You Must Check Drainage Holes Before Winter to Save Plants

Plants in raised containers against a backdrop of rain — (Image credit: Getty Images/Jacques Hugo)

Come winter, a lot of attention focuses on the damage that frost poses to plants in containers. However, there is a hidden danger lurking beneath the surface that can kill your plants – and it is really easy to avoid.

Drainage is integral to successful container gardening. If drainage holes get blocked, the pot fills with water, and plants suffocate. It can mean a death knell for plants during wet winters, especially when this excess water freezes and encases them in a block of solid frozen soil.

You need them in the base of pots, but you must also remember to check drainage holes before winter. It takes little to no time to assess if they are clear and unblock them if needed. A set of pot feet (like these on Amazon) is also a winter essential for keeping potted plants healthy over the colder months.

Winter Dangers of Blocked Drainage Holes

Foxgloves in vintage copper container outside a summer house

All pots and planters need drainage holes to allow excess moisture to escape. However, not all containers you can buy have them. That is why it’s crucial to check every pot before planting in it. Thankfully, it is simple to add drainage holes to planters with an electric drill (available at Ace Hardware).

Over time, though, drainage holes can block. This can be due to compacted soil, debris, pests, roots, or a buildup of crystallized minerals or salts. It becomes important to check that pots drain properly, especially ahead of winter. Blocked drainage holes are a simple winter container gardening mistake to avoid – it takes little time to check and fix.

Blocked drainage holes and wet, freezing winter weather can kill plants. Just as you make efforts to protect pots from frost, you also must think about preventing pots from waterlogging.

When pots waterlog, the plants are starved of oxygen. When the soil gets fully saturated, all the air pockets fill with water. This means a lack of oxygen, which starves the roots and causes rot.

Symptoms of a starved plant include yellow foliage, wilting, and then dieback. Under the soil surface, decaying roots turn black, mushy, and have a sour smell. The waterlogged soil also becomes a breeding ground for fungal diseases, including botrytis and wilt.

Any plant sitting in waterlogged soil during winter not only risks rotting, but also freezing to death. All that moisture in the soil can freeze solid during a frost. Any plants in containers are more susceptible to frost compared to those in the ground, but even hardy plants won’t survive sitting in a pot full of frozen soil.

The pots are also at risk as frozen soil expands and breaks them. When water in the soil, and any moisture in a porous pot material, freezes and expands, it can lead to your favourite terracotta planters shattering during winter.

How to Avoid Problems

It takes little time and effort to protect container plants from winter weather and keep your pots from waterlogging. It can be a five-minute job to add to any fall gardening checklist – though it may take longer depending on the size of your pot collection.

It starts with taking each pot and checking that the drainage holes are clear and functioning as they should. You may be able to tell by looking at the plant or the soil. More often than not, though, it will require lifting or tilting the pot to see the base.

Blocked drainage holes are easy to spot, and thankfully they are also simple to clear. Take a chopstick or wooden skewer (you can get a pack of wooden skewers on Amazon) and push it through each hole before twisting it to clear any debris that may be blocking it.

Once the holes are unblocked, go around and remove any plant saucers that are underneath the containers. They aren’t necessary for winter and, in fact, can create potential risks. Removing them ensures the pot will not sit in water or frozen water through the winter.

Containers also should not sit directly on cold, wet paving or concrete, which essentially seals the drainage holes. Instead, place them on pot feet to raise the containers off the ground so they can drain freely over winter.

To protect pots and planters from frost, consider moving pots together for winter. Grouping them together in a protected spot creates a beneficial microclimate that traps heat and shelters them. If you put them against a wall or beneath an overhang or eave, this also shields them from rain.

Finally, check your plants over the winter. Look for signs of overwatered plants, including discoloration, wilting, or mold growing on the soil surface. If you worry that they are getting too much rain, move them somewhere sheltered from the elements.

What to Shop

We mentioned that porous materials like terracotta and clay are vulnerable to cracking and shattering during the winter.

This makes fiberglass, fiberstone, resin, and wood among the best container materials for winter gardens, as they are more resistant to freezing temperatures. To protect containers against the worst of winter, wrap them in covers, such as these winter pot covers on Amazon.

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Drew has worked as a writer since 2008 and was also a professional gardener for many years. As a trained horticulturist, he worked in prestigious historic gardens, including Hanbury Hall and the world-famous Hidcote Manor Garden. He also spent time as a specialist kitchen gardener at Soho Farmhouse and Netherby Hall, where he grew vegetables, fruit, herbs, and cut flowers for restaurants. Drew has written for numerous print and online publications and is an allotment holder and garden blogger. He is shortlisted for the Digital Gardening Writer of the Year at the 2025 Garden Media Guild Awards.