This is a simple guide to assist you in achieving healthy tomato plant growth and so produce great tomatoes. This first article deales with general tomato plant health and growth. The following will deal with pest and disease symptoms and nutritionsl matters.
It is divided into sections for different types of tomato plant growth problems. There is a heading describing the problem or symptom followed by a paragraph with extra detail of possible causes and suggested solutions.
This article is based on growing tomatoes in New Zealand conditions so if you are reading this from another country there is likely to be growing conditions and solutions unique to your country not covered here. Ask a local expert (website) / garden center for suggestions. Healthy Tomato Plant Growth
General tomato plant health and growth.
Leaves small and possibly blotchy and purple tops to plant.
Can be Spotted wilt virus from thrips especially on young plants will result in severe stunting, thin stems and purple tops.
Short plant with purple nodes and purply young fruit trusses.
Possibly, phosphate deficiency which can be caused by severely cool root temperatures, environmental or of course incorrect phosphate levels in the growing media/soil. Tomatoes like warmth so warm the greenhouse air if in a greenhouse but this is not always possible, move to a sunny spot if in a pot or alter the fertiliser program if this is a possibility.
Plant with thin stems leaves and small fruit but normal colour in leaf and stems.
Typically the result of a plant under severe stress of some kind. Remove the stress and the plant may respond with new growth.
Causes can be many including:
Heavy fruit load in low light conditions. The heavy fruit will have a dominant effect on where the sugar from the leaves go, so until these fruit are picked the plants will remain under stress. The main objective is to reduce the stress on the plant by reducing the fruit load.
High fruit load but low leaf area due to too much deleafing or insufficient fruit thinning.
Low humidity combined with a low a CF is twice as effective in reducing plant health.
Too high a CF (fertiliser level) for the time of year of the age of the plant
Poor nutritional balance in the soil/media around the roots.
The long term effect of such a stress situation can be
1) Reduced growth in the growth points of the plant (tip, developing leaves and roots).
2) Root death from lack of sugar supply can have disastrous follow on effects. Total root death can result in the worst case scenarios. If partial death occurs then limited uptake of some nutrients will occur such as manganese, calcium and boron leading to blotchy plants and increased risk of Blossome End Rot (BER).
3) Reduced fruit growth and swelling.
4) Reduced leaf area will result in reduced transmission of moisture through the leaves into the greenhouse atmosphere so lowering the relative humidity. In summer this is not desirable increasing risk to Blossom End Rot.
Solutions to reducing stress on the tomato plants and improve tomato plant health.
Summer Stress Lowering Suggestions
Where possible increase humidity in the greenhouse by overhead watering and or wetting the concrete floor on sunny days. The water will slowly evaporate increasing the humidity in the greenhouse. Reduce ventilation especially on windward side.
Removing a top truss (ideally before the flowers open) can help to reduce stress on the tomato plant. This has the effect of directing sugars towards the growing tip, allowing for increased leaf expansion in the new leaves, which will consequently result in increased photosynthesis due to the larger leaves. Also increased shading of fruit and increased water transmission into the growing environment.
Increase leaf area of the plant by allowing a side lateral to 2 – 3 leaves and then remove the side laterals growing tip to stop future growth, don’t allow fruit to set on this side lateral as this will defeat the purpose.
Reduce the CF (fertiliser level) to increase the water uptake into the plant.
Alter the N/K ration in the feed to say 2:1 to give greater supply of nitrogen for vegetative growth.
Try to pick the heavy fruit by having a high average 24 hour temperature encouraging ripening.
If you are using hydroponics to grow your tomatoes, ensure the water temperature is not too high greater than 21 degrees can result in reduced oxygen level in the solution. Also that the flow rate in the gullies is no less than 2 litres per minute.
Truss prune for a couple of trusses, this means to reduce the number of ftuit per truss for a couple of trusses thereby reducing the demand for sugars from the leaves.
Reduce the light level into the greenhouse by shading though this will reduce production so it is probably better to provide sufficient moisture by effective relative humidity control.
Winter Stress Lowering Suggestions.
Many of these suggestions are relevant for greenhosue winter production of tomatoes.
Try the above solutions for summer if they are relevant.
Increase the light level if at all possible. Ensure the exterior surface of your greenhouse are clean from dust and pollen.
What is the 24 hour average temperature. If it is less than say 14 degrees celcius at night and less than 18 degrees celcius in the day then production of sugars will be less than optimal.
Truss removal will free up sugars and so provide relief to struggling roots and other growth tips.
Truss pruning to say 5 (or even 4) in the depth of winter can help.
Relative humidity should be kept at say 85 to 90 percent to try to maintain water movement through the plant. The cost of heating during the day needs to be kept in mind especially if the prices are low but the advantages are reduced botrytis (fungal) infection and improved transport of nutrients within the plant. This especially applies to calcium as a lack of calcium is the cause of Blossom End Rot.
Raise the night temperature to encourage ripening and so reducing the fruit load once picked
Reduce the plant density in May before going into winter. In winter a plant density of 2.4 to 2.5 plants per m2 of floor area is suggested, In summer up to 2.9 – 3.1 plants /m2 is possible in sunny warm locations.
Conclusion
If the problem does not fit into any of the above and the problem is more plant specific rather than across the complete crop then check for:
A stem infection such as botrytis or collar rot which will reduce the transmission of moisture to the leaves.
Tall vigorous plant, taller than the surrounding plants, called a Jack or rogue which is a genetic disorder and will never really produce fruit of consequence. Remove.
The next posting will deal with tomato plant root health.
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