While the warmer months are undoubtedly the main ‘boom time’ for many garden pests, don’t let this fool you into thinking winter is problem-free. From peckish mammals to newly hatched caterpillars and plenty more in between, there is a whole host of hungry creatures that can catch gardeners off guard at this time of year. Read on for our handy guide to protecting your plants against winter damage, with a few tips for how to reduce problems later in the year thrown in too. Prior preparation and all that!
Of course, it’s important to note here that while ‘pests’ to us, these creatures are simply doing their best to survive. Where possible, we recommend that all garden life should be left alone as part of a healthy, biodiverse ecosystem. By and large, this should be possible, providing you:
- Grow plants well suited to your conditions
- Avoid plants known to be highly susceptible to problems, e.g., things like box (blight), solomon’s seal (sawfly), fuchsia (gall mite), and brassicas (cabbage white caterpillar)
- Go for cultivars specially bred to have increased resistance to pests and diseases
- Buy your plants from reputable sources
- Keep on top of watering and feeding needs
- Apply an annual mulch
- Encourage a diverse array of wildlife into your garden
Ensuring your plants are healthy and thriving is the single best way to ward off problems. Having said this, we also know how frustrating it can be when prized plants come under attack. With that in mind, we thought we’d share our ‘at a glance’ guide to potential winter pest problems, along with the most sustainable and ecologically friendly ways to manage them.
Garden pests to watch out for in winter
-
Caterpillars
If you were dismayed last spring to see the leaves and blossom of your fruit trees eaten before they had even opened, and then went on to have a disappointing crop of fruit, there’s a good chance you’re dealing with winter moths. These pupate in the soil and emerge as caterpillars during winter and spring, when they crawl up the trunk and chomp away on buds and new shoots.
To interrupt the cycle, many gardeners apply grease around the trunks from late autumn to early winter (November is ideal). The easiest method is to go for special, ready-made grease bands, which should be fixed to the trunk approximately 45cm above soil level. Be aware that these traps will kill other beneficial insects too, so only use if absolutely necessary, and remember to remove when the females cease to be active in April.
Plums, cherries, apples and pears are the main fruit trees favoured by winter moths. Many ornamental trees are also affected, though as these are not grown for productive purposes the damage is usually considered more tolerable.
-
Slugs
While snails usually hibernate during winter, slugs remain active and will continue to feed whenever temperatures are above freezing. At this time of year, they eat mainly decaying leaves and so tend to go ‘under the radar’, though their presence will be felt in spring when, along with newly awakened snails, they gorge on all that lovely fresh plant growth.
Although spring slug defences may be the last thing on your mind as you settle with a good book in front of the fire, taking steps now can significantly reduce problems later.
At this time of year, the most effective intervention is trapping. A shallow dish sunk into the soil and filled with beer and works well (the beer remains effective for 2-3 days), or another tried and tested method is to lay old cabbage leaves or empty fruit skins (such as grapefruit or melon) on the surface of the soil, checking and emptying every morning. The most humane way of disposing of slugs is to either release them in a local wood, or bag them up and put in your freezer before binning them. You’ll feel more than a little bit bonkers doing either of these things, but they are said to cause the least amount of suffering.
While vigilance on your behalf is important, it is unlikely to make much of a dent on slug numbers without having allies in the natural world also working on the case. Hedgehogs are brilliant slug-hunters, as are foxes, birds, frogs, and toads. Learn how to encourage these into your garden in our How to create a wildlife friendly garden blog, and check out our RSPB-approved bird-friendly hedging to entice even more feathered friends your way.
-
Squirrels
At this time of year, these soft, scampering creatures become decidedly less charming to many gardeners, by seeming to assume that we have kindly buried our spring bulbs as a winter treat just for them. With a particular fondness for tulips and crocus, squirrels can undo hours of planting in a matter of minutes, our plans for a cheerful spring display destroyed in the swish of a tail. Given the chance, they are also partial to a good old raid of the bird feeders.
Chicken wire pinned to the surface of the soil after bulb planting can be a good deterrent, as can burying something prickly amongst the bulbs such as stems of gorse or holly. When shopping for bird feeders, remember to outsmart the crafty so-and-so’s by opting for a squirrel-proof design. Decoy predators such as owls are said to work if placed in nearby trees and moved around every few days.
-
Rabbits
We all know that rabbits love to graze on the soft, green growth of garden plants in the warmer months, but did you know they can cause a different kind of damage in winter? During spells of frost and snow when other vegetation is unavailable, hungry rabbits often graduate to stripping the bark off young trees. This can severely damage the tree, and, if the gnawing goes all the way round the trunk (known as ‘ringbarking’), can even result in its death.
