The Best Soil Mix to Germinate Tomato Seeds

Written by mindy mcintosh-shetter
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The Best Soil Mix to Germinate Tomato Seeds
A seed-starting medium for tomatoes needs to retain moisture without being soggy. (tomato plants image by Gina Smith from

The ingredients required for a tomato seed-starting medium vary, but the basic components are the same: peat moss, perlite and vermiculite. An additional application of fertiliser is required once the tomato seeds germinate. If you're new to growing tomatoes from seeds, there are a few choices, but a soilless medium is the easiest way to go.

Seed-Starting Mixture

This basic seed-starting mixture creates a soil that retains water without making it soggy. A soggy soil can cause fungal problems and damping off. To make this soil, combine four parts of peat moss, two parts perlite and two parts vermiculite. This soil mixture does not contain nutrients. Once the seeds germinate, apply a water-soluble fertiliser to the soil. This soil mixture is ideal for the experienced gardener who is in the habit of applying fertiliser to the plant material.

Cornell Mix

Developed by the horticulture department at Cornell University, this seed starter consists of two parts peat moss, one part each of perlite and vermiculite, 1 tsp lime, 1 tsp 0-20-0 fertiliser and 2 tsp slow-release 19-6-12 fertiliser. This soil mixture does not require additional fertilisation while the seeds are germinating. This soil mixture is ideal for the gardener who may forget to fertilise the seedlings.

Soil-Block Mix

Soil blocks require a mixture that holds together and retains a lot of water without being soggy. This soil is made from sterilised potting soil, peat moss and water, then mixed together in a wheelbarrow or large bucket until it becomes the consistency of peanut butter. Once it reaches this texture, push the soil-block mould into the prepared soil mix and press the mould against a wheelbarrow or bucket. Then release the moulded soil from the mould onto a tray or flat. Plant each block, and water from the bottom. Routinely mist blocks to keep them uniformly moist. This type of soil mix should only be used when the gardener is starting seeds in soil blocks.

Easy Soilless Option

This mixture is an easy one to use for those who are new to growing tomatoes from seeds. It requires one box of gelatin with sugar, small containers such as yoghurt cups, small baby-food jars and even muffin tins. To begin the process, mix the gelatin according to the directions and place 2 inches of gelatin into each container. Let the gelatin cool completely. Once the gelatin has cooled, place three seeds into each container and sprinkle with cinnamon. Cover the containers with a sheet of plastic or glass and place in a sunny window. As soon as the seeds begin to germinate, remove the plastic or glass from the top of the containers. Allow the tomato seeds to grow until two sets of leaves have formed. Once this has happened, remove the gelatin and the seeds from the containers and place in the soil. Gelatin is a great soilless mix to use because it is made from animal bone. This substance helps produce nitrogen, and the sugar in the gelatin feeds the seedling.

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