If you want to plant your own seeds instead of buying seedlings or transplanting plants, then you can either sow seeds directly into their final growing position, or start them in seed trays or pots, and later transplant them to their final growing position. Some plants you would only want to sow the seeds inside, and some plants you would only want to sow the seeds outside, whereas some plants you have a choice. I’m including potatoes, onions, and garlic within the category of seeds, even though you can grow them from the vegetable themselves.
Why sow seeds inside?
Too cold to plant outside. Some plants need to be started early enough in the year that it will be too cold to plant them outside. It’s recommended to plant these inside to get the most out of the growing season. If you wait to sow them outside then they’ll have a shorter growing period and they may not be ready to harvest before the end of the season, or you may get less, smaller or unripe fruit from them.
Quicker plant growth. By growing them inside, you can control the light and temperature that they are getting, making it warm enough for them to grow well and giving them extra light than they would be getting outside in winter and spring. This can give your plants a headstart, leading to bigger and/or stronger plants, as well as more fruit.
Reduce the damage from pests. Having plants inside removes the ability for most of the pests that may attack young plants to reach them, including slugs, snails and birds. You may still get flies or aphids, but usually less than if they were growing outside, and it’s usually easier to control them or deal with the problem. Seeds sown outside can be protected, as can outdoor seedlings, but this won’t always work and planting inside can remove some of those issues.
The ground is covered. If you have a mulch on your soil, or ground cover plants, then seeds sown outside are less likely to germinate as the layer of mulch or plants can prevent seeds from sprouting. Sowing these inside can increase the chance of germination.
Why sow seeds directly outside?
You don’t want to disturb the roots. Plants generally don’t like their roots being disturbed, but if you are careful (taking the entire pot or modules worth of soil or compost out with the plants) then many plants don’t mind being transplanted. However, crops where the roots are the main part of the crop (potatoes, carrots, etc.) do not like being transplanted.
The temperature has warmed up by the time the seeds want sowing. This is going to be most of the plants that were traditionally grown in the UK, as natural plants self-seed outside and grow on their own in their natural climate without human interference.
You have a way of protecting the young plants from the cold and frosts. Greenhouses, polytunnels, cold frames or fleeces can be used to keep them warm enough during the still cold spring. This can allow you to sow seeds outside and get similar results to sowing them inside.
You want to plant seeds the easier and quicker way. Needing to only plant once instead of double plant (sowing seeds inside and then planting the seedlings outside).
You want to save money. Sowing seeds inside will likely mean using heated propagators or heated mats alongside grow lights, which uses electricity and will cost some money to run. And if you don’t have the equipment already, it will cost money to get.
What equipment do you need to start seeds indoors?
Grow lights. Plants need light, and even southern facing windowsills don’t really give seeds enough light. You could get by, but the plant growth won’t be as good. A greenhouse or glass conservatory would provide enough light and be good enough, so you wouldn’t require grow lights, but they could still provide more light early on in the year when daylight hours are still limited.
Heated mat or propagator. Lots of seeds need to be warm to germinate, often between 20° and 30°C. The seedlings ideally want to stay above 10°C. Heat mats and heated propagators usually increase the temperature from that of the room by 10°C, so if you don’t have somewhere that will be warm enough, then heat mats or propagators may help you.
Trays or pots. Modular trays or individual pots are most commonly used for growing seeds inside, due to the ability to plant them out when it is time while minimally disturbing the roots. You may sometimes need to ‘pot up’ seedlings, moving the plant into a bigger pot as they get too big for their current pot. They can be bought from any garden centre and should be available in every shop that sells some garden things. Or you can use newspaper, like I sometimes do, with a paper pot maker (or any household item that you can get to work). Tear strips of newspaper and roll them up, making small pots. You can see a picture of these earlier in this post.
Compost. Use a light compost so that the seedlings can push through when they emerge. Compost should provide enough nutrients in that small pot for the seedlings until you plant them out to their final growing position.
Choosing inside vs outside
Inside. Some plants benefit from being planted inside. They can still be planted outside if you need to, but will do better being started off inside. Those from the beginner series are tomatoes, courgette, cucumber, winter squash, basil and coriander.
Outside. Some plants need to be started outside due to a dislike of being transplanted. Those from the beginner series are potatoes, radish, garlic, onion, carrots, parsnips, and beetroot. Any native flowers will do okay planted outside too, as that’s what they naturally do.
Either. Peas, broad beans, runner beans, kale, cabbage, lettuce and spinach can do well sown either inside or outside, and it’s personal preference as to which you choose. Lemon balm, oregano, sage, thyme, dill, parsley also fit into this category.
Neither. The following aren’t recommended to be started from seed or bulb, so don’t fit into this discussion about where to start seeds. Raspberries, strawberries, blackcurrants, gooseberries, mint, rosemary.
How I choose for myself is by prioritising those that do best when planted inside, and figure out how many of those I want to grow, based on the number of plants I want and adding some extras in as some won’t germinate and may die. I then see if I am able to sow any more seeds (number of pots, amount of compost, or space), and then if I do, pick from the list that can be planted in either. With those, I take into account the timings of when I’ll be growing them and when the seeds would need to be sown. I will be giving an example of this in the beginner series round-up.
I am proud to be affiliated with JustSeed, a company that I have bought seeds from for a few years now. I believe in what they are doing over there, and if you are going to buy seeds, garden tools, or seedlings, then please consider checking them out and using my link below to do so. Thank you for supporting me.
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