If you know there are rabbits in your area, we strongly recommend using rabbit guards on newly planted trees to prevent damage of this kind.
-
Mice and voles
During colder weather, you may become aware of mice and voles entering coldframes and greenhouses where they can munch their way through vast numbers of seedlings, sometimes destroying the whole lot in one night. They also have a tendency to nibble on shed-stored fruit such as apples, strip the bark from young trees (much like rabbits), and eat newly planted crocus bulbs (that’s if the squirrels haven’t got there first).
While frustrating, we urge you not to trap or kill these creatures as they play a vital role in the garden food chain (predating on slugs and snails, and themselves falling prey to birds such as owls, kestrels, and buzzards). Instead, try to tolerate them if you can, and make any affected places as ‘rodent-proof’ as possible (i.e., seal any gaps, and keep the space immediately around them clear and tidy). Bluebells, daffodils, and allium are also said to act as deterrents, as well as looking lovely!
-
Birds
While birds are a beloved and crucial part of the garden ecosystem, we admit they can have a few pesky habits when it comes to our gardens in winter. Edibles such as brassicas can attract unwanted attention, particularly from pigeons, and you might find winter bedding lying on its side, popped out of the ground by an inquisitive beak.
Traditionally, the advice was to run cotton thread back and forth above vulnerable plants, but nowadays this is not recommended as birds can too easily become trapped. Instead, cover edibles with a brightly coloured, fine mesh netting (checked daily to make sure no birds are entangled) and consider a deterrent kite shaped like a bird of prey. These relatively recent introductions have been found to be more effective than scarecrows or reflective CDs.
House plant pests to watch out for in winter
-
Aphids
Outside, the main danger period for these sap-sucking pests is March to October, however on houseplants aphid infestations can happen at any time of year. On milder days, move the affected plants outside for a few hours so birds can hungrily feast on these tiny green or black insects. Alternatively, try wiping them off with kitchen paper (you’ll need to do this repeatedly until the problem has completely gone), or in severe or persistent cases, introducing biological controls. While this may sound intimidating, it is usually very simple and tends to involve just a few seconds of sprinkling the contents of a sachet or tube around the base of the plant. This contains natural predators (often microscopic), which will reduce or eradicate the pest, usually without you even knowing they are there.
This RHS biological control document is very useful for both identifying the appropriate control and recommending trusted suppliers.
-
Sciarid fly
Also known as fungus gnats, you will see these little flies running around on the compost of houseplants, as well as flying in the air around them. While these pests can crop up at any time of year, they are more noticeable during winter due to us (and them) being confined indoors more. Although they are harmless to established plants, these flies can damage seedlings and cuttings, and large numbers can be irritating to live with.
Sciarid fly thrives on moist compost, so allowing your houseplants to dry out between watering can help, as does using a mulch of horticultural grit. If the problem persists, biological controls are known to be very effective (see above).
Final top tips for protecting your garden against winter pests
If you follow the advice above, the likelihood of any major pest issues in your garden should be relatively low. Finishing off are our two final golden rules:
-
Keep your garden tidy
There’s a fine line between creating a natural haven for wildlife and giving pests free reign. While it’s important to leave twigs and leaves as overwintering opportunities for insects, aim for this to be a few deliberate, out of the way piles rather than an entire garden covered in debris. Keep the space around sheds, greenhouses, and coldframes clear so there is less cover for mice and voles, and regularly tidy the area beneath bird feeders to avoid attracting rats.
-
Look out for early telltale signs of pests
When it comes to garden pests, it is usually far easier to ‘nip them in the bud’ than tackle once they’ve become an established presence in the garden. For this you’ll need to channel your inner detective – regularly carrying out a close inspection of your garden to identify suspected pests by the clues they leave behind. Slime trails in the morning? Signs of digging where you’ve planted spring bulbs? Teeth marks on young tree trunks? Holes in your winter kale leaves? Most of these won’t be glaringly apparent unless you deliberately look for them, making it important to stay connected with your garden, whatever the weather.
We hope you’ve enjoyed our lowdown on common garden pests to look out for during winter. The advice essentially boils down to growing healthy plants, working to achieve a biodiverse garden, and taking gentle, intelligent measures to protect precious plants from anything that wants to eat them! Simple really.
For more no-nonsense, jargon free gardening advice, head over to our regularly updated blog.
