Guide to the seedbed

Most of the vegetables we know are not sown directly in the garden, but are grown starting with the transplant.

The seedlings you can buy them from nurseries or trusted stores, but learn how to get them on your own it is an excellent step forward: it allows you to save money and grow the varieties that interest us for each species, since the purchase of seed packets can be organized in time and with a good choice compared to ready-made seedlings.

By seedbed or nursery we mean a transparent structure, usually covered with plastic sheets, glass or Plexiglas and whose function is to offer a warm microclimate to the seedlings that grow inside.

Why sow in a seedbed

The advantages that the seedbed technique offers compared to direct sowing in the garden are various and interesting.

  • Select some seedlings. First of all, we can sow more seedlings than those that are really needed in the garden, in this way when they are ready we will have the possibility to choose the best ones and those that are more evenly developed.
  • Optimize the space in the garden. With the fact that the seedlings spend the first phase of their life inside the seedbed, they keep the garden beds occupied for a shorter time, and these can be used for other crops earlier. Let's think of all those species that are transplanted only at the end of April or May, for example pumpkins: if we sowed them directly in the garden we would have to do it at the beginning of April, and the space would therefore be occupied already a month before, perhaps not allowing to grow spinach or salad on that same space previously.
  • Anticipate sowing. The seedbed is a sheltered place, where it is possible to sow a few weeks earlier than with direct sowing, as the internal temperature is higher.
  • Less work of weeding. We must consider that the transplanted seedlings have an advantage over weeds, even if we will soon have to intervene by hoeing, weeding or mulching.
  • Economic saving. As a last factor to consider, but not least, there is the savings on the purchase of plants, which will soon pay off the small initial investment to set up the structure.

Which vegetables are suitable for the seedbed

Although most of the horticultural crops can be born in seedbeds, it is necessary to know that some species do not tolerate transplantation, so it is good to know which crops are indicated for sowing in trays.

All cucurbits are very suitable for transplanting: pumpkin, courgette, melon, watermelon and cucumber. The technique is also valid for pepper, chilli, aubergine, tomato, head lettuce, chard, celery, cabbage and other vegetables.

Those are usually transplanted species that must be placed at well-defined distances in the garden, while it would be less comfortable for the species that are placed in a continuous line, such as rocket and parsley, or peas and beans, because in this way too many seedlings would be needed and therefore we might as well do direct sowing in rows. Some farms still transplant rocket, spinach and parsley, because with direct sowing in rows the rapid birth of the weeds would make it difficult to keep the row clean and therefore prefer to transplant the tufts of 3-4 seedlings on the perforated black sheets.

For carrots, turnips and radishes transplanting is not recommended because the taking root of the seedlings is difficult, being root species direct sowing in the garden is better, in order to obtain a more regular and well-sized vegetable.

If we have little space for the seedbed we have to make a choice between the plants to sow and those to buy. In this case, the purchase of leek and onion seedlings is preferable because they are placed in the garden at short distances and you need many: we would risk investing all our small space in the seedbed with these alone. In addition, the seeds of leeks and onions can be stored for a maximum of 2 years, so if there are left open sachets they could expire before their complete use.

Purchase or build the facility

If you are a carpenter and we enjoy manual work, it is possible build independently a load-bearing structure in wood, or alternatively in metal, to be covered with transparent material. The do-it-yourself seedbed is not difficult to do, the important thing is to provide comfortable openings to perform all the necessary operations later.

If we opt instead for thepurchase of the greenhouse-seedbed, the cost of buying it will still be amortized in a relatively short time, given the savings on the purchase of seedlings, you can choose from many different solutions that you find on the market, you have to select the most suitable based on the size and characteristics. For example, you can find a simple and inexpensive mini heated seedbed here, while you can find a serretta covered by a cloth on several floors here.

Characteristics of the seedbed

As we have already seen the seedbed is a wooden or metal structure with transparent walls and cover (therefore glass, plastic sheet or plexiglass panels), we see that other characteristics must have such as dimensions and positioning.

Position of the seedbed

To place our small greenhouse, you need to choose a location sunny but also sheltered from the winds. The seedbed can be placed directly in the garden but in this way it takes away useful space for crops, so it is good to evaluate other sunny corners outside this area. Given the frequent care that the seedlings require, the nearness of the seedbed to the place where you live or work, or alternatively have collaborations for daily care. In fact, the production of seedlings could be important shared activity between multiple garden growers.

The adequate size

There are no limits to the size of a greenhouse used as a seedbed, we must rely on the space possibilities we have. Ideally the space for putting the seedlings should be related to the surface of the garden. Usually a few square meters are enough, in which to exploit also the verticality with various shelves, as long as it is done without sacrificing light.

Minimal furniture

If the seedbed has the conformation of a real greenhouse for a vegetable garden, however small, it is useful that one or more tables from work that we need to do the sowing and then to keep all the containers lined up there. Obviously, if it is a small-scale seedbed, the work will be done outside and no furniture is needed other than the spaces to put the sowing trays.


Having a heated seedbed can be very useful for anticipating sowing and earning a few weeks. A sheltered environment with walls that let in light already tends to create a higher temperature than the room, but sometimes heating is useful. In order not to waste energy unnecessarily it is advisable to heat a small seedbed, which serves to germinate the seeds. For this purpose, cheap mats can be used, we explored in the article on how to heat the seedbed.

What is needed for sowing

Once the structure is built we will get to work, so let's see what is needed for sowing: from the pots to the soil, up to the seeds.

Containers for seedlings

For sowing we can begin to store all black trays that were sold to us with the previous plants, but it may be necessary to buy more. The black color of these trays has the function of quickly heating the soil contained inside and speeding up the birth of the seedlings. In theory it can be sown in any small container, piercing the bottom to avoid dangerous excess water stagnation, on a small scale you can use, for example, recycled yogurt pots, but in practice, however, to optimize space it is better to choose the classic trays for seedlings, which have a low cost and allow you to better organize the seedbed.

