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Growing Tomatoes From Seed

Elvis Elvis

Tomatoes adore the heat and as such, need a fairly long warm growing period in order to mature all the way from seed to fruit. Except in tropical or sub-tropical areas (top ½ of Australia, bottom parts of the US ect..), the summers are just too short between times of frost, for full plant maturation. This means if you start the plants in the ground after the last frost (good luck predicting that one…) and expect the plant to have fully finished fruiting by the end of Summer, you may well be disappointed.

Due to Tomato seeds not germinating until the frosts have ended and the weather warms a bit, you will find you’ll need to plant the tomatoes indoors in seed trays in order to give them a good head-start for the season. This way your plants will be nice and established by the time it is warm enough to transplant them outside.

When Should we Sow Seeds Indoors?

The best time to plant your tomato seeds would generally be around 6-10 weeks before the last expected frost in spring for your area. The seedlings would then be transplanted to their outdoor growing spot about 2 weeks after that date. As a general temperature guide, you will want the lowest overnight temperature not to fall much below 10 degrees C ( or 50 fahrenheit). If you have a couple of nights below this, the best way to protect your seedlings is to cover them with a frost cloth for protection. When growing tomatoes from seed it is important to gradually acclimate them to their environment.

Planting Your Tomato Seeds

Your seed containers should be approximately 7.5-15cm deep (3-6inches) this allows the seedlings room to grow in case they are in the seed trays longer than expected. You can either use the white plastic trays from seed places or you can get creative and make your own out of anything to hand. My favourite is using the clear 2-3L milk bottles. I cut them off and drill holes in the bottom. If you need to at the end of the season you can still recycle them, or reuse them next season

Growing Tomatoes From Seed

The best soil to use is a higher quality potting mix. Seed raising mix is ok for sprinkling over the top of the seeds, but this can get expensive if you are using a lot of it. The cheapest potting mixes often have large pieces of bark or other matter which can make it poor for raising seeds. The better quality potting mixes also have slow release fertiliser in them which is beneficial for your seedlings. Regular garden soil is not the best idea due to weed seeds, various fungal and bacterial agents, and it also compresses too much to allow the seeds the oxygen they need to grow.

In order to plant your seeds, you will need to thoroughly wet the potting mix. You can do this in a variety of ways, but the method I use is the following ;

1. Fill each container with the potting or seed raising mix to be used. Leave about 1cm of room from the top to allow covering of the seeds.

2. Find a dish that you can fill with water and sit as many of the containers in as possible. I use an older large oven dish for this purpose !

3. spray or pour water over the top while letting the water go through to the dish below. Once the water has seeped through the potting mix, fill the bottom container so that the water fully soaks the potting mix. Leave this overnight, then drain.

Once the mixture is damp but not soggy, you can mark out small furrows with a pen or similar. Drop the Tomato seeds in one by one, and lightly cover them with more seed raising mix or fine potting mix. Lightly pat this down. Water with a spray bottle which has a fine mist (I went to the $2 store and got a great one for this !). You will ned to spray them lightly with this spray periodically.

Tomato Germination and Growing

Tomatoes need warmth of 22-25 degrees (75-85 fahrenheit) to start the germination process. This can be achieved by putting them on a water heater or a warming mat. If you cant do this, a sunny window sill will suffice, but you will need to keep an eye on the moisture level and keep them covered until the seeds germinate and push through the surface.

Germination will likely take between 5-10 days to germinate but colder nights will make this a little longer. Keep a close eye on the containers until germination.

As soon as your Tomato seedlings have broken through the soil, you should make sure they have the most light possible right away.

While most will use a window sill, you will find that even a north facing window (or south facing in the northern hemisphere) will tend to make the seedlings leggy. A large fluorescent light or higher wattage lamp will allow your plants enough light to flourish until they migrate outside ! Tomatoes grow best in the temperature range 18-23 degrees (65-75 fahrenheit)

Pricking Out Seedlings and Planting Out.

When your tomato seedlings are around 5-7cm high (2-3 inches) and have at least 3 sets of leaves you can carefully prick them out to their final growing spot (assuming all frosts have gone).

With the help of a knife or fork, carefully lift each seedling from its container and place them in the new pot, container or soil a little deeper than they were growing in the seedling pot. If they have become leggy, you can bury them deeper than normal as the hairs on the stem actually become roots. Carefully press the potting mix around the seedling to foot it into the ground. Gently water around the plants and feed them about once a week from planting.

What to feed them is on another page, but I actually feed with A & B solution for hydroponics systems. Taper this off as the flowers come in and change to a tomato fertiliser with an N ratio less than P or K. (Check the NPK ratio on the package)

If you have planted them straight out into the garden, either stretch shade or frost cloth over the top of the plants to help them acclimate to the outdoors. Generally try to do this on a cloudy day or in the evening to give the seedlings the highest chance of survival. If possible, you might also like to mulch around the base to retain moisture and to keep weeds to a minimum.

Remember to keep your seedlings lightly sprayed with water, but make sure they dont get soggy. If kept too wet they are prone to root and become susceptible to many dieases.