What to Plant in August in Pennsylvania

August is secretly one of the most important planting months in Pennsylvania — and most people miss it completely. While your tomatoes and peppers are pumping out fruit, the clock is already ticking on fall. If you want fresh greens, root vegetables, and brassicas this October and November, the seeds need to go in the ground now.

I skipped fall planting my first few years of gardening and regretted it every time. The fall growing season in PA is actually easier than spring in a lot of ways — fewer pests, cooler temps that greens love, and the kind of steady moisture that makes everything grow without constant watering. August planting is how you take advantage of all that.

This post contains affiliate links. If you purchase through these links, I may earn a small commission at no extra cost to you.

What to Direct Sow Outdoors in August (All PA Zones)

The key to August planting is counting backward from your first frost date. Every crop has a “days to maturity” number on the seed packet — add two weeks to account for slower growth in cooling temps and shorter days, and that’s how far back you need to plant. Check your local PA frost dates before you start, or use the zone deadlines in the card above.

Lettuce

Lettuce is the workhorse of the fall garden. It’s fast (45–60 days), cold-tolerant (survives light frosts), and tastes better in cool weather than anything you’ll grow in summer. The challenge is germination — lettuce seed goes dormant above 80°F, so if you’re planting in early August heat, sow in the evening and keep the soil cool for the first few days.

Plant ¼ inch deep and thin to 6 inches apart for leaf types, 10–12 inches for heads. Butter lettuces (like Buttercrunch) and romaines hold up better in late-season cold than loose-leaf types. For zones 5b and 6a, row cover adds 4–6°F of frost protection and can extend your harvest by 3–4 weeks.

Spinach

Spinach is even more cold-hardy than lettuce — mature plants can survive temperatures down to 20°F with minimal protection. It also germinates more reliably in August heat than lettuce. Plant ½ inch deep, thin to 3–6 inches. Bloomsdale Long Standing and Tyee are reliable PA varieties that bolt slowly.

Spinach actually improves after a light frost, converting starches to sugars. Fall-grown spinach consistently tastes better than spring. Plant now and you may be harvesting into December with a cold frame.

Kale

Kale is the most cold-hardy brassica you can grow in PA, surviving hard frosts well below 20°F. Like spinach, frost converts the leaves to sugar, making post-frost kale noticeably sweeter.

Direct sow in early August for zones 5a–6a, or anytime in August for zones 6b–7a. Plant seeds ½ inch deep, thin to 12–18 inches apart. Lacinato (Tuscan) and Red Russian are go-to varieties for fall PA gardens.

Radishes

The fastest reward in the fall garden — 25–30 days from seed to harvest. Radishes that mature in cool weather are crispier and less peppery than ones that grew in summer heat. Sow ½ inch deep, thin to 1 inch apart, and succession plant every 10 days through September for a continuous harvest all fall.

Arugula

Arugula bolts in summer heat but thrives in the cooler temperatures of fall. It’s fast-growing (ready in 30–40 days) and cold-tolerant enough to keep producing after light frosts. Scatter seed on prepared soil and press lightly — arugula likes loose, well-drained conditions. The peppery flavor intensifies in cold weather, which arugula fans love.

Turnips

Turnips are an underappreciated fall crop that delivers two harvests in one: you can eat the greens at 30 days and the roots at 45–60 days. They germinate in warm soil and mature as the weather cools. Plant ½ inch deep and thin to 4–6 inches. Purple Top White Globe is the classic PA variety.

Beets

Beets take 55–70 days and are more cold-tolerant than most people realize — mature beets handle light frost just fine. Soak seeds overnight before planting to improve germination, plant 1 inch deep, and thin to 3–4 inches. The greens are edible at any stage. Cylinder and Detroit Dark Red varieties are reliable for PA fall gardens.

Cilantro

Cilantro bolts immediately in summer heat, but fall is its natural season. Plant now and it will produce lush, flavorful leaves through October and November. Direct sow ¼ inch deep and thin to 4 inches. Slow-bolt varieties like Calypso give you a longer harvest window.

What to Transplant Outdoors in August

Some brassicas are best started indoors in July and transplanted as starts in August. If you didn’t start them yourself, garden centers often carry six-packs of broccoli and cabbage starts in August.

Broccoli, Cauliflower, and Cabbage

These need to be in the ground by early-to-mid August in most PA zones to mature before frost. Broccoli and cabbage are more cold-tolerant; cauliflower is pickier and needs a longer head start. Space 18–24 inches apart. Cover with row cover immediately if Japanese beetles or cabbage loopers are active — brassicas in August can get shredded quickly.

Cauliflower is the trickiest — it needs consistent moisture and cool temps to form a proper head. In zones 5a–5b, it’s risky without a cold frame. In zones 6b–7a, it’s very doable if transplants go in by August 15.

