Red Sun and Autumn Beauty are two red types.
The seeds are usually roasted before eating, but raw sunflower seeds are tasty too. Their main nutritional benefit is their high protein content, along with vitamin E and several B vitamins. They are also high in fat because of their oil content.
Starting from Seed
Sunflower seeds won’t germinate in cold soil, so if you are going to plant your seeds directly into the garden, you need to wait until the soil has warmed and there is no threat of frost.
You can start them early indoors by planting seeds about an inch deep in small seedling trays. Keep them in a warm sunny spot, and they will likely sprout in about 2 weeks. Sunflowers don’t like to be transplanted so it’s best not to keep them growing in their little pots for too long. Get your seedlings started about 2 to 3 weeks before that last frost date.
Keep them in the sunniest place you can find so they don’t get too spindly. If they develop leggy stems at the start, they will never grow properly later on in the garden.
Whether you are planting seeds or seedlings, put them out about 2 weeks after your frost date. Keep them spaced about 14 to 20 inches apart, depending on how big your variety of sunflower is. If you are planting seeds, you can plant them closer and then thin out later to just the strongest plants.
Before planting, dig up the soil to loosen it and mix in some compost. Sunflowers aren’t that finicky when it comes to their soil but a little extra organic matter can help them get started.
If you have planted seeds, you really should cover them with a wire mesh or cover to keep squirrels or birds from digging the seeds out of the dirt. Once they have sprouted, it becomes less of a problem.
Taller varieties of sunflower will suffer in the wind, so either grow them against a fence or have stakes in place to support the plants as they grow. Don’t wait until the plants are tall to start sinking stakes or poles though. You’ll damage the roots.
Water your plants regularly until they are 1 to 2 feet in height, and then they should be fine with just rainfall.
Though they should grow well without additional feedings, you can also give them one application of fertilizer around mid-summer for really big flower heads.
Other than that, they are a pretty easy to grow plant, requiring little care once they get growing.
Though dwarf sunflowers fit best in pots, you can grow the really big flowers in containers too. You can take your pick from varieties that grow only 2 feet tall, to ones that will easily reach 6 feet or more. The really “mammoth” ones (over 6 feet) are not that great for container gardening.
Standard sunflowers can be grown in 5 gallon containers, but most dwarf varieties are fine in a 12 to 16 inch pot.
You’ll want to water them a bit more often than garden plants, and any sunflowers that are going to reach a height of 3 feet or more should have a support. And don’t anchor any poles right in the pot. Once the flower reaches full size, the pot alone won’t be heavy enough to keep it all upright. Fasten the pole or stake to something else.
Pests and Disease
The leaves of the sunflower can fall prey to any of the typical leaf-eaters of the garden, including cutworms, grasshoppers, caterpillars and more.
More specific to this plant are the sunflower beetles, which will also eat the leaves off your plant. They are striped beetles that look a lot like potato beetles. Once your plants are established, they shouldn’t have too much to worry about. Young seedlings can get their leaves stripped completely off if the beetles are not caught in time.
For any of these pests, watch your flowers and pick off the beetles or caterpillars when you see them. Give the plants a regular spray with an insecticide soap to help repel them.
Birds are a real problem with sunflowers once the seeds come in, so protect your plants (more on this with regard to Harvest below).
Harvest and Storage
Unfortunately, the best way to let your sunflower seeds dry and ripen is to leave the dead flower heads on the stalks. It’s not the most attractive method, but it works the best. Birds will almost certainly strip the flowers of every last seed, so you should either cover your sunflowers with netting, or tie a paper bag over each head. Don’t use plastic because it won’t allow moisture to escape and you may get rotten seeds.
If you must cut them off, at least wait until they start to “nod” and bend at the stem. Then keep the heads in a paper bag and hang in a dark spot that has lots of air ventilation until they are thoroughly dry.
Once they are dried, they should store fine in an air-tight and dark container for 4 months. If you need to store your seeds longer than that, put them in the freezer. You can keep them frozen for a full year.