Perennial herbs zone 7 (how to overwinter herbs)

Every home gardener has a few favorite herbs in their herb or vegetable garden. And these favorites tend to be perennial herbs that come back year after year.

Here in this article, we will share our favorite perennials and why we believe them to be the best perennial herbs for your garden.

We will also give you easy-to-follow tips and techniques to successfully overwinter a perennial herb whether you grow in pots or plant directly in the ground.

To round off the article, we will look at why we like to grow perennial herbs in our gardens.

9 best perennial herbs to grow as a container gardener

When I say best perennials, I mean best as in respond well to overwintering in our gardening zone.

Here, I would like to make one crucial point. We have successfully overwintered thyme and rosemary outdoors in winter temperatures of 15 below zero Celsius (5 Fahrenheit). We have protected our plants, and they have survived to come back the next growing season.

We have also lost plants in winters where temperatures rarely dipped below 5 degrees below zero Celsius (23 Fahrenheit). Why? It was a very wet winter with lots of rain.

It is not only about growing hardy herbs. Even the most notoriously winter-hardy herb will die if the roots are constantly wet.

1. Mint

Peppermint is quite a cold hardy herb and is grown as a perennial in zone 7. Generally speaking, established plants tolerate a cold climate better.

Other popular varieties include ‘Mojito’ mint (Mentha villosa), chocolate mint, and spearmint.

2. Sage

Sage is a great perennial herb
Salvia officinalis ‘Purpurascens’

Common sage or Salvia officinalis is one of our absolute favorites to grow as a perennial (zone 7).

And we always overwinter sage in pots indoors.

Managed properly sage can be grown as a perennial from zone 5 and probably lower.

Photo shows Salvia officinalis ‘Purpurascens’ grown in pot.

3. Lavender

Lavender is grown for tea and cooking but also as a decorative ground cover or edging plant for a flower bed. And even though lavender is often thought of as a perennial – it is not necessarily always true.

We primarily grow varieties of English lavender. And all types and varieties we have encountered are grown as perennials outdoors in zone 7.

There are however also hybrids with Portuguese lavender as well as other types like Spanish and French lavender that need to be grown in pots and containers and be sheltered over winter.

Lavender is also great for attracting pollinators. Another favorite use is to plant lavender in-between stepping stones to have them give off their wonderful scent as they are disturbed by passers-by.

4. Rosemary

Rosemary is a perennial often more easily grown from cuttings
Rosemary plant

Rosemary with its needle-like leaves requires well-drained soil to survive winter.

We always use organic matter and soil amendments like perlite to get the loosely structured and broken-up soil the plant needs.

We always overwinter rosemary indoors in pots.

Rosemary can be grown from seeds but also, and often more easily, from cuttings and root division.

5. Oregano

Oregano is a hardy perennial that can stay outdoors all year in hardiness zone 7.

The oregano plant goes dormant in the winter and then comes back in spring as the ground heats up.

Oregano, like many other herbs in the mint family, can be close to invasive if left unchecked. 

Interestingly many people believe marjoram and oregano to be the same herb. This is not the case and marjoram is a far less cold hardy herb than oregano.

6. Lemon balm

Lemon balm is best over-wintered in pots indoors
Lemon balm

Lemon balm is often listed as cold hardy in USDA hardiness zones 4-9 on seed packets. Still, we move our lemon balm indoors every winter.

We did lose a mature lemon balm plant (to freezing temperatures?) and have ever since moved the pots indoors for winter.

But, still to this day, I am not sure if it was the cold temperature or the wet February that followed (more likely) that killed the plant.

But, as lemon balm borders on being invasive in its growth, we prefer using pots to planting directly in our herb garden.

7. Chives

Chives are grown for flavor, texture, and color. Belonging to the same family as garlic and onion, it is also a great companion plant to use as a border for your herb garden.

Chives are a cold hardy herb and seed packets often list that it is a perennial in USDA hardiness zones 3-10.

Chives prefer full sun to half shade and a rich garden soil amended with compost.

8. Thyme

Thyme is a cold hardy perennial with evergreen leaves in many gardening zones.

There are even thyme varieties where seed packets list USDA hardiness zones of 2-10. Thyme requires soil that drains well and average soil quality straight out of the soil bag may be too compact.

Instead, use amended soil for better drainage and plant thyme in a sunny spot.

We have grown thyme in our garden beds successfully over the years. But lately, we have changed to using pots to control growth and spread.

9. Tarragon

We grow most of our tarragon in pots from the simple fact that French tarragon is grown from cuttings.

Russian tarragon can be grown from seeds and is also cold hardy with seed packets stating USDA hardiness zones from 4 to 7.

Understanding our method of overwintering perennial herbs

We grow in pots, containers, and grow bags as well as outdoors in raised garden beds and vegetable gardens.

