If you’re tired of mass-produced tomatoes in the supermarket, why not grow your own tomatoes from seed?
While the easiest way to grow tomatoes is with a store-bought seedling, starting from seed can be even more rewarding.
You can choose from countless varieties and enjoy unique flavours for all kinds of dishes — salads, sandwiches, and of course, pasta!
For successful germination, tomatoes need two main things: consistent warmth and moisture.
Knowing when to sow seeds is also important, as you don’t want to risk exposing the seedlings to very low temperatures or frost.
Here’s a step-by-step guide for growing tomatoes from seed, so you can enjoy a big and delicious harvest.
When to Sow Tomato Seeds | What You’ll Need | Growing Tomatoes From Seed | What to Do After Germination | Transplanting | Care Tips
What to Know Before Sowing Tomato Seeds
Before growing tomatoes, consider what they need to thrive, which varieties to plant, and where to transplant the seedlings once they sprout!
What do tomatoes need to grow strong?
It helps to understand what tomatoes need to thrive so you can give them the best start. Here are the optimal conditions for growing healthy tomatoes:
| Climate | Warm, dry climates |
| Ideal Temperature | 15°C–29°C |
| Soil | Rich, well-draining soil that’s slightly acidic to neutral (6.2–6.8 pH) |
| Light | 6–8 hours of full sun daily with some protection from intense afternoon heat |
While tomato plants prefer warm and dry climates, they can also adapt to tropical or subtropical regions.
But whenever possible, keep them sheltered from prolonged, heavy rains to reduce the risk of fungal or bacterial problems.
Tomatoes can also survive in colder places, but they’ll quickly die back if the temperature stays below 0°C.
Which tomato should you plant?
There are thousands of tomato varieties, and each is unique. It’s important to think about which tomatoes are best for your garden and your taste buds.
Here are a few factors to consider:
GROWTH HABIT: Determinate (bush) tomatoes stay compact and finish fruiting within 1–2 weeks. On the other hand, indeterminate (vining) types keep sprawling and producing until they die back.
FLAVOUR AND USES: Do you want heirloom tomatoes with a classic taste, sweet cherry tomatoes for snacking, or paste varieties for preserving?
(If you’re planting an heirloom variety, you can save tomato seeds from the fruit!)
GROWING SEASON: If you’re in a cooler region with a short growing season, go for early-maturing varieties. These can produce fruit just 60–70 days after planting.
DISEASE RESISTANCE: Some varieties are bred to resist common tomato problems like blight or wilt.
Where should you grow your tomatoes?
Another thing to consider is where to plant your tomatoes after the seeds have sprouted.
You have the best chance of getting a big harvest if you grow tomato plants outdoors in a raised garden bed.
This gives the plants enough room to sprawl (especially indeterminate tomatoes) and get adequate sunlight.
Just remember: do not plant tomatoes in the same soil where tomatoes or other nightshades (like eggplants and potatoes) have grown for the past 4 years.
Practice crop rotation to avoid soil-borne fungi and other organisms that can cause disease!
If you don’t have much space, you can grow tomatoes in pots and keep them in a sunny balcony or patio. Determinate types are more suitable for pots, since they stay compact.
Use a high-quality potting mix made for vegetables. Your container should be at least 40–50cm wide and deep, with drainage holes.
For those in colder areas, you can keep your tomatoes indoors. But bear in mind that this usually leads to fewer fruits due to limited sunlight.
To ensure adequate lighting, you’ll need full-spectrum grow lights. Keep them on for 14–16 hours, then the room should be dark for the next 8–10 hours.
When flowers appear, gently tap their stems a few times each day to help spread the pollen and encourage fruit set.
When to Sow Tomato Seeds in Australia
Sowing tomato seeds at the right time is important!
In cold regions, planting too early can expose young seedlings to frost, which may stunt their growth or kill them off.
