Guest Articles
"Love your sweetcorn" -an article by Mick Ryan New North Road
Did you know that maize, or sweetcorn as it is more commonly
known in the UK, is one of the oldest cultivated crops in the world?
Originally grown a food crop in Mexico some 7000 years ago it's
cultivation spread across the Americas and, after European
colonization, throughout the world. Now it is the staple food crop in
many parts of Africa and Asia. These days, in much of Europe and
North America it is mainly grown for animal feed, for food
processing(cornflour) and the manufacture of cornflakes and
popcorn. In the USA and, of course in the UK, sweet varieties of
maize are also enjoyed as "sweetcorn" or "corn on the cob".
For those of us lucky enough to have our own allotment plots
sweetcorn can be enjoyed at its best - straight from the plant. The
cobs rapidly lose their sweetness after harvesting as the natural
sugars turn to starch. Sweetcorn which has sat on a shop shelf for
two or three days just can't compare.
In order to successfully cultivate sweetcorn it is important to
understand the special needs of this unique plant. Plenty of sun,
regular watering and well drained, nitrogen rich soil give the best
results. Dig in plenty of well rotted compost, or grow on raised beds if
you prefer. Sweetcorn also requires intense pollination. By this I mean
that you can't just rely on passing bees to do the job. You've got to
roll up your sleeves and give them a hand. Let me explain. The
bulbous cobs, known as "ears" which appear on the stems just below
a leaf have a little tuft of hairs, known as "silks" growing from their
tops. These are the female flowers. Each strand represents one seed
of sweetcorn and every one has to be pollinated individually to
ensure a complete head of corn. If only half are pollinated, then only
half the seeds will form and the cob, when cooked will look ugly with
grey bald patches here there and everywhere. The pollen comes from
the male flowers, known as "tassels" which appear like a little palm
tree on the very top of the plant. Bees and other insects disturb the
tassels as they go about their business collecting pollen and some of
the grains float down onto the plant below. A few will land on the
silks and pollination occurs. Maybe this works satisfactorily in hot
subtropical climates where there are abundant flying insects to do
the job but here in the UK the plants may need some help. Once the
silks start "browning up" no further pollination can take place so
you've got to move fast.
The way we help the process is by firstly growing the plants close
together, about two feet apart and once the tassels have formed,
regularly tap the stems to release pollen. This is best done on warm
days when there is no breeze when the silks are most receptive and
the pollen won't blow away. Towards the end of the pollination
period you can carefully break off a few tassels, which are not directly
above any cobs and brush them across the silks. It is also a good idea
to grow a flowering companion crop between the plants. More of
this below.
The Three Sisters
The value of beans cannot be overstated. There few plants which can
so efficiently capture nitrogen from the air and "fix" it into the soil.
Sweetcorn needs nitrogen to thrive but can only absorb it from the
soil so it is a very good idea to plant beans between your sweetcorn
plants. Any variety of beans will do but I prefer french beans,
standard and climbing varieties. Plant the standard varieties after the
sweetcorn has become established and climbing varieties when the
sweetcorn is about waist high so as not to overwhelm them and
hinder the pollination process by covering the silks or tassels.
Another "must" for sweetcorn is to never let it dry out. Obviously
regular watering is top of the list but it is also a good idea to grow a
green mulch to shade the bottom of the sweetcorn plants and to stop
the sun drying the soil. Traditionally squashes are used, but
courgettes or melons will do just as well. Personally I don't like
squashes and there are only so many courgettes you can give away
before you neighbours start hiding behind their curtains every time
you pass by their houses. Melons need more attention than the
others and may not do so well. Whatever you do don't grow melons
and squashes together. They can cross pollinate with horrible results.
My personal preference is to grow a ground cover variety of
nasturtiums which have abundant flowers and make little demand on
the soil.
This method of complimentary companion cultivation is known as
"The Three Sisters" a title which has passed down through the ages.
Varieties
Not all maize is grown to be eaten as a vegetable of course and
increasingly varieties such as "white maize" appear on allotment
sites, which are flour varieties. Flour varieties are high in starch and
low in sugar and can be problematic insofar as cross pollination can
easily occur causing the sweetcorn varieties to produce cobs of poor
flavour. To avoid this it is important to check with your allotment
neighbours what type they are growing. If they are growing a flour
variety, or you are not sure, plant your own sweetcorn as far away as
possible and you should be OK. Be wary of accepting seeds of
unknown origin for the same reason. You may see many super sweet
varieties advertised on the internet but beware, these may be
unsuitable for our climate. As a general rule of thumb, the sweeter
the variety, the warmer the soil needs to be at the time of planting.
As usual, the safest option is to buy appropriate seed from a
reputable British supplier.
Finally, a tip for those who prefer to grow in rows rather than in
bunches or beds. Sweetcorn grows "two dimensionaly" by which I
mean the leave and cobs all grow left and right so that it is possible
to determine when first planting out the young plants how they will
look as adult plants, so by planting "leaf to leaf" you can optimize
space between rows making it easier for watering, tapping and of
course, picking those beans!