And even though we grow in zone 7 (USDA zone 7), our method should work for you as long as you take the time to understand the logic behind what we do.

Remember that successful container gardeners are not limited by hardiness zones. We just adapt and make it work for us.

Temperature is not the only factor in play

Hardiness zones are determined by the range of the annual minimum temperature for an area – or basically, how cold it gets during the year.

And yes, the temperature is an important factor when it comes to the survival of perennial herbs. But it is not the only factor.

I have lost many perennial herbs to mild temperatures when the winters have been extremely wet.

And I have had plants overwintering successfully outdoors during dry but very cold winters (-20 Celsius /-5 Fahrenheit).

So why is this?

There are other important factors to understand

Apart from the coldest or minimum temperatures and overly wet winters you should also take factors like the length of the growing season and the warmest temperature into account.

You should also include factors specific to your garden, for example, exposure to wind and access to direct sunlight.

When you understand your actual growing climate, you will be able to adapt and be successful.

Understanding the pros and cons of your herb garden

No one garden is perfect for all herbs and vegetables at all times. And this is why you need to understand what perennials need and how herbs grow in your garden.

If your lowest temperature is freezing cold (-5 degrees Celsius / 23 degrees Fahrenheit) you should overwinter sage plants in pots indoors – even if they do well in the ground during the growing season.

And mild temperatures will most likely not be enough to help your rosemary plant survive if your winters are very wet.

5 steps to overwinter perennial herbs

1. There are 2 types of perennial herbs

You have perennials with more wooden branches like thyme, sage, tarragon, and rosemary. These Mediterranean herbs require good drainage and will not survive if roots are wet when they rest over winter. And they can be tricky to overwinter outdoors in climates with lots of rainfall.

Then we have the softer stemmed herbs like oregano, chives, and lemon balm. These perennials die down over winter and are often easier to shield, protect and overwinter.

Regardless of type, a perennial herb will often do better indoors over winter. The exception to the rule is mature and established plants that are better left to continue growing where they are planted.

How to transfer a perennial herb to spend winter indoors in pots

  1. Dig out the plant making sure to get as many roots as possible
  2. Plant in a pot and fill the pot with lean potting soil as needed
  3. Trim back plant gently (prune damaged, broken, and odd branches)
  4. Place indoors in a location with adequate light (indirect)
  5. Water gently as needed
Many hardy herbs are drought tolerant and prefer a mild dry instead of soil that is too wet. Here good drainage and well drained soil is key for a plant to survive winter. 

2. Leave your plant to wilt and go to rest naturally

We stop harvesting perennial herbs 4-6 weeks before their time to rest and over winter.

Harvesting late in the year risks stressing the plant unnecessarily and also removes branches and foliage that could help protect the plant from ice, snow, and drying winds.

3. Add mulch to the root area

Adding a thick layer of mulch (8-10 cm / 3-4 inches) over the root area will help protect the root system by regulating temperatures.

Mulching is not about “warming the roots”. When you mulch you help keep the temperature more stable as well as protect the roots from excessive wetness.

The ground will most likely freeze during winter. But mulching will prevent the ground from freezing and then thawing over and over again.

5. Prune and cut back branches in early spring

Come spring when the soil starts to warm up it is time to wake up.

This is the time to prune and cut back last season’s leaves and foliage. Many herbs like sage, thyme, and oregano will hold their foliage over winter.

Water your pruned herbs and watch new growth emerge from the root area.

Choose to grow an annual or perennial herb

Many herbs we grow are annuals. There are true annuals like coriander (cilantro) and there are herbs that we grow as annuals like like basil and Thai basil.

The joy in growing annuals is in the germination and sprouting of first leaves as well as watching the seedlings develop in the herb garden. However, you also know that you need to start again from seed when that first season is over.

We can of course prolong the life span by providing an organic amendment like compost in combination with pruning and repotting.

But still, when we grow annual herbs there is always an implied “best before date”. That day is when the plant feels tired and has already provided many wonderful harvests of fresh herbs.

Many perennial herbs challenge us as gardeners

Perennial herbs are popular with new gardeners, but maybe even more so with experienced and seasoned gardeners.

There is of course cost savings. Perennial herbs come back year after year giving us harvests without having to spend time and money on developing new young plants every growing season.

But then there is the other side. A perennial herb challenges us as gardeners. There are many ways to kill perennial herbs from one growing season to another. We need to get it right and it brings out the best in us as gardeners.

The fact is, perennial herbs that come back every year are, for many of us, a big part of our gardening experience. We get invested in our plants. And frankly, so we should.

Meet the author: Mattias is an experienced gardener spending most of his free time on his knees among herbs, plants, and garden vegetables. For the past two years, he has been sharing gardening projects and how-to tutorials on the NordicLavender website and YouTube channel.