When I posted on twitter that I had sown my tomatoes in January, a few people seemed somewhat puzzled and suggested that the frost would have them and it was too early. On twitter it's hard to explain planting methods so I'll take the opportunity to discuss it here. (Pic below - Alicante tomatoes, with Defender courgette and a California sweet pepper).
My tomato plants never go outside these days, they are always under glass. I used to grow tomatoes outside, the bush type Red Alert cherry tomatoes were my favourite, but since I've had a greenhouse I go for indoor varieties because I can grow bigger tomatoes, get more of them and, avoid the all too common blight.
My tomato growing season starts around the 20th of January when I sow seed and place in a heated propagator in the house. Tomatoes can be grown from January to early March indoors, a heated propagator is handy but a warm windowsill with seeds in cells or a pot covered in a clear plastic bag with an elastic band will do the job.
What variety should you grow? Well, people rave on about Shirley F1 for greenhouse tomatoes but I've tried these and found them to be very expensive (£3.00 for a measly 12 seeds) and I had poor germination for early sowing. However, these are really popular so give them a go, you might get on better than me with them. Personally, I tend to sow cheap (£0.99p for loads) Alicante tomatoes which provide masses of good mid-sized 'normal' tomatoes. I also grow a few large Marmande 'beafsteak' type tomatoes, useful for pasta sauces. I used to grow the 'cherry type' varieties and you can't really go wrong with the cheap Gardener's Delight or Tumbler F1 if these are your bag. If you want to grow outside then go for a bush type like Red Alert though you can grow most types of toms in a good sized pot next to a sheltered south-facing wall. Check the packet to see if they are indoor/outdoor varieties.
A quick word on 'determinate' and 'indeterminate' tomatoes. Determinate types take little looking after in terms of removing shoots, they grow in a bush-like manner and should be left to get on with it; determinate types are usually outdoor varieties. Indeterminate tomatoes, usually indoor varieties, need to be tied to a cane or twisted around a vertical string as they grow; in other words the plants need support. Indeterminate tomatoes also need to be encouraged to grow into a strong single main stem so, all the side shoots need to be removed otherwise multiple stems will develop. Side shoots will grow between an existing horizontal leaf-stem and the main vertical stem - these need to be pinched out as they appear, leaving a single stem to grow up. Again the packet will tell you what's what. (Pic above - side shoot to be removed on indeterminate varieties. Pic below - first 'true' leaves develop on a seedling).
After sowing in a wide pot or cells, the tomatoes will (hopefully) germinate. As soon as enough appear, get them out of the propagator/remove the plastic bag and get them on a sunny windowsill. As it's early in the year I move my seedlings around throughout the day to get the best sunlight, if you have a south facing window then you're sorted. After germination the plants will put out a pair of elongated, smooth seed leaves; the next leaves the tomatoes will grow will be totally different, these are 'true' leaves, typical looking tomato leaves.
The hardest thing with early sowings of tomatoes is to keep them healthy through the short days of February and early March. Give them as much sunlight as possible, it's just too cold to put them in an unheated greenhouse, keep them in the house until things warm up. Don't over-do the watering either, I have a small drinks bottle that lets out a few drops at a time, I add water sparingly to the compost when it starts to dry out, usually a little once a day; don't soak the plants and keep them wet as they can 'dampen off', i.e go mouldy and die. Plants will go a bit 'leggy' due to the short daylight hours, i.e, they might look a bit spindly. Don't worry too much about this, just ensure that you turn them a quarter/half turn each day so they grow evenly towards the light.
When the seedlings have a couple of 'true' leaves, it's time to pot them on into their own small pots. If you've sown in cells or sprinkled seed into a single pot, you will need to gently dib out the best plants (I use a pencil) and transplant them into a small pot of their own. I tend to fill a pot with multipurpose compost, mixed with a bit of cheap builder's sand (for drainage), make a hole with a pencil in the compost and drop the seedling in, remembering to hold it by the leaves not the stalk. The toms are usually a bit 'leggy' with a long stalk, no problem, you can transplant them deeper; drop them further into your dibbed hole so the bottom most leaves are just above (but not touching) the soil in the new pot. Roots will grow from the buried stem; tomatoes benefit from being transplanted deeper.
Keep them indoors until the weather warms up a little. They can go into an un-heated greenhouse in March but beware of late frosts! If cold nights are forecast then cover them up with a bit of horticultural fleece or bring them back into the house. What's important now is sunlight. Towards the end of April the tomatoes can be planted out into their final large pots, grow bags or placed in their growing positions in the base of the greenhouse.
I grow in both large pots and direct into the soil in my greenhouse. I have experimented with a few methods and one that seems to work is growing in 'rings'. You can buy tomato growing rings for use in grow bags but I made a version for my greenhouse. I just cut the bottoms out of large pots then sink them half way into the soil of my greenhouse and fill them with new compost - the toms are planted into this. Disease build up is a problem when growing the same crops in the same place every year so the rings make it easy to replace the compost around the tomatoes without having to dig out the whole of the bottom of the greenhouse. The plants also get a few extra inches of depth for the roots to grow. (Don't forget to sink a cane next to your plant). (Pic below - toms planted out in my greenhouse using homemade 'rings' to provide extra depth and fresh compost).
You do have to keep an eye on indeterminate varieties as the side shoots will start to appear quickly. Check the plants over every few days, pinching out side shoots and tying in the main stem to the cane. Start feeding your plants with a liquid tomato fertiliser (goes in water - see fertiliser packaging for quantities and frequency) when the first 'truss' appears. You will recognise the truss as it will look different to the leaves as it will initially sprout flowers, the petals of which will die back revealing tiny green balls that will grow into the tomatoes. Trusses will develop up the main stalk of indeterminate plants every few inches or so; once your plant has reached at the most 7 or 8 trusses, or has grown to the roof, whichever is sooner, pinch out the top of the plant to stop it growing.
This may be a debatable topic but I'm in the camp that partially defoliates. When the first tomatoes have developed into a decent size but are still green, I begin to remove some of the larger lower leaves from the plant. I don't remove them all but just enough to let more light to the lower trusses. I work my way up the plant, taking out over half the leaves to let light in to ripen the tomatoes. This works for me as I find that modern varieties can have too much leaf growth. Of course, if you have outdoor bush determinate varieties, you just let them get on with it.
That's it really, keep pinching out side shoots, tying-in for support, feeding and leaf snipping (or just grow a bush type) - you should get a decent crop of lovely red tomatoes well into the late Autumn.
