How to grow tomatoes from seeds: Step by step from seedbed preparation to transplanting seedlings


Tomatoes are a favourite vegetable for most farmers. They don't require much space, produce a high value for the amount of space utilized and are a consumer favourite. They do however present a number of challenges for even the most experienced open-field grower. These range from wildly fluctuating prices to problems with weather conditions and diseases.

Growing your own tomatoes is simple and just a couple of plants will reward you with plenty of delicious tomatoes in the summer.

Growing tomatoes from seed isn’t hard, but there are a few things to be aware of. As with all things agrarian, timing, genetics and environment have to be in alignment to reap the rewards of your efforts.

Although it's very possible to grow tomatoes all year round, however, they are a warm season crop, and it's best to avoid growing tomatoes in winter until you have accumulated enough experience as growing tomatoes in winter is more difficult than doing so in summer where they easily do well.

There are many varieties of tomatoes, and they all come in different colors, sizes and flavours. There are basically two categories of tomatoes. These are determinate tomatoes and indeterminate tomatoes.

Determinate tomatoes are varieties that grow to a fixed mature size and ripen all their fruit in a short period (usually about two to four weeks). Once this first flush of fruit has ripened, the plant will begin to diminish in vigor and will set little to no new fruit.

On the other hand, Indeterminate tomatoes, also known as cordon tomatoes or vine tomatoes, continue to grow high and produce fruit throughout the summer. Because of this, they usually require trellising for support, or you can leave them to lie on the ground, which is however not a good way of growing tomatoes. They keep growing and get bigger and bigger as time goes on as long as you continue maintaining them by giving them water and more nutrients. They keep making tomatoes over time, so you can keep picking them over an extended period. This lesson is going to be biased towards indeterminate tomatoes.

There are so many tomato varieties and I will not name any of them because most varieties are country or region specific. Varieties popular in the United States are not known in Africa or Asia and varieties common in South Africa are only known to Southern Africa. So it's best to visit your reputable local seed shop and buy one of their recommended hybrid varieties. You can even start with extracting seeds from tomatoes bought in a fruit and veg shop. Although this is not recommended to commercial tomato farmers, however, it works pretty well, especially when you are not growing tomatoes for commercial purposes. Personally I have done it countless times, even on tomatoes i grew for commercial purposes. If you are going to use seeds from store-bought tomatoes, either you can dry the seeds first or you can simply squeeze tomato juice together with the seeds to your seed bed or seed pot and sow the seeds right away.

Planting seeds bought from the seed shop and planting seeds dried from store-bought tomatoes is basically the same. You have about three options which all depend on how many tomato plants you want to grow. For 30 or less tomatoes, you can use a small plant pot or an old plastic container to sow the seeds. Just make sure you pierce holes at the bottom of the plastic container so that water can drain freely and also provide oxygen to the roots.

If you are going to grow 50 or more tomato plants, then sowing the seeds on a seed bed or in float trays – also known as seed trays – will be your best option. For commercial farming, seed trays are the way to go because you will have a higher germination rate. Seed trays also reduce the risk of fungal diseases such as damping off on your seedlings.

As a general guideline, when sowing seeds, a trench or hole that you are going to mark for the seed should be deep enough to allow you to put the seed then cover it with a layer of soil or growing media that is twice the thickness of the seed. This means that if your seed's thickness is only 1mm, mark a shallow trench that is about 3mm deep. The first 1mm will be covered with the seed and the remaining 2mm will be covered with a layer of soil. You don't have to be precise, but this general guideline will help you improve the germination rate of anything you grow.

For sowing tomato seeds, you can use a match stick as a yard stick. A hole or trench that has the size of a matchstick head is good enough to germinate your tomatoes, bell peppers, onions, lettuce and most green vegetable seeds.

Again, for commercial farming or for best results, use growing media such as pine bark. There are far less chances of infecting your seeds or germinating seedlings with fungal diseases when you use growing media such as pine bark.

Having said that, now let's delve to the actual action of how to plant the tomato seeds.

