7 plants to mulch in October – insulating these tender plants before frost can save them from a winter demise

Tender or borderline hardy plants won’t appreciate being left outdoors in your flower beds all winter. Abandoning them to the elements risks certain death, but rather than lifting them to bring them indoors, you can cover them with the protection of mulch. This can be enough to ensure these tender plants live to see another season.

Some gardeners will routinely lift their tender plants in the fall. However, that is not always a possibility. There are those without the space to store large numbers of plants indoors, while big clumps can be tricky to move. That is where you need to look for an alternative way to overwinter tender plants in a garden.

A thick layer of mulch, such as compost, straw, or bark chippings, can protect overwintering borderline hardy plants, potentially even more tender ones. This guide features seven potentially tender plants to mulch in October, including popular perennials, tubers, and bulbs.

Plants to mulch in October

Whether or not mulching the following plants in October is suitable for you will depend on your climate and US hardiness zone.

The cooler the climate, and the milder the winter, the higher the chance of success. Mulching tender plants to overwinter a garden is not advisable in very cold climates with extreme winters, or in gardens with heavy soil types that are prone to winter waterlogging.

Dahlias

Many gardeners annually lift their tubers and overwinter dahlias indoors in the fall, and may be nervous about the prospect of leaving their precious dahlias outdoors through winter. But, if you grow dahlias in US hardiness zones 7 to 10, you can overwinter them in the ground – with some protection, of course.

I worked at Hidcote Manor Garden in the Cotswolds for several years, and they now routinely leave their dahlias in the ground over winter rather than rigorously lifting and storing them.

Cut back the foliage after it has been blackened by frost, and place at least four inches of mulch over the plants. This can be a layer of compost, bark, straw, or horticultural fleece - or wool, as Hidcote does it.

If you opt for straw, fleece, or wool, it is advisable to cover it with a wire cloche to keep the material in place. For example, you could use these wire cloche plant covers at Amazon, secured to the floor with landscape staples to keep it all in place.

Canna lilies

Cannas are great for bringing a tropical garden vibe to any bed, with their bold and bright blooms that can last right up until the first frost. If you don’t want to lift and overwinter canna bulbs, the rhizomes are potentially more cold-hardy than you expect and can tolerate temperatures down to 15°F.

That opens up the possibility for leaving canna bulbs in the ground over winter in US hardiness zones 7 and up. Cutting the foliage down and piling a thick layer of mulch over the rhizomes can be enough to protect them from winter.

However, if temperatures drop very low or you have a prolonged wet winter, the bulbs risk being damaged. Keep an eye on the conditions with a soil moisture meter that also records soil temperature, such as this 4-in-1 soil moisture meter at Amazon. If the conditions look risky, you can lift the bulbs to mitigate any losses.

Verbena

Verbena is a gorgeous perennial, typically topped with tall stems and purple blooms, but you can also get white or blue verbena varieties to enjoy. There are hardy and half-hardy varieties, with most perennial varieties hardy down to US hardiness zone 4.

All types of verbena will benefit from a good layer of mulch over winter, with half-hardy ones certainly welcoming of that protective layer to see them survive the cold. The best types of mulch for this are dry ones, such as straw, pine needles, or shredded leaves.

One of the advantages of growing verbena is that the plants are easily propagated by seed or cuttings. So, if you want to hedge your bets, you can take verbena cuttings or grow verbena from seed to cover any potential losses from extreme cold or wet winters.

Begonias

Before planning overwintering begonias, it is important to understand the type you are growing. This is because there are several different types of begonias.

Tuberous begonias and waxy begonias are typically used for summer displays, while it is the hardy begonias that can remain outdoors all winter, albeit with a covering of mulch.

These hardy begonia varieties can survive temperatures down to 32°F and remain in the soil throughout winter in US hardiness zones 6-9. To do this, cut the foliage back once it turns yellow, and then add a four-inch layer of organic mulch over the plant.

Half-hardy tuberous begonias need lifting to store the tubers, while waxy begonias can be treated as indoor plants during the colder months.

Gladioli

Gladioli are guaranteed to brighten up any summer borders, coming in a range of shapes and colors. These splendid plants originate from warm climates, and the traditional way to overwinter gladioli is to dig up the corms in the fall and store them for winter. However, they can be left in the ground.

Cutting back gladioli and covering the corms with 3-4 inches of mulch in the fall can provide enough protection to overwinter most types of gladioli successfully down to US hardiness zone 4. In colder climates, or if you grow gladioli in pots, then you’re safer to lift and store the corms.

Agapanthus

When you grow agapanthus, it will be one of two types. Hardy deciduous agapanthus varieties will die back in winter and can tolerate cold conditions down to 14°F, while evergreen types are more tender and likely to be damaged by frosts. Different approaches are best for each type.

Deciduous agapanthus in flower beds can overwinter in the ground, covered with three or four inches of mulch to insulate them against the worst of the winter colds. This layer can be compost, straw, or leaves, but needs to be removed in the spring to allow new growth to come through.

The more tender evergreen agapanthus, including those growing in pots, are best brought indoors for winter, as they are more vulnerable to damage from cold weather. If your beds are prone to waterlogging during winter, it is advisable to lift any agapanthus to avoid them rotting in the soil.

Fuchsias

There are different types of fuchsias to care for; you need to know your plants before thinking about overwintering them.

Tender fuchsias are compact plants typically grown in containers or hanging baskets. These need to be brought indoors ahead of any frosts anywhere below US hardiness zones 10+. However, many people enjoy them as annuals and don’t overwinter them, or take fuchsia cuttings to have new plants the following year.

Hardy fuchsias are suitable for zones 6-10, but their exact hardiness will depend on the variety. Even though they’re known as hardy types, it can still help to take steps to overwinter fuchsia.

If you have cold winters and fuchsia growing in the ground, it is beneficial to mulch around your hardy fuchsias with a good layer of compost, bark, or straw. The plants may die back in winter, but, with protection to insulate the roots, they can start to shoot again from the base in spring.

If you have hardy fuchsias in pots, you could cover the containers ahead of winter to keep the plants insulated. For example, these plant pot covers at Amazon snugly fit around the containers to shield the roots from winter colds.

Shop mulch

There are potentially other plants to mulch in October on top of tender ones in your flower beds. Mulching also plays a useful role in overwintering vegetables. It not only helps with soil health, but mulching the vegetable garden in the fall can protect root vegetables, such as carrots and parsnips. The layer of mulch insulates the soil and the roots against the cold, allowing you to keep crops outside for longer and making it easier to harvest them.