Diseases for tomatoes
Late blight (Phytophthora infestans) affects both tomatoes and potatoes.
Diseases for tomatoes
Key diseases for tomatoes:
Planting & spacing tomatoes
Spacing
Tomatoes need about 0.4 sq m (4 square feet) per plant, so you can plant them 60cm X 60cm (2ft X 2ft) or 46cm (18 inches) between in the row and 87cm (21/2 ft) between rows.
Planting
By the time conditions are suitable for planting, you may be able to see the first truss in bud or just opening. Your plants may need a small cane to support them if they start to flop over. It is very important to remove the first truss shoot early so that you get a strong first truss. This is a side-shoot that grows in the axil below the first truss. For details of how to remove side-shoots see our helpful video on YouTube: Twisting Tomatoes – (training and side-shooting tomatoes).
Make a hole with a trowel, and plant as deep as possible without burying any of the leaves, or covering the graft union (if your plants are grafted).
Soil preparation for planting tomatoes
Soil preparation for the tomatoes
Tomatoes prefer a well-drained soil or growing medium which encourages a deep and healthy root system. Organic matter is essential to develop and maintain good soil structure – well-made garden compost is ideal.
Soil preparation
Tomatoes prefer a well-drained soil or growing medium which encourages a deep and healthy root system. Organic matter is essential to develop and maintain good soil structure – well-made garden compost is ideal. The best way to find out the nutrient status of your soil is to have it analysed – The RHS offers a soil analysis service. Tomatoes prefer a soil pH in the range 6.0 – 6.5 i.e. slightly acid, but this is a bit too low for some crops such as lettuce and brassicas, so you might need to aim at between 6.5 and 7.0. However don’t apply lime immediately before planting tomatoes unless the pH is below 6.0.
You should aim to apply all of the Phosphorus and Magnesium needed for the whole season, part of the Potassium (also known as potash) but little or no Nitrogen, or else you will get lots of lush growth and your flowers won’t ‘set’ fruit. Don’t forget that your garden compost should contain a lot of nutrients. In the absence of a soil analysis, apply a high-potash fertilizer e.g. Chase Animal-Free Tomato Fertiliser according to the recommendations on the packet; fork in the fertilizer or compost to a depth of about 20cm.
To graft or not to graft tomatoes?
To graft or not graft for tomato growing?
To graft or not graft?
My advice is that grafted plants are worthwhile if you are growing tomatoes in the same soil year after year (usually in a greenhouse). You are unlikely to see a benefit from the disease-resistant rootstock if you are growing in grow-bags or containers using fresh growing media. You may still benefit from the extra vigour resulting in an earlier first pick or an extended harvest period at the end of the season. If you buy grafted seedlings, make sure the graft is above the surface of the compost when you pot them up or plant them. If you don’t, the scion may produce adventitious roots and you will lose the benefit of the rootstock.
Grow bags and containers
If you are using grow bags make sure they are placed on a firm surface, slightly sloping away from your path. If you’re using pots or other containers, the bigger the better, not less than 12 litres per plant; fill them with a good quality peat-free growing medium recommended for containers such as Fertile Fibre Multipurpose Compost or Melcourt Sylvagrow (peat-free, but not organic), both Gardening Which Best Buys.
Pests of tomatoes
Pests
Pests aren’t usually too much of a problem on outdoor crops, but in greenhouses commons pests include aphids, glasshouse whitefly and red spider mite (properly known as two-spotted spider mite). Commercial growers use biological control agents to manage these pests and these are available on our website: Natural pest control. Soft soap is useful for reducing the numbers of pests – use distilled, rain or soft tap water to dilute it.
There is a list of insecticidal soaps and oils here : Pesticides for Home Gardeners RHS Advisory Service February 2015.
Pollination and setting of tomatoes
In commercial greenhouses growers use bumble bees to pollinate their crops. If your plants are outdoors, there should be enough wind and insect activity for pollination. In the greenhouse, it is a good idea to gently shake the strings or other supports around mid day, or tap the trusses which have flowers open. If the weather is very hot and dry, it may help to water the paths in order to increase the humidity and cool the greenhouse.
Watering and feeding tomatoes
Water the plants in well to settle the soil around the roots (this is known as ‘ball watering’). Thereafter you need to adjust the watering according to the size of the plants and the weather. Giving plants a thorough water rather frequent light sprinklings will encourage deep rooting in the early stages, but once the fruit start to swell you want to maintain an even moisture in the soil as erratic watering can cause blossom-end rot and fruit splitting. However, you want to keep the plants on the dry side as this gives smaller, more highly-flavoured fruit. You can feed every watering with a dilute high potash feed, or once a week with a more concentrated dose – follow the instructions on the packet e.g. Neudorff 1L Organic Tomato Feed or make your own liquid feed from comfrey or nettles: instructions here.
Growing tomatoes to planting stage
Growing to planting stage
Tomato plants need as much light as possible, so keep them in a conservatory or on a sunny windowsill (but don’t leave them behind the curtains). On warm, sunny days you can put them outside, but don’t forget to bring them inside at night. Ideal temperatures at this stage are 15°C at night and 20°C minimum during the day.
Growing to planting stage
Tomato plants need as much light as possible, so keep them in a conservatory or on a sunny windowsill (but don’t leave them behind the curtains). On warm, sunny days you can put them outside, but don’t forget to bring them inside at night. Ideal temperatures at this stage are 15°C at night and 20°C minimum during the day.
Your plants may need to stay in their pots for several weeks until the weather is suitable for planting. Space them so the leaves don’t overlap. They may need liquid feeding, especially if you have used seed compost to pot them up (it is usually lower in nutrients than potting compost). Use a proprietary high potash tomato feed made up according to the label recommendations. Typically they will need feeding from about 4th true leaf stage, but if the bottom leaves start to turn yellow or purple, this can be a sign that they are running out of nutrients (purplish tints can also be due to low temperature).
Pricking-out tomatoes
Although you can successfully plant the seedlings directly into the soil, we recommend that you pot them on first.
You will need one pot for every seedling – at this stage allow about 10% extra. Pots with a diameter of 13cm (volume 1 litre) are a good size. You can use the same compost that you used for sowing, but you may need to liquid feed the plants if you are growing them for several weeks in the pots.
Fill the pots to the brim as the compost will settle once it is watered. Make a hole deep enough to take the roots without curling. Plant them so that the cotyledons are just above the surface of the compost. Do not firm them in – water them in gently. Check them every day and give them a light watering as required. Make sure the leaves are dry before evening, as the seedlings are more likely to ‘damp off’ (rot) if they go to bed with wet leaves.