Grow the Best Tomatoes

Optimum soil temperature for germination: 27 degrees Celsius
Bottom heat is recommended for germination. Sow seeds in February if you plan on growing plants in an unheated greenhouse. Sow seeds in March if you plan on growing plants outdoors.
After seeds germinate remove from bottom heat and grow under bright lights.
Seedlings should be watered regularly. They prefer moist soil.
Night time temperatures should reliably be above 10 degrees Celsius before planting outdoors.
Tomatoes are more robust than other tender plants so they can handle lower temperatures but they will not thrive.
If temperatures are too cold, tomato seedlings will have a purplish look. This is a sign that plants are not taking up enough phosphorus due to the cool weather and not that there is a deficiency in the soil. When consistently warm weather shows up, the plants should have normal dark green leaves.
When planting tomatoes bury them up to their first pair of true leaves. This will encourage greater root growth, helping with both nutrient uptake and the plants’ ability to stand up to dry conditions.

Growing Conditions

Tomatoes are heavy feeders, so amend soil with compost prior to planting. A balanced organic fertilizer should be applied to each planting hole.
If growing in containers use a slow-release fertilizer when planting and a water soluble fertilizer bi-weekly.
Regular watering is vital, but don’t let the plants sit in water. If plants dry out, and then are watered too much it can cause tomato fruits to split or crack.
Drip irrigation is the best way to provide plants with even moisture and it also doesn’t get foliage wet, which is a great way to prevent powdery mildew and late season botrytis.
Tomatoes are tropical plants so they require full sun and lots of heat. The optimum temperature for tomato fruit set is 18.5 - 26.5 degrees Celsius. The ideal night time temperature for tomatoes is 16-18 degrees Celsius.
If growing in an unheated greenhouse ventilation is crucial so the right temperature range can be maintained. Use a fan and ensure you can open doors and windows in the summer months.

Indeterminate vs. Determinate Tomatoes

Vine (indeterminate):

Vine (indeterminate) varieties will require some kind of support such as a wire to grow up, or a trellis to be tied to as the plant grows. They grow as a vine and can be trained to reach over 6 feet tall.
Large-fruited, indeterminate varieties generally begin to ripen later than bush tomatoes.
Fruit ripens over a period of time, so indeterminate varieties are ideal for having fruit all summer.

Bush (determinate):

Bush (determinate) types benefit from the support of a tomato cage in order to prevent sprawling. They grow as a small shrubby plant.
Determinate (bush) varieties ripen earlier so are better for those with short seasons.
Fruit ripens all at once in a shorter time period than determinate varieties, so bush tomatoes are ideal for people interested in canning.

Tomato Pollination

If tomato plants are grown under cover, you can encourage pollination and fruit set by tapping the stem from time to time. Tomatoes do not rely on insects for pollination. Vibrating the plant shakes pollen loose within the flowers, which then self-pollinate.

Maximizing Fruit Yields

Reduce watering around the end of July to encourage the fruit to ripen.
By the mid-August if tomato vines still have a lot of green fruit on them, then prune the leader off the plant so tomato plants will put more energy into ripening fruits, instead of growing more foliage.
Pruning: Indeterminate tomato plants benefit greatly from correct pruning and training. Fruit production is increased by removing extra growth that diverts energy away from developing fruits. Removing extra growth redirects energy back to the fruits and reduces fruit shading, both of which will help fruits mature more quickly. Pruning also improves airflow, which reduces humidity and provides a less favorable for fungal and bacterial disease development.

Storing Tomatoes

The usual practice is to wait until just before a killing frost to pick mature green tomatoes (these are full size and light green).
In a warm fall, plants may begin to decline before a killing frost. Fruit that has gone from dark green to lime green should be picked. Once tomatoes get to that lighter shade of green they will ripen off the vine.
Tomatoes can be kept one layer deep in shallow boxes or trays in a cool, dark place. Kept at 10-15°C, most tomatoes will hold for several months.
To finish ripening, bring tomatoes to room temperature. They don't have to be exposed to light to ripen, though it will increase their colour somewhat. Check on the stored tomatoes often to remove ripening or rotting fruit.

Common Tomato Problems

Late Season Blight: Tomato blight is a disease that attacks the foliage and fruit of tomatoes, causing rotting. It is most common in warm, wet weather. The best way to prevent late season blight is to grow tomatoes undercover. On the wet, west coast it is very common for tomatoes grown outdoors to get late season blight.
Blossom End Rot: Blossom end rot is a physiological disorder of tomato where the blossom end of the fruit breaks down and rots. This is caused by a lack of calcium in tomato fruits. Most soils have enough calcium, but for calcium to reach the parts of the plant that are furthest from the roots there needs to be a good flow of water through the plant. Regular watering and a tomato fertilizer with calcium will prevent blossom end rot in the future. Once a tomato fruit has blossom end rot there is nothing that can be done, but you can prevent subsequent fruits from being affected.
Botrytis: Botrytis affects dying foliage on plants and it looks like a gray fuzzy coating. Botrytis can get into stems, however, through injuries where leaves are pruned off, killing the plant. In the summer there is little risk of Botrytis infection, but in the fall the risk is so high that it is not a good time to prune leaves.
Heat Stress: When tomato plants are exposed to excessive heat, flower and fruit production decreases. Foliage will curl inward as an attempt to reduce the surface area of foliage. If tomatoes are showing signs of heat stress shade cloth would be beneficial.

More Info:

Tomato pruning guide
Growing tomatoes from seed
Want to purchase tomato seedlings? Or learn more about different varieties? Check out the varieties we grow here.
Want to learn more about growing vegetables from seed? Check out our resource on starting veg from seed.

Greenhouse Growing