Sunflower in Zone 7A — Pacific Northwest

Sunflowers bring a cheerful burst of color to the garden, and their seeds are delicious roasted or enjoyed as a snack. Plus, the tall stalks make excellent natural supports for climbing veggies. Here in the PNW, the cool nights actually help concentrate the sweetness of the seeds, making them even more flavorful.

While we don't get the scorching summers that some other regions do, you can definitely grow sunflowers successfully in our Zone 7A gardens. Our 183-day growing season gives you plenty of time to get them to maturity, especially if you're mindful of timing and choose varieties that thrive in milder conditions. Just keep an eye out for those common PNW challenges like slugs when the seedlings are young.

Starting sunflowers indoors isn't usually necessary, as they direct sow so readily, but it can give you a head start if you're eager to get blooms as early as possible. If you want to go this route, start seeds indoors from late March through mid April, about three weeks before you'd like to transplant them outside. Use seed trays with good drainage and a seed starting mix, and keep them in a warm spot with plenty of light—a sunny windowsill or under grow lights works well.

Bottom watering is great for seed starting in our wet springs. It helps prevent damping off, which can be a problem with our overcast spring days. Just set the tray in a shallow dish of water and let the soil soak it up from the bottom.

Transplant your sunflower seedlings outdoors from late April through late May, once the danger of frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. Start with an hour or two of shade and increase the time each day.

When transplanting, space them 18-24 inches apart to give them plenty of room to grow. Our wet springs can sometimes bring slugs, so be sure to protect your young transplants with slug bait or other deterrents.

Direct sowing is the easiest and most common way to grow sunflowers in our region. Sow seeds directly into the garden from mid April through mid July, after the soil has warmed up a bit. Sunflower seeds germinate best when the soil temperature is consistently above 50°F.

Prepare the soil by loosening it and adding some compost or other organic matter. Plant seeds about 1 inch deep and space them 18-24 inches apart. Keep the soil consistently moist until the seedlings emerge, which should take about a week or two.

Sunflowers are moderately drought-tolerant once they are established, thanks to their deep taproots, but they still need consistent watering, especially during dry summer months. Aim to water deeply but infrequently, allowing the soil to dry out slightly between waterings.

During our wet springs, you may not need to water at all unless the weather is unusually dry. Once the dry summer months arrive, check the soil moisture regularly. Stick your finger about 2 inches deep into the soil; if it feels dry, it's time to water. Generally, an inch of water per week is sufficient, but increase that during heat spells. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our humid climate.

Signs of underwatering include wilting leaves and stunted growth. Overwatering, on the other hand, can lead to root rot, which is characterized by yellowing leaves and a mushy stem base. A layer of mulch around the base of the plants can help conserve moisture and suppress weeds.

You can expect your first sunflower harvest from early July through mid October, about 80 days after planting. For seeds, wait until the back of the flower head turns brown and the seeds are plump and slightly loose. You might need to cover the heads with netting to protect them from birds.

To harvest the seeds, cut the flower head off the stalk and hang it upside down in a dry, well-ventilated place until the seeds are completely dry. For cut flowers, harvest them when the petals first open for the longest vase life. As our first frost approaches around mid- October, harvest any remaining flower heads, even if they're not fully mature, and allow them to dry indoors.

Here are a few common issues you might encounter growing sunflowers in the Pacific Northwest:

Birds Eating Seeds *What it looks like:* Sunflower heads with missing or damaged seeds. You might see birds actively pecking at the flowers. *What causes it:* Birds are attracted to the nutritious seeds, especially as they ripen. *How to fix/prevent it:* Cover the developing flower heads with netting or paper bags to prevent birds from accessing the seeds. You can also try using bird deterrents like shiny tape or scarecrows.

Sunflower Moth *What it looks like:* Small holes in the sunflower head, webbing, and caterpillars feeding on the seeds. *What causes it:* Sunflower moths lay their eggs on the flower heads, and the larvae burrow into the seeds to feed. *How to fix/prevent it:* Inspect flower heads regularly for signs of infestation. Remove and destroy any affected heads. Encourage beneficial insects like parasitic wasps, which prey on sunflower moth larvae.

Downy Mildew *What it looks like:* Yellow patches on leaf tops with fuzzy gray-purple growth on undersides. Leaves brown and die from the bottom up. *What causes it:* Oomycete pathogen that spreads in cool, humid conditions via wind-carried spores. Different species affect different plants. *How to fix/prevent it:* Remove affected leaves immediately. Improve air circulation around plants. Water at the base, never overhead. Copper-based fungicides can be used for prevention. Plant resistant varieties where available.

Pacific Northwest Specific Challenges: Our mild summer heat and dry-summer rainfall actually help minimize some sunflower problems, like fungal diseases. However, our cool soil in spring can slow down germination and early growth, and slugs can be a nuisance for young seedlings. Be sure to start seeds at the right time and protect your plants from slugs to give them the best start.

Sunflowers are great companions for many plants in the PNW garden. Cucumbers and squash benefit from the sunflower's tall stalk providing shade during our warmer days. Green beans can climb up the sturdy sunflower stalks, saving space in the garden. Corn also thrives alongside sunflowers, as they both have similar nutrient needs. Lettuce planted near sunflowers can enjoy some protection from the intense afternoon sun during our mild summers.

Avoid planting potatoes near sunflowers, as they can compete for nutrients and both are susceptible to similar fungal diseases, which can spread between the two.