You never taste the finest sweet corn unless you grow it yourself. Buying frozen or 'fresh' cobs, from the supermarket or even a farmer's roadside stall, will not guarantee you really fresh. Even if you grow sweet corn yourself it's likely you may still not have had it absolutely fresh. You see in only a matter of minutes sweet corn starts to deteriorate, in particular it becomes more starchy and less sweet. The drive home in your car is long enough to reduce the quality noticeably.
I am not joking I put the saucepan of water on to boil before I go to pick the cobs, then having plucked them I dehusk them whilst jogging back to the kitchen. Seriously, try it for yourself, pick one cob and mark it then half an hour later pick another and immediately put both in boiling water; you will taste the difference I promise you.
But first, as Mrs Beeton is supposed to have said, catch your rabbit. Growing sweet corn in our fickle climate is only sporadically successful. Fortunately it's neither pest nor disease prone, indeed sweet corn is simple enough to cultivate and not even too demanding as to soil. But for a good yield of sweet cobs they need to be growing, and even more importantly ripening, during sunny weather. I'm lucky I'm in the sunniest part of the UK and most years East Anglia has good summers. Even so only one out of three or four batches of sowings will be really excellent, and some years not even that. In the cooler, less bright North and West sweet corn becomes more difficult still. However with ingenuity, or by taking it under cover, crops can be grown even in Scotland.
There are distinct advantages to growing lots of sweet corn to the point of excess. Firstly it really does need to be planted in blocks to ensure pollination. But it also really wants to be sown in batches to hit the best growing and ripening windows with at least one lot. Thus I grow at least four or five separate batches; I will eat the best, process the second best for winter use and then dry the poorer batches for chicken and bird food. And because sweet corn does not suffer many pests or diseases common to our vegetables or fruits it is an excellent crop for filling up spare capacity and providing shelter for others nearby.
Indeed sweet corn is an easy plant to inter-crop with companion plants. Sweet corn needs a fairly wide spacing to give big cobs and the dappled light underneath is well suited to most of the marrow family who can run between the stems and in warmer countries melons thrive under corn. Likewise the corn can carry a crop of climbing beans either for eating green or for drying and the beans feed the corn with the nitrogen they crave so improving the cobs. In fact when De Soto the explorer first saw sweet corn it was being grown by South American indigenous peoples as one of a triple crop with both beans and squashes. I find you can also grow dwarf peas and even potatoes underneath by expanding the corn's spacing a bit more. Trailing Nasturtiums do best of all, they love running under and over corn and I pickle the seeds which are cleaner if they are off the ground.
But back to the problem of growing a good crop in the first place. The first essential is a good summer but we can't do much about that except try and improve their micro-climate as much as possible in ways I described in a previous article. Sweet corn is unhappy in cold wet soils and can be damaged by hard frosts but cold winds often do the most harm to the young plants by shredding their leaves. So some early protection, such as cloches, is useful, especially in exposed places and or the plants may be started off under cover and planted out later when they are sturdier and the weather has improved. However it is rather unfortunate but corn does not like being grown in pots and positively resents transplanting. Thus great care has to be taken or the plants sulk or bolt either way giving a poor crop however this method is more certain than sowing directly in situ which gives the best plants, when ever they come up.
I prefer Organic or my own saved seed as I don't reckon the coatings of chemicals they apply to some commercial seed do any good, and they probably do harm. They certainly don't stop the seed rotting. Coming from a warmer country sweet corn needs warmth to germinate so sowing in pots of poor wet compost simply causes the seeds to rot no matter how much fungicide they're soaked in. The compost must be open and free draining, and not wet or too rich, although corn is a hungry plant it's roots are sensitive to the ammonia given off in cold wet compost. The roots rot then the leaves yellow and die.
Sweet corn also needs lots of compost, preferably in deep rather than wide pots. I have grown the plants in toilet roll tubes, newspaper tubes and in blocks of turf, all worked, and the turf best of all, but pots are more convenient. I sow two seeds per pot and if both germinate leave them both as although a single plant apparently does better I find I get more cobs with pairs of plants grown together.
