Seed Sowing

By : | 0 Comments | On : April 22, 2016 | Category : Gardening

One gets the same questions every year: “Why aren’t my plants popping up?” “Why don’t I get good germination?” And one of the most frequent complaints to seed manufacturers is: “Your seeds are no good!”

In fact, out of a tonne of, say, cabbage seed, only a few dozen ounces don’t germinate, and usually, the seed company can prove their germination rates. For that reason, for example, I am always distrustful of those magazine-type tests, where they compare germination rates of different seeds. As with everything, it’s a matter of statistics, and you don’t get that amount of scientific kudos by sowing a few packets.

The old-fashioned gardener was not about winning prizes. His job was to produce something to eat all the year round. It didn’t matter if the crops didn’t look perfect – just so long as they tasted good! Too often we buy the seeds labelled ‘New’ or ‘Improved’ or ‘Super F1 Hybrid’. For me, I would prefer a plant that has been tried and tested in this climate year-on-year. So I still buy ‘Alicante’ tomatoes and ‘All Year Round’ cabbage and ‘Kelvedon Wonder’ peas and ‘Musselburgh’ leeks. They served my father, his father and his grandfather – and they are still going strong.

The major reason why plants fail to germinate is a lack of heat. Seeds need a rise in temperature to make the chemistry happen that generates life. It is an interesting fact that seeds are described in the Bible as being dead, and they come alive, thus the cycle of death and new life. But scientifically speaking, you would expect this description to be a little way off – though it is actually pretty near the mark.

For the most part, especially in early spring, the temperature is not far from freezing, and chemistry doesn’t happen that much at 0°C. Botanists talk of the T10 figure, which is how much extra temperature is needed to double the metabolic rate, and in most seeds this means the plant does nothing until the temperature (around the seed) is about 14°C.

Lower than this not much happens – but you have to remember this is the seed temperature. It can be quite warm in the room, but since you have repeatedly dipped the seeds in cold water, the poor innocents are still bereft of growth.

Also, sometimes we water them once and then leave them, leaving the compost to act like a blanket to cover the seeds. Blankets keep warm things warm, and cold things cold! Seeds need a little warm water to match the air temperature – it’s not rocket science I know, but needs to be said all the same.

Some plants need extra heat, which can be supplied by an external heater, or in the case of seeds, under-tray heating. All it consists of is a heating wire buried in sand, and the pots are placed on the top. You can set the heat to a specific level, and the thermostat does the rest.

Obviously, plants need water to live. It is a basic fact of life, but the consequences of water and seeds are special and many. First, the water must be reasonably clean. I have to say I am not a fan of water-butts. People make organic teas by putting a pillowcase full of manure in them. If you water seeds and seedlings with this liquid you will have the situation where the seeds will more readily get a fungal infection called ‘damping off’.

I knew of a man who once filled his greenhouse with new seeds in trays and pots, ready for a new season. He was ‘rearing to grow’, as they say, and he said he would have been self-sufficient in whatever it was he was growing. However, not a single seed germinated.

He contacted his seed supplier, who said that they had almost 100% germination, and they certainly couldn’t think of what happened, but they replaced his seeds anyway. This second lot didn’t fare much better, and an investigation showed his water was contaminated from the anti-algal chemicals he was putting on his roof. It had run off into his water-butts, which contaminated his water and killed his seeds.

If we had the time, I would set you a task – to see if you can get the triple point of water in a container in the greenhouse. The triple point is where you get all three states of water at the same time, and can be seen at about 0.01°C – and yes, I have seen it in my greenhouse, but you wouldn’t get plants growing, so we’ll move on.

However, as you heat the water, and there is a lot of it trapped in a greenhouse or polytunnel, then the humidity will build up – along with excess heat, becoming the ideal place for the growth of fungi. The reason for mentioning the triple point is that you often see incubators with drips of water in them and steam inside – a double point, and a perfect medium for killing your seedlings.

You should have plenty of ventilation to reduce the humidity of your seedlings.

The compost you grow plants in is important. The tendency today is to grow your seeds in compost bought from the garden centre. I must say there is an awful lot of poor compost out there! The big tests of a good compost are: does it smell like an old rotting river? (If you ever go near an industrial river, you’ll know what I mean.) And are there white fungal mycelia growing in the compost? In both cases don’t use it.

I suppose it’s going to be hard to take it back to the shop – hence the smell test. But you should compost it a bit longer until it is sweet.

Seed compost is not simply compost – it contains soil too, and some mineral additives.
John Innes seed compost (the traditional mix for sowing almost any type of seed, with sufficient nutrient for early development) is not a product. This year I saw a bag of seed compost that said: “With Added John Innes”, which told me the product was no good – because, John Innes is not a substance or mixture – it is a recipe.
It should consist of:
2 parts sterilised loam
1 part peat substitute (notice the word substitute – no one should be using real peat these days)
1 part sand
The loam and peat is put through a 9mm riddle, and then for each cubic metre of mix the following is added:
0.6kg ground limestone
1.2kg superphosphate
These give some nutrition to the growing seedling. The sand is there for drainage and the peat substitute is there to absorb water. Some modern mixes contain mica or perlite too.
Notice also, the loam is sterilised – if you want to sterilise your own you can put the loam on an upturned lid (I used a garden oven until recently), and then stand the lid on some bricks over a bonfire.

Forcing the material through a riddle makes the whole mixture light and fluffy – full of air, with plenty of oxygen to keep young roots healthy.

Years ago we used wooden boxes to sow in, but these have been superseded by plastic trays with clear lids. Frankly, I’m not that keen on the lids, but they do keep a stable environment for the seedlings – free from draughts.

These days, however, we tend to sow in modules, a couple of seeds per cell, and trim away all but the best grower. Some selection takes place early on, and there is a little thinning out at the planting stage. You can keep your plants stable and grow them on for a long time, which has all kinds of implications for the better – seedlings are better hardened off, they are easier to transplant, and there is much less handling of the plants during the whole process. Consequently, people don’t often sow plants for themselves, instead they buy plugs that are sown and planted and nurtured by machine.

But it is nice to know how to do it yourself – just in case.

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