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The golf ball-sized Moonbeam has the highest level of TCL at 4.2mg. Photo / Supplied

With warmer temperatures both day and night and a break from the seemingly never-ending rain of recent months, I now have summoned the confidence to get into some summer vegetable planting this week.

Myself and 12 colleagues from independent garden centres around New Zealand have worked with the Whanganui-based Heritage Food Crops Research Trust to bring out a new series of tomatoes under our Ican brand.

These are plants selected for their beneficial health-giving properties, using the results of 2021 scientific studies. It is an interesting thought to choose which fruit or vegetables to grow based on what will be the most healthy for our human bodies.

As a society, we are becoming more aware of the foods we eat that are not so good for our bodies and many are consciously looking for those that are. Tomatoes are a great area to look at.

The first tomatoes introduced to Europe were golden orange in colour and came from Mexico. The golden colour would have come from tetra-cis-lycopene, a powerful antioxidant readily absorbed by the human body.

Red tomatoes, discovered in Peru and northern Chile, contain all-trans-lycopene which is not so readily absorbed by humans. In the course of history, as varieties of tomatoes were crossed to produce new ones to appeal to the consumer, the recessive "orange" tetra-cis-lycopene was removed in favour of the "red" all-trans-lycopene.

The health potential of golden tomatoes lies not just with the abilities of tetra-cis-lycopene, but also the unique intermediate compounds that come with it, such as neurosporene and zeta-carotene, and higher levels of phytoene and phytofluene - all compounds with health benefits for humans.

Tetra-cis-lycopene is a powerful cancer and heart disease-fighting antioxidant, absorbed from both raw and cooked fruit.

The real beauty of these Ican High Health tomatoes is they can be eaten raw to gain the health benefits of tetra-cis-lycopene, unlike red tomatoes which have to be cooked for the all-trans-lycopene to be absorbed by the human body.

Read the full story at Heritage Food Crops Research Trust "History of the Tomato" www.heritagefoodcrops.org.nz/history-of-the-tomato/

The Ican High Health Tomato range has five of the top-ranking varieties chosen from the 2021 trials for their high levels of tetra-cis-lycopene, health-enhancing properties and great taste.

Moonbeam: Lovely mild flavour, prolific golf ball-sized fruit. Highest level of TCL 4.2mg. Golden Bell: A bright orange bell-shaped fruit of medium size. 3.6mg of TCL. Good levels of phytoene, phytofluene and zeta-carotene. Golden Grape: Bite-sized golden orange fruits that kids love. Tasty and highly attractive, great for salads. 3.1mg of TCL. Wally's Spanish: Meaty bright orange beefsteak variety with great taste. 3.1mg of TCL plus the highest levels of phytoene, phytofluene and zeta-carotene. Golden Light: A good producing and tasty low acid Roma style tomato 7-10cm long. 3.2mg of TCL.

These tomatoes can be eaten raw or cooked and the TCL is better absorbed and stays in the body longer than lycopene from red tomatoes. You do not need to cook them but if you do, you will get even more lycopene than from cooked red tomatoes.

How to grow Tomatoes grow best in a full sun position but sheltered from the wind. They grow best at 21-24C and do not thrive at temperatures below 10C or above 27C and do not tolerate frost.

Tomatoes tolerate a wide range of fertile and well-drained soils tending acid within a pH range of 5.5 to 7.0. Some lime may need to be applied to very acid soils when growing tomatoes.

The plants perform best if they are rotated with other vegetable crops to prevent a build-up of soil-borne pests and diseases. They should not be grown in the same patch of ground year after year. This can be a problem in small gardens and greenhouses. If pests and diseases are not a major problem and the soil is boosted with regular applications of compost and fertiliser, rotation may not be necessary.

Tomatoes are also grown very successfully in containers and this is another popular option.

