Sunflowers: Your Guide for Planting, Growing, and Harvesting

Sunflowers grow best sowed directly into the soil, indoors or out. The plants germinate in late spring, and you'll want to hold off planting until the frost has passed, or when the soil has reached an average temperature of 50°F.

Since sunflower seeds aren't picky, all you need is well-draining soil. For best results, aim for a neutral to slightly alkaline spot with a pH of 6.0 to 7.5, and watch the flowers thrive. Once planted, your seeds will require nutrient-rich soil filled with compost, granular fertilizer, or organic matter.

Growing plants need space to stretch out, so compact soil isn't ideal. Sunflowers have long taproots, so whether growing them indoors or out, plant seeds one to 1-½ inches deep and at least six inches apart. Keep height and width in mind too; they vary widely by type, reaching a few inches tall to a few feet.

One of the best things about sunflowers is that they can grow in just about any climate. With the exception of hardiness zone one, any environment with sunny days and warm temperatures is acceptable; long, hot summers offer the ideal growing season.

Once spring temperatures start heating up, aim for a spot with six to eight hours of direct sunlight between April and mid-July. Gardeners in southern states should plant earlier, from mid-March to early April.

Watering is based on the plant's rate of growth. While plants are still small, start watering daily — about three to four inches from the stem, near the root zone. This helps moisture reach the deepest parts of the root system, encouraging early growth.

Once sunflowers start growing, you can water less frequently, but you'll need several gallons to get the job done. Aim for once a week as petals develop.

Sunflowers attract numerous pests, but most of the issues are easy enough to remedy. Moths and worms might crawl into the blooms, but these are easy to pick away. Birds, squirrels, and rodents take the most interest in the seeds, so you may need barriers or netting to keep them at bay.

Fungal diseases are the most common detriment to sunflowers, but they are treatable if you know what to look for. Alternaria leaf blight and Phoma blight cause leaves to become brown or black with irregularly shaped lesions, eventually killing off plants. These diseases thrive in hot weather with high humidity and frequent rainfall, and they can be carried via weed hosts or infected seeds. Downy and powdery mildew thrive in dry, humid conditions, producing cottony growth and powdery patches, respectively.

Take a proactive approach by spraying down seeds with a fungicide prior to planting. If an issue does occur, keep fungus under control by pruning infecting leaves and spraying the remainder with a foliar fungicide. Keep spacing adequate to boost air circulation, destroy any post-harvest debris, and ensure that sunflowers remain in full sunlight.

Stagger your plantings every six weeks, and you'll achieve bountiful blooms all season. Avoid overfertilizing, and keep fertilizer away from the plant's base. Overfeeding causes the reverse effect of what growers want; it weakens stems, so they often break once these lofty, top-heavy blooms reach full growth. Keep taller varieties strong by placing supports behind every stem.

Ready for another round of planting? Propagate sunflowers from your last batch using cuttings. Look for a six inch stem with mature leaves, but no buds or flowers — this boosts rooting without requiring hormones. Cut the plant directly where it attaches to the main stem, then cut off the top 1/2 inch and remove the lowest leaves, revealing root-producing nodes.

Plant in a half-sand, half-peat moss blend, keeping the leafless region beneath the mixture, and progress through the growing process as usual.

Ready for sunflower seeds? Dry out flowers until the heads become brown; seeds will appear plump and loose, which makes them easy to gather. Once drying is complete, cut off the plant's head, catching loose seeds as they fall. Place the head on a flat surface and rub the seeded area, pulling off loose seeds as you go.

If you prefer, rub the sunflower head across a washboard and collect the seeds that way.

Mammoth sunflowers are the most popular variety, growing to 12 feet tall with abundant seeds and petals reaching over 14 inches. The American Giant can grow even higher, rocketing to over 15 feet with a full foot of seed space. By contrast, Teddy Berry sunflowers only reach two or three feet with five-inch blooms. A middle contender, Sunrich Gold is a favorite for bouquets, growing to five feet, on average, with four-to six-inch flowers.

Colored varieties include Terracotta, Eartha, with brown, red, and gold hues, Ms. Mars, with purple at the center and yellow at the tips, Moulin Rouge, with bold red blooms, and Chianti, with rich, wine-colored petals.