Planting herbs outside requires waiting until the soil has fully warmed in late spring. Knowing exactly when to plant herbs outside can mean the difference between a thriving garden and stunted plants that struggle all season. Many gardeners make the mistake of setting out tender herbs too early, only to watch them suffer in cold, wet soil.
This guide covers everything you need to know about timing your herb planting. We will walk through frost dates, soil temperature, and specific herb types so you can plant with confidence.
When To Plant Herbs Outside
The simple answer is: wait until after your last spring frost date. But that is only part of the picture. Soil temperature matters just as much as the calendar date.
Most culinary herbs are warm-season plants. They originate from Mediterranean climates. They need warmth to grow well. Planting them in cold soil slows root development and invites disease.
Here is a quick rule of thumb:
- Hardy herbs like parsley, chives, and thyme can go out 2-4 weeks before the last frost.
- Tender herbs like basil, cilantro, and dill need to wait until 1-2 weeks after the last frost.
- Very tender herbs like rosemary and lavender need warm soil (above 60°F) and no chance of frost.
Check Your Local Frost Dates
Your local frost date is the average date of the last spring frost in your area. You can find this online through your county extension office or a gardening website. Enter your zip code to get a specific date.
But remember: that date is an average. It is not a guarantee. A late frost can still happen. Always watch the 10-day weather forecast before you plant.
Soil Temperature Is The Real Key
Air temperature can be warm while the soil is still cold. Soil warms up slowly. Use a soil thermometer to check. Insert it 2-3 inches deep in the morning.
Target soil temperatures for common herbs:
- Basil: 65-70°F
- Cilantro: 55-65°F
- Parsley: 50-60°F
- Rosemary: 65-70°F
- Thyme: 55-65°F
- Chives: 50-60°F
- Dill: 55-65°F
- Mint: 50-60°F
If you do not have a soil thermometer, use this trick: sit on the ground. If it feels cold to your skin, it is too cold for most herbs.
Hardy Herbs: Early Planters
Some herbs can handle a little cold. These are called hardy herbs. They can be planted a few weeks before the last frost date. They will survive light frosts without damage.
Parsley
Parsley is a biennial, but most people grow it as an annual. It can go outside 2-3 weeks before the last frost. Seeds are slow to germinate, so soaking them overnight helps. Soil should be at least 50°F.
Chives
Chives are very cold tolerant. They can be planted 3-4 weeks before the last frost. They actually prefer cool weather. They will start growing as soon as the soil is workable.
Thyme
Thyme is a hardy perennial. It can handle light frosts. Plant it 2 weeks before the last frost. It prefers well-drained soil and full sun.
Sage
Sage is another hardy perennial. It can be planted 1-2 weeks before the last frost. It likes dry soil, so avoid overwatering. Sage is slow to start but very durable.
Mint
Mint is extremely hardy. It can be planted 3-4 weeks before the last frost. In fact, mint can become invasive. Plant it in a container to control its spread.
Tender Herbs: Wait For Warmth
Tender herbs cannot handle frost at all. They will die if temperatures drop below 32°F. Even a light frost can kill them. These herbs need warm soil and warm air.
Basil
Basil is the most popular tender herb. It is very sensitive to cold. Do not plant it outside until the soil is at least 65°F and all frost danger has passed. Basil planted too early will sit and sulk. It may develop black spots or root rot.
Wait until nighttime temperatures stay above 50°F. In most climates, that means late May or early June.
Cilantro
Cilantro is a bit more tolerant than basil. It can handle cooler soil, but not frost. Plant it 1-2 weeks after the last frost. Soil temperature should be at least 55°F. Cilantro bolts quickly in hot weather, so planting early gives you a longer harvest.
Dill
Dill is similar to cilantro. It prefers cool weather but cannot handle frost. Plant it 1-2 weeks after the last frost. Dill does not transplant well, so direct sow seeds in the garden.
Rosemary
Rosemary is a tender perennial. It is not frost hardy at all. Wait until soil is at least 65°F and all frost danger is gone. In cold climates, grow rosemary in a pot and bring it indoors for winter.
Warm-Season Herbs: The Late Starters
Some herbs need real heat to thrive. These are warm-season herbs. They should be planted later in spring, even after the last frost date.
Lavender
Lavender loves heat and dry conditions. It needs soil above 65°F. Plant it 2-3 weeks after the last frost. Lavender hates wet feet, so good drainage is essential.
Oregano
Oregano is a perennial but it prefers warm soil. Plant it 1-2 weeks after the last frost. Soil temperature should be at least 60°F. Oregano is drought tolerant once established.
Tarragon
Tarragon is a bit tricky. French tarragon is the culinary variety. It needs warm soil but not too hot. Plant it 1-2 weeks after the last frost. It prefers partial shade in hot climates.
How To Prepare Your Herb Garden
Timing is only part of the equation. You also need to prepare your garden properly. Here are the steps:
- Choose a sunny spot. Most herbs need 6-8 hours of direct sunlight per day.
- Test your soil. Herbs prefer slightly alkaline to neutral soil (pH 6.0-7.5).
- Amend the soil. Add compost or well-rotted manure to improve drainage and fertility.
- Remove weeds. Weeds compete with herbs for water and nutrients.
