Plant Tomatoes by May 20 and Kale in August: 15 Vegetables Matched to Pennsylvania’s 3 Climate Zones
Pennsylvania spans Zone 5 to Zone 7 — a 6-week planting gap between Bradford and Philadelphia. These 15 vegetables are matched to your zone with exact transplant dates and a summer heat strategy.
Philadelphia gardeners transplant tomatoes in early May. Bradford gardeners — just 280 miles north — wait until the last week of May, because their last frost doesn’t arrive until May 15. That six-week gap defines Pennsylvania vegetable gardening: one state, three overlapping growing seasons, and a list of “best vegetables” that shifts depending on which region you’re in.
This guide covers 15 vegetables proven across all three PA climate zones, with zone-specific planting windows for each one and a summer heat strategy for the humid stretch that trips up even experienced growers.
Pennsylvania’s Three Growing Zones
Pennsylvania spans USDA hardiness Zones 5a through 7a, but frost dates — not zone numbers — are the practical planning tool. Based on NOAA 30-year climate normals, here’s how the state divides into three workable growing regions:
| Region | Zone | Cities | Last Spring Frost | First Fall Frost | Frost-Free Days |
|---|---|---|---|---|---|
| Southeast PA | 6b–7a | Philadelphia, Reading, York, Allentown | March 30–April 14 | Oct 19–Nov 17 | 188–232 |
| Central PA | 6a–6b | Harrisburg, Pittsburgh, Williamsport | April 10–April 28 | Oct 10–Oct 28 | 165–201 |
| NW PA / Mountains | 5a–5b | Erie, Scranton, Bradford, Poconos | April 24–May 15 | Sept 28–Oct 14 | 136–174 |
Elevation drives most of this variation, not latitude. State College sits only 60 miles north of Harrisburg but stands 1,200 feet higher — and loses nearly 50 frost-free days as a result. Gardeners in ridge and valley terrain should plan as if they’re a half-zone colder than the map shows.
For more on how Pennsylvania’s microclimates affect all your plantings, the regional gardening growing guide covers the AHS heat zone layer that frost dates alone miss.
Cool-Season Vegetables: Plant Before the Heat Arrives
Cool-season crops need cold temperatures to germinate and grow, and in Pennsylvania that means two windows: early spring (March–May) and late summer into fall (August–October). Penn State Extension’s cool-season guide notes that quality deteriorates once summer heat arrives — timing is the key skill.
1. Peas
Peas are Pennsylvania’s first vegetable of the year, direct-sown without any indoor starting. Soil needs to reach only 40°F for germination, which means seeds go in long before the last frost. Zone 7 gardeners sow in mid-March; Zone 6 targets late March to early April; Zone 5 waits until late April. Days to maturity: 60–70 days. The catch is heat: peas stop producing once daytime temperatures consistently exceed 75°F, so a delayed planting in Zone 7 shortens your harvest window sharply.
2. Lettuce
Lettuce germinates at soil temperatures as low as 40°F and matures in 45–60 days, making it one of PA’s most productive spring crops. Sow outdoors 4–6 weeks before your last frost: mid-March for Zone 7, early April for Zone 6, mid-April for Zone 5. Above 80°F, lettuce bolts — it sends up a seed stalk, turns bitter, and stops producing. In Central PA’s humid July heat, a second planting in early August extends your season into October. Bolt-resistant varieties such as Forlina or Arroyo handle PA’s summer shoulder seasons far better than standard types.
3. Spinach
Spinach germinates at 45–75°F soil temperature and tolerates hard frost down to the mid-20s°F when established — one of the few vegetables you can plant in Zone 6 before the snow is fully gone. Direct sow 6 weeks before last frost: late March in Zone 7, early April in Zone 6, mid-April in Zone 5. Like lettuce, spinach bolts in heat; a fall planting in late July or early August often yields more than the spring run. Winter Bloomsdale is the most cold-tolerant variety for fall harvest in Zones 5 and 6.
4. Kale
Kale is the one vegetable you can grow in Pennsylvania virtually year-round. For spring: direct sow 4–6 weeks before last frost in each zone. For fall: sow in early August across all three zones for harvest from October through December. Kale planted in early August in Zone 6 will feed you well past Thanksgiving. The flavor improvement after frost is real — cold converts stored starches in kale leaves to sugars, which is why October kale tastes noticeably sweeter than July kale. Lacinato and Red Russian are the standard PA choices for fall harvest; both develop full flavor after two or three hard frosts.
