How to Properly Start Seedlings? Equipment Guide for the Spring Season

Spring is approaching and it's time to start preparing for the upcoming growing season. If you want to get a head start on the weather, start seedlings at home and your plants will reward you with rapid growth, robust health and an early harvest. What will you need and how do you do it? We have prepared a clear guide to pre-growing seedlings for you.

Why pre-grow seedlings?

Starting seedlings indoors in the comfort of your home is a great way to get ahead of the season. Avoid the risks associated with unpredictable spring weather and your plants will adapt quickly to outdoor conditions after transplanting. Another advantage is that pre-growing allows you to cultivate species that otherwise might not thrive in our climate.

• Ideal conditions: Germinating and pre-growing seedlings indoors lets you create an optimal environment for the plants.
• Faster growth and earlier harvest: Plants spend their first weeks of life in a protected environment where they can strengthen and develop a rich root system. After planting out they then grow faster and mature earlier than when sown directly outdoors.
• Ability to grow a wider range of species: Many plants take too long to mature to finish in our geographical conditions. By pre-growing these species before spring begins, you can shorten that period.

Which plants are suitable for pre-growing?

Not all plant types need to be pre-grown; some, like radishes, peas or carrots, are sown directly in the bed because they do not tolerate transplanting or they grow and mature very quickly. The most commonly pre-grown crops include:

• Fruit vegetables: tomatoes, peppers, eggplants, chilli
• Medicinal and exotic species: plants grown in controlled environments
• Cucurbit vegetables: cucumbers, courgettes, pumpkins
• Leafy vegetables and brassicas: lettuces, broccoli, cauliflower, cabbage
• Aromatic herbs: basil, marjoram, thyme, rosemary
• Ornamental flowers: marigold, petunias, dianthus, lobelias

What you'll need to pre-grow seedlings at home?

Although it is possible to pre-grow seedlings on a windowsill or in a conservatory, you will achieve the best results in a grow tent, where you can create a protected and stable environment for the plants. Inside a grow tent you can easily control temperature, humidity and light levels so seeds can germinate and grow without exposure to weather fluctuations. Seedlings grown in a stable environment grow faster and are more resistant to pests, mould and disease.

Besides the grow tent, you will also need the following to pre-grow seedlings:

• Propagator: Mini greenhouses will help you create the ideal climate for germinating seeds and young plants. For some species, propagators with heating are suitable.
• Seedling tablets, cubes or plugs: Seedling cubes make germination and handling seedlings easier. They can be made from various materials such as mineral wool, coconut or peat. Remember that seedling cubes are intended for germination and after a few days the plants will need to be transplanted into a suitable growing substrate.
• Growing substrate: The choice of growing substrate for seedlings depends on the species and the cultivation method. It is important that the substrate is airy and does not contain high amounts of fertilizers that could burn young plants. You can read about the advantages and disadvantages of different growing substrates here.
• Grow lighting: For rapid growth plants need plenty of light. For pre-growing seedlings, energy-efficient LED grow panels with a growth spectrum are the most suitable.
• Heating mat: Some species germinate and grow better at higher temperatures. Heating mats are especially suitable for cultivating warmth-loving species like tomatoes or chilli.
• Sprayer: Hand-watering young plants can easily wash them out of the substrate, so we recommend adding a hand sprayer to your cart.

Not sure which equipment to choose for pre-growing seedlings? We have prepared complete seed-starting kits that contain everything you need to kick off the outdoor season.

How to pre-grow seedlings — step-by-step guide

1. Selecting seeds and preparation
   • Use only high-quality seed with a high germination rate.
   • Seeds of some species (tomatoes, peppers) should be soaked for several hours in lukewarm water before sowing.
   • To increase germination success for rare or old seeds use a germination stimulator.
2. Sowing and first watering
   • Sow the seeds into a sowing substrate or into seedling tablets, cubes or plugs.
   • Cover them with a thin layer of substrate and gently moisten with a sprayer.
   • Place the seeds in a warm, well-lit spot (20–25 °C).
3. Ideal conditions
   • Temperature: Most plant seeds germinate best at 20–25 °C.
   • Light: Provide at least 12–16 hours of light per day.
   • Moisture: Keep the substrate moist but not waterlogged.
   • Ventilation: Regularly ventilate the propagator to prevent mould formation.
4. Transplanting and hardening off
   • Once seedlings have developed their first true leaves, transplant them into larger pots.
   • Water seedlings regularly and you can use a mild growth fertilizer.
   • Before planting outdoors, harden off the plants. Start by leaving them outside for a few hours a day, then gradually increase to a whole day.

Looking for more growing tips and professional gardening advice? Check out our Higarden blog, where you'll find recommendations and guides for both beginner and advanced growers.