1. Prepare your seed bed using a garden folk or a hoe. If your soil is not very rich in organic matter, you can apply compound C fertilizer or compound S fertilizer, which is a bit more pricey. If you have animal manure such as rabbit droppings, chicken manure, cow manure, pig manure or even horse manure, you can also mix with with soil to enhance your seed bed. Use a garden folk or hoe or shovel to work the fertilizer or organic manure into the soil then gently level the seed bed.

If you are growing the tomatoes for commercial purposes or if you want to plant over a thousand seeds where germination rate must be as close to to 100% as possible, then consider using float trays or plastic seed trays and pine bark or any other commercial growing media. Using a commercial growing media helps you germinate healthy seedlings that are free from fungal diseases such as damping off which are found in the soil. When using growing media such as pine bark, all you have to do is to add water, preferably none-municipal water, should resources permit. Don't worry about adding organic manure or synthetic fertilizers such as compound C or compound S because pine bark is naturally a form of organic manure, so your seedlings are going to grow well anyway.

2. If you are going to use float trays and pine bark, then use a match stick to perforate a small hole at the centre of each cell. The depth of the hole should be around the size of the match stick head. Drop a single tomato seed in each hole until all holes are filled. Use the edge of the match stick to lightly cover the hole and the seed with a thin layer of your growing media. Then use a fine sprayer to water the seeds you have just sown. Place the seed trays in a warm place where the seeds are not exposed to direct sunlight for lengthy periods of time. Your garage, store room, under a shade or better still in a greenhouse will be a good area. Continue watering once or twice daily until germination has begun, usually around day 7 to day 10, depending on your weather and climatic conditions.

If you are going to sow on the traditional seed bed, get a small stick and mark shallow furrows that are about 10cm apart. You can simply separate the furrows with your fist, that's a good spacing to work with. The furrows themselves should be very shallow, about the size of a match stick head. Sow the seeds thinly in shallow furrows. You could use the same stick you marked the furrows with to cover the seeds with soil, or you can get more soil and sprinkle on the furrows to cover the seeds with a thin layer of soil. The layer of soil should be about twice the thickness of the tomato sees you have just planted. When you are done, irrigate, preferably with a knapsack or a fine sprayer. Continue irrigating this way until a week after your tomatoes have begun germinating.

3. Now that your tomatoes have germinated. The next thing is to care for them for about 2 weeks, before we transplant them. There is nothing much that you need to do other than to simply water them, usually once a day. If you live in hot countries such as most parts of Africa, then you may need to water the new plants twice a day for the first 5 or so days. Allow evaporation to take place and let your soil or growing media's moisture greatly reduce before you water again. If you keep the soil very wet and damp then your seedlings are certainly going to suffer from damping off, a fungal disease that wipes off almost all seedlings on your seed bed when it strikes.

4. Although we will do another topic specifically for damping off, lets quickly go through it, so that you know how to prevent it or try to fight it should it attack your seedlings. One first line of defence against damping off is to only water again when your soil is about to get dry. If you keep the soil always wet and damp then damping off will absolutely pay you a nasty visit. Second way to prevent damping off is to apply a fungicide such as copper oxychloride or mancozeb once a week on both your seed bed, about a week after germination and on your seedlings every week after transplanting. These two fungicides do not only fight against damping off, they help prevent many other fungal and bacterial diseases such as early blight, bacterial spot and powdery mildew. The good thing about copper oxychloride is that you can spray it on your tomatoes today and still harvest them tomorrow. However, first confirm with the packaging of your specific brand, there may be changes, but in all the brands of copper oxychloride that I have dealt with over the years, copper oxychloride has always had a 0-day withdrawal period.

We also need to talk about seedling hardening. You will hear about this quite a lot and wonder what it is really about. Seedling hardening is the process of gradually water-starving your seedlings as you prepare them for transplanting. When it's about 5 days before you transplant most seedlings, begin giving them less and less water until the day of transplanting where you should never irrigate them at all, until you have transplanted. You should only water the seedlings soon after transplanting them. This will greatly improve your transplant success rate. Fewer seedlings will die due to transplant stress if you first harden them.