5. Broccoli
Broccoli needs 10–12 weeks from transplant to harvest, so timing both spring and fall plantings precisely is essential. For spring: start transplants indoors 6–8 weeks before last frost and move them outdoors 2–4 weeks before that date — Zone 7 targets mid-March outdoor transplant, Zone 6 targets late March to early April, Zone 5 targets mid-to-late April. For fall — which is the better crop in PA’s humid climate — transplant outdoors by early July in Zone 7 and by early-to-mid July in Zones 5 and 6, so heads mature in the cooler September and October air. The Penn State Philadelphia planting guide confirms early July as the Zone 7 target for fall broccoli transplants. Fall-grown broccoli also faces substantially less aphid and caterpillar pressure than summer crops.
6. Carrots
Carrots need loose, rock-free soil to form straight roots — a challenge in much of Pennsylvania where clay soils are common. The practical fix is raised beds with a 70/30 soil-to-compost mix, which Penn State Extension recommends for clay-heavy PA gardens. Direct sow when soil reaches 55°F: late March in Zone 7, early April in Zone 6, mid-April in Zone 5. Days to maturity: 70–80 days. Like beets and turnips, carrots taste sweeter when harvested after frost — the cold converts starches to sugar, and a fall succession sown in late July can stay in the ground into November in Zones 6 and 7.
7. Beets
Beets germinate at soil temperatures of 50–75°F and mature in 50–60 days, making them one of PA’s faster cool-season crops. Direct sow in late March (Zone 7), early April (Zone 6), or mid-April (Zone 5). The same frost-sweetening mechanism applies as with carrots. For a second harvest, sow again in mid-to-late July across all three zones; they mature in September and October and can be pulled as needed through early November with light mulch protection.
8. Cabbage
Cabbage tolerates light frost but collapses in PA’s humid mid-summer heat. Start transplants indoors 6–8 weeks before last frost and move them outdoors 3–4 weeks before that date: mid-March for Zone 7, late March to early April for Zone 6, mid-April for Zone 5. For fall, transplant by early-to-mid July across all zones, putting harvest in September and October when cool nights produce tight, dense heads. January King is a cold-hardy variety that survives into November without damage — a reliable choice for Zone 5 fall gardens where the window is tight.
Warm-Season Vegetables: Time to Your Last Frost
Warm-season crops require both warm soil and warm nights — temperatures below 50°F cause most of them to stall, drop blossoms, or produce bitter fruit. Penn State Extension advises that eggplant, peppers, and tomatoes should not go outdoors until nighttime air temperatures are consistently above 50°F and soil is warm, which in much of PA means late May to early June for the coldest zones. A useful rule: add 10–14 days to your last frost date before transplanting warm-season crops. For PA-specific tomato timing by zone, the tomato planting guide covers the full calendar.
9. Tomatoes
Tomatoes are Pennsylvania’s most-grown vegetable and require the most zone-specific planning. Transplant 10–14 days after last frost when overnight temperatures hold above 50°F: early May in Zone 7, around May 15–20 in Zone 6, late May in Zone 5. For Zone 5 gardeners in Bradford, Scranton, or the Poconos, variety selection is the difference between a full harvest and a failed season: use short-season types with under 75 days to maturity. Early Girl (57 days) and Stupice (65 days) are the standard choices. Start seeds indoors 6–8 weeks before transplant date. Tomatoes stop setting fruit when daytime temperatures consistently exceed 90°F — a July issue in Central PA — but resume production once temperatures fall back below 85°F.
10. Peppers
Peppers are more temperature-sensitive than tomatoes and the last warm-season crop to go in the ground. They require soil temperature of 60°F at three inches depth and consistent nighttime air temperatures above 50°F to set fruit — conditions that arrive in late May to early June across most of PA. Zone 7 gardeners transplant around May 15; Zone 6 targets late May; Zone 5 should wait until early June. Bell peppers need 70–85 days to maturity, which gives Zone 5 gardeners a tight window — shorter-season varieties or hot peppers (which mature faster) are the safer bet.