On the other hand, if you start too late, the tomatoes might not have enough time to produce fruit before intense heat or frost arrives.
Here’s a guide for when to sow tomato seeds in different Australian climates:
| CLIMATE | WHEN TO SOW TOMATO SEEDS |
| Tropical and Subtropical | March to April (start of dry season) |
| Cool and Cool Temperate | 6–8 weeks before the average last frost date |
| Warm Temperate | 6–8 weeks before spring |
Keep in mind that these timelines are just estimates. Local weather can vary, so you might need to adjust the timing as needed.
What You’ll Need for Sowing Tomato Seeds
To get started, you’ll need tomato seeds, a good seed starting mix, and containers.
You also need a warm location where you can place the seeds you sowed while waiting for them to germinate.
Tomato seeds
Always buy tomato seeds from a reputable garden centre or supplier — this helps ensure they’re healthy and disease-free.
Before planting, check the seed packet for any relevant growing instructions.
Seed starting mix
Use a light, well-draining seed starting mix. You can buy a ready-made one from most garden stores.
A good seed raising mix for tomatoes usually contains:
- vermiculite (for aeration)
- perlite (to enhance drainage)
- peat moss or coco coir (for water retention)
Do not use regular garden soil — that’s usually too heavy for tomato seeds and might even carry pests (like fungus gnats!) or diseases.
Depending on how many tomato plants you want to grow, you might need plenty of seed raising mix, so make sure you have enough.
Seed starting containers
To get sturdy seedlings, use small pots about 7–10cm wide and 10–12cm deep. This size gives the plant’s roots enough space to grow deep and strong early on.
Plastic pots or even drinking cups can work as long as they have drainage holes. For cups, simply cut a few small holes at the bottom.
If you’re planting a large batch, you can use a seedling tray with multiple compartments or “cells.”
Just note that tomatoes grow quickly, so you’ll likely need to move them to individual containers before long.
Location
It’s best to start tomato seeds indoors or in a greenhouse, especially if the weather is still chilly.
In warmer climates, you can use a shaded and sheltered spot outdoors.
A protected environment helps young seedlings develop until they’re strong enough to handle direct sunlight and outdoor winds.
How to Grow Tomatoes From Seed
Once you have everything you need, it’s easy to plant tomato seeds!
But how do you get the seeds to germinate? Two things that can speed up the process are consistent moisture and warm temperatures.
Step 1. Dampen the seed starting mix
Put the mix in a bucket or basin, ideally one with drainage holes at the bottom.
Slowly add water while mixing it with your hands or a trowel. Continue doing this until the entire batch is evenly damp.
When you’re done, the soil should feel like a wrung-out sponge — slightly moist but not soggy.
Step 2. Prepare your containers
Fill each pot about three-quarters full with your lightly dampened seed starting mix. Tap the sides or bottom of the container to remove large air gaps.
Do not pack the soil down. You want to keep it loose and fluffy to ensure that the tomatoes’ roots can grow easily.
Step 3. Sow the tomato seeds
Because tomato seeds are so tiny, it’s important not to plant them too deeply!
Use your finger or a pencil to make small, shallow holes in the soil surface. The holes should be about 0.5cm deep.
Drop 1 or 2 tomato seeds into each hole. The second seed is merely a backup in case one doesn’t sprout.
Lightly cover the seeds with a thin layer of seed starting mix — just enough to hide them.
Fill a spray bottle with water, then lightly mist the surface. This settles the soil and gives the seeds the moisture they need to germinate.
Do not use a watering can with a strong stream, as that can wash the seeds out of place.
Step 4. Label containers
If you planted different tomato varieties, it’s a good idea to label each pot. Write down the name of the tomato variety and the date you sowed the seeds.
You can use wooden sticks, plastic tags, or masking tape placed on the side of the pot.
Step 5. Create a humid environment
After sowing seeds, cover the container with a clear plastic bag or a transparent plastic dome.
