When To Plant Herbs In Pa

Getting your herb garden started in Pennsylvania means working with the state’s unique climate. Knowing when to plant herbs in PA is the key to a thriving garden that gives you fresh flavors all season long. Our weather can be tricky, with late frosts and humid summers, but with the right timing, you can grow a beautiful and productive herb patch.

This guide will walk you through the best planting times for all your favorite herbs. We’ll cover everything from hardy perennials that survive our winters to tender annuals that need warm soil. You’ll learn how to use your specific USDA hardiness zone and get practical tips for starting seeds indoors and moving plants outside.

Pennsylvania spans USDA hardiness zones 5b through 7a. This means the last spring frost can happen anywhere from late April in the southeast to mid-May in the northern and mountainous regions. The first fall frost typically arrives from late September to mid-October. These frost dates are your most important calendar markers.

Herbs fall into three main categories for planting: hardy perennials, half-hardy herbs, and tender annuals. Each group has its own perfect planting window.

Understanding Your Pennsylvania Growing Zone

First, find your exact zone. This will fine-tune your planting schedule.

Zone 5b (Northwest & High Elevations): Last frost around May 15. First frost around October 10.
Zone 6a & 6b (Most of Central & Southern PA): Last frost between April 25 and May 5. First frost between October 10 and October 20.
Zone 7a (Southeast around Philadelphia): Last frost around April 15. First frost around October 25.

When in doubt, wait a week. Planting to early into cold, wet soil can stunt growth or kill seedlings.

Planting Hardy Perennial Herbs

These tough herbs survive Pennsylvania winters and come back year after year. You can plant them in early spring as soon as the ground is workable, or in early fall.

Examples: Sage, Thyme, Oregano, Mint, Chives, Lavender, Tarragon.
Spring Planting: Plant seedlings or divisions 2-4 weeks before your last frost date. The soil is moist and cool, which helps them establish roots.
Fall Planting: Aim to plant at least 6-8 weeks before your first hard frost. This gives the roots enough time to anchor before winter.

A tip for mint: always plant it in a container or a seperate bed. It spreads aggressively and can take over a garden if left unchecked.

Planting Half-Hardy and Tender Perennial Herbs

These herbs like warmer weather and won’t survive a harsh PA winter. They are best planted after all danger of frost has passed.

Examples: Rosemary, Bay Laurel, Lemon Verbena.
Best Time: Wait until nighttime temperatures reliably stay above 50°F. This is usually late May for most of PA. You can grow these in pots and bring them indoors to a sunny spot for the winter.

Planting Tender Annual Herbs

These herbs complete their life cycle in one season and are very sensitive to cold. They need warm soil and air to grow well.

Examples: Basil, Cilantro, Dill, Parsley (often grown as an annual), Summer Savory.
Best Time: Plant seeds or transplants outdoors 1-2 weeks after your last frost date. The soil should be warm to the touch. For a continuous harvest, sow seeds of cilantro and dill every 3-4 weeks through the summer.

Step-by-Step: Starting Herbs from Seed Indoors

Starting seeds indoors gives you a head start, especially for slow-growing herbs. It’s also more economical than buying transplants.

Timing: Check your seed packet. Generally, start seeds 6-8 weeks before your last expected frost date. For most PA zones, this means starting in mid-March.
Containers & Soil: Use clean seed trays or pots with drainage holes. Fill them with a sterile, lightweight seed-starting mix—not garden soil.
Planting: Sow seeds at the depth recommended on the packet. Most herb seeds are tiny and need only a light covering of soil. Gently water them in.
Light & Warmth: Place trays in a warm spot (65-70°F). Once seeds sprout, they need 12-16 hours of strong light daily. A south-facing window might work, but a grow light is often better in our cloudy springs.
Hardening Off: This is crucial! About 7-10 days before transplanting outside, begin acclimating your seedlings. Set them outdoors in a sheltered, shady spot for a few hours each day, gradually increasing their time outside and sun exposure.

Direct Sowing Seeds Outdoors

Some herbs grow so easily that it’s best to sow them right in the garden. They don’t like their roots disturbed.

Best Herbs for Direct Sowing: Dill, Cilantro, Parsley, Chives, Chervil.
When: Sow these seeds as soon as the soil can be worked in spring (for cool-season herbs like cilantro) or after the last frost (for warm-season herbs). The soil temperature should be at least 45°F for cool-season herbs and 60°F for warm-season ones.

Keep the seed bed consistently moist until the seedlings are well established. Thin them according to packet instructions to prevent overcrowding.

Monthly Planting Guide for Pennsylvania

Here’s a quick-reference calendar. Adjust dates based on your specific zone.

March – April

Start seeds indoors for basil, oregano, thyme, sage, and parsley.
As soon as soil is workable, plant bare-root or potted divisions of hardy perennials like mint, chives, and tarragon.
Direct sow parsley and chervil seeds in late April in warmer zones.

May

After last frost, transplant hardened-off seedlings of tender herbs like basil.
Direct sow seeds for dill, cilantro, and summer savory.
Plant rosemary and other tender perennials outdoors in late May.

June – July

Continue successive plantings of dill and cilantro for a constant supply.
This is a good time to take cuttings from herbs like mint and oregano to propagate new plants.

August – September

In early August, sow cilantro and parsley for a fall harvest.
Plant new perennial herbs or divide existing ones by early September to allow for root establishment before winter.

Essential Tips for Pennsylvania Herb Gardeners

Our humid summers can pose challenges like fungal disease. Good practices make a big difference.

Sunlight: Almost all herbs need at least 6 hours of full sun daily. Lavender and rosemary demand even more.
Soil & Drainage: Herbs hate wet feet. Ensure your garden bed or container has excellent drainage. Amend heavy clay soil with compost to improve texture.
Watering: Water deeply but infrequently, allowing the soil to dry out slightly between waterings. Its better to underwater than overwater most Mediterranean herbs.
Harvesting: Regularly harvesting encourages bushier growth. For most herbs, the best time to harvest is in the morning after the dew has dried but before the sun gets to hot.

FAQ: Planting Herbs in Pennsylvania

What is the best month to plant herbs in Pennsylvania?

There isn’t one single best month. For hardy perennials, early spring (April) is ideal. For tender herbs like basil, the best month is May, after the last frost. Fall (September) is also excellent for planting many perennial herbs.

Can I grow herbs in pots in PA?

Absolutely. Container gardening is a fantastic option. It provides perfect drainage and allows you to move tender plants indoors for winter. Just ensure pots are large enough and have drainage holes.

When should I start herb seeds indoors in PA?

Start most herb seeds indoors 6 to 8 weeks before your last spring frost date. For zone 6, this is typically mid-to-late March. Always check the seed packet for specific recommendations, as some herbs germinate faster than others.

Which herbs come back every year in Pennsylvania?

Hardy perennials like mint, chives, thyme, oregano, sage, and tarragon will reliably return. With extra winter protection (like mulch), lavender and rosemary can sometimes survive milder winters, especially in zones 6b and 7.

How do I protect my herbs over a PA winter?

For perennial herbs in the ground, apply a 2-3 inch layer of mulch (like straw or shredded leaves) after the ground has frozen in late fall. This prevents freeze-thaw cycles that can heave plants out of the soil. For potted tender herbs, bring them inside before the first frost.