Yellow Squash in Zone 8B — Southeast

Yellow squash is a must-grow in the Southeast. Its mild, sweet flavor makes it incredibly versatile in the kitchen – from grilling and sautéing to adding it to casseroles and breads. Plus, the satisfaction of harvesting armfuls of these sunny beauties throughout our long summer is hard to beat.

Our hot and humid summers here in Zone 8B can present some challenges with fungal diseases and pests, but with proper timing and care, you can easily enjoy a bountiful harvest. Our long 255-day growing season gives us plenty of opportunity to get it right.

While yellow squash thrives when direct-sown, starting seeds indoors from late February through mid March, about three weeks before transplanting, can give you a head start. This is especially useful if you're eager to get an early harvest.

Use seed trays or small pots filled with a good seed-starting mix. Keep them warm (a heat mat helps) and provide plenty of light with grow lights or a sunny windowsill. Remember to water from the bottom to encourage strong root growth and prevent damping-off.

Given our moderate spring weather, direct sowing is generally preferred. But if you want a jump on the season, indoor starting is a good option.

Transplant your yellow squash seedlings outdoors from late March through early May, once the danger of frost has passed and the soil has warmed up.

Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind. Space plants 24-36 inches apart to allow for good air circulation, which is vital in our humid climate. Keep an eye on the forecast; a late cold snap can still happen, so be ready to cover your young plants if needed.

Direct sowing is the easiest and most common way to grow yellow squash here in the Southeast. You can sow seeds directly into the garden from mid March through mid September, giving you a long window for multiple harvests.

Choose a sunny spot with well-drained soil. Yellow squash loves warm soil, so wait until the soil temperature reaches at least 60°F. Plant seeds about an inch deep and 24-36 inches apart. They sprout quickly, and you'll be amazed at how fast they grow.

Yellow squash needs consistent watering, especially in our hot and humid Southeast summers. Aim for deep watering at the base of the plant to encourage strong root growth and avoid wetting the foliage, which can lead to fungal problems.

During the warmer months, check the soil moisture regularly using the "finger test"—stick your finger about two inches deep into the soil. If it feels dry, it's time to water. Typically, yellow squash needs about 1-2 inches of water per week, either from rainfall or irrigation. Water in the morning so the leaves have time to dry before nightfall.

Signs of underwatering include wilting leaves and stunted growth. Overwatering, on the other hand, can lead to root rot, indicated by yellowing leaves and a mushy stem base. A layer of mulch around your plants helps retain moisture and suppress weeds, which is a big help in our climate.

You can expect your first yellow squash harvest from early May through mid November, about 50 days after planting. The key is to harvest them when they're young and tender.

Look for squash that are 6-8 inches long and have smooth, glossy skin. The skin should be tender enough to dent easily with your fingernail. Use a sharp knife or pruners to cut the squash from the vine, leaving a short stem attached. This helps prevent rot.

Harvesting regularly encourages the plant to produce more squash. As the first frost approaches around mid- November, harvest all remaining squash, even if they're a bit smaller than usual. They may not ripen fully off the vine, but they're still delicious.

Yellow squash, unfortunately, can be prone to a few problems in our Southeast gardens. Here's how to tackle them:

Squash Vine Borer

• What it looks like: Wilting vines, especially during the hottest part of the day. Small holes at the base of the stem with sawdust-like frass (larval excrement).
• What causes it: Moth larvae that bore into the stems of squash plants, disrupting water and nutrient flow.
• How to fix/prevent it: Wrap stems with foil or nylon stockings to prevent moths from laying eggs. Inject stems with Bacillus thuringiensis (Bt) to kill borers. Remove and destroy infested vines after harvest.

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. Plant resistant varieties.

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. Companion plant with nasturtiums.

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. 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 heat and humid humidity, combined with wet-summer rainfall, create a perfect environment for fungal diseases like powdery mildew. Regular monitoring, good air circulation, and preventative treatments are key. Japanese beetles can also be a nuisance, so be prepared to hand-pick them or use traps. Deer can also be a problem, so consider fencing or deer-resistant sprays.

Companion planting can help your yellow squash thrive. Corn provides a natural trellis for climbing bean varieties, which in turn fix nitrogen in the soil, benefiting the squash. Radishes deter squash vine borers, and marigolds repel nematodes and other pests.

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