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Starting Annual Vegetable Seedlings Indoors


In a cold climate, such as in Melbourne, Australia, the summer is never quite long enough to grow all your summer annuals vegetables, such as tomatoes, chillies, capsicums and so on. The best way to get a long productive season is to start the seedlings early indoors, so they can be planted out in the garden as soon as the weather is warm enough. By sowing the seeds earlier, the plants will of course fruit earlier, and with warm weather continuing after fruiting, they can then produce a second round, doubling your yield for the season.

The summer vegetable seeds can be started indoors in later winter (August in the southern hemisphere), so the plants have a few weeks to grow enough in size to be planted out time for spring (September in the southern hemisphere).

The advantage of starting plants early indoors is that you can continue your gardening grow plants while the weather is still too cold outside, and you can utilise the heat within the house to not only warm yourself in late winter, but to grow your plants as well.

It’s very easy to start seedlings indoors, there isn’t much you need, and you’ll see results in a week!


There’s a few points I’d like to bring up in regards to planting seeds which are worth discussing. The first is the matter of growing medium and the second is direct sowing versus sowing on containers.

1. Growing Medium

Growing medium is basically the medium (the “stuff”) that you grow your plants in. Plants do grow in various materials, from their natural soil to a range of man-made potting mixes. The textbooks will insist that you specifically use “seed raising mix”, you can find small bags of this in commercial stores, and it’s fairly expensive, but the reality is that you don’t need it. Seriously, a lot of it is just plain bunkum. Seeds have been naturally falling on soil and sprouting without human intervention for the last few million years before commercial seed raising mix was ever thought up. From personal experience, I find that in practice you can use virtually anything that plants will grow in to raise seeds in.

Sure there’s common sense, if you’re planting very fine seeds you might not be able to use a really coarse mix with large pine bark pieces in it as it wont surround the planted seeds closely enough to retain moisture, and soil can retain more water retentive than artificial mixes, which may be a concern for moisture sensitive plants, but this is not a problem for annual vegetables, they grow in anything.

Just keep in mind that gardening, if done sustainably, is all for free, as nature provides everything you’ll need.

My folks have been starting their vegies indoors for as long as I can remember, in plain garden pots filled with garden soil, Did it work? To put it simply, it worked brilliantly. Just keep in mind that gardening, if done sustainably, is all for free, as nature provides everything you’ll ever need.

Working in the garden nursery industry, I meet many gardeners who have had problems sowing seeds in seed raising mix – they find that their seeds sprout but their seedlings only reach a very small size and then STOP GROWING, and the resultant seedlings are very thin and spindly! That’s because seed raising mix has absolutely no nutrients in it, and is totally unsuitable for sowing seeds in. It’s actually misnamed, it really should be called SEED COVERING MIX, because that’s what it’s designed for. You need a nutrient-rich mix underneath such as quality potting mix to raise seedlings!

2. Direct Sowing

Most seeds can be sown into pots or punnets (flat seedling trays), and then be transplanted into the garden or even into bigger pots. But there are some plants that don’t take too kindly to having their roots disturbed, and become badly affected by transplanting, so these plants must be directly sown, that is, the seeds are put into the ground where you intend the plant to grow.

Here is a quick list of plants whose seeds are best sown directly straight into the ground:

Broad Beans
Jerusalem Artichoke
Spring Onions
Sweet Potato

How to Sow Seeds

Sowing seeds is not that difficult, there are a few basic rules to follow, and nature does the rest!

The general rule for planting seeds is that they should be planted three times as deep as the diameter of the seed.

There’s no real need to get this exact, as seeds will often germinate regardless of soil depth, just try to get it fairly close.

Follow seed packet instructions for planting depth, and if sowing directly into the garden, follow the recommendations for spacing – how far apart from each other the plants should be spaced.

Most seeds need to be buried, while some seeds require light to germinate, and prefer to be sown directly on top of the soil. This will be specified on the seed packets.

Note – if you’re collecting your own seeds or are given seeds, and don’t have “instructions”, you can look up the seed sowing recommendations in a good gardening book or search for the information online.

To sow vegetable seeds indoors for an early start, you will need:

Here are the basic steps, they’re quite straightforward and easy to follow.

As well as being an instructional guide for starting annual vegetable seeds in pots, this set of instructions is also a basic guide in seed planting for any kind of seeds you wish to grow.

Step 1:

Firstly, you’ll need some kind of container to plant your seeds in. You can use anything that can hold your growing medium (seed raising mix, potting mix or even regular garden soil) and that has holes in the bottom to let excess water drain out.

Here I’m using a seed tray with plastic seedling containers (pictured below), because the divided sections keep the seedling roots separate and makes it easier to pull out the seedlings for planting.

Step 2:

Fill your container with your growing medium, such as seed raising mix, potting mix or even regular garden soil. Level off the surface of the growing medium and pick off any large particles such as rocks or pieces of bark in the mix if present.