- Loosen the soil. Dig to a depth of 8-10 inches to help roots spread.
- Water deeply. Water the soil a day before planting to settle it.
Hardening Off Seedlings
If you started herbs indoors, you cannot just put them outside. They need to acclimate. This process is called hardening off.
Here is how to do it:
- Start 1-2 weeks before planting.
- Place seedlings outside in a shaded, protected spot for 1-2 hours.
- Increase time by 1-2 hours each day.
- Gradually introduce them to more sunlight.
- Bring them indoors at night if frost threatens.
- After 7-10 days, they are ready to plant.
Skip this step and your herbs may suffer transplant shock. They might wilt, drop leaves, or even die.
Direct Sowing Vs. Transplanting
Some herbs grow better from seeds planted directly in the garden. Others do better as transplants.
Herbs To Direct Sow
- Cilantro
- Dill
- Parsley
- Chives
- Basil (in warm soil)
- Fennel
Direct sowing is simpler. You do not need to harden off plants. But you must wait until soil is warm enough.
Herbs To Transplant
- Rosemary
- Lavender
- Thyme
- Sage
- Oregano
- Mint
Transplants give you a head start. You can buy them at a nursery or start them indoors 6-8 weeks before planting.
Regional Timing Guide
Your location affects when to plant herbs outside. Here is a rough guide by region:
Northern Climates (Zones 3-5)
Last frost is usually late May to early June. Soil warms slowly. Plant hardy herbs in mid-May. Wait until early June for tender herbs. Use black plastic to warm soil faster.
Central Climates (Zones 6-7)
Last frost is mid-April to early May. Plant hardy herbs in early April. Tender herbs go out in mid-May. Soil warms quickly here.
Southern Climates (Zones 8-10)
Last frost is February to March. You can plant hardy herbs in late winter. Tender herbs go out in March or April. Be careful of heat stress in summer.
Coastal Climates
Coastal areas have mild winters but cool summers. Soil stays cool longer. Wait until soil reaches 60°F before planting tender herbs. Use raised beds to warm soil faster.
Common Mistakes To Avoid
Even experienced gardeners make mistakes with timing. Here are the most common ones:
- Planting too early. This is the biggest mistake. Cold soil stunts growth and causes root rot.
- Ignoring microclimates. Your yard may be warmer or colder than the general area. Check your own garden.
- Not watching the weather. A late frost can happen after a warm spell. Always check the forecast.
- Overwatering after planting. Cold, wet soil is a death sentence for tender herbs.
- Planting in shade. Most herbs need full sun. Shade makes them leggy and weak.
Extending The Growing Season
You can start your herb garden earlier by using season extenders. These help warm the soil and protect plants from cold.
Use A Cold Frame
A cold frame is a box with a glass or plastic lid. It traps heat from the sun. You can plant herbs 2-4 weeks earlier inside a cold frame. It also protects from frost at night.
Use Row Covers
Floating row covers are lightweight fabric that lets light and water through. They add a few degrees of warmth. Use them to protect tender herbs from light frosts.
Use Black Plastic Mulch
Black plastic absorbs heat and warms the soil. Lay it down 2 weeks before planting. Cut holes for your herbs. This works well for basil and rosemary.
Use Raised Beds
Raised beds warm up faster than ground soil. They also drain better. This is a big advantage in cool, wet climates.
Herb Planting Calendar Example
Here is a sample planting schedule for a zone 6 garden (last frost around May 1):
- Mid-April: Plant parsley, chives, thyme, sage, mint.
- Early May: Plant cilantro, dill, oregano.
- Mid-May: Plant basil, rosemary, lavender.
- Late May: Plant any remaining tender herbs.
Adjust this based on your actual frost date and soil temperature.
Frequently Asked Questions
Can I plant herbs outside in March?
It depends on your climate. In zone 8 or warmer, yes. In colder zones, March is usually too early. Soil is still cold and frost is likely. Wait until at least April for hardy herbs.
What happens if I plant herbs too early?
They may not grow. Cold soil slows root development. Leaves may turn yellow or purple. The plant becomes stressed and more prone to disease. In severe cases, the plant dies.
Can I plant herbs outside in the fall?
Yes, for some herbs. Hardy perennials like chives, thyme, and mint can be planted in early fall. They will establish roots before winter. Tender annuals like basil should not be planted in fall.
Do herbs need full sun?
Most culinary herbs need 6-8 hours of direct sunlight. A few, like mint and parsley, can tolerate partial shade. But they will be less productive.
How do I know if the soil is warm enough?
Use a soil thermometer. Insert it 2-3 inches deep in the morning. If it reads above 50°F for hardy herbs or above 65°F for tender herbs, you are good to go.
Final Thoughts On Timing
Knowing when to plant herbs outside is not complicated. Check your frost date. Measure soil temperature. Watch the weather. Match the herb to the conditions.
Start with hardy herbs like parsley and chives. They are forgiving. Move to tender herbs like basil when the soil is warm. Use season extenders if you want to push the season.
Your reward will be fresh herbs all summer long. There is nothing like picking basil for pesto or rosemary for roasted potatoes straight from your garden.
Take the time to do it right. Your herbs will thank you with vigorous growth and abundant flavor.