Growing Tomatoes

Tomatoes are the jewels of summer and always taste best when home grown. With good soil preparation and the careful selection of varieties you can successfully grow delicious tomatoes even in Sydney where the fruit fly creates challenges for the tomato grower.

Growth habits and planting needs

Choose a site that gets full sun for at least 8 hours a day when growing tomatoes.

Make sure that you do not plant in a bed that has had tomatoes, capsicums or eggplant growing for at least 2 years to avoid soil borne diseases that can build up with constant plantings.

It is important to prepare the beds for seedlings well ahead of planting. Tomatoes prefer a soil which is fertile with a good tilth. Dig the bed over well removing clods and stones to a depth of 40-60cm and dig in well aged compost, thus creating a fairly open structure. Dig in aged cow manure to enrich the soil. Sprinkle over 10 gms of sulphate of potash per square metre and dig in. A soil that is moderately rich in nutrients and one that is well drained, yet retains sufficient water to insure a constant supply during drought, is the ideal soil structure for the best root development. For quick growth and rapid maturity a lighter soil is preferable and a heavier one for the late-maturing crop.

Dig in a handful of dolomite lime per square m into the bed two months before planting to allow it to release calcium over a long period to help prevent blossom end rot. Mix it through the composted soil and let the bed stand before planting. Time is needed for the nutrients to become available to be taken up by the plants.

Tomatoes prefer slightly acidic soils witha a pH between 6.0 – 6.8, ideally between 6.5 – 6.7 so test the soil and amend accordingly. Here is a link to more information on understanding soil pH.

Tomatoes should follow a previous leafy crop in the crop rotation system because tomatoes need potassium and not so much nitrogen which stimulates leaf growth at the expense of fruit.

Ideally, starting the seedlings indoors allows the plants to grow to a good size for planting out when the weather warms. Unlike other vegetables, the tomato is a plant that transplants well. The following images show the development over eight weeks of tomatoes grown in a greenhouse over winter in Sydney. The warm conditions favour early growth of the plants.

IMG_20160709_140058-Tomato seedlings — Ron’s tomato seedlings growing in the warmth of the greenhouse, 3 weeks after being sown.

Select a variety that will grow well in your zone. Here is a link to a site describing some of the many varieties of tomato from which to choose. Tomatoes can be determinate (bush tomatoes) that grow from 90 cm to 1.2 m tall. The fruit ripens at the same time over a couple of weeks. Indeterminate tomatoes are vine type tomatoes that can grow to 1.8 m tall. In Sydney early cropping and late cropping varieties seem to do better by avoiding the main fruit fly season. Cherry tomatoes grow well and are not affected by fruit fly and give heavy crops in good conditions.

IMG_20160716_093534-tomato seedlings 4 — The tomato seedlings one month from sowing, first true leaves.

Tomatoes can be sown around 2 months from planting out and the expected temperature in the garden should determine when it would be best to sow the seeds in the greenhouse. Don’t begin too early as cold soil and air temperatures will hinder and stunt the growth of the transplanted seedlings.

Sow seeds 6 mm deep in seed trays or small punnets in a good seed raising mix. Firm down, water with liquid seaweed tonic and keep moist until they germinate. Keep them moist all through the seedling stage.

The seeds germinate best at temperatures over 23ºC and seedlings grow best at 21ºC.

The seedlings should emerge after 10 – 14 days. When true leaves have grown and the plants are well established, transfer the seedlings to larger individual pots to allow them to develop a strong root system and stem.

IMG_20160730_125131-Tomato seedlings in pots — The tomato seedlingsat 6 weeks, transplanted into individual pots.

IMG_20160813_124911-Tomato seedlings 3 — Ron’s tomato seedlings two months from sowing. Note the strong stems and healthy leaf growth.

Tomato plants should be well grown before transplanting into the garden. The plants should be 15 -20 cm tall with a thick tough stem and lots of dark green leaves. The root system should be well established to withstanding transplantation well.

Temperatures should should be consistently warm before planting out the tomatoes. Day temperature of 15 – 18º C and night temperatures of 10 – 15º C are still too cool for transplantation.

Harden off the plants by cutting back on watering a little to make them stronger before transplanting into the garden beds.