Step 3:

Water the growing medium to dampen it, it needs to be moist as seeds need moisture to germinate.

Step 4:

Next, you’ll need a tool to make small dents of the correct depth in the surface of the growing mix to put the seeds into.
The tool for this is a dibber (also called a dibble) – this is a just a pointed stick for making holes in the ground so that seeds, seedlings or small bulbs can be planted.

You can substitute a chopstick or a pencil or any other such implement for this purpose.

Shown below is a picture of one made of plastic, with depth measurements along its length.

Press the end of the dibber into the surface of the growing mix to make small holes approximately three times deeper than the diameter of the seeds.

In these trays pictures, I’ve made two holes per section so I can put two seeds in. That way, if one seed fails to germinate, the space will be occupied by the other seedling and doesn’t go to waste.

Step 5:

Take the seeds you wish to plant. pour some into the palm of your hand, and then pick the seeds one by one and place them in the holes made with the dibber in the growing medium.

If the seeds aren’t very viable, and don’t have a high rate of germination (that is, they don’t always sprout), you can put more than one seed into each hole.

Step 6:

Use the dibber to close up the holes with the seeds in them, push the moist growing medium in to fill the holes with the seeds in them.

Step 7:

Label your seedling trays!

When planting up containers such as the ones pictured, you can just label each row, just make sure you’ve planted the same thing in each row though!

Labelling is important, I can’t stress this enough. There’s nothing worse than having a large number of vigorous seedlings come up successfully, only to have forgotten what they are!!! You might think you’ll remember, but plants take weeks to grow to size ready for transplanting, and everyone can forget. I know from experience…

Here, I’ve planted two varieties of tomato, Australian Red Tomatoes and Cherry Tomatoes, and some Rhubarb. The Rhubarb seedlings will look different to the tomato seedlings, but the tomatoes will both look the same, hence the use of labels!

Step 8:

The seedlings will eventually need to be watered, and if the seedling tray is going to be inside, you’ll need some form of drip tray underneath the container (as pictured below) to catch the excess water so it doesn’t run all over your furniture!

Place the drip tray under the container, as shown below, as the container will still be dripping wet on the bottom.

Step 9:

Place a cover of some sort over the container to keep the moisture in until the seeds have sprouted. You can use a piece of glass, timber, cardboard, cling-wrap, whatever will cover the top of the container. This will only stay in place until the seeds have come up, then it will need to be removed to give them light and space to grow.

In the picture I’m using a plastic propagator lid, which is designed to fir with the trays. This has the advantage of being high enough to permit some vertical growth, and lets light in. The green “butterfly” vent can be turned to open the holes in the lid to let air in, or closed to retain heat, making it a mini-greenhouse. It’s a luxury, but not a necessity.

If you think you need the fancy gear to grow seedlings, think again! Pictured below is a cheap plastic pot, with tray below it, filled with spinach and rocket seedlings. This weather beaten old pot, year after year, has been filled with garden soil from the backyard, sown with tomato seeds, covered with a scrap piece of wood, and placed on top of the kitchen cabinet. From here hundreds of productive tomato plants have sprung forth!

Step 10:

Place the covered container on top of the refrigerator (as pictured below) – if this is a warm spot, place your hand there first to check, if it feels warm, it’s a good spot to use. Somewhere high up near the ceiling also works well, as heat rises and it will be warmer higher up. A warm sunny window is also good.

Make sure you check every few days to see if the seeds have sprouted, for once they have, the cover needs to come off and they need exposure to sunlight. If you forget them there too long covered up or in low light, they will become tall and spindly, bent and misshapen.

Step 11:

When the seeds sprout remove cover, and put them in a place where they can receive enough sunlight to grow, while still staying warm indoors.

Pictured below are the seedlings – tomatoes and rhubarb, after 7 days. I’ve opened the vent at top to let air flow through (so they don’t get too damp and get mouldy) and I’ve placed them on a kitchen bench that gets midday sun.

Water the seedlings when they need it, and give them a weakened organic fertilizer weekly, you could mix up a half strength fish emulsion for example, and some seaweed extract or worm casting liquid might help too.

Shown below are the same seedlings, with the cover off. These will grow over the next few weeks until the weather is warm enough to plant them out in the garden.

They can also be transplanted out into bigger pots for faster growth when the time is right. The rule with transplanting seedlings is to do it when they get their first pair of “true leaves”.

The true leaves are not the original long, thin leaves that come up when the plant first sprouts, but the next ones that grow, which will be a different shape and resemble the mature leaves, but just be smaller in size.

When the plants are big enough, and the last frosts have passed, the seedlings can go into the garden, ready to lap up the sunny weather and grow, grow, grow!

Starting your warm season annual vegetable seedlings indoors in late winter is a great way to get a good head start of a few weeks before spring arrives. By the time the weather is suitable for planting out seedlings, you’ll have nice strong seedling plants that will better survive pests and inclement weather!

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