What you need to know.
Sunflowers are the most dramatic thing in my garden. Mammoth Russian gets 10 to 12 feet tall with heads the size of dinner plates. I plant them along the back fence every summer and they tower over everything else. They are also one of the easiest plants I grow — direct sow after the last frost, water occasionally, stand back.
I grow three types: Mammoth Russian for the classic giant single-headed sunflower, Autumn Beauty for branching plants with dozens of smaller heads in red-orange-yellow mixes, and Lemon Queen for a slightly smaller, airy plant that pollinators absolutely love. All three do well in Zone 7b. Branching types like Autumn Beauty and Lemon Queen produce more total flowers and have a longer bloom period than single-headed giants.
"A 12-foot Mammoth Russian sunflower in August is one of the most satisfying things I have ever grown. They look impossible."
Step by step.
Direct sow seeds 1 inch deep after the last frost when soil is warm — in Zone 7b, that is late April to early May. Sunflowers grow so fast from seed there is almost no advantage to starting them indoors. Space Mammoth types 18 to 24 inches apart. Branching types can go 12 inches apart.
Stake or support tall single-headed varieties before they need it — a 10-foot sunflower in a summer rainstorm can snap at the base. I pound a wooden stake in next to each plant when it reaches about 3 feet tall and loosely tie the stem at a few points as it grows.
To harvest seeds, wait until the back of the seed head turns completely brown and yellow. Cut the head off with about 12 inches of stem, hang it upside down in a dry, well-ventilated shed or garage for a few weeks, then rub the seeds out with your hand. Store them for eating or save some for next year's planting.
When to plant in Zone 7b.
Plant in Zone 7b from late April through early June. Sunflowers from an April planting bloom in late July and August. A June planting blooms in September and October as temperatures cool. I do two plantings — one in late April and one in late May — to extend the bloom season.
Sunflowers generally reach bloom about 70 to 100 days from sowing depending on variety — giant types take longer than branching ones. Autumn Beauty blooms in about 75 days. Mammoth Russian takes 80 to 90 days. Plant accordingly if you want them blooming for a specific time.
Problems I ran into.
Birds eat sunflower seeds the moment they are even close to ripe — sometimes before the head has fully dried. If you want to harvest seeds, cover the head with a paper bag secured at the stem once petals fall and the seeds are visibly forming. This keeps birds off while the seeds finish maturing.
Deer are a problem if you have them in your area. They eat the entire plant, heads and all. I have not had deer in my yard but my neighbor does and she uses repellent spray around the base. Sunflowers grown against a fence with other plants seem less targeted.
What I make with it.
Roasted sunflower seeds are one of the best snacks that come out of the garden. Rinse the seeds, toss with salt and olive oil, and roast at 350 degrees for 15 to 20 minutes until golden. Cool before eating.
Sunflowers are also genuinely important for pollinators — bees, butterflies, and beneficial insects work them constantly all summer. Even if you never harvest a single seed, they are worth growing just to watch what lands on them. Browse the recipes page for my roasted seed recipe.