Dave's germination bed

Tomato seed starting and growing tips

Tomato seedlings

Below are the top 10 tips for starting and growing your tomato seeds. For hothouse growers, we are not far from getting the seed going on heatmats. mid July will get you seedlings to plant in a hothouse mid to late September! Not far away. If you need tomato seed feel free to look here.

1 – Grow your seedlings individually in pots and use a heatmat for bottom heat (21 C min ideally).

If you are starting tomatoes from seed, bottom heat will help your rates of germiantion plus give the seedlings room to branch out. Yes, that means thinning the seedlings to one strong plant per small pot. If some seedlings look weak and small compared to others, don’t bother, compost it. Crowded conditions adversely affect growth once they start getting their true leaves, which stresses them and leads to disease later on. Transplant tomato seedlings into their own pots shortly after they get their first set of true leaves.

2 – Provide as much light as you can.

Tomato seedlings need strong, direct light. Days are short during winter, so even placing them near a sunny window may not provide them with sufficient natural light. Ideally a hot house is better than indoors, but you can only do your best. If they get spindly, it is a lack of light but you still can rectify this later by planting the seedlings deep.

3 – on warmer days, put them outside.

Tomatoes grow strong stems when they experience the realities of outside such as winds. So don’t be scared to get them out there on days that are not freezing (ie: 13 C daytime is fine for a few hours in the sun).

tomato seedlings about 8 weeks old, ready for planting
tomato seedlings about 8 weeks old, ready for planting

4 – Pre-heat your garden bed soil.

We are prone to up and down weather in spring/early summer. So lay some black plastic down to help with soil temperature. The plants will appreciate it on those cold days. Plus the extra degree or two of temperature will help to provide some earlier tomatoes.

5 – Plant seedlings deep.

No matter how they look, take the bottom set of leaves off and plant deep. The tomato will grow a stronger set of roots (those hairs on the stem become roots).

6 – Pre-Prepare the garden bed.

In August/September, add some cow/sheep manure to the bed and compost. Don’t go hard on fertilisers, it is best to fertilise in November when soils warm up as Tomatoes need warm soil to take up nutrients.

7 – Don’t mulch until x-mas time.

Mulch generally is light in colour and lowers the soil temperature. Wait until around x-mas time to mulch for soil moisture conservation. Timing depends on the weather of course.

8 –Trim lower leaves.

This really applies to all types of tomatoes. Trim the lowest leaves so no leaves come in contact with the soil. This really helps with reducing soil born bacteria like Septoria from splashing up onto the plant. Once you mulch when the soil and weather is warm, this is some added protection.

9 – Maintain Soil Moisture.

The biggest tip in minimising Blossom End Rot is to use drip irrigation or at least stick to regular watering. I really recommend consistent watering. If the soil dries out and the tomato is stressed for a time, it will draw calcium out of the fruit causing blossom end rot. This is not generally because your soil is short of calcium, it is because the tomato can’t draw it out of the soil due to stress. Oh and a side tip. When raising seedlings, do not over-water them. It may pay to even wait occasionally till you see them wilt then water. They will be stronger (but don’t do this when the plant is growing strong with flowers as per above).

10 – Pruning.

My advice is if you are growing indeterminate tomatoes. Grow two or three leaders and pinch the laterals off. In mid-January on, I let another lateral ow two continue maybe. Pruning laterals and growing either up poles or string makes it much easier to manage the plant, monitor fruit and get larger sized fruit. I wouldn’t bother with the cherry tomatoes however. I can’t say you will yield a higher volume of tomatoes, but it is much easier to manage and having trialled pruning and not, you do get on average bigger tomatoes as the plant doesn’t have to focus on so many fruits. In the end it is your decision. We all have our methods and that is the way it should be.

Final tip: Fertilising

I don’t go overboard. I put a handful of potash in the hole at planting time. I use Complete Organic Fertiliser in around mid Nov once growth kicks in and then in mid Dec and mid Jan and then I stop. I do water with Seasol every 3 weeks ish. But my garden beds get topped up with compost in winter and well-aged cow manure is added in August. That is about it. And blossom end rot will happen at times no matter how perfect we are (However drip irrigation really does help this). Often the first few fruits of some varieties are affected, then all good. Some varieties are renowned for issues in dry times. Some varieties I have never seen impacted. The joys of tomato growing. Butt most of us love it don’t we! And every spring is a chance to start again.

Happy Growing


PS: water your seedlings from down low  and not above the leaves. And when sowing seed, don’t use a propagation bag mix. Finding quality mixes is hard. A bag of quality compost with some propagation sand added and a few organic fertiliser pellets will be enough. And for some additional help I also wrote this post if you missed it

tomato plants
Tomatoes early December. Planted closer as these are grown for seed rather than yield.

Some reader top tips:

  • Make your own potting mix: He is a recipe I use (well I make large batches which is a bit different to this, but for small home gardeners I have made this):
    • Your aim is to have a well draining, aerated mix that nourishes the plant
      • 1 part peat or coir
      • 1 part vermicultite or perlite or propagation sand
      • 1 part compost (you can get bags of compost from shops – use a sifter if it is very barky to remove large bits)
    • Cover the seed tray with a piece of glass or perspex before germination, to maintain even moisture and don’t water again until germination (from Kate Flint).
    • Germinate mine near the wood heater then move them near a window before they go into the hothouse. (From Rachel Sammut)

1 thought on “Tomato seed starting and growing tips”

Leave a Comment

Your email address will not be published. Required fields are marked *

Shopping Cart