Is it time to start filling up your greenhouse?
We still have a lot of empty benches, but good news, we have saved a lot of money on heating. But we will need to start potting next week and have just sown our tomatoes, peppers and chillies.
If you were lucky enough to see the sun last week, I think you will find it was powerful enough to warm your greenhouse up, always a good sign.
So can I start now?
It depends how deep you pockets are, do you spend some money and heat your greenhouse or wait patiently for some warmer weather.
I have mention before how bad the light levels are in January, we could choose to start later to save money on heating.
I think most amateur greenhouse are in two groups heated and unheated.
Heated greenhouse gardeners
heated greenhouse gardeners often have favorite plants they want to keep over the winter and using the heat they can start sowing and growing earlier. You can recognise them quite easily, the greenhouses will be lined with bubble wrap to save on heating costs, quite often you will find heated benches or propagators a sure sign of an enthusiast.
Heated greenhouse gardeners will be busy sowing seeds, most will have invested in some electric lights to make up for the poor sunlight. They soon start filling up with young plants, and can make sure the plants are ready earlier or bigger.
Unheated greenhouses
Unheated greenhouses often look like a storeroom, you might find frost tender plants covered in bubble wrap or fleece to protect them over the winter. A collection of gardening paraphernalia pots, compost, tools etc. Sometimes some winter bedding is growing like violas, bellis or primroses. With a unheated greenhouse you should wait a bit longer to start sowing, but you can take advantage of the warmth of your house to start seed sowing aiming to bring the established seedlings out to your greenhouse later on.
When do I start.
Heated greenhouse, you may have already started sowing or potting, that is okay, with the low light levels you just need to be extra careful with watering, temperature and humidity. Your bubble wrap will reduce any available sunlight by another 20-30%.
Unheated greenhouses are warm enough by early May, perhaps earlier in the south, to allow plants to grow. However, if you can provide some frost protection, it could be 3 or 4 weeks earlier, perhaps early April.
Using this we can decide when to sow, most seeds take 7-10 days to germinate, then 14-28 days in the warmth to establish, before heading off to the greenhouse.
So this means you can sow them in the house then move them to the greenhouse, or use a small heated propagator to heat a small area of the greenhouse.
As a rough rule of the thumb sow 6 weeks before you move them to a frost-free greenhouse.
In the South, this would be Mid February for April
Further North perhaps Mid March for May.
Top tips for early spring crops
- Clean your glass, dirty glass will reduce light levels by up to 20%
- Use the vents to reduce humidity and improve the CO2 levels. In a tightly insulated heated greenhouse CO2 levels can drop.
- Use lukewarm water when watering, cold water can chill the plants and compost for 24-48 hrs
- Warm up potting compost in the house, cold compost can take 3-4 days to warm up.
- Use bubble wrap on the sides of your greenhouse, allow the sunlight to penetrate the roof, use fleece or bubble wrap to seal the roof at night to save heat (We call that a thermal screen).
- Monitor the temperature with a digital thermometer, if you feel warm its probably too hot, the correct temperature will save you money.
- Hang up sticky traps to catch pests, everyone you catch now makes a big difference.
- Use a fan to move the air, it will reduce the humidity.
- Use plug trays when sowing seeds, it makes life much easier.
Need help choosing a Thermometer ? click how Warm is it
