Tomato varieties can be divided into three groups according to their growth habit: ‘indeterminate’, ‘semi-determinate’ and ‘determinate’.
Indeterminates (also known as cordon varieties) provide a continuous harvest from about mid-June (cherries) or early July (others) until first frost. This type produces side-shoots, which must be removed, and needs to be ‘stopped’ (have the growing point pinched out) in the first week of September for cherry tomatoes or early August for other varieties. In a commercial greenhouse, each tomato plant produces over 30 trusses and grows for up to 50 weeks (including propagation). The stems grow up to 15m long. All of our varieties apart from Lizzano and Tumbler are indeterminate.
Semi-determinates are in between and do not need side-shooting or stopping; Lizzano is a semi-determinate variety suitable for growing in patio containers or hanging baskets; it may need staking if grown in open ground.
Determinates are short and bushy (they are also known as bush varieties). They grow to about 90cm (3ft) tall and usually don’t require support. Determinates provide lots of ripe tomatoes at once and are suitable for growing in containers. They do not require ‘stopping’. Tumbler is a determinate variety.
Symptoms are yellowing of the very youngest leaves at the top of the plant, with even the smallest veins remaining green; usually caused by over-watering and/or poor soil aeration. It can be treated by spraying with a proprietary iron foliar feed, but you also need to fix the underlying cause.
Symptoms are yellowing of the older leaves with the main veins staying green. This can be due to a number of causes:
- Low soil magnesium levels (especially if potassium level is high)
- Root problems caused by waterlogging, disease, over-application of soluble fertilizers
- Stress due to heavy fruit load
Removing the underlying cause should alleviate symptoms. Use a liquid feed which contains magnesium as well as potassium. Have your soil analysed and apply magnesium fertilizer before the next crop (if required). If it’s really bad you can spray with 1 litre per 10 sq m of a 2% solution of Epsom’s salts, with a little washing-up liquid as a wetter. Be careful, as this can scorch the leaves if done in sunny conditions.
Uneven ripening and fruit that tastes ‘flabby’ (low acidity) is usually due insufficient potassium. Feed every watering with a high potash tomato feed. Have your soil analysed and apply high potash fertilizer before the next crop (if required).
Early in the season, there can be large differences in temperature between the warm, sunny days and cold nights. These wide diurnal fluctuations can cause the leaves to roll up or curl. This is due to large amounts of carbohydrates accumulating in the leaves because the nights are too cold for the plants to assimilate them. It is usually a temporary problem that cures itself as the nights get warmer.
Disorders usually indicate that something is wrong the growing environment, watering or nutrition of the crop.
Late (potato) blight
Late blight (Phytophthora infestans
) affects both tomatoes and potatoes. The disease survives over winter on volunteer potatoes (plants growing from tubers left in the ground). Spores can also blow in from nearby infected crops. In warm, wet seasons the disease spreads rapidly – it’s less of a problem in fine weather. Commercial potato growers use ‘Smith periods’ to predict when their crops are at risk (two successive days with temperatures above 10°C and relative humidity above 90% for more than 11 hours each day). You can see when these are forecast here: Blightwatch
. The only materials available to gardeners for the control of blight contain copper and are ‘protectants’ which means they have to be applied before the plants are infected, with coverage of all surfaces. Copper is toxic to aquatic organisms and it accumulates in the soil so we don’t use it in our garden.
If you are in a high-risk area, choose some blight-tolerant varieties; we have selected six of the best for our Blight-tolerant Outdoor Tomato Collection.
Other leaf diseases
Many modern F1 varieties e.g. Shirley F1 are resistant to the most common leaf diseases such as Leaf Mould (Cladosporium) and Tomato Mosaic Virus (TMV) (Gardener’s Delight is NOT resistant to TMV). Powdery mildew can also be a problem in some years.
If you have a small greenhouse and always grow your tomatoes in the same place, then there can be a build up of soil-borne diseases such as Fusarium (wilt; crown and root rot), Verticillium wilt and Corky root rot. You can get round this either by not growing in the soil or by using grafted plants.
Pests, diseases and disorders of tomatoes
If you can’t find the answer to your problem here, tweet your veg gardening woes to me and I’ll advise/sympathise @AgonyPlant, or if you’re not on twitter, email firstname.lastname@example.org
Pests, diseases and disorders
If you can’t find the answer to your problem here, tweet your veg gardening woes to me and I’ll advise/sympathise @AgonyPlant, or if you’re not on twitter, email email@example.com.
There are 3 key areas:
Firstly, decide what sort of tomato you want to grow. Cherry varieties get ready before larger types and have a more concentrated flavour. Large varieties such as plum and beefsteak are trickier for beginners. I recommend:
Shirley F1 AGM: very early, short-jointed variety suitable for heated or cold glass/polytunnels; heavy yields of top class fruits; resistant to TMV, Cladosporium and Fusarium.
Sungold F1 AGM: golden-orange cherry – good yield of attractive round fruit; good flavour
Sweet Million F1 AGM: red cherry – long trusses of sweet fruit; good yield
Tumbler F1: early bush variety for baskets & tubs; red cherry-sized fruits with excellent flavour
I have grown all of the above varieties outdoors in East Anglia.
Disorders of tomatoes – page discussing disorders – Blossom-end rot
Blossom-end rot (BER) is due to a lack of calcium in the distal end of the fruit (the end where the flower dropped off) opposite the calyx (where it is joined to the plant). Sometimes there is an internal black rot with little or no external signs. It is seldom due to an actual deficiency of calcium in the growing medium or soil. Calcium is taken up passively and carried in the ‘transpiration stream’. It can only be absorbed by actively growing root tips. All this means that there can be several underlying causes:
- erratic watering, especially in peat bags
- sudden transition to low humidity after a period of dull weather
- root damage
- surge in vegetative growth due to high Nitrogen liquid feed or fertilizer, particularly if there is a high proportion of ammonium rather than nitrate-N
- excessive fertilizer or feeding
Take off all the affected fruit (it tastes bitter). Try to maintain an even amount of moisture in the soil or growing medium. Feed with a high potash feed once the fruit start to swell, according to the instructions on the packet. If the plants are growing in a greenhouse, don’t keep the vents closed during humid weather, leave slightly open. Plum and beefsteak tomatoes are much more prone to this disorder than cherry varieties.
Diseases for tomatoes
Late blight (Phytophthora infestans) affects both tomatoes and potatoes.
Diseases for tomatoes
Key diseases for tomatoes:
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.
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).