The best time of day to transplant tomatoes plants is the late afternoon and on a cloudy day so that transpiration will be less and more water taken up by the plant. The soil should be moist but not wet, so water well the day before and at planting.

The plants should be placed several inches deeper in the soil than they were in their pots. The tomatoes will stand better and new advantitious roots will develop along the stem. This promotes the growth of a larger and more deeply penetrating root system. Deep planting also holds the plant more upright and rigid and prevents damage from wind after transplanting and before the roots have re-established.

The following image shows the root development from the deeply planted stem.

Tomato roots 1 — Tomato roots showing advantitious roots growing from the buried stem 4 weeks after transplanting. Source: Soil and Health Library.

This image shows the extensive root development of a mature tomato plant under optimal growing conditions. This highlights the importance of good soil preparation and tilth that allows good root growth.

Tomato roots — Roots of tomato 2 months after transplantation. Source: Soil and Health Library. (grid measure in feet)

IMG_20160814_114851-Tomato bed prepared — The tomato bed prepared for planting

As the indeterminate or vine tomato has a habit of sprawling over the ground, staking plants or providing frames or cages to support them growing is important when preparing beds. Staking and pruning vine varieties will make them come into fruit earlier and improves the fruit size and quality by keeping it clean but will reduce yield. Perhaps using a cage with this type of tomato could overcome the downside of staking. Individual preferences, cost and space in the garden will drive the ultimate choice. Determinate or bush tomatoes may not need staking depending on the variety chosen and the size of the fruit.

If staking and pruning make sure to allow plenty of leaves to cover the fruit to prevent sunburn.

Give the plants plenty of space for air circulation by allowing a spacing of 30 -60cm between plants for bush varieties and 35 – 50 cm for vine varieties.

Careful loosening of the soil between the plants to prevent the soil from compacting and affecting aeration of the roots and is important in early growth, as is keeping weeds from growing and competing for nutrients. Mulching can conserve moisture by preventing evaporation and also prevents the crusting of the soil. Mulching therefore also enhances the growth of roots in the soil surface and maintains moisture during hot periods.

IMG_20131019_115627-Tomato plants in garden bed — Young Wapsipinicon tomatoes, well mulched and staked

Water is vitally important throughout the growing and fruiting of tomato plants. A drip irrigation system will make sure that water is delivered to the roots consistently and and that there is no splashing of soil onto the leaves which promotes diseases. Keeping tomatoes evenly moist helps to prevent blossom end rot. Tomatoes are predisposed to the disease when the rapidly growing plants are exposed suddenly to a period of drought. The plant’s roots will not be able to transport enough water and calcium to the rapidly developing fruits and the rotting occurs at the blossom end.

IMG_20131108_104814-tomato plants 2 — Staked heritage Wapsipinicon Peach tomatoes growing in a raised garden bed.

Feed the tomatoes 2-3 times over the growing season with diluted fish emulsion or a liquid tea made up of cow manure diluted in water and allowed to stand before using . It is important not to apply high nitrogen fertilizers which promote lots soft leaf growth at the expense of fruit. This also makes the plants more susceptible to pests.

Another successful way of protecting tomatoes from the fruit fly which devastates tomatoes in the Sydney area is by providing a canopy of fine mesh shade cloth to enclose the plants. The image below shows the excellent result using this method.

IMG_20141220_094123-tomato plants 4 — Dave’s tomatoes grown under a fine mesh to protect from fruit fly.

IMG_20141220_094106-tomato plants 5 — A closer view of the quality of tomatoes grown under mesh

Companion planting with basil improves the flavour of tomatoes and planting marigolds protects from aphids, white flies and nematodes that affect the soil where tomatoes are grown. Borage grown nearby is very attractive to bees and will aid pollination when tomatoes are in flower.

IMG_20141202_114407-tomato plant 3 — Tomatoes interplanted with marigolds and basil

Harvesting

When the tomatoes will reach maturity will depend on the variety chosen and will be around 8 – 17 weeks.

Determinate, or bush varieties will come to maturity at once within a matter of weeks and are usually early varieties. Vine varieties will continue to produce fruit over the growing season and can be harvested as they ripen and in the garden we are still harvesting well into Sydney’s temperate winter this year.