This month is when we begin sowing most crops in the open garden. So although we have been doing so for years it may pay to consider what we need to do to ensure success, and what we ought to have learned to avoid. Certainly I have had reports from many of poorer emergence, especially of root vegetables, in recent springs; perhaps the weather, or our own errors are to blame.
I am personally guilty of repeatedly sowing with knowledge and despite so knowing, of seeds too old to have much chance of ever germinating. I suppose I have the feeble excuse of ‘experimentation’, after all it is what I do. But I even persist in sowing the remaining musty vestige of seeds from a favourite with some vague hope a few might just miraculously germinate –even when I could so easily get a fresh pack with almost guaranteed success. In a genuine trial I sowed early pea seeds from a couple of years old back to ten -and none of them came up. Not even the two year olds! It was a cold wet year and even they, as well as all the older seeds just rotted.
Without doubt then the first rule when sowing must be “Sow good seed”. Of course you could still be unlucky but generally fresh packets of seed work, old and not so old but badly stored packets do not. True some seed lasts several years, some almost forever such as poppies. But many go off very quickly especially parsnips. If you are not sure and want to minimize the risk to your efforts in the open ground sow some seed in a pot indoors a few weeks ahead. If those in the pot never show or show sparsely then buy a new packet in time. If however they come up like cress then your old packet is worth risking outdoors –but probably not in a really cold wet year only a good one; seed loses vigour.
I also believe it is sensible choosing the established tried and tested varieties rather than new allegedly improved sorts that have not proved their value by enduring. True there are improvements all the time, but these varieties too often also have drawbacks yet to be found out. Grow what does well in your area already is a good motto. I also prefer organically grown seed as I’m certain this gives the seedlings more vigour and a better chance –would you adopt the athletes’ or the junkies’ baby?.
Having secured good seed the next key to success is hitting the best sowing window. The seed packet will doubtless tell you when the seed may be sown- but obviously the vendor wants to make it as wide a choice as possible and will thus credit you with a perfect microclimate. (You can apparently sow parsnips from February –really, and even sow spinach before midsummer without it bolting ….) Perhaps if you knock a week or two of either end of the suggested period you might be safer. Generally most annual plants do just as well sown a tad late as a tad early, and take far less looking after that way.
But even having narrowed down the period it is difficult to know exactly when to sow. Here a belief in astrological planting can be a comfort as the decision is made for you. However, regardless of any truth in such ideas I’m quite convinced some days are certainly better than others, it’s just it may not be the astrologically predicted one. So you are better off sowing in several small batches over a week or more so that some sowing or the other may hit the right window of weather etc. Don’t believe me -try sowing ten radish seed every morning for a month and see for yourself.
Another most critical factor in germination is the soil temperature. The old method was to sit, naked, on the ground, and if you could take it comfortably then the soil was warm enough. Others preferred the more accurate way of waiting till the flushes of weed seedlings appeared on bare ground as a sign. You can even use a thermometer and it may necessary in erratic springs. It is little use sowing expensive tender seeds when the soil is so cold they rot rather than germinate. It is not difficult to raise the soil temperature significantly with a little preparation. Cloches, either old glass or modern plastic obviously do a grand job and continue to protect the seedlings after emergence. Laying clear or black plastic sheet on the ground warms the soil (though thick mulches work differently and stop it warming up). A combination of plastic sheet underneath and cloches on top enables me to sow and grow melons and watermelons in the garden by continually raising the temperature of the soil from early in the year until I start sowing in May when it needs to be 70 Fahrenheit.
Simply darkening your soil with soot or more humus has a warming effect, as does raising the ground to less of an angle with the sun, and likewise sowing on raised ridges and mounds. All these are different ways to get warmer soil and thus better germination. None is more convenient than a mini-cloche, or rather dozens, made from a plastic bottle. They warm the soil and keep off pests and weather.
