Growing Tomatoes From Seed

How To Grow Tomatoes From Seed

Starting your own tomato starts from seed is a great way to get lots of healthy seedlings that will be the size you want them when you want them.

There are three important components to starting tomatoes from seeds. Although a lot of these steps are similar to starting other plants, we have some other great tips for you that will make sure you have the healthiest tomato plants possible.

Starting with healthy plants is the first step to ensuring a great harvest.

1. The Tomato Seed Starting

When starting tomatoes from seed it is best to start with a free draining, sterile potting mix.

There are many of these commercially available but you can easily sterilize your own mix by baking it in the oven.

It takes about 30 minutes at 200-250 F to kill anything that could harm your seedlings. 

This includes bacteria and molds that can cause seedling rot which you don’t want.

To ensure good drainage, you can add 1 part sand to 3 parts peat or soil base.

You can also use vermiculite or perlite if you like at the same ratio.

It is also really helpful to add something that encourages good root growth because healthy roots means a healthy plant.

Anything with phosphorous in it is really good for this. 

Amendments like kelp meal, bone meal, rock dust and blood meal are great for this. Blood meal even has a bit more nitrogen in it which tomatoes love.

tomato seedlings

To plant your tomatoes, start with a tray or small cell packs because you will be transplanting them later.

You can start your tomatoes easily up to 8 weeks before planting out if your growing season is short.

Pre moisten your potting mix to make sure the water is distributed evenly throughout the container.

 Lightly pack the soil and add a bit more to account for the compaction. Sow the seed spaces about ½” and cover them with 1/8” potting mix.

Water in well and place in a warm bright location or under lights.

A cover it optional but will help you keep the seeds moist until they sprout.

Just be sure that the sprouted seedlings do not stay too wet themselves.

TIP: At this stage bottom heat will speed up sprouting and also increase the percentage of seeds that sprout successfully. It can also help prevent certain types of rot caused by cold.

2. Caring for the Growing Seedlings

As your seedlings grow they will become less sensitive but require more water in a day.

hanging tomato

Let them grow to reach the 3-5 leaf stage and then prepare to transplant them.

Take some time to let them adjust to drier air if they are still covered.

Next, take a soil mix like before but be sure to add something for food for them.

Kelp meal or some well composted manure is great at this step.

Remove the seed leaves (long skinny ones) and bury the seedlings in new pots up to the next set of leaves.

The part of the stem that is buried will grow more roots, strengthening the root system.

Transplanting them at this stage can be done into larger cell packs if space is limited or up to a 4 inch pot.

If these plants are intended for hydroponic culture, large cell packs are hands as it won’t be long before they are moved to water culture.

TIP:You can also repeat this transplanting process, moving up pot size and burying more stem, to get plants with extra-large and strong roots systems for soil culture.

At this point you will want to make sure your plants are still getting bright light and that they are receiving a good amount of air movement.

An old desk fan works great for this and helps strengthen the stems of your plants while at the same time keeping the leaves dry and ensuring the plants can breathe properly.

As the plants grow they will need more food. Start a weekly fertilizer regime at a low strength like 5-5-5 NPK and if signs of yellowing occur in the new growth increase fertilizing.

3. Planting out

Prep your site well.

The planting site of a tomato should have properly amended and aerated soil.

It is best to dig a hole at least 12” deep or a bit deeper if you have very tall seedlings to accommodate.

Add well composted manure or other nitrogenous material to the hole and water it in well to ensure you are starting with some ground moisture.

It can also help to add mineral dust or crushed shale for micro nutrients if your soil is low on inorganic material.

Follow the same principal you used for transplanting you seedlings and burry some of the stem again.

This is especially key for indeterminate tomatoes as they will just keep getting taller.

Don’t worry about burying too much of a determinate/bush tomato stem as their plant size and life span is already pre-determined.

Also, be sure to loosen up the root clump some to allow for new outward root growth.  

Replace the soil around and water in well. Mulch to conserve water and keep down weed growth.

TIP: Marigolds make great companions for tomatoes as they attract bees and ward off pests like aphids and nematodes.

Finishing Up

Once you have sown your tomato seeds, seen them germinate, then planted them, you must look after them to raise a crop successfully.

The usual method of growing tomatoes is as cordons, ie they have one main stem with leaves and trusses (sprigs of tomatoes) coming off it although some varieties can be grown as bushes which have multiple stems. 

There are also trailing varieties that can be grown in containers and hanging baskets.

Extra care must be taken if tomatoes are grown in containers, baskets or ‘grow bags’ that they do not dry out.

Cordon Cultivation

  • As the plants grow, periodically tie them to the bamboo poles you put in when they were planted.
  • Every few days check for side growths between the main stem and leaf stems and remove them when they are large enough to handle, probably about one inch long.
  • When there are four or five trusses of tomatoes on a plant, remove the growing tip from the main stem about two leaves above the top truss so that the plant’s energy goes into growing and ripening the fruit.

General Cultivation

  • Do not allow tomatoes to dry out. If they do, the fruit might split or the crop reduced.
  • In dry weather, they can need as much as 2 gallons (about 10 litres) per plant weekly.
  • Once the first fruit has set, feed with a special high potash tomato fertiliser, following the directions on the bottle.
  • Harvest tomatoes as they ripen.

General Cultivation

If the weather turns cool before all the fruit have ripened, usually September or October, it might be possible to ripen them on sunny windowsills or by wrapping them individually in clean newspaper and put them in a drawer or box.

A few ripe tomatoes or a banana is said to help the process. Personally, I prefer to make green tomato chutney because tomatoes ripened this way are never as good as those ripened naturally in my opinion.