Germinating your seeds indoor

Planting seeds – or sowing seed, to use the correct term – is a simple and inexpensive way of growing new flowers and vegetables for your garden. Sowing seed indoors allows you to start the growing year much earlier than if sowing seeds outside. When growing salad and vegetable crops, it’s a good idea to sow a small amount of seed every two weeks, to ensure you have a long season of fresh produce to eat throughout summer. This is called ‘successional sowing’.

Process of Seed Germination

During the beginning stage of the germination, the seeds take up water rapidly and this results in swelling and softening of the seed coat at an optimum temperature. This stage is referred to as an Imbibition. It starts the growth process by activation of enzymes. The seed activates its internal physiology and starts to respire and produce proteins and metabolizes the stored food. This is a lag phase of the seed germination. By rupturing the seed coat, the radicle emerges to form a primary root. The seed starts absorbing underground water. After the emergence of the radicle and the plumule, the shoot starts growing upwards. In the final stage of seed germination, the cell of the seeds become metabolically active, elongate and divide to give rise to the seedling.

Conditions Necessary for Seed Germination

Here are some important requirements which are essential for a seed to germinate into a seedling and to a plant.

Water: It is extremely necessary for the germination of seeds. Some seeds are extremely dry and need to take a considerable amount of water, relative to the dry weight of the seed. Water plays an important role in seed germination. It helps by providing necessary hydration for the vital activities of protoplasm, provides dissolved oxygen for the growing embryo, softens the seed coats and increases the seed permeability. It also helps in the rupturing of seed and also converts the insoluble food into soluble form for its translocation to the embryo.

Oxygen: It is an important and essential source of energy required for seed growth. It is required by the germinating seed for the metabolism and is used as a part of aerobic respiration until it manages to grow green leaves of its own. Oxygen can be found in the pores of soil particles, but if the seed is buried too deep it will be deprived of this oxygen.

Temperature: For a seed to germinate, it requires a moderate temperature of around 25-30°C. Quite obviously different seeds require different optimum temperatures. There are some seeds which require special requirements either lower or higher temperature between 5 to 40°C.

Light or darkness: This can act as an environmental trigger. Many seeds do not germinate until sunlight falls on them.

Managing Factors Affecting Seed Germination

Apart from seed dormancy – This is a condition in which the seeds are prevented from germinating even under favourable conditions – major factors that affect seed germination can be managed quite easily indoor. 


Water: The poor or additional supply of water affects the seed germination.

Temperature: This affects the growth rate as well as the metabolism of the seed.

Oxygen: Germinating seeds respire vigorously and release the energy required for their growth. 

Therefore, deficiency of oxygen affects the seed germination.

In certain cases, a temperature below the moderate level slows down the seed germination and promotes fungal growth. In some cases, the germination stops at the temperature above the moderate level.

Invest in pots and a propagator or build your own

You don’t need a lot of kit to sow seeds. Many gardeners buy propagators but a seed tray or a few plastic pots will also do the job. If you don’t have plastic pots then try using old yoghurt pots with holes punched in the bottom, or tomato or mushroom punnets instead of a seed tray. Any vessel that can hold compost and allow water to drain freely is suitable.

Buy a quality seed mix is always best. Some very small seeds need specialist ‘seed compost’ to germinate, but multi-purpose compost is fine for most seeds. To maintain an even temperature and keep the soil moist, it’s a good idea to cover the soil with a clear piece of plastic. A bespoke propagator will come with its own clear plastic lid, but you can use cling film, old freezer bags or any clear plastic bag. Use cellotape or an elastic band to fix it to the pot.

HOW to plant your seeds 

Fill small pots or seed trays with compost. Use a watering can fitted with a fine rose to thoroughly wet the compost, and leave to drain. Then add your seed on top and cover the seed with a thin layer of compost, about the same depth as the size of the seed (the smaller the seed, the thinner the layer of compost). Cover the pot or tray with a piece of glass or clear plastic, to maintain an even temperature for germination, and keep the compost moist. Place the pot of seeds on a well-lit windowsill or in a heated propagator. >60% humidity and 25-28 degrees is optimal. Remove the plastic or glass cover as soon as the seeds have germinated. After a couple of weeks, the young plants will be large enough to pot individually into larger pots, or planted outside in well-prepared soil. Handle plants gently and water well. Don’t allow the soil or compost to dry out.