December 17: Sow seeds; try not to overheat greenhouse plants; looking after container plants in winter
This is the time of year when the gardening is best done inside. We are about to start thinking about sowing next year's summer bedding and getting the vegetable seeds started to get a long season. If like me you have been to busy with everything else, try and plan your garden or read the seed catalogues and get your order in.
•A Christmas cactus in full flower is a wonderful sight and Schlumbergera species can be covered in flowers for the best part of the winter but it does take a little know how to keep them in good condition. The crucial thing is to not move the plant unless you really have to as any movement can cause bud drop. Moving the plants is the main reason for the lack of flower. Also, never repot until the roots are filling the container as this, too, has a tendency to put the plant off flowering for some time. Water and feed, Christmas cactus freely with a high potash fertiliser, such as tomato fertiliser when they are in flower. Although these are succulent plants, they do need a lot of moisture when the flowers are forming. If you get one for Christmas, keep it in a bright position at a constant room temperature. Once the flowering has finished, reduce the watering and water sparingly for the rest of the year. To get the best flowers for next year, allow the plant to dry out for at least six weeks during the summer and then start to water more frequently in November. It is possible to keep the plant outside in a half shaded spot during the summer months.
•In the greenhouse, it is important to continue caring for plants over winter although it is a tricky business when temperatures plummet. Try not to overheat the greenhouse as it costs too much (for one thing) but it can also cause the plants to produce fleshy new growth, which is vulnerable to frosts. Avoid too much water. If anything, it is better to be on the safe side and keep your plants a bit dry and take care not to slop water on the floor of the greenhouse or onto the foliage of the plants. Plants in full flower for Christmas and New Year will need plenty of water to keep them producing blooms. These can include indoor Azaleas, Solanum and bulbs.
•A question often asked is 'How do I look after my container plants in winter?' Most people are aware of winter flowering pansies, bulbs and ornamental kale which pretty much take care of themselves in winter but many potted containers will have shrubs like camellias and even dwarf trees such as Japanese maples and these tend to stay in the same pots for years at a time. During the wet winter months, the compacted compost and poor drainage can kill these expensive plants. One way to protect these is to raise the pots on feet, pallets or bricks to allow excess rainwater to drain away. Top dress with bark chippings or grit to help water drain away from the neck or trunk of the plant. If the weather is very wet, it is worth using a piece of plastic to cover the pot and keep off the worst of the wet but remember to check the plant is not drying out on warmer days. Wind chill is every bit as destructive as over watering, and fragile trees such as Japanese maples are especially vulnerable to winter winds. Place the pots in a sheltered corner, and wrap the plants loosely with fleece.