How To Grow Tomatoes | Kings Seeds

Ever tasted a tomato so good it made you question every supermarket one you’ve ever bought? That’s the magic of growing tomatoes at home, and it all begins with knowing how to sow tomato seeds the right way. Whether you’ve got a sprawling garden or a few pots on the deck, tomato growing in NZ is easier (and more addictive) than you think. Here’s how to grow tomatoes that burst with flavour, thrive in our unique climate, and keep you stocked all season long - even into winter, if you dry them right.

How to Sow Tomato Seeds

Tomato growing in NZ begins before the summer sun warms your garden beds. To give your plants the best head start, sow tomato seeds indoors 6 to 8 weeks before the last frost. This is usually around late August to early October, depending on your zone.

Use seed trays filled with a fine seed-raising mix. Gently press your tomato seeds about 6mm deep and water lightly. Keep the mix damp but never soggy. For quicker germination, place trays somewhere warm, like a sunny windowsill or on a heat pad. The ideal temperature range for germination is 20°C to 30°C. Once seedlings appear, make sure they get plenty of light—lack of it leads to leggy, weak stems.

Soil and Sunlight Needs

Tomatoes are sun-seekers. Choose a position in your garden that gets at least 6 to 8 hours of direct light each day. If you're growing tomatoes in containers or plastic tubs, place them where they won't be shaded by trees or buildings.

The best soil for growing tomatoes indoors or out is free-draining, rich in organic matter and slightly acidic (pH 6.0 to 6.8). Mixing in compost or well-rotted manure adds nutrients and improves drainage. If unsure, use a specific tomato mix.

Watering, Feeding & Mulching

Tomatoes prefer deep, consistent watering. Aim for three times a week, adjusting with the weather. Avoid overhead watering to reduce disease risk; instead, water at the base of the plant.

Fertilise monthly with a tomato-specific feed or a balanced mix like seaweed and herb concentrate. To keep moisture in and weeds out, apply mulch around the base of the plants once they're established. 

Watch out for common tomato diseases and issues like yellowing leaves, which can be a sign of nitrogen deficiency. A liquid feed can help bring them back to health.

More tomato tips here.

Spacing & Staking

Plant your seedlings deeply, burying two-thirds of the stem. This encourages strong root growth. Space your tomato plants about 60cm apart, and 90cm between rows. For larger varieties, allow even more room.

Staking is vital for indeterminate (vining) varieties. Use wooden stakes, cages or trellises. Tie stems loosely using soft material like cloth or wool. This keeps fruit off the ground, reducing rot and pest risk. If you're growing tomatoes in pots, staking is still important—just ensure your pot is deep enough to support the plant.

More about indeterminate vs. determinate varieties here.

When & How to Harvest

Tomatoes are usually ready for picking about 80 to 90 days after transplanting. Check your specific variety for more precise timing.

Pick when fruits are fully coloured and slightly soft to the touch. Harvest regularly to encourage ongoing production. Cherry varieties like "Matt's Wild Cherry" or "Cherry Berry F1" tend to ripen earlier, while beefsteak types take longer.

Use scissors or gently twist fruit off the vine to avoid damaging the plant. Harvesting in the morning ensures firmer fruit that stores better.

How to Dry Tomatoes for Later Use

Drying tomatoes is a great way to extend your harvest. Choose firm, ripe fruit—roma varieties like 'Sicilian Sauce F1' or 'Speckled Roman' work well.

Steps for drying:

• Wash and slice tomatoes evenly.

• Remove seeds if preferred (optional).

• Sprinkle with salt and herbs like oregano or thyme.

• Dry in a dehydrator at 55°C to 60°C for 8 to 12 hours, or use an oven on low heat with the door ajar.

• When leathery and pliable, store in airtight jars or containers.

Store dried tomatoes in olive oil with garlic and herbs for a delicious pantry addition. Or rehydrate with boiling water for cooking.

Tips for Growing the Best Tomatoes

• Start seeds early for strong seedlings.

• Choose NZ-friendly tomato varieties.

• Prune regularly by removing suckers to promote airflow.

• Companion planting works - basil and marigold help deter pests.

• Rotate crops each year to avoid soil-borne diseases.

• Avoid overcrowding; airflow is key to healthy plants.

Tomato Growing FAQs

How long do tomatoes take to grow?

Tomatoes typically take 80–90 days from transplanting to harvest.

When to plant tomatoes in NZ?

Start seeds indoors from late August, transplant outdoors after the last frost - usually late October to mid-November.

How often to water tomatoes?

Three times a week deeply at the base, more in hot dry weather.

How to prune tomato plants?

Remove side shoots (suckers/laterals) from leaf axils to direct energy into fruit.

What grows well with tomatoes?

Basil, marigolds, chives and lettuce all make great companion plants.

What month to plant tomatoes in NZ?

In New Zealand, plant tomatoes from September to December, plant seedlings outside after the last frost.

Do you remove side shoots from tomato plants?

Yes, removing side shoots (suckers/laterals) helps the plant focus its energy on producing fruit.

How do you care for a tomato plant?

Care includes regular watering, staking, using mulch, fertilising and monitoring for pests and diseases.

How to Grow Tomatoes Step-By-Step

1. Choose a sunny location with free-draining soil.

2. Start seeds indoors 6-8 weeks before the last frost.

3. Harden off seedlings by gradually acclimatising them to outdoor conditions.

4. Plant seedlings deeply and space them 60cm apart.

5. Stake or cage plants for support as they grow.

6. Water, mulch and fertilise regularly for optimal growth.

7. Monitor for pests and trim as needed to maintain healthy plants.

 

 

Ready to Grow Your Best Tomatoes Yet?

From planting tomato seeds to picking your first ripe harvest, growing tomatoes is a rewarding and delicious journey. With the right mix of sunlight, soil, care and timing, your garden can produce a generous supply to enjoy fresh, cooked or dried.

Spring is the signal. Tomatoes are the mission. If you’ve been waiting for the right time to start growing tomatoes in NZ, this is it. From how to plant tomato seeds to harvesting juicy fruit for salads, sauces and drying, Kings Seeds have you covered. We supply New Zealand's largest selection of tomato seed varieties, suited to every garden and growing condition. Browse our online store to find your favourites, stock up on seed-raising supplies, and make this tomato season your most bountiful yet.

Happy growing from the team at Kings Seeds, your trusted source for quality seed and advice for over 40 years!