11. Cucumbers
Cucumbers need soil at 65°F before sowing or transplanting. Transplant or direct sow after the soil has warmed fully: early May in Zone 7, mid-May in Zone 6, late May in Zone 5. Days to maturity: 55–65 days. Penn State Extension notes that cucumbers turn bitter when nights drop too cold, so Zone 5 gardeners using row covers to push the fall season should monitor nighttime temperatures closely. Harvest at 6–8 inches for slicing types and pick every 2–3 days — a single cucumber left to go to seed shuts down the entire plant.
12. Snap Beans
Snap beans are direct-sown only — they don’t transplant well — which means waiting until soil reaches 60°F. Below that threshold, seeds rot before sprouting rather than just germinating slowly. Target mid-May for Zone 7, late May for Zone 6, and early June for Zone 5. Days to maturity: 50–55 days for bush types. Provider (50 days) is the most cold-soil-tolerant variety and the best choice for Zone 5 short-season gardens. In Zones 6 and 7, two or three successive plantings spaced two weeks apart extend harvest into September. Harvest every 2–3 days once pods reach finger thickness — beans left too long become tough and signal the plant to stop producing.
13. Zucchini
Zucchini is one of the most productive plants in a PA garden and one of the easiest to overplant. One or two plants per household is genuinely enough — each produces 6–10 pounds per week at peak. Sow or transplant when soil reaches 65°F: early May in Zone 7, mid-May in Zone 6, late May in Zone 5. Days to maturity: 45–55 days. Harvest at 6–8 inches for best flavor; zucchini left past 10 inches develops tough seeds and signals the plant to slow production. In PA’s humid summers, powdery mildew arrives by August — full sun with good airflow and avoiding overhead watering delays it significantly.
14. Sweet Corn
Sweet corn needs soil at 55°F minimum and is direct-sown only. Target early May in Zone 7, mid-May in Zone 6, and late May in Zone 5. Corn is wind-pollinated and must be planted in blocks — a minimum 4×4 arrangement — rather than single rows. A single row produces almost no ears because pollen from the tassels can’t reach enough silks. Days to maturity: 70–80 days for standard varieties. In Zone 5 with under 150 frost-free days, choose early varieties like Peaches and Cream (78 days) and target a single planting rather than successive sowings.
15. Garlic
Garlic is the most hands-off vegetable on this list — planted in October, requiring almost no winter attention, and harvested in late June. Separate cloves from a seed garlic bulb and plant them pointy-end-up, 2 inches deep and 6 inches apart, in late October across all PA zones. They overwinter as small plants, resume growth in March, and are ready when the lower leaves yellow in late June. There’s no transplanting, no indoor starting, minimal weeding in winter, and the late-June harvest arrives just as summer crops hit their stride. Hardneck varieties such as Rocambole or Purple Stripe perform better than softneck in PA’s cold winters and deliver noticeably better flavor.
Pennsylvania’s Summer Heat Strategy
Central and Eastern Pennsylvania regularly hit the 90s°F in July and August, and that heat affects vegetable production in ways that catch new gardeners off guard. The primary mechanism with tomatoes: pollen becomes sterile above 95°F daytime temperatures, and plants stop setting fruit when nighttime temperatures exceed 75°F. This isn’t a disease or a soil problem — it’s a heat response, and it’s temporary. Once temperatures fall back below 85°F in late August, tomatoes resume setting fruit and will often push a second flush in September and October. Don’t pull plants in frustration during a July heat wave.
Peppers drop blossoms under the same conditions. Cucumbers and zucchini slow production. Lettuce, spinach, and beets bolt. The Penn State Extension heat guide recommends 30–50% shade cloth for most vegetables during heat waves, installed so the cloth doesn’t contact foliage — when shade cloth touches plants, it can burn them in wind. A 30% shade cloth over tomatoes during a three-day heat event reduces canopy temperature by up to 10°F, which is enough to keep pollen viable. University of Delaware Cooperative Extension also notes that heat-tolerant bean varieties such as Annihilator and lettuce varieties such as Arroyo show significantly less production loss during heat events.
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→ View My Garden CalendarThe other heat strategy is a timing one. August 15 is the target date across Zones 5 and 6 for fall broccoli, kale, and spinach transplants, according to the Penn State Extension fall gardening guide. These seedlings establish while summer heat is still moderate and mature into October’s cool, moist air — the best growing conditions Pennsylvania offers. Radishes sown by September 10 mature in under 30 days. This August–September succession is the most underutilized window in Pennsylvania vegetable gardening.