An eco-sustainable alternative to classic plastic or polystyrene trays is the soil blocker system, which also has great advantages on the cultivation side.

Substrate: which soil to use

For substrates it is good do not choose the classic universal soil, because it contains a bit of coarse material, not functional for putting small seeds in a jar. The professional soil for sowing it is finer and therefore better, but over time we can also learn to use less soil by mixing it with the soil and compost, both previously sifted.

A good recipe for self produce the seeding soil is to mix garden soil, silica sand and brown peat (a third can be made for each component). The use of earthworm humus in the substrate is also positive, in addition to nourishing it helps rooting.

There are also ready-made peat pads (like the ones you find here), it is a decidedly less economical solution, even if more convenient. Those who grow on the balcony can choose it for not having around bags of soil that dirty.

The best seeds

To cultivate an organic garden it is advisable to choose seeds that come from organic farming, or that at least have not been tanned with fungicides. Ideally it is also useful to learn how to preserve and reproduce the seeds of some vegetables for which this operation is simple, such as tomatoes and peppers.

How to sow seedlings

There are large-seeded species, such as zucchini and cucumbers, for which sowing is very simple. In each hole of the black trays, completely filled with soil, we can put a single seed from which a plant will be born.

For the species with small seeds, such as lettuce, cabbage, chicory or peppers, it is advisable to make the “seed tray”, that is to spread so many seeds on the wet soil in a tray to be covered with a thin layer of earth passed through a sieve. Many plants will be born that we will soon submit to repatching, the technique that consists in gently extracting the seedlings and replanting them in new containers with soil, each in its own tray compartment. This operation must be done when the seedlings are very small and have a long but still not very branched root. For repatching we help ourselves with a stick to gently push the root of the seedling into the soil. The seedlings usually take root without problems and grow independently of each other, each with its own bread of earth. There are also those who let them all grow together and only separate them at the time of transplanting, but generally the plants grown together have a slightly spun appearance, because they have taken away light from each other.

Remember to put labels that indicate which vegetable you have sown in each jar, you can also make them very nice.

When to sow the different species

Between first seedlings of the season that we are going to sow in the seedbed there are head lettuce and the chicory catalonia, which are born at only 4 or 5 ° C. Soon we can continue with chard, cabbage, borage and tomatoes, and when the temperatures are mild we sow them cucurbits, pepper, basil and eggplant.

For the autumn vegetables (all the cabbages and the various endives and chicory) we sow from June to July, while the fennel is sown only in July and transplants in August, because anticipating the sowing of fennel before 21 June exposes it to the risk of pre-flowering. To avoid this, the days must in fact begin to shorten and July is the most suitable period.

For these summer sowing however the seedbed must always remain open on the sides, acting at that point as a roof that protects the plants from thunderstorms and summer hailstorms.

For certain species the sowings can be staggered and it is a very recommended choice because it allows to obtain crops distributed over time. Lettuce, chard, courgette, cucumber, cabbage and leek are very suitable for sowing.

After sowing

Let's see what care you need to have in the seedbed after putting the seed, in order to favor sprouting and then to let the seedlings develop correctly.

Irrigation in the seedbed

The seedlings should be watered with the watering can with shower, for a gentle jet, you can also use a nebulizer. Irrigation does not have to be daily because it depends on the climatic conditions. In spring there are very humid and still cold periods during which the soil of the plants does not dry out every day, as well as very hot and sunny days during which it may be necessary to water twice a day. The only certain rules are to check and observe the state of the soil and the seedlings well and irrigate as needed, preferring the cool hours of the day to do so.


The precautions to be taken for the care of seedlings in seedbeds are basically two:

  • Water with water at room temperature, keeping a full container inside the seedbed or mixing the tap water so as to obtain it lukewarm. In fact, cold water can induce stress to the seedlings;
  • Air the seedbed during hot days, opening all the openings to circulate the air and avoid condensation. In the evening, however, it is always good to close the structure.

Possible diseases and pests of seedlings

Seedlings in the seedbed can be eaten by snails, so if there is any doubt that they can enter, it is advisable to distribute a little iron orthophosphate around the sowing containers, a slugicide allowed in organic farming.

It can also be noted the onset of fungal diseases, favored by the humid microclimate that is established in these environments, and among these we remember pithium which together with others causes the death of the seedbeds. This problem must be managed by treating with a product based on the antagonist fungus Thricoderma. If we can save the seedlings from the disease and transplant them, then it will be appropriate disinfect containers in which they have been soaking them for a few hours in water and vinegar.

When the seedlings are to be transplanted

For understand when the seedlings are ready some observations need to be made e know the stage of those being sold. Head lettuce and chard generally have at least 4 leaves, the tomatoes are about 15 cm tall, but the definitive proof is that by extracting the stick of earth from the alveolus the roots they keep it all and it doesn't crumble. If we see that the roots are too wrapped and developed around the stick of earth this is a symptom that we have waited further and to confirm this we will notice that the seedling begins to yellow, because that earth is no longer enough. After the transplant, he generally recovers, but it is always good not to get to this point.

From sowing to transplanting does not always pass a definite time, because the germination and development of the seedlings are related to the ambient temperatures. Seedlings sown in February can arrive after a month and a half to transplant, while those sown in late spring are ready much earlier.

Once ready, the seedlings must not be transplanted immediately, but it is advisable to take them out of the greenhouse while still keeping them in the containers acclimatize for a day or two, and only after transplanting them into the space we have chosen for them in the garden.

Video: Seedbed Preparation, Planting Vegetables And Sowing Seed (October 2021).