This works like a mini greenhouse that traps heat and soil moisture, creating the ideal conditions for seed germination.
Still, make sure there’s some airflow — poke a few holes in the bag or keep the cover loose.
Step 6. Move containers to a warm location
Tomato seeds don’t need light to germinate, but they do need warmth! For the best results, keep the soil temperature between 20°C and 25°C.
You can place the containers on a sunny windowsill or even on the top of a fridge (if that gives off some heat).
Alternatively, use a heat mat to keep the seeds warm.
Step 7. Keep the soil moist
While waiting for the tomato seeds to germinate, make sure to keep the seed raising mix moist.
Check the soil daily by touching the surface. If it’s dry, lightly spray the surface.
Bottom watering is another good option. Just place the containers in a tray filled with water for 10–15 minutes. This lets the soil soak up moisture through the drainage holes.
When the top of the soil is damp, you can remove the container from the tray.
Step 8. Wait for the tomato seedlings to appear
Tomato seeds usually germinate in 5–10 days, but this can differ depending on the variety, soil temperature, and humidity.
The first to appear would be a tiny sprout with two seed leaves or cotyledons. These aren’t true tomato leaves, but they store energy to help the seedling grow.
Once the seed leaves emerge, remove the plastic bag or dome to ensure good air circulation.
This helps prevent ‘damping off,’ a fungal disease that can kill tomato seedlings!
Caring for Tomato Seedlings After Germination
When the tomato seeds have germinated, the next step is to get them ready for outdoor conditions.
Provide sunlight and moisture
Once the tomato seedlings emerge, they need plenty of light!
Place them where they can get 6–8 hours of bright, indirect sunlight daily. Rotate the container every 2–3 days to prevent leggy or uneven growth.
If natural light is limited, use a grow light and place it about 5–10cm above the seedlings.
Also, keep the soil consistently moist. Water gently with a spray bottle or a small cup whenever the top of the soil feels dry.
Many gardeners also prefer bottom watering for seedlings, since it encourages the roots to grow deeper.
Thin out tomato seedlings
If two tomato seedlings emerged in the same pot, you’ll need to thin them to prevent competition for water and nutrients.
Wait until the first true tomato leaves appear — the small, multi-lobed leaves that grow after the first seed leaves.
Use scissors to snip the weaker seedling at the soil line. Do not pull it out, as that can disturb the roots of the stronger seedling.
Some gardeners try separating the roots and replanting each seedling, but this can be tricky. If you try that, take care not to damage the roots!
Move seedlings to a bigger container
If you started your tomatoes in a tray with small cells, move them to larger containers once they have at least 2 sets of true leaves. Leaving them too long can stunt growth.
(However, you can skip this step if you planted in bigger containers from the start.)
Use a pot 7–10cm wide and about 10–12cm deep. Fill it with a high-quality potting mix for vegetables, then make a hole in the centre.
Gently remove the tomato seedling from the tray, place it in the new pot, and water lightly to help it settle.
Harden off tomato seedlings
You’ll need to harden off your tomato seedlings around a week before transplanting.
That means gradually exposing young plants to outdoor conditions to avoid transplant shock.
Before you start, wait until the danger of frost has passed and it’s at least 15°C at night.
When the weather is warm enough, place the tomato seedlings in a sheltered spot outdoors for just 1–2 hours.
Each day, slowly increase the amount of time they spend outside and introduce more sunlight and wind.
While hardening off, watch for signs of stress such as yellowing leaves or weak growth. If this happens, let the plants recover indoors.
After about a week, you can leave the tomato seedlings out overnight.
Once tomato plants can spend a full day or two outdoors without stress, they’re ready for transplanting to a garden bed or a bigger pot.
Transplanting Tomato Seedlings
Proper transplanting reduces the risk of transplant shock and sets up your tomatoes for healthy growth!
