How to Start Garden Vegetable Seeds Indoors for Transplanting

Ask any gardener what his favorite gardening job is, and the chances are he will say propagating from seed. There is something magical about sowing your seed and then peering into the container, looking for the first signs of life popping through the soil that you prepared. In just a few days, you can be watching the tiny green leaves make their appearance. It feels like you have created life itself.

Why Grow from Seed?

Why grow from seed,  is a fair question, given that many nurseries will now sell you ready to plant seedlings. You can save time, and you can eliminate the risk of your seeds not taking or succumbing to some fatal disease during that vulnerable early stage in life.

Well, there are many good reasons to grow those seedlings yourself. First, a packet of seeds is always cheaper, sometimes way cheaper than a tray of seedlings. Secondly, you will often end up with far more seedlings if you grow them yourself. This may seem a waste but as every gardener knows, sharing seedlings with other gardeners is a good investment. It inevitably leads to them giving you some of their excesses, and pretty soon, you have a much wider array of varieties and different plants. Some of the excess plants can be held back and planted later so that you have a succession of ripening dates and, therefore, a longer crop availability time.

The third reason is that growing from seed is just so much fun. During those cold winter months, you can sit down indoors with a cup of coffee and page through those seed catalogs to decide what you will be experimenting with the following spring. In the gardening world, this is known as seed porn. You also get to use seed that you harvested yourself, and there is something special about having controlled a process from start to finish.

A Little about Seeds

Although each plant produces seed with different characteristics, there are certain characteristics that are common to most seed.

  • Testa: This normally hard outer layer is mainly to protect the inside of the seed.
  • Hilum: The small mark or scar where the seed was attached to the parent plant.
  • Micropyle: You may just be able to make out a tiny hole near the Hilum, which is there to allow water to penetrate the seed after sowing.
  • Cotyledon: Inside the seed is a food reserve composed of starch and which will provide enough food to help the seed germinate and make it through the soil to the light.
  • Radicule: This is the embryonic root that is normally the first thing to emerge from the seed.
  • Plumule: The embryonic shoot that will start pushing outwards and upwards as the seed begins to grow.

Common Germination Requirements

Germinating seed requires three things: water, warmth, and light. The trick lies in knowing which quantities of each to supply. Don’t worry. There are common rules that we will look at a little later. Once the moisture penetrates the seed, it dissolves enzymes that trigger the growing process and supply the first food. The Taproot normally emerges first and pushes downwards, and soon after that, the first shoot will begin pushing upward in search of light.

A gardener must provide the correct growing medium in which all of this can happen and the ideal temperature. One of the main reasons for planting your seeds in trays indoors is that the extra warmth will encourage the seeds to germinate earlier than they would if they were outdoors and thus to extend the growing season.

The Growing Medium

The growing medium is the mixture into which the seeds will initially be sown and where they will quickly germinate. One might think that seeds could just be planted into ordinary potting soil or even garden soil, but seeds can be fragile. The nutrients and acids that exist in these products could damage the seeds and cause rotting, so they are planted into seed compost instead. This is a fine growing medium that is chemically neutral and has been sterilized. Although it contains no nutrients, remember that your seed already contains those starch reserves by way of the cotyledon, and these are ideally suited to getting those seeds off to a good start. Only once the first true leaves appear will you have to start thinking about feeding your plants.

You can place your seed compost into trays, pots, or even ice cream cartons. Just make sure that there are plenty of holes in the bottom to allow drainage. Fill the tray or chosen container and then gently press down to firm the medium but do not compact it. Make sure there are no big gaps in the soil but that there is still some air. You should water before planting as this will stop the pressure of the falling water from moving or uncovering the seed. Prepared soil should be damp but not wet.

Sowing Options

Now that your trays or containers are prepared, it is time to sow the seed. Your options vary mainly due to the size of the seed itself. For larger seed, you can make drills. This is a fancy term for rows, and you can make these using the back of a pencil or the side of a small trowel and drawing it through the soil.

The accepted rule is to plant your seed at twice the depth of its diameter. With large seed, this is easy because you can pick them up with your fingers and place them in the drill as you want them. Most seed packets give you a standard depth at which they recommend you plant, and it is almost inevitable you will have more seed than you require actual plants. It is better to plant too much than too little. That way, you can thin out weak or spindly plants or give away extra seedlings. Many seeds deteriorate over time, so rather plant too many and share than have too few plants.

Once the seed is in the drills, cover with soil and firm down lightly. You can now cover your seed tray with clear plastic or a sheet of glass and place it on a sunny windowsill. Within a few days, the first signs of life will start to appear. You can purchase an electric propagator that warms the trays from underneath, and this speeds the germination process. If you are keeping the seed trays in a heated house, then it probably won’t be necessary, but it is handy if you are leaving them in a cold potting shed.

Smaller Seed

Some seeds are tiny, and you won’t be able to pick them up individually. These you can sprinkle across the surface of the growing medium by rubbing between thumb and forefinger. Really tiny seed should first be mixed with some fine sand to make the spreading process easier and to keep spread as evenly as possible. After that, place some of the growing medium in a sieve and gently shake it over the seed until it is lightly covered. Remember that seed is better off being planted too shallow rather than too deep because they contain a limited amount of food, and you don’t want your seedlings to use all of their available energy just getting to the surface of the soil.

