Grow Your Own Tomatoes
In the UK, tomatoes are commonly grown in a greenhouse, although they can also be grown in mild, sheltered positions outside. Frames, mini greenhouses and cloches make it possible to grow tomatoes in less favourable areas.
Of the numerous tomato varieties, long stemmed crops are the most popular. Bush tomato plants are less common but do not require staking and trimming. In addition to red varieties, yellow fruits are also available.
Tomato Trusses and Leaves Explained
To save confusion, here’s an explanation of two common terms used when discussing tomato growing. A truss grows from the main stem and is the flower and fruit bearing part of the tomato plant. A single tomato plant will produce several trusses. A leaf is a lateral stem that also grows from the main plant stem and will produce no flowers or fruit - just foliage.
Growing Tomatoes from Seed
Depending on where you plan to grow your tomatoes, sow your seed around eight weeks before transplanting into the final planting positions. Outdoor planting takes place from early June, cold glass planting (non-heated greenhouses) in mid April and heated greenhouse planting from mid February.
Sow the tomato seeds thinly into a seed tray and cover lightly with sieved compost. Maintain the temperature at 18C (65F) until germination in 7-10 days. Be careful not to soak the seedlings too much but keep them evenly moist.
Pricking Out the Tomato Seedlings
Pricking out involves moving the tomato seedlings from the seed tray into small peat or plastic pots. Pricking out takes place 10-12 days after sowing and is best carried out with a dibber or knife inserted under the seedling roots and gently pulling from the leaves. Fill the small pots with a general potting compost and plant the seedling to the same depth as in the seed tray. Maintain the same temperature as when sowing the seed. Water little and often and lower the temperature by a couple of degrees to around 16C (60F) as the plants begin to shade each other.
Final Tomato Planting
It’s time to plant when the tomato plants are 6-9 inches tall and flowers are starting to open on the first truss. A truss is one of the flower (and fruit) bearing parts of the plant. At this stage, get rid of any plants affected by disease.
For planting in grow bags or directly into soil, space the tomato plants 18 inches apart. If planting directly into soil outside, spread the area with black polythene to help conserve moisture and heat around the roots. Simply cut slits into the polythene and plant the tomatoes into the holes. Tomato plants don’t tolerate cold or windy positions so it may be necessary to provide the plants with a polythene or netting windbreak. Apply a general tomato fertiliser before planting outside in early June.
You can also grow the plants in 9 inch pots filled with compost and placed directly on the soil either in the greenhouse or outside in a sheltered spot. Water the tomato plants well before and after planting. If planting directly into greenhouse soil, double dig the area and introduce well rotted manure or compost and plant with the top of each root ball level with the surface of the soil.
Supporting the Tomato Plants
With greenhouse tomato plants, attach a wire above the row and suspend garden string above each plant. Loosely tie the string around the tomato plant stem just beneath the lowest leaf. As the tomato plants grow, support the stem by gently twisting around the string. Take care not to make the string too tight otherwise the plants will become constricted. An alternative method is to use canes pushed into the soil with the plant supported with string tied gently around the main stem.
Tomatoes grown outside can be supported with 5 ft bamboo canes gently tied to the plant stem at intervals of 12 inches.
Removing Side-shoots and Trimming Tomato Plants
Side shoots develop within the angles (axils) between the main stem and the leaves. Side shoots must be removed while they are still small to avoid taking nutrients and water from the main plant. Try and remove side-shoots as soon as they appear by simply pinching them off with your finger and thumb. Side shoots that are allowed to get larger are best removed with a knife to ensure a clean cut.
When the tomato plants reach 4-5 ft tall, use a knife to remove the lower leaves up to the first truss on each plant. This will help improve air circulation around the plant base reducing the chances of fungal diseases.
Stopping Tomato Plants
Stopping is the practice of removing the leaders or top growing points to prevent the tomato plant growing taller. If growing tomatoes in a heated greenhouse, cut out the growing points of the plant two leaves beyond the top truss as soon as 6-8 trusses have set fruit. Cold (unheated) greenhouse plants normally produce no more than six trusses so remove the growing point (leaders) two leaves above the sixth truss or when the plant reaches the greenhouse roof. Outside tomato plants normally produce no more than four trusses so remove the growing points as soon as the fruit on the fourth truss begins to swell. Bush tomato plant varieties don’t require trimming or side-shoot removal.
Feeding and Watering Tomato Plants
Grow bags contain few nutrients so regular feeding and watering is essential. Water little and often - 3 or 4 times a day during hot summer months is normal. Too much water will kill roots systems and cause the plants to wilt. Plants grown in pots will also require constant attention. Tomatoes grow directly in the soil are slightly easier to manage because the soil provides a buffer of moisture and nutrients.
Use a liquid based tomato feed and follow the instructions carefully. It’s worth pointing out that nitrogen encourages foliage growth whilst potassium improves the quality of the fruit.
Tomatoes grown in the greenhouse will ripen on the plant and can be picked as required. Outdoor fruit can be ripened on the plant by untying the stems from their supports and laying the stems on a bed of straw covered with a cloche. Continue to water the plants without wetting the fruit until the tomatoes are ready to pick.