When to transplant tomato seedlings
After hardening off your tomatoes, they’re likely strong enough to handle outdoor conditions. That means they’re ready to transplant.
The plants should be around 15–20cm tall, with at least 3–4 sets of true, healthy leaves.
How to transplant tomato seedlings
Carefully remove each tomato plant from its current container, and cut off the lowest set of leaves.
Dig a hole at the planting site, whether a garden bed or a larger pot. The hole should be deep enough to bury about two-thirds of the tomato’s stem.
Tomatoes grow roots from any buried part of their stem, so this will help the plants become more stable.
You can also add finely ground or crushed eggshells into the planting hole. Mix it with the soil to provide a natural calcium source for your plants.
Lower the seedling into the hole, then backfill with soil. Gently firm the soil around the base of the plant, and water thoroughly.
Providing support for tomatoes
At the time of transplanting, you’ll need to set up support for your tomatoes. This keeps the plants upright, and lifts the leaves and fruit away from the soil.
For determinate tomatoes, use a sturdy stake about 1–1.5m high. On the other hand, large cages are better for indeterminate tomatoes, since they sprawl continuously.
As your tomato grows, gently tie the stem to the stake or cage using soft garden ties or strips of cloth.
Care Tips for Tomato Plants
Once your tomatoes are in their permanent home, they need consistent care to stay healthy and produce plenty of fruit.
Water tomatoes regularly, especially during hot weather and when they start flowering and fruiting.
Consistent moisture helps prevent problems like blossom end rot (dark patches on the bottom of the fruit).
Fertilising tomatoes is also a must. In the leafy growth stage, use a slow-release, balanced NPK fertiliser.
Once flowers appear, switch to a fertiliser with more phosphorus and potassium, and lower in nitrogen.
Avoid excess nitrogen at that point, since it can lead to more leaves instead of fruit.
Don’t forget to prune tomato plants regularly, too. Remove dead or yellowing tomato leaves, plus any that are touching the ground.
FAQs About Growing Tomatoes From Seed
Got some more questions about tomato seeds or how to raise the seedlings? Find more tips in the Q&As below!
Do you have to soak tomato seeds before planting?
No, soaking isn’t necessary. Tomato seeds germinate just fine when planted directly into moist soil.
Some gardeners soak seeds for a few hours to help soften the seed coat, but that’s optional!
How to grow cherry tomatoes from seed
The process of sowing seeds is the same, whether you’re planting cherry, Roma, beefsteak, or other types of tomatoes.
You’ll need a good seed starting mix and small pots. After planting the seeds, make sure they get steady warmth and moisture.
How often to water tomato seedlings
There’s no strict rule, so check the soil daily! For tomato seedlings (and even mature plants), aim to keep the soil moist but not waterlogged.
Poke the soil to feel if the top 1cm is dry. If it is, you can water the seedlings.
How to care for leggy tomato seedlings
Tomato seedlings usually grow leggy because they’re trying to find more light.
The quickest fix is to move them to the brightest spot you have. Rotate the container every few days for even exposure.
If you’re using grow lights, try lowering them a bit closer to the plants.
Other possible causes of legginess include overcrowding, poor airflow, or containers that are too small.
If that’s the case, move the seedlings to individual, slightly bigger containers. You’ll also need to thin out multiple seedlings growing in the same pot.
Why are my tomato seedlings not growing?
If the seedlings aren’t growing, they might not be getting enough light.
It’s also possible that they’ve outgrown their container — particularly if they’re in a tray with tiny compartments.
Place your seedlings in a bright, warm spot or use grow lights. You may also need to move them to a slightly bigger container (7–10cm wide) to give them enough space to grow.
What causes yellowing leaves on tomato seedlings?
This is a sign that your tomato seedlings are under some kind of stress. Common causes are:
- Insufficient light
- Cold temperatures
- Overwatering or underwatering
Make sure to move seedlings to a warm, bright spot. And water only when the top of the soil has dried out.