Ideally the young plants need maximum light and to be kept frost free but not too warm. If the plants are kept in bright conditions but too warm they flourish but grow too big and soft. In the more preferable bright but colder conditions they need to be kept on the dry side to prevent their roots rotting. In dim conditions they simply sulk and die. To try and hit the best window I sow several batches starting in early April and later go on to direct sowing in May.
My plants in pots are not usually potted up as such but may be 'topped up' at the bottom. When the roots poke through the holes the plants are carefully evicted so an extra layer of compost can be inserted and the plants slipped back in again. The roots must be prevented from growing out of the holes or they will be damaged when the pot is removed. Other than repotting the best way is to have the pots standing on rigid wire netting or glass so that the roots see the light which repels them and they are then more inclined to stay within the compost. Standing the pots in a tray is inviting the roots to mat outside the pot and should be avoided.
When the plants and weather are ready I plant out, normally plants are hardened off for several days first but I use individual plastic bottle cloches and pre-warmed holes. The holes are made, covered with a cloche a week or so early to warm up. Normally I set the holes about two feet each way depending on any inter crop and the number of doubles which require more space than singletons. The holes are made deep and the plants set deep within, watered in and given a bottle cloche each.
Once the plants have established and grown big enough to fill the bottle then the protection is removed. Ideally this is done early on a still grey morning so they can get used to the blast of the raw elements. At the same time their bases are earthed up in their holes, this secures the plants and ensures copious basal rooting. With the extra roots the plants usually tiller so forming three or more shoots apiece with as many cobs per plant though as I've said much more depends on the weather.
For plants sown in situ a similar process is performed with the seed sown in deep holes and cloched to be earthed up later when the cloche comes off. The later direct sowings may well be done unprotected from the weather but a bottle does also give protection from the slugs and snails roving around in May and June. Indeed I find the tubular walls of a plastic bottle are more use than a simple 'bottom cut off' cloche made from the same. True the latter is warmer but stifles the plants whereas the wide open tube allows air in but still prevents wind buffeting.
Unless the soil is amazingly rich then adding well rotted manure or compost will certainly improve the crop but far more effective is ensuring adequate moisture. I have found a straw mulch keeps the soil moister but too cool to allow sweet corn to be sown in colder years, bare soil is warmer. By comparison with copious water the effect of any fertiliser is minor. The biggest plants and yields have been in hot summers on plants I trench irrigated so their soil was always moist. They grew like a jungle and the cobs were magnificent. On poor soils definitely add organic material just for the water holding capacity, and for fertility the traditional way try fish wastes. Mind you the local moggies love you if you don't mix them in well.
Planting in blocks helps sweet corn plants pollinate each other, they are naturally wind pollinated when the tassels at the top drop their yellow flour on the silks hanging out of the swelling cobs. You can improve this by running your hands over them and shaking them. I find this very important under cover where otherwise the set tends to be poor. It is vital not to cross pollinate different sorts as it can cause all sorts of problems in the kernel formation. Believe me I've done it too often, mind you they still tasted good most times. Anyway keep the different sorts well away from each other, build a barrier between them or sow one lot all early and the other all late. Only old fashioned open pollinated non F1 varieties will keep true if you want to grow your own seed,
As the kernels are actually changed by different pollens then GMO contamination of sweet corn is not just a potential problem for growing your own seed but just for eating the cobs. So if the ******** are doing trials in your neighbourhood then grow sweet corn under plastic to prevent contamination by any of their damn GMO pollen that's blowing around. Under plastic the plants grow leggy so choose short varieties, and you can keep the ventilation fully open to the breeze until just before flowering and restore it again once the silks have withered.
As to variety, the quicker ones have some advantage but flavour is all important and too personal to recommend something as variable as corn to other gourmets. You will have to try them all out on your own soil. The various new varieties are certainly sweeter but I find them less flavoursome. The weird coloured sorts are more use for feeding my chickens than the table. Pop-corns are special varieties, they need a good summer to ripen well but then are excellent value. (But the small seeded ones are better for growing to feed the wild birds in winter.) Oh and one other thing, try cutting down a strong stem, peel it and chew. You will find it's surprisingly sweet, in fact so sweet that syrup can be made from it.