March 2023 - Everything you ever wanted to know about tomatoes!
Hi everyone, this month we thought we would talk about tomatoes, covering the difference between determinate and indeterminate types and lots of other 'tomato speak' that you may not be familiar with.
Firstly, let's acknowledge what a wonderful fruit a tomato is. Incredibly versatile, they can be grown under glass or outside in a sheltered spot and have so many uses in the kitchen, from simple salads to roasting to chutneys and sauces and even drying, canning and confits. What we all aim for first and foremost is a great harvest so hopefully the information you find here will help you.
The terms Determinate and Indeterminate refer to the growth habit of each individual plant. It makes sense therefore to know this so that you can treat each plant accordingly to maximise your harvest.
In simple terms Determinate types grow and then stop when they have reached their optimum height, Indeterminate continue to grow and produce fruit all season. Semi-Determinate varieties continue to grow but tend to be smaller with a bushier growth habit. This information should be readily available at the point of purchase for both seeds or plants but if you have some already growing and are not sure then check out the highest or leader stem, if there are leaves at the top it is most likely indeterminate and if there are flowers then most likely determinate.
Determinate varieties are also referred to as bush types, and they stay smaller and more compact. Many will not need staking and can lend themselves to container planting but may require some support when laden with fruit. Their fruit also tends to mature earlier than indeterminate types.
Once the first sets of flowers have appeared you can prune the leaves below them to keep them off the soil and help to prevent the spread of disease
Indeterminate varieties are sometimes also referred to as climbing, vine or pole tomatoes and are great if you have a long growing season over which you will have a continuous harvest. These types, given the correct conditions and time can reach 3-4 metres high. Because of their size, vigorous growth habit and the need for more water and tomato feed they are unlikely to thrive that well in containers but are an excellent choice for vertical gardening as they are so easy to train. Support will be required.
Prune the plants to just one or two leader stems and train up a pole or string. These types also need to be 'pinched out' - this is where you remove a sucker like growth that appears at the junction of the main stem and a flower/fruit bearing stem. Please see the picture below. Removing these and pruning in this way helps to improve air flow and reduces the likelihood of disease. It also reduces the energy the plant spends on foliage rather than fruit.
Semi-Determinate - as the name suggests they are a bit between the two. As with Determinate types, produce the flowers at the end of their stems and will eventually stop growing but although needing less support than indeterminate types they will produce fruit over a longer period. Compact and sturdy they are suitable for containers.
Removal of lower foliage and suckers below the first is recommended, we also continue to remove higher suckers but you don't have to.
Blossom End Rot so named because the blossom end will have ugly, brown rotten bottoms. Larger types are more likely to suffer from this and it is rare to see it on Cherry tomatoes. It is caused by a lack of calcium, root injuries, heavy handed applications of nitrogen fertilisers and fluctuations in soil moisture. Good root systems are imperative so they can distribute the calcium uptake from the soil throughout the plant and it is often seen early in the system due to under developed roots. Some advocate grinding eggshells and adding it to the soil. You can help avoid by...
- Don't plant too early, wait to plant out at least two weeks after your last expected frost date.
- You want your seedlings to have at least two to three sets of true leaves before transplanting.
- You also need to harden off before planting out - hardening off is the term used for acclimatising your seedlings to cooler weather conditions i.e. place out in the daytime and bring in at night for a while so you do not shock your seedling.
- Don't plant in cold soil, (they need at least 15°C) or in clay soil that you have not improved with compost.
- Water consistently and keep moist during the growing season. Allowing plants to dry out and then waterlogging them can cause the fruit to have a growth spurt and split their skins
- Put a layer of mulch down to help retain moisture.
- If you do get it don't lose heart - later fruits may be fine.
Catfacing showing as scarring on the blossom end of your fruit and ranges from minor to major distortions. Most common on large varieties. Can be caused by unseasonably hot or cold temperatures, flower disturbance, high nitrogen levels and exposure to herbicides. You can help avoid by...
- Avoid excessive pruning
- Avoid excessive fertilising
- Water adequately and consistently as above.
Blight is a disease caused by a fungus organism. Affecting both leaves and fruit it spreads rapidly, especially in warm wet weather. First symptoms can be seen in a rapidly spreading watery rot of leaves which then shrivel and turn brown. You may well see brown spots on leaves and stems, sometimes with white growth. Brown spots will appear on green fruits whilst fruit further along the ripening stage will quicky decay. This disease will cause catastrophic loss to your crop and fast action is required.
- Burn affected plants
- Disinfect everything that has come into contact with the affected plant
- Keep the foliage on your plants as dry as possible
- Do not reuse the soil or compost it, redistribute over an area not used for crops
- Blight spores are wind blown so those grown in a greenhouse are less like to be affected but if the spores do get in through vents etc the humidity will exacerbate the issue