What is my Plant Hardiness Zone?

Ever wondered why some of your plants seem to thrive while others just barely manage to survive? It could have everything to do with your hardiness zone. You might be asking, but what is my plant hardiness zone? In short, it’s a geographic area in which a particular plant can be expected to grow and thrive.

It’s important to choose plants that are suited to the hardiness zone where you live. In this post, we’ll explain everything you need to know about plant hardiness zones, including how they’re classified and what the differences are between hardiness zones in the USA and the UK.

Viola flowers in a terracotta pot in the winter frost

What Are Plant Hardiness Zones?

Plant hardiness zones are a way of classifying areas based on the average minimum temperature that they experience. This is important because it allows gardeners to choose plants that are suited to the conditions in their area. For example, if you live in an area with a mild climate, you’ll be able to grow plants that wouldn’t survive in a colder climate.

There are different ways of classifying plant hardiness zones around the world. Perhaps the most widely recognised system for defining zones is that created by the United States Department of Agriculture (USDA).

Hardiness Zone Maps

The USDA Hardiness Zone Map is the most commonly used classification system around the world. This map is divided into 13 different zones, ranging from Zone 1 (the coldest) to Zone 13 (the warmest).

USDA Plant Hardiness Zone Map
This map from the United States Department of Agriculture (USDA) shows the 13 zones used by gardeners in the US and beyond.

While certain USDA zones can be used to define areas of the UK, we also have more specific guidance from the Royal Horticultural Society (RHS), which uses a slightly different system. The RHS divides the UK into 7 different hardiness zones, ranging from H1 (the coldest) to H7 (the warmest).

UK Hardiness Zones

If you’re wondering which zone you’re in, the map below – from gardenia.net – provides a handy, visual guide to the UK hardiness zones.

This map from Gardenia.net shows the widely recognised UK Hardiness Zones

Once you know which zone you’re in, you can also use the following table for a clearer picture of what this means for your plants:

RHS-Hardiness Ratings UK
This table from the Royal Horticultural Society (RHS) gives some clarification about what the different zones actually mean in practical terms.

Why Are Plant Hardiness Zones Important?

Plant hardiness zones are important because they help gardeners to choose plants that are suited to the conditions in their area. If you choose a plant that isn’t well-suited to your hardiness zone, there’s a good chance that it won’t survive.

For example, let’s say you live in the UK in an area classed by the RHS as zone H5. This means that your area experiences average minimum temperatures of -15°C to -10°C. If you were to choose a plant that was only suitable for Zone 3 (average minimum temperatures of -5°C to 1°C), there’s a good chance that it would die when exposed to the colder temperatures in your area.

Rose Canina Plant covered in frost in cold winter garden

On the other hand, if you choose a plant that is happier in a colder climate than where you live, it might not thrive either. This is because plants often need a certain amount of stress in order to produce flowers and fruit. So, if you live in an area with very mild winters, choosing a plant that is only suitable for colder areas might mean that it doesn’t produce as many flowers or fruits as it would in a colder climate.

Of course, temperature isn’t the only factor that determines whether or not a plant will thrive in an area. Soil type, amount of sunlight, and rainfall are also important considerations. You might also be able to grow pants under cover or use other methods to expand your growing possibilities. But if you can find plants that are well-suited for your hardiness zone, then you’ll be off to a good start.

How to Grow Plants that are Outside Your Hardiness Zone

If you’re determined to grow plants that are outside your hardiness zone, there are a few things you can do to protect them from cold weather.

Firstly, choose plants that are more tolerant of temperature variations. For example, some plants such as fuchsias and geraniums are relatively cold-hardy, so they might be able to survive in a slightly colder climate than they are used to.

Secondly, you can also use growing techniques such as mulching and providing winter protection (e.g. insulating the root system) to help your plants survive the cold months. At the very least, you could use special fabric, such as gardener’s fleece, to give your plants a little extra protection from the elements.

Finally, you might be able to keep some plants under cover – in a greenhouse or cold frame. Plants grown in pots or containers could even be moved indoors during winter, providing there is enough sunlight available to keep them going. Somewhere like a cool conservatory might be the ideal spot for plants in the colder months.

Final Thoughts

In conclusion, plant hardiness zones are very useful because they help gardeners to choose plants that are suited to the conditions in their area. If you choose a plant that isn’t well-suited to your hardiness zone, there’s a good chance that it won’t survive. Use a hardiness zone map to find out what zone you’re in. Then when your choosing plants for your garden, you can be confident that they should be able to cope with the local climate.

Where do you live, and what’s your hardiness zone? Which plants do best where you are? Any tips for getting through the cold? Let us know in the comments!

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