Here is a description of how I sow seeds indoors.
Personally I start pretty much everything off in pots, rather than straight in the ground. Then I transplant them to the ground when they are bigger (or keep them in pots if that was the plan all along).
I use shallow round pots about 4″ in diameter. I use a soil based SEED SOWING compost, usually referred to as John Innes Seed Compost. (Definitely not a general compost, and in my case I have tried soil-free [i.e. peat or similar] seed composts and not liked them).
Fill the pot to the bottom of the lip (about 1/2″ or so below the surface) and use the bottom of another pot to tamp down and firm the soil, and make it level. Don’t press it too hard, firm will do.
At this stage you can water the pot(s) and let them drain. Use the bottom of another pot to level the soil if it has got disturbed. However, I don’t water at this point, I do it later, but I use a fancy piece of kit [see below] and if you don’t have a decent watering can I reckon watering now will do as well
I open the seed pack and pour the seed into a little dish – e.g. a ramekin
Seed size varies, if you can pick them up one-by-one and see them (i.e. they are not identical colour to the soil!) I would place them individually in the pot. I use a pencil – I can lick the point to make a seed stick, or use my fingers and then use the pencil to nudge the seed away from its neighbours.
The seeds should be about 1/2″ apart, more if its a large seed. Some seed packets only contain half a dozen seeds, so if that’s the case then place them evenly around the pot. If there are millions of seeds in the packet do not be tempted to try to sow them all in one pot – they will come up too thick, and all die competing for light and water, and are likely to get “damping off disease”
If the seed is smaller and you cannot use the pencil trick then get a pinch of seed between thumb and forefinger and rub the two fingers together so that the seed is distributed evenly. You can practice this back into the little dish the seeds are in, or onto a sheet of contrasting-colour paper, before you do it “for real”
Okay, so the seed is in the pot, on the surface.
If the seed is big it needs to be covered to a depth equal to the seed’s diameter. I use the pencil to gently push the seed into the soil. But this is only really needed for seed that is 1mm or bigger. If you are growing a bean then it needs to be pushed a decent way into the soil (and actually something as big as a bean would be better sown in individual pots, or plug trays)
I sprinkle some vermiculite on top. (vermiculite is a very light, white material [looks similar to small polystyrene balls] which keeps the heat in and retains moisture, but is light enough for the new shoots to push out of the way). But that’s one more thing to have to buy when you are starting out, so sieving a thin layer of seed compost over the top will do. Use a kitchen strainer as the sieve – rather like flour-sifting over a cake. Don’t try to do it by sprinkling from your hand, it needs to be a thin layer and even. (Having said that I do sprinkle Vermiculite by hand, the pieces are too large for a sieve, and it is so light the seedling can easily push through even if it is a bit thick – it only needs a layer thick enough that the dark colour of the compost can no longer be seen)
The reason I use vermiculite is because things that take a long time to germinate tend to grow slimy algae over the surface of the soil by the time the seeds are up, and vermiculite prevents that.
OK, seeds are sown and covered.
This is when I water. It is crucial that this watering is gentle. I use a Hawes can with an upturned rose. Blinking expensive piece of kit, but the water comes out as fine as rain.
Check the packet for what temperature the seeds need to germinate, but I put mine on a West facing window ledge, once they germinate open the top of bag (i.e. leave the pot in the bag, but let air in) and put them in brighter light. Whilst it is closed the water in the bag can’t escape, so there is no need to water the pots – at least not for 3 months or so.
Note that most seeds need some light to germinate, and the moment they germinate they need plenty of light – otherwise they will get leggy, and are liable to fail. So if you put the seed pot in the airing cupboard to get it going make sure you check every day for signs of growth. Very fine seedlings can be very hard to see, so if you are not familiar with what the seedlings will look like make sure you look very carefully.
I take care that they don’t get sunburn – i.e. keep them out of bright sunlight in the hotter months. I give a fine misting every hour or two so that they are not stressed – but I am careful not to get the humidity too high which can encourage disease.
I use tap water, not rain water, for seedlings (because rain water picks up fungal spores and so on as it runs down the roof to be collected). I also use Cheshunt Compound to reduce the chance of damping off disease. (This is only useful for seedlings, not fungal disease in older plants, and it lasts a long time, so probably best to buy sachets, rather than a tin / tub, as the sachets will be easier to keep dry and “fresh”)
In the early months of the year I use a little plastic greenhouse inside my conservatory so that I can close it up at night, or on chilly / overcast days. (I put a light in the bottom on chilly nights to give a bit of warmth)
That’s it. When the plants are big enough I prick them out.
When pricking-out, or potting-on, I use a potting bench. I tip a decent amount of general purpose compost (usually J Arthur Bowers, but all makes seem to be pretty variable, find what you like and suits you) onto one side of the bench, then rub it through my hands to make a pile on the other side. This breaks up any lumps (e.g. where it has become compacted whilst the bag was stacked on a pallet at the garden centre), and I find any larger bits of twigs etc and chuck them out.
I then scoop a 3″ pot into the fluffy pile I have just made so that it is full to the brim – I scrape off any excess with the back of my hand. I do NOT firm the compost. I use my pencil to make a hole in the middle, ready for the little plant.
I tease a little plantlet out of the seedling pot with the pencil, holding it very gently by the first/bottom leaf, dangle the root(s) into the hole in the new pot and use the pencil to push the soil back around it. I then press it down well with my fingers – at which point the compost is level with the bottom of the lip. I water with my fine rose, as above, and the compost settles down to the bottom of the lip over a couple of days.
Back into my little nurturing plastic grow-house for a few days until they are stronger and then out into the greenhouse etc. for growing on.
More difficult seeds
Some seeds – like Sweet peas – need chitting; usually because they have a hard coat. I put these in a ramekin with some fairly warm (but not hot – don’t want them cooked!) water and leave them for 24 hours. The ones that have swelled I plant, the others I drain and put fresh warm water.
For beans, sweet corn, courgettes/marrows/squash I use kitchen paper. Put a sheet of kitchen paper in a Tupperware container, place the seeds on top, another sheet of kitchen paper and then make the paper thoroughly wet – draining off any excess moisture – i.e. there should not be any standing water. Check daily, and as soon as a little root is showing plant them. I use this method so that I can plant just the “viable” seeds directly into individual pots. I don’t like the advice “Sow two to a pot and remove the weaker seedling” as I have never been able to work out which one is weaker before they have both grown too big! and it seems a tragic waste of very nearly half of the seed.
Beans generally need to be planted on edge with the concave side down, convex side up. I chit climbing beans (Runners and French) on kitchen paper, and then plant them in modules – they grow like stink! so don’t need a 3″ pot to themselves, they will need to be in the ground in a couple of weeks anyway, otherwise they will be too tall to handle.