What to Plant in March in Pennsylvania
March in Pennsylvania is mostly an indoor month. For zones 5a–6a (Pittsburgh, Scranton, mountains), everything stays under grow lights or in cold frames. For zones 6b–7a (Philly suburbs, Reading, York), you can start getting seeds into the ground by late March — but only the cold-tolerant stuff.
The biggest mistake I see people make in March is planting too much too early. That first 60°F day feels like spring, but your soil is still in the 30s and a hard frost can show up through mid-April in most of PA. This month is about setting up your spring — not rushing it.
Find Your Zone — March Action Plan
That first 60°F day feels like a green light, but your soil is still in the 30s and hard frosts can show up through mid-April in most of PA. March is about setting up your spring — not rushing it.
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What to Start Indoors in March (All PA Zones)
March is prime time for indoor seed starting. If you haven’t set up a grow light station yet, now’s the moment — PA’s March daylight isn’t enough to keep seedlings from getting leggy on a windowsill.
Tomatoes
Start tomato seeds indoors 6–8 weeks before your last frost date. For most of PA, that means early to mid-March is the window.
| Your Zone | Last Frost (avg) | Start Tomatoes Indoors |
|---|---|---|
| 7a (Philly) | March 30 | Late January – mid-February |
| 6b (Reading, York) | April 12–14 | Mid-February – early March |
| 6a (Pittsburgh, Harrisburg) | April 10–20 | Early – mid-March |
| 5b (Scranton, Erie) | April 24 – May 1 | Mid-March |
| 5a (Mountains) | May 10–15 | Late March – early April |
Tomato seeds germinate best at 75–85°F soil temperature — but your basement or garage in March is usually well below that. A seed-starting heat mat pays for itself in faster, more even germination every single year.
If you’re in zone 6a, early March is your sweet spot for tomato starts. Use a heat mat under your seed trays — tomato seeds germinate best at 75–85°F soil temperature, and a basement or garage is usually colder than that in March.
Peppers
Peppers need more time than tomatoes — 8–10 weeks before last frost. If you’re in zones 6a–6b and haven’t started peppers yet, do it this week. Zone 5b gardeners should start peppers in mid-March.
Peppers are slow germinators. Don’t panic if nothing pops up for 10–14 days. Keep the soil warm (80°F is ideal for germination) and be patient.
Brassicas (Broccoli, Cabbage, Cauliflower)
Start these indoors 4–6 weeks before last frost. They’re tougher than tomatoes and peppers — they can handle cool conditions and even a light frost once transplanted. For zones 6a–6b, start them in early March for an April transplant.
Herbs
March is the right time to start basil, parsley, and cilantro from seed indoors. Basil especially needs warm soil to germinate (70°F+), so treat it like peppers. Parsley is notoriously slow — it can take 3 weeks to germinate, so don’t give up on it.
Other Indoor Starts
- Eggplant — needs 8–10 weeks, same timeline as peppers
- Celery — needs 10–12 weeks, should already be started but not too late if you start now
- Lettuce and kale — can start indoors for an early transplant, though you’ll also direct sow these later
What to Sow Outdoors in March (Zones 6b–7a Only)
If you’re in the Philadelphia area or the warmer southeastern counties, late March opens the door for some direct sowing outdoors. The key: stick to cold-hardy crops that can handle frost. These plants actually prefer cool soil.
Direct sow after mid-to-late March (zones 6b–7a):
- Peas — the classic early spring crop. Sow as soon as soil can be worked. They handle frost fine and actually prefer cool weather. Plant 1 inch deep, 2 inches apart, with a trellis or support for climbing varieties.
- Spinach — germinates in soil as cool as 35°F. One of the earliest things you can plant. Direct sow ½ inch deep.
- Lettuce — sow a mix of varieties for a cut-and-come-again harvest starting in May. Lettuce bolts in summer heat, so the earlier you get it in, the longer you harvest.
- Radishes — fast growers (30 days to harvest). Great for impatient gardeners and kids. Sow ½ inch deep, thin to 1 inch apart.
- Arugula — cold-tolerant and fast-growing. Will bolt once temps consistently hit 80°F, so plant early.
- Kale — can handle hard frost. Direct sow or transplant. One of the most forgiving crops in PA.
Don’t sow these yet (even in zone 7a): Beans, corn, squash, cucumbers, or anything from the tomato/pepper family. These are warm-season crops that need soil temps above 60°F and zero frost risk.
Cold Frame Planting
If you have a cold frame, you can get a 2–3 week head start on the outdoor list above in zones 6a–6b. A cold frame is basically a low-tech greenhouse — a bottomless box with a glass or plastic lid that traps solar heat. Even an old window propped over a raised bed works.
In my experience, a cold frame adds at least 15°F to soil temperature on a sunny March day. That’s enough to get spinach, peas, and lettuce going in early March even in zone 6a.
