Sunflower

Sunflowers (Helianthus annuus) are fast-growing, warm-season annuals with tall, upright stalks. Each plant goes from seed to seed in a single growing season. The species is native from the southwestern United States to Mexico.

There are sunflowers for almost any space, from dwarf types about 1 foot (30 cm) tall to giants that reach 10 feet (3 m) or more, with flowers in yellow, cream, orange, red and chocolate brown. They’re great for wildlife too: bees and other pollinators visit the flowers, and finches and small mammals eat the seeds.

Sow outdoors after the last frost. Sowing directly where the plants will grow is the recommended method. Wait until the danger of frost has passed and the soil is warmer than 50 °F (10 °C), then sow seeds ½ inch (1.3 cm) deep. They usually sprout in 7 to 14 days at 70–75 °F (21–24 °C).

Or give them a head start indoors. Starting seeds in pots indoors gives tall types a head start and keeps the seeds safe from mice and squirrels. Sunflowers dislike root disturbance, so sow only 2 to 3 weeks before you plan to plant them out. Harden the seedlings off, then plant them outside once the soil is warming up and there’s no risk of frost.

Choose a sunny spot with rich soil. Sunflowers love sun, and a spot with 6 to 8 hours of direct sunlight a day is ideal. They like well-drained soil improved with organic matter such as composted manure. Tall varieties do best somewhere sheltered from strong winds.

Spacing. Gardening experts suggest sowing seeds about 12 inches (30 cm) apart, but spacing depends on the variety, so follow your seed packet.

Pots. Dwarf sunflowers are perfect for patio containers. Plants in pots dry out quickly, so water whenever the compost feels dry, even daily in hot weather.

Watering. Annual sunflowers are thirsty plants, and tall types in particular mustn’t be allowed to dry out. A layer of compost or other mulch after planting helps hold moisture in the soil; leave a gap around the stems.

Feeding. Branching and large-flowered types can be heavy feeders, so a regular slow-release fertilizer helps. Gardening experts suggest a potassium-rich tomato fertilizer to encourage flowering. Don’t overdo nitrogen: too much makes plants grow too vigorously, with oddly shaped flowers.

Support. Most annual sunflowers need support because they get top-heavy. Put a sturdy cane in at planting time and loosely tie the stem to it as the plant grows. Giants over 8 feet (2.4 m) are best planted next to a house wall and tied to it, while dwarf types 1–2 feet (30–60 cm) tall usually don’t need support.

Don’t pinch single-stem types. Pinched single-stem sunflowers give poor blooms or none at all.

Slugs and snails love young sunflowers, so plant out only strong, hardened-off seedlings or protect them. Seeds sown outdoors can be eaten by mice and squirrels before they sprout. Caterpillars and beetles may also chew the leaves.

Powdery mildew, leaf spots and rust can affect sunflowers, and sclerotinia may appear in wet summers. Overall, sunflowers have few insect problems. Left to self-seed, they can become weedy.

Cut flowers. Sunflowers can be cut when the color first shows, or later when they’re almost fully open, depending on how you’ll use them.

Seeds. Leave the flower head on the plant for at least two weeks. Once the petals have faded, cut the head off and leave it in a sunny, warm, dry place for another week. Then rub the head gently over a sheet of newspaper and the seeds will fall out. You can also leave the plants standing in autumn so finches can feed on the seeds; just collect a few for next year first.

Keep saved seeds in an envelope or paper bag in a cool, dry, dark place until you sow them in spring.

Sunflower leaves and stems can be rough and hairy and may aggravate skin allergies, so wear gloves when handling them. The seeds are eaten as a snack and used for cooking oil, the petals are edible, and young flower buds can be steamed like artichokes.