As we work on the back garden and wait for the weather to warm the soil I have invested in germinating seeds indoors in preparation.
Last year I germinated my seeds when the sun was shining through the windows – but as we learnt, this is too late for planting if you then have a heatwave; making all your root vegetables bolt.
The seeds start off on the heat mat and then once they have germinated (as soon as the first two leaves have opened) I move them on to the floor. Depending on the time of year and the seed type Oh you might not need a heat mat at all. Tropical hot weather plants need high heat to germinate and then warm frost free place to grow. If you have a sunny window then the sunshine might be enough heat for most seeds (chilli peppers and melons need the most heat -radishes probably the least, and spinach won’t germinate much above 25C); some people will say that you need to cover the seeds with plastic when indoors to maintain humidity but I find that can lead to mould growing before the seed germinates – warm damp soil is enough humidity for most seeds (nobody in the wild is covering seeds with plastic). If planting directly outside when cool, a cover such as cloche can keep the seed/soil warm and encourage germination.
For vegetables that don’t take well to transplanting at all such as carrot and radish – I just wait until spring and sow directly into the soil as they grow fast enough to not miss out on any of the season. (see individual seeds for planting methods)
Different vegetables need different lengths of season in order to get big enough to produce fruits/roots. Melons like a lot of warm weather so need many sunny warm days in order to grow fruit. Some need more than 120 days of warm weather; last year the melon I grew called Charentais is labelled as 85 days so I don’t think it was planted early enough to take advantage of the weather. This year I have a ‘Minnesota midget’ which is specially developed for short season at 65 days so we will if that is a better fit.
Not all vegetables need hot weather to grow but still need sunshine and some warmth in order to get big enough before winter comes. Brussel sprouts need 110 days before they will produce sprouts so need to be put in the ground well before the cold comes.
The balance lies in getting enough sunshine and warmth but not too much that would confuse the plants into thinking winter has been and gone. If you get a cold snap followed by really warm weather some biennials (plants that seed in the second year) will go to seed before they have had a chance to provide you with food.
There are all kinds of suggestions on the internet and in books letting you know about the best seed raising mixture. To be honest I have never purchase (or made up) a compost specifically for sowing seeds – I just use what ever compost bag I have bought in general. Seed raising mixture just needs to be loose and fluffy enough so that the seeds don’t have to struggle to push their way through it. If you think the compost that you have is too heavy then sift or crumble a separate pile for seeds; use the regular stuff underneath the seed and then the fine stuff on top.
I don’t really plant to the suggested depth as I will transplant them later, so can plant a little deeper in their final spot if needed. The bigger the seed the deeper you plant it; large seeds I push under the surface- tiny seeds can be sprinkled on the surface and patted down. If you are impatient and curious like me, you can plant seeds between thin layer of damp paper towel – that way when they have germinated you will know and then can transfer them to pots. This is also a good way to test seeds’ fertility – the seed packets often have a use by date much earlier than necessary (they want you to buy new seeds) often the seeds are fine but you can test some in paper towel to make sure.
Seeds can be planted in anything – the containers that vegetables are packed in the supermarket can make good seed trays for initial sowing and then the large ones for planting on (berry containers already have holes).
Initially seeds should be planted in a small amount of soil so it can heat up quickly and not be too wet – after the seed germinates and you see roots coming out of the bottom of the pot then pot them up into something bigger so they plants are not cramped before you plant them outside.
Some may grow faster than others; courgettes seem to be quite fast where as cucumbers tend to take ages to establish themselves
When repotting seedlings plant them a little lower in the soil than as germinated, this will help to stabilise them and produce stronger stems. Plants in the nightshade group (tomatoes, potatoes, peppers) and the cucurbit family (cucumber, melon, squashes) (also some of the brassica such as kale) will grow extra roots on any stem in contact with the soil – so bury the stem up to the first set of leaves and it will create a stronger plant.
Plant outside in spring when it is sunny and warm enough to grow each plant, see the seed list for soil temperatures, seedlings should be around 6 inches tall at least to survive outside as smaller plants will be more likely to be eaten by insects. If the weather isn’t warming up like expected keep the seedlings indoors but make sure to pot up if they grow too big or look sickly. Plants that have been grown indoors and/or under lights may receive a shock if it is too cold or too sunny as they must have time to get used to the changes
You can get the seedlings used to the cool weather by hardening them off; a process of leaving plants outside in shade during the day and bringing them in overnight for around a week – hopefully then the weather is ok and the plants are used to it.