Having a warm enough soil is no use if it is too wet or too dry. The latter is unlikely to be the case in early spring but does seriously hamper later sowings. Most of our earlier sowings are into a soil too cold and too wet, adding more water just makes it worse. It may be worth sowing into or topping off over the seed with a gritty sowing compost rather than letting it rest in cold wet mud. Seeds need to breathe oxygen to germinate and if they are in anerobic conditions –such as mud, then they will quickly fail. They need a moist aerated medium. An old tip was to put some coarse sand, proper gritty sowing compost or just old potting compost in the drill or hole. And even better is putting some baked coarsely sieved charcoal in which will help keep the soil healthier. Bone charcoal provides phosphates into the bargain and makes an amazing difference to turnips.
Often overlooked, an absolutely essential ingredient often lacking, and particularly short in well fed well mucked and composted gardens, really necessary for almost every plant is lime. This mops up any acidity produced and keeps the soil sweet. Lime is important to almost all vegetables in particular the Brassicas, and also to Stone fruits. Any shortage of lime will give dire results especially when sowing and a soil test ought to be done regularly every few years. If in doubt try sprinkling some lightly over half a row of seeds and see. I prefer calcified seaweed as my source of lime but Dolomitic is another.
Never, repeat, never, add nitrogenous fertilizer, when sowing and particularly not with early sowings. Fertiliser may degrade in stagnant conditions giving off ammonia which is nearly as affective as drowning for killing seed. (Though adding lime and charcoal as well in a sowing compost might just have saved you.)
Likewise avoid presoaking seed which coud help in drier conditions but may unfortunately start seed germinating in soil too cold and wet for it to proceed. This may be a serious source of failure, I found the old advice of soaking peas before sowing counter –productive for the early and only worthwhile for the late sowings.
Still seeds do need to absorb a lot of water to make tissues and convert fuel. So if the soil is too dry then water must be added. But be careful with what you use especially for early sowings. Ideally make sure it is aerated rather than stagnant, warmer not colder, and hopefully sterile as fusarium, pythium and wilt moulds are no help. In other words avoid water butts and if possible squirt hot tap water into a watering can to aerate it a bit and then use that before it cools. Or use a hose to fill a barrel and let it warm up before watering from a can. Only in really warm soil can you risk watering seed drills and holes with cold water, unless of course you wait for them to warm before sowing.
Depth of sowing is probably the next most crucial a factor. Too shallow and seed dries out, gets eaten, or has too little mass above it to push against to root down successfully. Sown too deep and seed is too cold, too wet, or just too far from the surface to make it. Take more care with your depth, generally making it deeper in lighter sandier soils and less in heavier clayey ones. It may be worth station sowing in improved spots rather than all along a drill, this can also ease thinning later, but may cause erratic depth unless you are careful. Sowing into the soil itself may be inherently risky so that a sowing drill lined with a gritty sterile compost is best employed. This can be well firmed without becoming claggy and thus can be more accurately leveled, sowed, topped off and leveled again than a muddy soil.
Using a lining of a gritty sowing compost or a topping also gets round a couple of other problems. No matter whether light or heavy some soils cap or crust and make it hard for seedlings to emerge. So a surrounding of sowing compost does not just aid the crop seed germinate but it also helps it emerge. And a proper compost should have no weed seeds and thus far fewer emerge to compete and be eliminated later. With all slow to germinate seeds it is probably worth using such a sterile compost just to make spotting their sowing site easier to weed around. Of course for big roots it’s traditional to fill crowbar holes with such a mix and to sow but three seeds to a station at a good distance apart and ruthlessly thinning to the best singletons later. But for a mixture of sizes and ease it’s hard to beat careful broadcast sowing. I strew carrot seed, all sorts of varieties, all colours, diluted with sand, thinly over a raked bed. Then I cover it with a layer of clean gritty compost, firm this down and cover all with anti-root fly mesh. What a wonderful mix I get for every meal!