Tomatoes are one of the most popular crops to grow at home, and with the right fertiliser and method, you can achieve an abundant and flavourful harvest. In this guide, we go through everything you need to know about pre-germination, choosing growing methods and why the right fertiliser is essential for your tomato plants.
When and how do you propagate tomatoes?
Pre-germination of tomatoes is necessary in Denmark to ensure a long enough growing season. The best time to start is February to March, but if you have a greenhouse or a warm, sunny location, you can still make it in April. If you start later, you can also buy pre-germinated plants in May to save time.
Choice of pre-emergence method: Seed trays vs. Conventional method
One of the most common mistakes when pre-germinating tomatoes is to sow them directly into large containers. This can result in poor root development and over-wetting. Therefore, it is recommended to use seed trays.
Advantages of seed trays:
Better root development: Each plant gets its own space and develops a healthy root system.
Less risk of overwatering: Small spaces in seed trays ensure more controlled humidity.
Easier transplanting: The plants are easier to handle and repot without damaging the roots.
If you have an interest in our seed trays, please click here!
Choosing soil and fertiliser for germination
Tomatoes require a well-drained and nutrient-rich soil to germinate and grow optimally. A good seed soil should be light and airy. Start with a seed soil without too much fertiliser, as too much nutrients in the beginning can inhibit germination.
Coconut mould vs. regular soil
There are many different types of soil, but a popular alternative to traditional soil is coco coir.
Here's the difference:
Coconut flour is light, airy and retains moisture well without over-wetting the plants. It's also a more environmentally friendly choice as it's a by-product of the coconut industry and often free from weed seeds and pests.
Ordinary soil can be heavier and more compact, but usually contains more natural nutrients. However, it often needs to be mixed with sand or perlite for better drainage.
For tomato propagation, a mix of coconut and regular soil can be a good combination as it provides optimal moisture and air for the roots.
Choosing the right fertiliser for tomatoes
For best results, we recommend Organic Tomato Focus Fertiliser 1Lspecially developed for tomatoes, providing the perfect balance of nutrients for healthy, flavourful fruit.
Comparing our fertilisers and their effects
To give tomatoes the best growing conditions, you can also supplement with the following products during the different stages. According to our Tomato fertiliser chart, you can follow a structured approach to fertilisation throughout the growing season:
| Week | Growth stage | Big Grow | Big Calcium | Big Roots | Big Boost | Big Shield | Water |
|---|---|---|---|---|---|---|---|
| 1 | Germination | 1ml | 1ml | 2ml | 1ml | 0 ml | 1L |
| 2 | First leaves | 1ml | 1ml | 2ml | 1ml | 1ml | 1L |
| 3 | 2nd-3rd leaves | 2ml | 2ml | 2ml | 1ml | 1ml | 1L |
| 4+ | 4.+ leaves | 3ml | 2ml | 2ml | 2ml | 2ml | 1L |
The purpose of fertilisers:
| Fertiliser | Best for |
| Big Calcium | Strengthens plant cell walls and prevents rot, important for strong stems |
| Big Bloom | Supports the flowering phase and helps with higher yields |
| Big Shield | Protects against pests and diseases, especially important in humid environments |
| Big Roots | Stimulates root growth for stronger and healthier plants |
| Big Ro Base | Suitable for soft water and osmosis water, ensures proper nutrient supply |
| Big Flower PK Booster | Improves flowering and fruit set |
| Big Boost | Boosts growth in the early stages |
| Big Grow | Perfect for balanced growth, especially in hydroponic systems |
| Big Diamonds | Improves flavour and aroma in the final stages of growth |
| To give tomatoes the best growing conditions, you can also supplement with the following products during the different stages: |
| Fertiliser | Best for |
| Big Calcium | Strengthens plant cell walls and prevents rot, important for strong stems |
| Big Bloom | Supports the flowering phase and helps with higher yields |
| Big Shield | Protects against pests and diseases, especially important in humid environments |
| Big Roots | Stimulates root growth for stronger and healthier plants |
| Big Ro Base | Suitable for soft water and osmosis water, ensures proper nutrient supply |
| Big Flower PK Booster | Improves flowering and fruit set |
| Big Boost | Boosts growth in the early stages |
| Big Grow | Perfect for balanced growth, especially in hydroponic systems |
| Big Diamonds | Improves flavour and aroma in the final stages of growth |
When should you start fertilising?
Finishing the planting phase
Once your tomatoes are planted out, it's important to continue to give them the right care to ensure strong growth and an abundant harvest. Keep the soil moist, but not waterlogged, and support the plants if they are tall-growing varieties. Regular fertilisation with the right nutrients will ensure that the plants develop healthy fruits. By combining the different fertilisers, you can ensure optimal growing conditions throughout the season.
First phase (germination phase): No fertiliser is needed.
When the first real leaves develop: Start applying a mild liquid fertiliser like Organic Tomato Focus.
After transplanting to larger pots: Use a more nutrient-rich fertiliser to support growth, for example Big Boost.
Lighting
Finding the right lighting is a super important factor here, often during the hot summer periods there is plenty of heat and light, which means that there is not as much need for extra lighting.
However, during the pre-germination phase it is of great importance as it can be one of the factors that make your plants not grow enough, here we often advise to go for a full spectrum grow light as it can have a big impact on your tomatoes, so they can come out of the pre-germination phase and get ready to be planted.
Here you have the opportunity to find some of our Grow light that we think are great for growing tomatoes.
Conclusion
Growing tomatoes is a rewarding experience, and with the right fertiliser and method, you'll have healthy plants with an abundant harvest. Use seed trays for a better start, give your plants the nutrition they need and enjoy your home-grown, flavoursome tomatoes!
If you would like to read something about grow light for tomatoes, read our colleague's guide here