What NOT to Plant in March in PA
Tomato/pepper transplants outdoors, beans, corn, squash, cucumbers — these need warm soil (60°F+) and zero frost risk. Tender annual flowers and tropical herbs like basil outdoors should also wait until after your last frost, minimum May for most zones.
March Prep Tasks (All Zones)
Even if you can’t plant anything outdoors yet, there’s plenty to do in March to set your garden up for a strong season.
Soil Prep
- Test your soil if you haven’t in the last 2–3 years. Penn State Extension offers affordable soil testing that tells you your pH, nutrient levels, and exactly what amendments your soil needs. For $10, it’s the best investment in your garden.
- Don’t work wet soil. If you grab a handful and it forms a sticky clay ball, wait. Working wet clay destroys the soil structure and compacts it further. Let it dry enough to crumble when squeezed.
- Add compost or aged manure to beds you’ll plant first (peas, lettuce, radishes). Work it into the top 6–8 inches.
Pruning
- Prune fruit trees before buds break. March is the tail end of the dormant pruning window for apples, pears, and stone fruit. Once you see green bud swell, stop.
- Prune grape vines if you haven’t already — they bleed sap heavily once growth starts.
- Cut back ornamental grasses to 4–6 inches before new growth emerges.
- Don’t prune spring-blooming shrubs (lilac, forsythia, azalea) — they set their flower buds last year. Prune those after they bloom.
Gear Check
- Inventory your seed supply and order anything you’re missing now. Popular varieties of tomatoes, peppers, and herbs sell out quickly.
- Check grow lights, heat mats, and seed trays. Replace burned-out bulbs.
- Sharpen pruners, shovels, and hoe blades. Clean with rubbing alcohol to prevent disease transmission between plants.
- Service your lawn mower before the spring rush at repair shops.
March Planting Calendar at a Glance
| Task | Zone 5a–5b | Zone 6a | Zone 6b | Zone 7a |
|---|---|---|---|---|
| Start tomatoes indoors | Late March | Early March | Late Feb – early March | Already started (Jan–Feb) |
| Start peppers indoors | Mid-March | Early March | Mid-Feb | Already started |
| Start brassicas indoors | Mid-March | Early March | Late Feb | Late Feb |
| Start herbs indoors | March | March | March | March |
| Direct sow peas/spinach | Not yet | Cold frame only | Late March | Mid-March |
| Direct sow lettuce/radishes | Not yet | Cold frame only | Late March | Mid-March |
| Prune fruit trees | Early March | Early March | Early March | Already done (Feb) |
| Soil testing | Now | Now | Now | Now |
FAQ
Can I plant anything outside in March in PA?
In zones 6b–7a (Philly area, Reading, York), yes — cold-hardy crops like peas, spinach, lettuce, and radishes can go in the ground by late March. In zones 5a–6a (Pittsburgh, mountains, northern PA), March is still an indoor-only month. Use a cold frame to push the timeline earlier.
When should I start tomato seeds indoors in Pennsylvania?
6–8 weeks before your last frost date. For zone 6a (most of PA), that’s early to mid-March. For zone 7a (Philly), you should have started in January or February. For zone 5b (Scranton, Erie), mid-March works. Use a heat mat for best germination.
Is March too late to start pepper seeds?
Not for most of PA. Peppers need 8–10 weeks indoors before transplant. If you’re in zone 6a (Pittsburgh, Harrisburg), starting in early March gives you transplant-ready plants by mid-May. Zone 5b gardeners still have time in mid-March.
What’s the soil temperature for planting in March?
Cool-season crops like peas and spinach germinate in soil as cool as 35–40°F. Lettuce needs about 40°F. Tomato and pepper seeds need 75–85°F, which is why they start indoors under heat mats, not in March garden soil.
Should I start seeds on a windowsill or under grow lights?
Grow lights, every time. March daylight in PA (roughly 12 hours, much of it cloudy) isn’t enough for seedlings. They’ll stretch toward the light and get leggy and weak. A basic shop light with daylight-spectrum bulbs hung 2–3 inches above seedlings works fine and costs under $30. The Old Farmer’s Almanac seed starting guide has a solid primer on indoor lighting setups.
Can I plant trees in March in Pennsylvania?
In zones 6b–7a, late March is a good time to plant bare-root fruit trees before they break dormancy. For zones 5a–6a, wait until April when the ground has fully thawed. Bare-root trees are cheaper than container trees and establish just as well.
March Planting Guides for Pennsylvania
- When to Plant Peas in Pennsylvania — one of the earliest direct-sow crops in PA
- When to Plant Broccoli in Pennsylvania — start indoors in late February or direct-sow in March
- When to Plant Lettuce in Pennsylvania — cold-tolerant and ideal for early PA spring
- Starting Seeds Indoors in Pennsylvania — timing guide for tomatoes, peppers, and more
