They struggle below 10C, above 27C, or in frost.
They grow in a wide range of fertile, well-drained soils with a slightly acid pH between 5.5 and 7.
Very acidic soils may need a light application of lime.
To avoid soil-borne pests and diseases, rotate tomatoes with other crops rather than planting in the same spot each year.
In smaller gardens or greenhouses, if rotation cannot be achieved, changing or replacing the soil is another option to reduce the risk of disease.
Tomatoes grow very successfully in containers, which is a great option for smaller spaces.
Prepare the soil by working in “Tui Tomato Mix” or “Ican Planting Mix” to a depth of at least 30cm, as tomatoes develop deep root systems and are heavy feeders.
Incorporate a tomato fertiliser before planting – tomatoes require high levels of phosphate but low nitrogen.
Side dressings during the growing season with “Ican Tomato Food” or similar products are beneficial. Slow-release options such as “Manutec Tomato Tablets” or “Jobes Tomato Spikes” are particularly effective for tomatoes, capsicums, and cucumbers grown in pots and containers.
Sowing and planting
Tomato seeds sown now will produce crops in February or March, while seedlings planted out now can yield ripe fruit from late December, depending on the weather.
To stagger your harvest, consider sowing a few seeds now. Use a clean seed tray filled with a quality seed-raising mix, firmed and levelled about 20mm below the top.
Moisten thoroughly, let drain, then sow seeds evenly and cover with 3-5mm of mix.
Ideal germination temperature is 21-24C. Seeds will germinate at lower temperatures, but more slowly.
Cover trays with glass and paper to retain humidity, turning the glass daily to remove condensation.
With good preparation, no further watering should be needed until seedlings emerge.
High humidity at this stage helps seedlings shed their seed coats.
Prick out seedlings when their first leaves (cotyledons) are fully expanded – usually six-12 days after sowing at warm temperatures. Gently lift seedlings by a seed leaf, not the stem, using a small stick or teaspoon to loosen the roots.
Pot the healthiest seedlings into 5–6cm pots using “Ican Premium Potting Mix” or “Tui Tomato Mix”. Discard weak ones.
Provide good ventilation and plenty of light. Seedlings tolerate short cool spells if day temperatures stay above 7C and soil is around 10C. If frost threatens, protect young plants with cloches or plastic covers supported by stakes.
Routine care
Once the soil has warmed, water and mulch thoroughly. Container-grown plants need more frequent watering and regular feeding to replace nutrients lost through leaching.
Avoid overwatering or overfeeding, as both can reduce flavour.
Always water the soil, not the foliage, to prevent fungal problems – use a watering can, soaker hose, or micro-irrigation system.
Begin removing laterals (the small shoots that grow between the main stem and leaf branches) about three weeks after planting and continue weekly.
Snap or pinch them off when dry to reduce the risk of infection.
Remove any old or crowded leaves to improve air circulation and allow sunlight to reach ripening fruit.
Grafted tomatoes can usually be left to grow without removing laterals, as their stronger root systems support larger plants.
Pests and diseases
The two main tomato problems are blight and the tomato/potato psyllid. Blight, a fungal disease common later in the season, can be prevented and controlled with “Gro Safe Free Flo Copper”.
The psyllid, a small sap-sucking insect, is readily controlled using “Yates Mavrik” or “Yates Success”. Both products are bee-friendly once dry.
With a little preparation, care, and patience, your tomato plants will reward you with an abundant, delicious harvest – perfect for salads, sandwiches, and snacks all summer long.
Gareth Carter is the general manager of Springvale Garden Centre in Whanganui.
