A common problem affecting otherwise healthy tomato and capsicum plants during heat waves is blossom end rot, where partly formed fruit develops a dark, sunken patch furthest from the stem.
This is caused by calcium deficiency, and is not a disease. Like us, plants need a good supply of calcium to form a strong structure. Hot and very windy days increase transpiration (water loss) from plants in the same way we perspire to keep cool, and calcium can only be absorbed by plants as water-soluble, electrically-charged ions. This problem can also affect zucchini, pumpkin and melon plants.
During heat waves, daily watering rarely solves the problem. A deep watering a couple of times a week is more beneficial. If soil around plants is mulched to keep roots cooler and reduce water loss, an efficient way to water quickly is to place juice or soft drink bottles, neck down, beside plants. See: Watering in drought conditions
Other causes of blossom end rot are:
• Erratic watering
• Soil is too acidic (soil pH less than 6)
• Poor fertilising routine
• Overuse of fertilisers high in nitrogen or potassium, including some seaweed fertilisers
• Rarely, in very alkaline soil where calcium becomes insoluble.
There is nothing like the taste of vine-ripened tomatoes, and this is how my neighbour, Cheryl, keeps her tomatoes cropping through winter on the Mid-North Coast of NSW. The tomato plants self-seeded in the rose garden in front of her north-facing verandah and, as they grew, she trailed the foliage across the verandah surface. The plants get plenty of sun during the day and the verandah roof keeps the plants warmer at night and protects them from frost. This clever idea has worked very well and Cheryl has so many tomatoes, she has been giving them away.
Tomatoes can also do well during the colder months in pots on a protected north-facing verandah, as the potting mix in black plastic pots stays warmer than soil in garden beds. Fruiting on tomatoes depends on warm air and tomatoes do not need bees for pollination. Don’t forget to water the plants regularly, and give them a light application of complete organic fertiliser as flowers start to form, to ensure a sweet-tasting crop.
We all know that an adequate supply of phosphorus is essential for healthy root growth but, during hot, dry months, we can further assist some of our vegetables to produce extra roots.
Pumpkins produce a huge amount of foliage – too much for the original root system to supply adequate water to the entire vine. Consequently, these plants and some other members of the squash family have evolved to produce roots at nodes (stem joints) along their runners. (See photo below.)
We can assist this auxiliary root formation by carefully lifting the runner and scratching the surface of the soil beneath where roots buds appear. Then cover this with a shovelful of compost and settle the runner back onto the compost. Encouraging extra roots to form will increase your crop.
These sections may be hidden by foliage but it will help to identify them if you place a soft drink bottle or large juice bottle (with the base removed) neck down beside this area. When watering, water not only around the base of the plant, but also into the bottles to supply water directly to the extra roots without wetting the foliage.
Tomatoes in their natural state, grow along the ground and will also form auxiliary roots along their stems, but our method of growing tomatoes tied to stakes prevents this. However, you can give them a helping hand to produce extra roots before planting out by lying potted seedlings on their side when they are 10-12 cm tall. Leave them like this for a week or so, depending on the growth rate, and remember to stand them upright for watering. As you can see in the photo, the main stem with make a 90-degree turn, and root buds will form on the horizontal part of the stem. Plant them out with the growth tip vertical and the horizontal stem just below the soil surface.
You can also hill up soil around tomato plants (a little at a time), and sweet corn plants to encourage extra roots to grow on the lower parts of the main stem.
Jenny has previously not had a lot of luck growing tomatoes and wants to know whether she should prune the side shoots that form on tomato stems.
When growing staked tomatoes, it is common practice to prune the small shoots that form in leaf axils because tomato plants do not have strong apical dominance. That means the leading shoot does not contain a lot of the hormone that prevents side shoots from growing. If left to their own devices, tomato plants produce multiple stems that flop onto the ground, producing additional roots from where stems touch soil. In removing the side shoots (by snapping them sideways when small, or cutting with a sharp knife when larger), growth is concentrated in the lead shoot. A second leader can be allowed to form from just below the first bunch of flowers and, once the plant reaches the top of the stake, you can pinch out the tip of the leaders.
This type of cultivation originated in cooler climates to allow more sun to get to the fruit by removing excess foliage, and make weeding easier. Where summers are hot, plants are better left unpruned once the main leaders are established because fruit can become sun scalded, especially where air pollution is low.