For mulching during summer, use straw or shredded leaves at 2–3 inches rather than black plastic. Black plastic raises soil temperature — the opposite of what you need when trying to keep root zones cool enough for pepper and tomato fruit set. Save black plastic for early spring soil warming before transplanting, not for summer use.
All 15 Vegetables at a Glance
| Vegetable | Zone 7 (SE PA) | Zone 6 (Central PA) | Zone 5 (NW/Mountains) | Days to Maturity | Season |
|---|---|---|---|---|---|
| Peas | Mid-March | Late March–early April | Late April–May 1 | 60–70 | Cool |
| Lettuce | Mid-March | Early April | Mid-April | 45–60 | Cool |
| Spinach | Late March | Early April | Mid-April | 40–50 | Cool |
| Kale | Late March / early Aug | Early April / early Aug | Mid-April / early Aug | 55–65 | Cool |
| Broccoli | Mid-March transplant | Late March–early April | Mid-April | 60–80 | Cool |
| Carrots | Late March | Early April | Mid-April | 70–80 | Cool |
| Beets | Late March | Early April | Mid-April | 50–60 | Cool |
| Cabbage | Mid-March transplant | Late March–early April | Mid-April | 70–90 | Cool |
| Tomatoes | Early May transplant | May 15–20 transplant | Late May transplant | 57–80 | Warm |
| Peppers | May 15 transplant | Late May transplant | Early June transplant | 70–85 | Warm |
| Cucumbers | Early May | Mid-May | Late May | 55–65 | Warm |
| Snap Beans | Mid-May | Late May | Early June | 50–55 | Warm |
| Zucchini | Early May | Mid-May | Late May | 45–55 | Warm |
| Sweet Corn | Early May | Mid-May | Late May | 70–80 | Warm |
| Garlic | Late October | Late October | Late October | 240 (June harvest) | Cool |
For more heat-tolerant additions to your summer planting, the best summer vegetables guide covers crops that thrive in Pennsylvania’s July–August stretch. If you’re building your first vegetable garden, the complete vegetable gardening guide covers soil prep, spacing, and watering fundamentals. And for keeping beds healthy year to year, crop rotation for vegetables is worth building into your plan from the start.
Frequently Asked Questions
What is the easiest vegetable to grow in Pennsylvania?
Garlic is the most hands-off option: plant in October, minimal winter maintenance, harvest in late June. Among spring vegetables, snap beans come closest to foolproof — direct sow after last frost, no thinning required, and the harvest signal is obvious. Zucchini produces prolifically with minimal care but needs consistent harvesting every 2–3 days to stay productive throughout the season.
What can I plant in August in Pennsylvania?
August 15 is the critical planting date for fall crops across Zones 5 and 6. Kale, broccoli transplants, and spinach all go in around that date and mature in October when cool air improves their flavor. Beets and carrots sown in mid-to-late July still harvest in October. Radishes sown by September 10 mature in under 30 days. The Pennsylvania gardening guide covers the full fall schedule for each part of the state.
Do I need raised beds for Pennsylvania vegetables?
Not for every crop, but for root vegetables — carrots, beets, parsnips — raised beds make a real difference in Pennsylvania’s clay-heavy soils. Penn State Extension recommends a 70/30 soil-to-compost mix in raised beds, which drains better than native soil and lets carrots form straight roots without hitting clay layers. Greens, beans, and tomatoes grow well in amended in-ground beds, particularly if you work in 2–3 inches of compost before planting. Soil pH for most vegetables should sit between 6.8 and 7.2 — a Penn State county extension soil test is the reliable way to check.
Sources
- Cool-Season vs. Warm-Season Vegetables — Penn State Extension (cited inline above)
- Master Gardeners Philadelphia Planting Guide — Penn State Extension (cited inline above)
- Season Extenders and Growing Fall Vegetables — Penn State Extension (cited inline above)
- Beginning a Vegetable Garden — Penn State Extension
- Heat Proofing Your Vegetable Garden — Penn State Extension (cited inline above)
- Protecting Your Garden Vegetables from Heat Stress — University of Delaware Cooperative Extension
- Pennsylvania Frost Dates by Region — GetHandyOutdoors (based on NOAA 30-year climate normals)
