By Linda Lane, managing director of Griffin Glasshouses
There is always work to be done in a greenhouse, even in December. Indeed, there is often a lot of colour in this darkest month of the year with cyclamen, primula, azaleas and other plants destined for the house about to break into bloom in time for Christmas.
The secret to a healthy and successful December greenhouse – heated or not – is maintaining a good ventilation flow. But do watch out for potentially fatal draughts and remember to close up doors and windows after a sunny day. Check all plants regularly for signs of disease or infection and treat accordingly. Remove all dead and yellowing leaves and ensure that the soil surface is clean and healthy.
Maintaining a high standard of greenhouse hygiene is very important. A warm, Sunny day will quickly create a moist, humid atmosphere that is perfect for a variety of potentially harmful pests and diseases. I’ve said it before, but don’t use the greenhouse as an additional storeroom. Leave only essential items and tools inside.
December is rarely the coldest month but has the shortest hours of daylight. There is still time to insulate the inside of the greenhouse with bubble wrap and clips. Watering at this time of the year can be challenging as most plants do not need massive volumes and should be allowed to partially dry out. As a general rule, do not leave plants standing in trays of water.
There simply isn’t room in this brief monthly report to talk about pruning greenhouse vines. Once all the leaves have fallen is the time to undertake this work and it is best to seek specialist advice.
It may be December but it’s time to start seed planting in readiness for the 2023 season. Make sure all seed trays and pots have been washed and disinfected before starting work and that you have sufficient compost.
You can begin planting seeds of lettuce, carrots and some French beans but seek out those that are identified as suitable for planting under glass and follow instructions on the pack. If you plan to use a heated propagator, it is essential that the tray and clear plastic cover are clean and disinfected, and that all seed trays or pots are similarly treated before you start planting.
Happy Gardening!