Where summers are very hot, tomato plants can do better under light shadecloth (which reduces transpiration) because it is actually warm air that allows tomatoes to ripen, rather than hot sun. As you know, tomatoes that have started to colour can be ripened indoors, although these will be lower in the anti-oxidant lycopene than vine ripened tomatoes.
Removing side shoots will also increase the size of fruit by limiting the amount of fruit that forms. However, other factors are more important in fruit quality. They are: providing a soil pH of around 6.5–7 because tomatoes will develop blossom end rot if they don’t have access to adequate calcium; providing sufficient well-balanced fertiliser such as mature compost, worm castings or poultry based fertiliser; regular deep watering rather than a daily sprinkle; and mulch to reduce fluctuations in soil moisture.
Just another hint: Plastic plant ties can cut into plant stems. When staking tomatoes, use a piece of knit fabric cut across the stretch, instead. Being more flexible, this type of tie won’t damage soft plant tissue.
To improve the quality of your tomato crop next year, save seed from one or two plants that have cropped well for you this year because these seeds will be from plants that have already adapted to your local growing conditions.
It is easy to save tomato seed from plants that were grown from open-pollinated seed. Hybrid seeds are unreliable because seed from hybrid varieties can be sterile, or revert to the traits of only one of the parent plants. A wide range of open-pollinated seed for tomatoes is available, with varieties to suit all Australian and New Zealand climate zones. You can order them by mail on the internet from companies including Greenpatch Seeds, Green Harvest or Eden Seeds. To save tomato seed, first select one or two fully ripe tomatoes that you would like to grow next year. For medium to large tomatoes, one fruit is usually enough for the home gardener. For best results, keep them at room temperature until they are just beginning to get soft.
Then cut the tomato into segments and use a teaspoon to transfer the seeds and their surrounding jelly into a clean glass jar. For Italian type tomatoes that don’t contain a lot of jelly, you can add a very small amount of water to keep the seeds moist, but don’t drown them.
Leave the jar undisturbed in a warm place, out of direct sunlight, where you can observe fermentation. Within two or three days a foamy mould will form on the surface of the tomato mixture and it will look as though something has gone horribly wrong. Don’t worry. This is a beneficial fermentation process that kills off several diseases that can affect tomato plants, but the mould can cause premature germination of the seed, if it is left too long. As soon as the thick foam forms, scoop it off and fill the jar will clean water. Viable seed sinks to the bottom of the jar. Carefully pour off loose jelly floating at the top of the jar, then pour the jar contents into a sieve. Wash the seeds thoroughly in the sieve to remove all the jelly, then tip the seeds onto a sheet of smooth paper. Avoid using paper towels for tomato seeds because they are hairy and difficult to remove from absorbent paper. Allow the seed to dry for thoroughly, indoors. After they have been drying for a few hours it is easy to rub them between your hands to separate any clumps of seed. I usually leave them to dry for a week before packaging in a paper envelope and storing in a biscuit tin in a cool place, until they are needed.
Sometimes home grown vegetables crop so well the family gets tired of eating them. If you find yourself with more tomatoes than you and your friends can use, freeze them for use during winter months. Vine-ripened tomatoes are a rich source of lycopene. This antioxidant helps keep the reproductive system healthy, and is said to be particularly beneficial to the prostate gland.
We use a simple method that has no added flavourings so that the thawed tomatoes can be used in soups, casseroles, or pasta sauces, as the occasion demands. Many flavours, such as onions, garlic and other herbs taste better when they haven’t been frozen.
We chop fully ripe tomatoes without peeling them as the skins float to the top of the pan during cooking, and can be skimmed off. Nor do we bother to remove the seeds but, if you don’t want seeds, you can either scoop them out with a teaspoon before cooking or put the cooked mixture through a sieve. Removing seeds before cooking also removes a lot of moisture from the tomato pulp and the seedless mixture requires constant stirring to prevent it sticking to the pan.
Place the chopped tomatoes in a heavy saucepan and gently heat to boiling, while stirring the mixture. Reduce heat, and allow tomatoes to simmer gently, uncovered, for about 20 minutes, stirring occasionally. Do not leave the mixture unattended as ripe tomatoes contain natural sugars and the mixture can stick if the heat is too high or the mixture is not moved around in the pan. After 20 minutes, turn off heat and cover the saucepan. Allow tomato pulp to cool, then ladle two, four or six cupfuls into separate freezer containers for later use.