A sudden cold snap or a prolonged period of chilly weather can cause damage to roots or tender shoots, while rain can harm the roots of plants as compost becomes waterlogged. Here’s how to keep your plants in good shape over the chilly months ahead.
Protecting pots from frost
Frost can easily penetrate the sides of pots and kill off roots, especially those that are made out of terracotta. Fortunately there are many ways of safeguarding them so they make it through winter.
If a cold snap is forecast, simply move plants that are at risk to a frost free place until the danger is over – a shed, garage or greenhouse is ideal. Alternatively, if you don’t have space indoors for a pot or it’s too heavy to move, wrap the outside of the container with a sheet of bubble wrap or hessian, ensuring it is held securely in place with garden twine.
For convenience, next time you pot up a plant, place a piece of bubble wrap around the inside of the container before adding compost – you’ll never have to rush out with sheets of protection material again.
Wrapping up pots can be a bit of a chore if you have a garden full of containers, so make life easier for yourself. Push pots up against the wall of the house, where it’s slightly warmer, and pack them together tightly so they help to insulate each other. A single strip of protection material can then be run around the outside of the group.
Many architectural plants come from tropical climates and need careful cosseting to help them survive. Sheets of horticultural fleece, bubble wrap and straw can be used to protect the tops of plants.
Gardening books often tell you to over-winter tender plants in a greenhouse or porch, but what if you don’t have one? If they are in small containers, find an empty spot on a light, sunny windowsill. If plants are too large to be indoors, tightly wrap the pots in bubble-wrap or hessian to protect the roots from frost. Group pots closely together so they help insulate each other and raise them on pot feet (or bricks) to let rainwater drain. When a cold snap is forecast, drape a sheet of horticultural fleece over the top. Some fruit trees are vulnerable to frost, so slip a fleece jacket (available from garden centres) over the plant, taking care not to damage buds or early flowers.
Surviving winter rain
Plants in pots are vulnerable to excessive moisture caused by winter rain. Wet, soggy compost or puddles building up at the base of pots can result in roots being starved of oxygen and literally drowning, leading to them rotting and the plant eventually dying.
To avoid problems, always buy pots with drainage holes in the base and fill with the right compost - most prefer a well drained, loam based compost, such as John Innes 3.
You can further reduce problems by raising containers up on ‘pot feet’. These are widely available from garden centres and may be made from terracotta, stone or cast iron. Some are wedge shaped, while others are more elaborate, but they all do the same job. Put three under a container to raise it 2-3cm above the ground, allowing excess moisture to escape through the drainage holes. The gap under the pot will also give plants a boost, by proving better air circulation to the root area.
Sorting out old pots
Sort your old pots out so they are ready for spring. Discard (or save for crocks) any that have cracks or breaks, then wash out the rest in warm, soapy water. Use a nailbrush, old toothbrush or even a specially shaped pot brush, aiming to remove any caked-on compost, along with pests or their eggs that may be lurking. Although it can be tempting to simply re-use pots, any pests or a soil-borne disease in dried compost can easily be passed on to whatever you decided to grow next.
Find out more about winter gardening