Growing Tomatoes inside gives the plants better protection from the climate, always useful here in the UK. In general, this will mean growing them in a greenhouse, polytunnel or possibly a conservatory. Although there are now specially designed growhouses that can hold up to four tomato plants and can be erected on the patio (or wherever).
There are three main methods of cultivating indoor tomatoes, planting directly into the ground, planting into pots, planting into growbags. Of the three using growbags is my preferred method but I will cover all three here.
Planting directly into the ground
Tomatoes can be grown in a bed in the greenhouse using the same planting method as described for growing tomatoes outdoors. The downside to this using this method is that unlike planting outdoors where they will be part of the crop rotation cultivating them in a bed in the greenhouse means that the same soil is used year after year. This leads to a depletion of the nutrients in the soil, no matter how much fertilizer you use. It also leads to a build-up of disease in the soil. The way around this is to change the soil every two years, which is much more work than you might think.
Planting into Pots
The pots must have a top diameter of at least 12 inches and be at least 9 inches deep. First, put some broken crocks in the bottom to ensure good drainage. Then fill with a general-purpose compost and plant using the hole/fill method described in growing tomatoes from seed. Insert a cane to give support, if the plant grows very tall, you may need to give additional support to the cane at the top. Alternatively, you can tie some string to the roof of the greenhouse and then anchor it into the pot.
Planting into growbags
A growbag is a plastic sack filled with compost and will hold three tomato plants. The usual method is to cut the top of the bag along the lines indicated to make two flaps where each plant is to be planted and to cut some slits along the side for drainage. But follow the instructions on your bags. Once this is done make a hole in the compost the size of the pot that the pant is in, remove the plant from its pot and place it into the hole, firm the compost around the plant. Insert a cane for support or use string. Then water well.
As I said earlier using growbags is my preferred method, but I use a slightly different technique to the one just described. There are several reasons why I use this method, firstly I do not think that there is enough compost in a growbag to support three tomato plants, secondly watering and feeding can be haphazard both of which reduce your yield.
The method I use gives the plants more compost and makes watering and feeding much more accurate (you do have to do it though). I use something called a Plant Halo from Harrod Horticulture. These are 8-inch pots with a serrated edge and three will fit nicely onto a standard growbag. Screw the pot into the growbag in the same place as you have cut and then remove the plastic. Now half fill the centre with general-purpose compost, make a hole the size of the pot your plant is in, remove the plant from its pot and place into the hole, firm the compost around the plant. Insert a cane for support. Fill the outer part of the growpot with water. The outer part of the growpot is used for watering and the inner part for feeding. This allows for much more accuracy.
Because of the higher yield obtained by using this method I have been able to reduce the number of plants grown, hence giving more space in my greenhouse.
If you have planted cordon type tomatoes (see Tomato Types) you will need to remove the side shoots at least once a week, this is done so that the plant puts it’s energy into fruit production and not into foliage production. These side shoots start at the junction of the main stem and the leaf. The earlier these are removed the better. But be careful not to remove the trusses which are the stems that have the flowers on. One trick here is if you are short of a plant or two leave a side shoot to grow to about 6 inches cut it off and put it into a pot of wet compost this will develop into another plant.
Once the plant has set five or six trusses it should be stopped, this is done by removing the top of the main stem. Stopping encourages the plant to divert it’s energy into the fruit, helping them to mature before the end of the season.
At the end of the season, it becomes a race to get the fruit to ripen. I help this process by removing the lower leaves from the plant to expose the fruits to the sun. Now, this is where the crystal ball comes in before the first frost I harvest all fruit of a reasonable size, green ones can be used for chutney etc, or ripened off.
I hope this has given you all you need to know about growing tomatoes inside.