Yellow Squash in Zone 6B — Southeast

Yellow squash is a must-grow in any Southeast garden. Its mild, slightly sweet flavor makes it incredibly versatile in the kitchen, perfect for grilling, sautéing, or adding to casseroles. Plus, there's nothing quite like the satisfaction of harvesting armfuls of these sunny veggies from your own backyard throughout our long summer.

Our hot and humid summers can bring challenges like fungal diseases and pests, but with a little planning and the Southeast's generous 208-day growing season, you can easily enjoy a bumper crop of yellow squash. The key is timing your planting right and staying on top of watering.

Starting yellow squash indoors isn't the most common practice here in the Southeast, since they transplant best when direct sown. However, if you're eager to get a head start or want to ensure germination, it's certainly an option.

If you're going to start indoors, do so from late March through mid April, about three weeks before you plan to transplant outdoors. Use seed trays with a good seed-starting mix, provide warmth (a heat mat helps), and ensure they get plenty of light, either from a sunny window or a grow light. Bottom watering will help prevent damping off. Keep in mind that our springs can have temperature swings, so be ready to protect your seedlings if a late frost threatens.

Transplanting yellow squash in the Southeast should happen from mid April through late May, once the soil has warmed up. Before you put them in the ground, harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Space your plants 24-36 inches apart in well-draining soil. Even though we have a wet-summer climate, heavy clay soil can still cause problems if it doesn't drain well. Watch out for late frosts, which can still happen in early spring; be prepared to cover your young plants if needed.

Direct sowing is the easiest and most reliable way to grow yellow squash in the Southeast. These plants grow quickly from seed, and they don't love having their roots disturbed.

Sow your seeds from mid April through late August, ensuring the soil temperature is at least 60°F. Plant seeds about an inch deep and space them 24-36 inches apart. Yellow squash needs full sun to thrive, so pick a spot that gets at least 6-8 hours of direct sunlight each day. With consistent watering, you'll see sprouts in just a few days.

Yellow squash are thirsty plants, especially in the hot and humid Southeast climate. Consistent watering is crucial for preventing blossom end rot and ensuring a good harvest. Aim for deep watering at the base of the plant, rather than overhead watering, to minimize fungal disease.

During the spring and fall, when temperatures are milder, water deeply once or twice a week, providing about 1-2 inches of water each time. In the peak of summer, when temperatures soar into the 90s and humidity is high, you may need to water every day, particularly if we're in a dry spell between our typical afternoon thunderstorms. Stick your finger about 2 inches into the soil – if it feels dry, it's time to water.

Overwatering can be just as bad as underwatering, leading to root rot, so make sure your soil drains well. Yellowing leaves can indicate overwatering, while wilting leaves signal underwatering. A good layer of mulch will help retain moisture and keep the soil temperature consistent, which is especially important with our clay soil.

You can expect your first harvest of yellow squash from early June through late October in the Southeast, about 50 days after planting. The best time to harvest is when the squash are 6-8 inches long and the skin is still tender enough to dent with your fingernail.

Use a sharp knife or pruners to cut the squash from the vine, leaving a short stem attached. Regular harvesting encourages continued production, so check your plants every other day once they start producing. As we approach our first frost in late October, harvest any remaining squash, even if they're a bit smaller than usual. They may not ripen much off the vine, but you can still use them in cooking.

Yellow squash, like many plants in the Southeast, can face its share of problems due to our hot and humid climate. Here are some common issues and how to tackle them:

Squash Vine Borer *What it looks like:* Wilting vines that suddenly collapse, often with small holes near the base of the plant and sawdust-like frass. *What causes it:* Moth larvae that bore into the stems and feed on the plant's tissue. *How to fix/prevent it:* Wrap the base of stems with aluminum foil to prevent egg-laying. Check vines regularly and slit the stem lengthwise to remove borers. Mound soil over the cut area to encourage rooting.

Powdery Mildew *What it looks like:* White or grayish powdery coating on leaves, stems, and sometimes fruit. Leaves curl, yellow, and die. *What causes it:* Various fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it. *How to fix/prevent it:* Improve air circulation through spacing and pruning. Remove affected leaves. Neem oil or potassium bicarbonate sprays help. Milk spray (1 part milk to 9 parts water) is surprisingly effective.

Squash Bugs *What it looks like:* Gray-brown shield-shaped bugs on leaf undersides. Bronze egg clusters on leaves. Wilting leaves that turn brown and crispy. *What causes it:* Sap-sucking insects that inject toxin while feeding. Adults overwinter in garden debris and emerge in spring. *How to fix/prevent it:* Hand-pick adults and crush egg clusters. Board traps (adults hide under boards at night — flip and destroy in morning). Neem oil spray. Remove plant debris in fall.

Blossom End Rot *What it looks like:* Sunken, dark brown or black leathery patch on the bottom (blossom end) of fruit. Often affects first fruits of the season. *What causes it:* Calcium deficiency caused by inconsistent watering. Not a disease — it's a nutrient uptake problem triggered by drought/flood cycles. *How to fix/prevent it:* Water consistently (the single most effective fix). Mulch heavily to maintain even soil moisture. Don't over-fertilize with nitrogen. Calcium sprays help marginally. Remove affected fruit.

Southeast Specific Challenges: Our hot, humid summers create a perfect environment for fungal diseases like powdery mildew. The wet-summer rainfall can lead to inconsistent soil moisture, contributing to blossom end rot. And, of course, Japanese beetles can be a nuisance, though they rarely do significant damage to squash.

Companion planting can be a great way to improve the health and productivity of your yellow squash in the Southeast. Corn provides a natural trellis for climbing beans, which in turn fix nitrogen in the soil, benefiting the squash. Radishes can help deter squash bugs and other pests. Marigolds are another excellent companion, as their scent repels many unwanted insects.

Avoid planting yellow squash near potatoes or brassicas (like cabbage and broccoli). Potatoes compete for the same nutrients, while brassicas can attract pests that also target squash.