5. The next stage is to transplant the seedlings. But before I go there, let me explain that you should avoid applying fertilizer to your seedlings after germination has already begun, otherwise you risk scotching the juvenile plants. You only fertilize the soil before you even sow the seeds. Again, before transplanting the seedlings, make sure where you are going to transplant your tomatoes, there is enough organic manure. If not, do any of the following:
a – Broadcast compound C fertilizer to the area you are going to transplant the tomatoes then mix with the soil using a garden folk.
b – Dig shallow ditches about 30cm or 12 inches deep along each row. Fill the ditch with animal manure or compost then cover with a layer of soil.
c – Dig trenches that are about 50 to 60cm or 19 to 23.5 inches deep. Fill these trenches with multiple layers of animal manure and compound C fertilizer. Cover each layer of manure or compound C fertilizer with another layer of soil until you fill up the trench. The trenches should have a width of about 50cm or 20 inches. This is the same width size your raised ridges should have. When you are done, make the raised ridge where you will plant your tomatoes. This is the best method for greenhouse farmers, or those who intend to use a drip irrigation system. With a drip irrigation system, the distance between the water emitters will usually determine the spacing of your tomatoes within the same row. Most horticulture drip lines have 30cm or almost 12 inches between emitters. This is good spacing for greenhouse farmers, where space is a limiting factor. If you are not using a drip irrigation system, then work with a 40cm to 50cm or 15.75 inch to 19.7 inches spacing within the same row. The spacing between rows should be anything between 1.2 metres and 1.5 metres, that is between 47 inches and 59 inches. The number of tomatoes you want to grow and how much space you have will have to determine the specific distance you are going to work with.

6. After preparing where to plant the tomato seedlings, you will need to water the area first. You also need to spray either copper oxychloride or mancozeb to the field you are going to transplant the seedlings, so that the fungicide will help fight some of the many diseases that live in the soil. Since we are transplanting seedlings that have been hardened and are literally very thirsty, it's good to give the soil a little watering and get the soil wet. After spraying with a fungicide and lightly watering the field, use your hand or a pointed object such as a wooden stick or a metal rod to make holes about 10cm or 4inch deep. These are the holes where we will transplant our tomato seedlings, therefore they have to be 30cm apart when using a drip irrigation system, or 40 to 50cm (15.75 inch to 19.7 inches) apart if you are not going to use a drip irrigation system.

7. If you had sown your seeds in a seed tray, then transplanting will be a little easier. It's just a matter of pulling the seedling by its stem, as close to the growing media as possible and the whole plant including the roots and the growing media will pull out of the cell. Without disturbing the roots, you just place the seedling into the hole you made with a wooden or metal rod, then compact the soil surrounding it a little bit with your fingers so as to make the plant firm. If you had planted on a traditional seed bed, then use a small garden folk to remove the seedlings from seedbed without cutting off or disturbing the roots. Remove one plant at a time from the butch and plant it into the holes you made earlier. Avoid what we call J-rooting. This is a situation where a hole you made for transplanting purposes is smaller than the total length of the roots and the roots can't fit such that the end part of the roots will have to point upwards like the letter J. So make sure the hole is deep enough to accommodate the whole length of the plant's roots. Now compact the soil surrounding the newly transplanted seedling with your fingers and give it a firm grip.

8. When you are done with transplanting, it's time to water the plants again. You will need to water your tomato plants everyday and within the first 2 to 3 days probably twice a day if you live in very hot countries such as most parts of Africa. But remember, if you over-water them damping off is likely to hit your young plants. So keep spraying copper oxychloride or mancozeb every week to prevent fungal diseases such as damping off. For healthy tomatoes, you should spray this fungicide until the last week of harvest.

The next steps will be the actual tomato farming itself. This was just the planting stage. It's so demanding but very crucial. If you cut corners during the transplanting stage then you are going to bear the consequences which often include poor harvest, serious loss of plants due to fatal diseases such as damping off and early blight, and small tomatoes due to lack of adequate feeding and nutrients. As this lesson has already been so long, a part two of growing tomatoes follows this first part and it talks about fertilizers to use throughout your tomato growing season, pests and diseases to watch-out for, how to prune and when to prune your tomatoes, among other crucial stages of the tomato farming process, so be sure to watch part 2 of the lesson.