What does it mean to 'overwinter plants' and why is it so important to help gardens survive the cold season?

Once the winter weather hits, your plants become extremely vulnerable to heavy rains and unforgiving frosts. This doesn't mean you need to bid your leafy friends farewell, though; instead, it simply means it's time to try overwintering.

It can feel impossible to protect your garden from heavy rain during the autumn and winter seasons, even more so when the frosts start taking over your plants. However, you needn't give up on your perennials and fruit trees simply because warm days of summer are over.

While you're sorting out your garden post-summer, it is a good time to take stock of which plants can be helped through the harsher months and learn how to overwinter them properly. To help you with this important task, we have consulted gardening experts to get the low-down on all things overwintering.

What does overwintering plants mean?

Overwintering is the process of protecting plants from frost and cold weather conditions during winter. This act of protecting plants is essential for ensuring their survival during adverse seasonal conditions to promote healthy growth in the spring.

"Overwintering involves protecting plants from freezing temperatures, which can catastrophically damage plant cells if the moisture within them is frozen, as the cell walls are ruptured, which can lead to parts of plants dying if not the whole plant," says Lucie Bradley, gardening expert at Easy Garden Irrigation.

"Temperature drops can also prevent plant roots from getting the moisture they need and could also cause them to freeze, damaging the cells and causing them to die," she adds.

Lucie also points out that you need to protect your plants from cold, dry winds, too, which can not only break branches and stems but also lead to desiccation. This is when plants dry out, which in turn makes them even more vulnerable to frost damage.

Lucie Bradley

With over 28 years working in the garden industry, Lucie has been fortunate enough to spend every day speaking to both amateur and professional gardeners. Encouraged to garden since she was old enough to walk, she believes that you can never know everything about gardening, as it is constantly evolving.

What are the benefits and disadvantages of overwintering?

As with many garden trends and practices, there are both advantages and disadvantages; however, overwintering does come with overwhelming benefits.

"Firstly, tender plants are protected from frost damage and cold weather that would otherwise damage cells or hinder their water and nutrient uptake. It will also help you save a lot of money as you can keep current plants; you do not need to buy new plants every spring," explains Richard Barker, horticulture expert and Commercial Director at LBS Horticulture.

"Some plants will be able to live for years, potentially growing larger and more productive thanks to overwintering. Plus, established plants will have a more developed root system, which enables them to bounce back faster and grow bigger in spring than new seedlings would," he continues.

On the other hand, there are a few things to consider when overwintering your plants. Once the labour that goes into the task is complete, you'll need to check plants for pests, prepare their protective measures, and continue to monitor their conditions for the entire winter.

"If you have a lot of plants or larger plants, it can be hard work, and if plants are stored somewhere that is too warm, they can potentially break dormancy too early in spring, and any new growth will be vulnerable to frosts," says Richard.

He also points out the issue of pests. If you choose to overwinter your plants indoors or keep pots close together, this can introduce and spread pests. Richard says that the humid conditions created by overwintering can also create an ideal environment for fungal diseases.

Richard Barker

With 4 years in the industry, Richard is an expert in horticulture and the commercial director at LBS Horticulture. He is keen to share his knowledge with both experienced and beginner gardeners, and prides himself in keeping up to date in the latest horticultural trends.

FAQs

Which common plants need overwintering?

If you've not already learned how to overwinter olive trees or dahlias, then you may not even know which plants in your garden need the extra help over winter.

"There is a range of common flowering tender perennials which you will need to overwinter, including cannas, coleus, cosmos, dahlias, fuchsias, impatiens, osteospermum, and mandevilla. All originating in warmer climates, they can suffer frost damage to their foliage, whilst frozen ground will not only prevent them from being able to absorb the moisture they need it will also damage their roots," says Lucie.

"Whilst many enter a dormant state to survive the winter months, ideally you would apply a thick layer of mulch over the ground where they grow to help insulate their roots, whilst some can be lifted from the ground and stored indoors until the following spring, including cannas, tuberous begonias and dahlias," she adds.

If you're wondering how to protect your banana plant in the winter, overwintering is the best method. That goes for other tropical plants too, Lucie says, "With tropical plants originating from hot and humid parts of the world, they are unable to survive the cold and frosty winter weather of the UK, so will need to be overwintered by either bringing indoors or protecting the roots of the more hardy tropicals."

Hardier tropical plants, like cordylines, can be left to grow outside as long as you wrap their main stem in horticultural fleece and insulate their roots with a layer of mulch.

"There are several traditional herbs which you will need to overwinter, including basil, lemongrass, rosemary and sage. These tender herbs need to be dug up and overwintered indoors or in a greenhouse or cold frame so that they are kept frost-free, as freezing temperatures can damage their roots, resulting in them dying," finishes Lucie.

What are the best methods for overwintering?

From mulching to glass cloches, there are many ways you can successfully overwinter your plants during the wet seasons. No matter what way you choose to overwinter, there are some steps that need to be taken regardless.

“Overwintering your garden plants requires a bit of extra effort, but the rewards are well worth it for the new year," says Julian Palphramand, head of plants at British Garden Centres. "By following my tips below, you can help your plants survive the harsh winter months and emerge refreshed and ready to thrive in the spring. With a little care and attention, your garden can remain a vibrant and beautiful space year-round."

• Prevent disease: "Clear any fallen leaves, dead plants, and other debris that could harbour pests or diseases in your containers and borders," says Julian. "This will help prevent problems when warmer weather returns. Trim back perennial plants to encourage healthy growth in the coming season. Pruning also helps to remove any damaged or diseased parts."
• Provide protection: "A layer of mulch around your plants acts as an insulating blanket, helping to retain moisture and protect roots from freezing temperatures," Julia explains. "You can use organic materials like straw, leaves, wood chips or horticulture fleece."
• Move vulnerable plants: "If your plants are in containers, move to a sheltered location and reduce watering significantly during the winter months," suggests Julian. "If you can't bring them indoors, wrap the pots in insulation and move them to a sheltered location against a fence, hedge, or a row of tall plants."
• Feed and water: "While plants may need less water during the winter, it's important to avoid letting the soil dry out completely," warns Julian. "Check the moisture level regularly and water as needed. For a boost of nutrients, apply a slow-release fertiliser to your garden in late autumn or early winter. This will help to nourish your plants and prepare them for spring growth."

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Julian Palphramand

Overseeing the procurement and selection of indoor and outdoor plant varieties for the company's 62 retail stores across the UK makes Julian an expert in sourcing the perfect plants. His expertise in horticulture and his passion for fostering a love of plants among customers help drive the continuous growth and success of the group.

Why is overwintering so important?

With so many plants to bring indoors this winter, you may be wondering if it's really that important. After all, it's no easy job preparing every plant for harsh weather.

"Overwintering is important as many of the plants which we grow in our gardens have originated from warmer climates, which means that they are unable to withstand the freezing temperatures which a British winter can bring," starts Lucie.

"By providing these less hardy plants with some form of protection - whether that involves mulch to insulate their roots, fleece to protect their foliage or moving them undercover where they will be frost-free - means that they will be kept free from frost damage and be fit and healthy to start growing vigorously again in the following spring," she continues.

So make sure you add overwintering to your essential gardening jobs each year, you'll be glad you did when spring rolls around and your garden is still thriving and full.

If you didn't have a chance to bring your tender plants indoors this autumn, don't worry, you can still protect them from now on, thanks to the milder winter we're having so far.