Prepare the soil by working in Tui Tomato Mix or other such products. Mix in the soil at least 30cm deep as tomatoes develop a deep root system in this range and are gross feeders. Work in tomato fertiliser before planting; tomatoes need high levels of phosphate, but low levels of nitrogen. Dressings of fertiliser, such as Tui Tomato Food, during the growing season are most beneficial. The use of slow-releasing Manutec Tomato Tablets or Jobes Tomato Spikes I have found the most effective for the ongoing feeding of tomatoes, capsicums and cucumbers in pots and containers.

Sowing and planting Tomato seeds planted now will produce a crop in February–March whereas tomato plants planted out now can produce ripe fruit from late December, depending upon weather conditions. For a successional crop you may like to sow some seeds now as well as planting out some seedlings.

Seed is best sown in a seed-raising mix in clean seed trays. Fill trays to about 20mm below the top then firm and level carefully. Soak the tray and mix until it is thoroughly wet before the seed is sown and stand for a while to allow excess water to drain off. Sow seeds evenly across the tray and cover with a 3-5mm layer of seed-raising mix.

The best temperature for germinating tomato seeds is 21-24C. Germination will occur at much lower temperatures, but it is slower. It is beneficial to cover seed trays with a piece of glass and paper during germination and to turn the glass over daily to remove any condensation.

A well-prepared tray should require no further watering until after seedlings have emerged. High humidity at the time of their emergence helps the seedlings to shed their seed coats.

Seedlings should be pricked out when the seed leaves (cotyledons) are fully expanded. In temperatures of 21-24C, this can be 6-12 days after sowing. Before pricking them out loosen them by sliding a small label/iceblock stick/narrow teaspoon or similar under the roots, lift the plants by one of their seed leaves – not the stem, to avoid damage. Only vigorous healthy seedlings should be pricked out into a good quality potting mix such as Tui Tomato Mix. Discard remaining seedlings.

Transplant into 5-6cm pots at the two or three-leaf stage and give the seedlings ample ventilation, space and light. They can stand short periods of low temperature as long as day temperatures don't fall below 7C, soil temperature is about 10C and the risk of frost is over throughout most of Whanganui, except possibly in upper Aramoho.

If necessary, cover with cloches or plastic over a frame or stake supports in the early stages to provide shelter.

Routine care Once established, tomato plants grown in containers need more frequent watering and supplementary tomato fertiliser to complement the loss of leached-out nutrients. Avoid watering the foliage as this may lead to fungus infection; apply water directly to the soil over the root area or use a watering can, soaker hose, micro irrigation drippers or similar.

In mid to late summer some like to remove the growing tip (terminal shoot) to three leaves above a fruit truss to discourage further height and encourage the remaining fruit to ripen.

Laterals should be removed about once a week, beginning about three weeks after planting. They readily bend and break off from a healthy plant. Carry out this task when the plants are dry as there is less risk of disease infection. The same applies to unwanted foliage. As leaves grow older they shade one another and the fruit. Removing some improves air circulation and further reduces the risk of disease and allows more sunlight to ripen the fruit.

Grafted tomatoes can be grown without the need to have any laterals removed, as the more vigorous root system will support the larger plant.

Pests and diseases Some pests and diseases of tomatoes include damping off of seedlings, mites, whiteflies, tomato caterpillars, bronze wilt, nematodes, fruit flies, tomato psyllid and tomato blight. Tomatoes under cover are susceptible to whiteflies, mosaic virus, grey mould (Botrytis), tomato leaf mould, magnesium deficiency, boron deficiency, stem rots, foot and root rots and blossom end rot. Many of these problems are rare and can be controlled readily if observed.

The two most common problems in Whanganui are blight and tomato (also potato) psyllid. Blight is a fungal problem and can be prevented and controlled with the use of Organic Certified Gro Safe Free Flo Copper. The tomato/potato psyllid is readily controlled by the use of Yates Mavrik or Yates Success. Both these sprays are bee-friendly once dry.

Come and see us at the garden centre with a photo or sample of your plants if you encounter any of these problems and we can advise on the best means of control. For more gardening information visit www.springvalegardencentre.co.nz

• Gareth Carter is general manager of Springvale Garden Centre.

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