Brussels Sprouts

Brussels sprouts need a long season (90–110 days) and are usually started indoors in June for August transplanting. If you have starts ready, get them in immediately — they need all the time they can get. The good news: Brussels sprouts are extremely cold-hardy and actually taste best after hard frost. Late October and November harvests are peak flavor.

What NOT to Plant in August

Summer’s momentum makes it tempting to keep planting warm-season crops, but these are done for the year:

• Tomatoes, peppers, eggplant — no time to mature before frost, even in zone 7a. Focus on keeping your existing plants producing instead.
• Beans — bush beans planted before August 10 might squeeze in a harvest in zones 6b–7a, but it’s tight. After August 15, don’t bother.
• Corn, squash, cucumbers, melons — way too late. These need 60–100 warm days that just aren’t available.
• Basil and warm-season herbs — your existing basil will keep going until frost, but starting new plants in August doesn’t make sense. Focus on cilantro, parsley, and dill instead.

August Lawn Care (Critical Timing)

This section alone might be the most valuable thing on this page if you care about your lawn. Late August through mid-September is the single best time of year to work on PA lawns.

Overseeding

Overseed thin or bare areas now. The soil is warm enough for fast germination, the air temps are dropping, and fall moisture does most of the watering work for you. Prepare the area first — rake out dead grass and thatch, loosen the top ½ inch of soil, then spread seed at the labeled rate. Keep lightly moist until germination (7–14 days), then water deeply and less frequently as roots establish.

Use a seed mix appropriate for your conditions: tall fescue blends for sunny areas with average soil, Kentucky bluegrass for sunny areas where you want a dense traditional lawn, shade-tolerant fescue mixes for tree canopy areas.

Aeration

Core aeration (the kind with hollow tines that pull plugs) is most effective in fall for cool-season grasses. It relieves compaction, improves water penetration, and helps seed-to-soil contact when combined with overseeding. Rent a core aerator or hire it out — spike aerators don’t provide meaningful relief and aren’t worth your time.

Fertilizing

Apply a fall lawn fertilizer (higher potassium, lower nitrogen than summer formulas) in late August or September. This builds root reserves for winter and gives the lawn a strong start next spring. Avoid high-nitrogen formulas in late fall — you’re feeding roots now, not top growth.

Maintaining Your Summer Garden in August

Watering

August heat is hard on everything. Cool-season transplants and seedlings need consistent moisture to get established. In-ground established plants need about 1 inch per week, but containers may need daily watering during heat spikes.

Water at the base of plants, not overhead, especially for tomatoes, squash, and brassicas. Wet foliage in PA’s humid August weather is a fast track to fungal disease. Water in the early morning when possible.

Tomato Care

August heat above 90°F causes blossom drop in tomatoes — the flowers fall off without setting fruit. Don’t panic. This is a temperature issue, not a disease, and your plants will resume setting fruit once nighttime temps drop below 75°F, which usually happens by late August or early September in most of PA.

Keep picking ripe tomatoes regularly. Leaving overripe fruit on the vine signals the plant to slow down production. Side-dress with compost or a balanced fertilizer to fuel the late-season push.

Pest Watch

• Squash vine borers are in full swing in August. If your zucchini or squash plants suddenly wilt on a sunny day, check the base of the stem for a small hole and frass. You can slit the stem, remove the borer, and mound soil over the wound — sometimes the plant recovers.
• Japanese beetles peak in July–August. Hand-pick into soapy water in the morning when they’re sluggish. Avoid Japanese beetle traps — they attract more beetles than they catch.
• Tomato hornworms can defoliate a plant in days. Look for large caterpillars and distinctive dark droppings. Hand-pick — they’re harmless to handle. If you see white rice-shaped cocoons on the hornworm, leave it — those are parasitic wasp eggs doing your pest control for you.

Garlic: Order Now, Plant Later

You won’t plant garlic until October, but August is when you need to order it. Quality seed garlic from reputable suppliers sells out by September every year. The best varieties for Pennsylvania — hardneck types like Music, Chesnok Red, and Pennsylvania Dutch Red — are bred for cold winters and perform far better than anything you’ll find at a grocery store.

Order 1 pound of seed garlic per 25 feet of row. Store it in a cool, dry, well-ventilated spot (not the refrigerator — it needs air circulation). Plant in mid-to-late October when soil temps drop to around 50°F, 2 inches deep and 6 inches apart. Mulch with 4–6 inches of straw after the ground hardens. You’ll harvest next July — one of the most satisfying crops in the PA garden. See the full PA planting guide for more on the fall-to-summer garlic cycle.

August Planting Calendar at a Glance

FAQ