We know you love your Rhododendrons, Camellias and Azaleas but are they ready for the winter weather?
Pots and Containers
Plants in pots and containers are more vulnerable to problems than those planted in the ground. We all worry a lot about the cold temperatures and, although these can be an issue if they get too extreme, actually it is the wet weather that can do the most damage. This is because the plants rate of transpiration (breathing through the leaves) slows in colder weather and so the plant is unable to lose excess water gathering at the roots. The other danger to your plants is cold winds.
So how can you protect your plants?
If your pot is sitting on a flat surface water surface tension can be a problem. Remember this from school science lessons? This attraction creates a layer of water between the bottom of the pot and the surface it is sitting on. If this freezes then it effectively blocks the bottom of the pot and the pot will fill with water and if it stays like this the roots will die and rot away.
The easiest answer is to raise the pot off the ground using pot feet and so break the surface tension. These are easy to find at any good garden centre and you can usually find terracotta, stone or glazed versions to match most pots. Another solution is to sit it on a gravel surface where surface tension will not be an issue.
The other useful tip is to move any pots close to walls. They will be dryer, warmer and there will be less wind chill factor. If you don't have suitable walls then try moving them under the base of larger shrubs and trees, again this gives shelter and less fluctuation in temperature. What's lovely about this time of the year is that is you look closely at larger rhododendrons and camellias when getting them ready for winter you should be able to see next spring's flower buds.
TIP - Choosing the right sized container for your pot will help protect it from winter weather. The pot should be the same size or a little narrower than the canopy (this is the diameter of the leaves) of the plant. This allows the umbrella shape of the plant to help by diverting some of the excess water away from the rootball.
TIP - Improving drainage is always a bonus. Instead of the traditional broken crockery in the bottom of your pot use a thin layer of clean pine bark chips. These help break the surface tension on paving and so aid drainage.
Check any plants that have been planted less than a year to make sure that they have not slipped down too low in the soil. The top of the rootball should be level or up to 2cm higher than the surrounding soil. If not ease the plant up until it is, re-firm the soil around it and add a 5cm layer of pine bark chip mulch.
It is a good time generally to mulch. A mulch is simply a layer of another material on top of soil or compost. Choose a top quality 10-20mm chip size, it may be harder to find that the normal bark chips but it is a completely different quality. This mulch will insulate the soil keeping temperature fluctuations to a minimum but also help the soil aeration by reducing compaction. An important but less well known side effect is that the protected area under the mulch is the perfect home for bacteria and mircrorganisms which thrive and then help in breaking down the mulch. This process releases among other things humic acid in the spring, a wonderful substance that releases bound up nutrients such as phosphorus and iron to the plant, carbon dioxide to the plants and ammonia in the form of food (nitrogen) to the plant.
If your soil is a neutral pH, only just acidic or if your plant looks slightly pale this is a great time to apply sulphur chips over the roots to keep the pH nice and low. Like the pine bark chips it can be hard to find in a garden centre but is easy to track down online. Apply this great value, beneficial product now and again in April.
These precautions will hep your Rhododendrons, Camellias and Azaleas weather whatever the winter may throw at them and make sure they are in the best shape for the coming season!