An important note here is that you should label the seed trays with whatever it is you have planted. Some seedlings might look different from others, but when you are growing different cultivars of the same plant, it can be all too easy to forget what you planted where.

Thinning Seedlings

Your seeds will start to sprout their first two leaves after they appear through the soil. The timing for this will vary depending on the conditions and mainly on the crop. These first two leaves are not true leaves but are what we call cotyledon or seed leaves. These are actually part of the original seed and provide the first food for the young plant. Now, you can remove the plastic or glass covering. You need air to circulate freely now, and excess humidity can lead to a disease known as damping off, which we will look at later.

If you have just sprinkled the seeds, then things will start to get too crowded and you may need to do some thinning. As they grow, the next leaves to appear will be the first true leaves. You can now gently removing excess plants by tugging them out by pulling one of those two true leaves. Keep the healthier plants and thin those that are weaker. Don’t be tempted to pull on the stem but stick to pulling the leaves. The stems are very fragile at this point, and if damaged, the plant will die. The excess seedlings can be planted into containers as reserves for unforeseen casualties later in the season, or as giveaways. You don’t want to leave the thinning process too late. Otherwise, the roots will get established, and they will interfere with the plants you want to keep as you tug them out.

Your seedlings should end up evenly spaced and looking healthy. They can continue to grow indoors until they are bigger. It is important to make sure that the soil remains damp but not too wet. If you suspect that things are starting to get dry, then water by standing the tray in a sink of water and allowing it to absorb from the base, always allow the tray to drain well after doing this.

With the appearance of the first two proper leaves, the plant will start to photosynthesize, and light becomes more important. If they are on a bright windowsill, then that will be sufficient, but if they are somewhere else indoors, they will need artificial light either from a grow lamp or a neon light source. Aim to provide twelve to sixteen hours of light per day.

Potting Up

Smaller plants will be happy to remain in the seed tray they were planted in until you are able to plant them outdoors. Larger plants will need to be put into individual pots so that they have room and depth to continue their rapid growth. Potting up is performed when the seedling has developed several leaves and is starting to look a little bushier. The plants can be potted up into pots individually or in twos and threes.

Fill the pot with potting soil and plant the seedlings into their new temporary home at the same level as the top of the soil at the base of the plant from the seedling tray. If more than one plant goes into a pot, then keep them far enough apart that their roots don’t become entangled as they continue to grow. The potting soil will contain nutrients because the plants will no longer have any reserves from the seed, and the first soil was nutrient-free. Those that remain in their initial trays will need to be fed with a lite general-purpose fertilizer.

Hardening Off

Once you decide that your seedlings are sturdy and large enough to be planted out into their beds, there is one more crucial step that you must take. Your seedlings have been getting mommy coddled in their nice warm environment. If you transfer them outdoors without giving them time to adapt, there is a strong possibility that the sudden change in the environment will kill or damage them. You can avoid this by placing the trays outdoors during the day and then bringing them back in at night for three or four days. This process, called hardening off, makes the adaption process more tolerable. When outside, place the trays in a semi-shaded position so that they are spared the shock of sudden exposure to bright outdoor light.

Planting Out

After several days of hardening off, your plants are finally ready to be planted into the bed, which should be their final home. Before planting the bed and or the pots should be watered. Congratulations, you have just successfully propagated your first vegetables.

Possible Problems

Nature is incredibly robust, and seeds are no exception. There is one problem that may face you, and that is a disease called damping off. This is a collective name for several different fungal diseases that can affect small seedlings. It often happens overnight. One day the plants are looking fine and healthy, and the next day they are dead. Because this is not caused by one particular problem, it is difficult to isolate it or to cure it. Sometimes the initial problem starts in the root and in other instances in the stem. If you look at the plants and see that some of them have gone over, immediately remove any dead material to try to prevent contamination of the remaining plants.

The best way to avoid damping-off is through good hygiene.

  • Use a sterilized planting mix with no nutrients. You can steam your soil by placing it in a covered container in a microwave for around seven or eight minutes. In small quantities, this is doable, but it is too much effort for anything more than that.
  • Clean trays and pots well so that no disease can be introduced. Bleach is a good disinfectant if reusing old pots and planters.
  • Make sure that air can circulate. Fungal diseases thrive in conditions of damp humidity.
  • Water from the bottom up and always allow excess water to drain away. Don’t leave the trays standing in water for too long.
  • Don’t overwater. One of the most common ways of killing plants is by giving them too much water.
  • If you spot dead plants, then act quickly to get rid of the dead material.

The only good news about damping off is that it only attacks small and vulnerable seedlings. If you can get them through that fragile stage, then you won’t have any more problems with this one. Obviously, the quicker you can get them past the vulnerable stage, the better. You do this by ensuring they have ideal growing conditions and as much light and air circulation as possible.

There are chemical fungicides on the market, but I would suggest that you avoid these. The disease strikes so fast that by the time you apply them, the plants are likely to have either recovered or died. They are expensive, and most importantly, they diminish any organic advantage you were hoping to gain by growing your plants.

Some people apply biological treatments such as sprinkling with cinnamon, but in most situations, it should be early enough in the season to replant and start the process again. 

So there you have it. Starting your seeds indoors is an exciting adventure for all gardeners.  There’s nothing more rewarding than watching the entire process of going from soil to seeds to plants.


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