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When to plant herbs outside in PA depends on your local frost dates and the specific herbs you’re growing.
Knowing when to plant herbs outside in PA is the key to a thriving garden because Pennsylvania’s climate varies from zone 5 in the north to zone 7 in the southeast.
If you’ve been wondering when to plant herbs outside in PA, the short answer is that most herbs go out after the last spring frost, which typically falls between mid-April and late May.
But that’s just the starting point, as some hardy herbs can go out earlier while tender ones need warmer soil.
In this post, we’ll break down when to plant herbs outside in PA by herb type, region, and soil conditions.
Let’s dig into the details so you can get your herb garden off to a strong start.
When to Plant Herbs Outside in PA: The Frost Date Factor
The single biggest factor in when to plant herbs outside in PA is your last expected frost date.
Pennsylvania stretches across USDA hardiness zones 5a to 7b, which means frost dates shift by a couple of weeks depending on where you live.
For eastern PA near Philadelphia, the last frost usually happens around April 10–20.
For central PA around Harrisburg, plan for late April to early May.
For northern and mountainous areas like Scranton or the Poconos, the last frost can linger into mid-May.
So when to plant herbs outside in PA really starts with checking your local frost forecast, not just a calendar date.
But remember, the soil temperature matters just as much as the air temperature for when to plant herbs outside in PA.
1. Cool-Season Herbs Can Go Out Earlier
If you’re asking when to plant herbs outside in PA for cold-hardy varieties, you have some wiggle room.
Herbs like parsley, cilantro, dill, and chives can handle light frosts and even a few freezing nights.
These can be planted outside in PA as early as 2–4 weeks before your last frost date.
So for central PA, that might mean late March to mid-April.
These herbs actually prefer cooler soil and will bolt or go to seed quickly if it gets too hot.
Planting them early gives you a longer harvest window before summer heat kicks in.
2. Tender Herbs Need Warmer Soil
For tender herbs like basil, rosemary, and lemongrass, when to plant herbs outside in PA shifts later.
These herbs are frost-sensitive and will die if temperatures dip below 40°F.
You should wait until at least 1–2 weeks after your last frost date to plant these outside in PA.
Even better, wait until nighttime temperatures consistently stay above 50°F.
Basil, in particular, is super picky, so it’s worth holding off until late May or even early June.
The soil temperature for tender herbs should be at least 60°F before transplanting.
3. Perennial Herbs Have Their Own Timeline
When to plant herbs outside in PA also depends on whether you’re planting annuals or perennials.
Perennial herbs like thyme, oregano, sage, mint, and chives can be planted in spring after the frost risk passes.
But they can also go in the ground in early fall, about 6–8 weeks before your first fall frost.
This gives them time to establish roots before winter dormancy.
If you’re planting perennials in spring, aim for the same window as cool-season herbs, which is a few weeks before the last frost.
These tough plants can handle a light frost, so you don’t have to baby them as much.
Regional Planting Windows for Herbs in PA
Since Pennsylvania has varied climates, let’s get more specific about when to plant herbs outside in PA by region.
This helps you fine-tune your planting schedule rather than guessing.
1. Eastern PA (Philadelphia, Allentown, Reading)
In eastern PA, the last frost usually arrives by mid-April.
So when to plant herbs outside in PA for this region means cool-season herbs can go out in late March.
Tender herbs like basil should wait until early to mid-May.
The warmer coastal influence means you can sometimes push this earlier, but don’t risk it with a surprise cold snap.
2. Central PA (Harrisburg, Lancaster, State College)
Central PA has a slightly shorter season, with the last frost around late April to early May.
Here, when to plant herbs outside in PA for hardy herbs is early to mid-April.
For tender herbs, wait until mid-May to be safe.
This region can have unpredictable temperature swings, so keep row covers handy.
3. Western PA (Pittsburgh, Erie)
Western PA is similar to central PA but can be a bit cooler near Lake Erie.
The last frost in Pittsburgh is usually around late April, but Erie often sees frost into early May.
For when to plant herbs outside in PA here, start hardy herbs in mid-April.
Tender herbs should wait until the second half of May, especially near the lake.
4. Northern and Mountainous PA (Scranton, Williamsport)
The coldest parts of PA have the shortest growing season.
The last frost can happen as late as May 15–25 in the high elevations.
So when to plant herbs outside in PA in these areas means waiting until early May for hardy herbs.
Tender herbs in this region often don’t go out until late May or early June.
You might also consider using raised beds or containers to warm the soil faster in these cooler zones.
Soil Temperature and When to Plant Herbs Outside in PA
Beyond frost dates, soil temperature is a big clue for when to plant herbs outside in PA.
Herbs have different optimal soil temperature ranges for germination and transplanting.
For cool-season herbs, soil temps around 45–60°F are ideal.
For warm-season herbs, you need soil temps of at least 60–70°F.
You can easily check soil temperature with a simple probe thermometer.
If the soil is too cold, tender herbs will just sit there, rot, or get stunted.
If the soil is too hot, cool-season herbs will bolt quickly and become bitter.
So while frost dates give you a rough idea of when to plant herbs outside in PA, soil temperature is the real green light.
Tips for Success with Planting Herbs in PA
Once you nail the timing for when to plant herbs outside in PA, a few extra tips will help your herbs thrive.
1. Harden Off Your Seedlings
If you started herbs indoors, they need a gradual introduction to the outdoors.
Start by placing them outside in a shaded spot for an hour a day, then gradually increase their time and sun exposure over a week.
This reduces transplant shock and makes a big difference in survival rates.
2. Use Frost Protection
Even after your target date for when to plant herbs outside in PA, a surprise frost can happen.
Keep row covers, old sheets, or cloches ready to throw over your herbs on cold nights.
This saves your tender herbs if temps dip unexpectedly.
3. Test Your Soil Drainage
Herbs generally hate wet feet, so ensure your planting site drains well.
If your PA soil is heavy clay, consider raised beds or mixing in compost.
Good drainage also helps the soil warm faster in spring.
4. Mulch After the Soil Warms
Once your herbs are planted and the soil has warmed, add a light layer of mulch.
This keeps the soil moist, suppresses weeds, and prevents temperature swings.
But don’t mulch too early if the soil is still cold, as it can keep the ground chilly.
So, When to Plant Herbs Outside in PA?
When to plant herbs outside in PA comes down to your last frost date, soil temperature, and the specific herb’s tolerance.
Cool-season herbs can be planted outside in PA a few weeks before the last frost, typically from late March to mid-April.
Tender herbs should be planted outside in PA after the last frost, usually from mid-May to early June.
Perennial herbs offer flexibility with both spring and fall planting windows.
No matter where you live in PA, always monitor local forecasts and soil temps rather than relying on the calendar alone.
This gives you the best shot at a productive herb garden from spring through fall.
Happy planting, and enjoy those fresh herbs straight from your Pennsylvania garden.