Time to plant out your tomatoes
Mid October and Labour weekend are the traditional time for planting out summer flowers and vegetables and a great time to get into all aspects of the garden.
This week we are focusing on tomatoes as they are one of the top vegetables grown in our gardens. Every year in October many thousands of tomato plants are planted in the hope that a great crop will be harvested.
Ripe tomato fruits come in red, yellow, orange, pink or white and round, flat plum or pear shaped. Some may even develop unusual protuberances. Size varies from a 2-3cm diameter in the small cherry tomatoes to approximately 10cm in say beefsteak. All can be eaten raw or cooked.
Tomatoes grow best in a full sun position but sheltered from the wind. They grow best at 21-24˚C and do not thrive at temperatures below 10˚C or above 27˚C 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 then 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 since 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 feeds such as; ‘Tui Tomato Fertiliser’ during the growing season are most beneficial. The use of slow releasing ‘manutec tomato tablets’ I have found the most effective for the ongoing feeding of tomatoes, capsicums and cucumbers in pots and containers.
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.They’re 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 to 24˚C. Germination will occur at much lower temperatures, but it is slower. Cover seed trays with a piece of glass and paper during germination and 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 — this can be 6-12 days after sowing. 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 the rest. 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 so long as day temperatures don’t fall below 7˚C, soil temperature is about 10˚C and the risk of frost is over through out 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.
All tomato types should be watered and mulched thoroughly once the soil is warm. Plants in containers need more frequent watering and supplementary tomato fertiliser to complement the loss of leached out nutrients. Over watering or overfeeding reduces flavour. 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 or micro irrigation drippers.
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. Do this when the plants are dry to avoid infection. Removing some foliage improves air circulation, reduces the risk of disease and allows more sunlight to ripen. Some pests and diseases of tomatoes are 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 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 Gro Safe Free Flo Copper or Yates Tomato Dust. The tomato/ potato psyllid is readily controlled by the use of Yates Mavrik or Yates Success. Both these sprays are bee friendly.
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.
Have a good week!
■ Gareth Carter is general manager of Springvale Garden Centre.
Tomatoes come in all colours.