Last weekend I was back in the polytunnel and sowed a few trays of seeds which I wanted to start on the heat bench (onions and leeks). It is still very early days but there are seeds that can be sown indoors both for planting outside later or to be planted in the polytunnel.
I use my tunnel for growing warm climate crops like tomatoes and peppers which wouldn't thrive outside but also to get earlier harvests of vegetables normally sown outdoors. I have made a quick list of what can be sown in February which I've split into plants for outdoor planting and plants for the tunnel but before we get into that I thought I better include some notes on early sowing.
I should point out that it is easy to get carried way with early sowing, especially if you have a propagator. It is easy to get seeds to germinate with heat at any time of the year but it's what happens next that might cause you problems. Here's a couple of things to think about before you go crazy with the seed packs:
Can the plants survive without heat once they have germinated? This is a good question as if plants need artificial heat after the have germinated there is a good chance they will need artificial light to balance the heat/light ratio. The problem is that seedlings growing in warmed compost will grow at a rate relative to the heat. They will also be expecting light levels that would normally correspond to that heat; if it's not there they will grow quickly to try to find it.
The resulting growth is spindly and weak which, in most cases, can't be corrected and will result in a poor yielding plant. This will often be the case with tomatoes sown too early which remained on a warm windowsill when light levels outside were too low. If you don't have a propagator where you can reduce the temperature and are growing on a windowsill you are better waiting till early March to sow.
If your plant can survive off the heat it is a different story. Once removed from the heat source growth will slow and be more in balance with the available light. We do this regularly in our tunnels and use heat just to get the seed to sprout before quickly removing the trays and placing them on an unheated bench (don't put them directly on the ground as it's too cold). You also need to cover with horticultural fleece at night to protect from frost.
When and where will the plants be planted out? There is no point in sowing early plants if they end up sitting in pots for longer than they should because it's too cold to plant them out. A seed sown in an 84 cell seedling tray (the handiest for most outdoor crops) will need to either be potted on or planted out in 4 weeks or the roots will coil around the inside of the cell and become pot bound.
It is important to know how long your seedlings can safely sit in the tray or pot and only sow them if they can be planted out or potted on to a larger pot at the end of that period.
Sometimes it is necessary to start plants early, usually to ensure enough time for fruit to ripen (e.g, tomatoes, peppers and cucumbers). These plants need to remain on the bench for a long period and will need looking after including feeding and re-potting in order to produce a top quality plant. There are few hardy plants like broad beans that will also benefit from an early start but in general you are better off waiting for the optimal sowing times.
Sowing Vegetable Seeds For the Garden I have already sown broad beans two weeks ago (I made a video btw, it's not my best work, a lot of 'em's' and 'er's', you can watch it above if you like) but last weekend I also did a couple of trays of onions and leeks.
Onions grown from seed need an early start to give enough time to form good size bulb. Leeks can be sown in February for an Autumn crop but I also sow in mid March and early May to have leeks through the Winter.
In general February sowings are best left until the middle of the month when light levels are increasing. At this point you can also sow oriental salads, early cabbage, turnip, spinach, lettuce and spring onions. Be aware that the success of these crops will be dependent on the weather outside in March, they may need cloches for protection.
For the Polytunnel Peppers, chillis and aubergines should be sown in mid February. You can also sow tomatoes towards the end of the month.
For early crops of 'outdoor' plants you can sow early cabbage, calabrese, cauliflower, celery, coriander, dill, kohlrabi, lettuce, mangetout peas, perpetual spinach, swiss chard and spring onions.
Using heated propagators Apart from broad beans you will need heat to germinate any other vegetables in February. There are a number of options including heated propagators of various sizes and price points (the Vitopod is the most expensive but it's also the best) and heated cables for making your own heat bench.
I have included a link to our propagation section below which you can access by clicking the blue button. If you need any advice on propagation or what heated propagator might best suit your needs please don't hesitate in giving me a call.