There are several types of gene sweetness described in increasing
order of sweetness SU (Sugary), SE (Sugar Enhanced), SH2 (Supersweet)
and finally the new tendersweet versions. The first two can be grown
together usually without problems*. The SH2 or Shrunken seed's gene
isn't that stable so pollen from SU or SE types can make it revert to
field maize i.e not sweet at all. The same applies to the Tendersweet
varieties. The SH2 seed looks shrunken or dried up in the packet btw.
If the packet says grow apart, that's often an indication it's not SU
or SE in type rather than the description.

The Supersweet SH2's are sweet but tend to have a harder corn seed
when eating them, so the Tendersweet was created to keep the increased
sweetness but have the creamy texture of the older varieties. The
other important thing about super and tender sweet varieties is that
they keep that sweetness longer once cut (several days) and so are
more use to the commercial food distribution network, for which they
were created for. SU and SE will keep sweet for a day, bit longer in
the fridge.

Sweetcorn crosses easily being wind pollinated and it is the seed that
we eat so it is not a problem that affects only those saving seed for
next year.

Many people grow several varieties based on how long they take to
mature. There are described as early, mid and late season or often in
number of days. So either choose several from the SU/SE group or ones
from the others. It's usually quoted at 300ft+ to keep the two groups
apart if they produce pollen (ie mature) at the same time. Otherwise
growing ones from both groups can be done if their maturity dates are
kept more than 2 weeks apart. Not easily with our varied summers
messing growth up.

There is a lot of info on the web about sweet corn varieties, often
from US universities
http://cahe.nmsu.edu/pubs/_h/h-223.html
Googling a variety by name will usually yield it's gene type and days
to harvest. SH2 types need warmer soil to germinate than others and so
in a UK climate, late season (90+ days) might not make harvest in
time. Btw there are loads of different block planting spacings
around, nearly all work out at at least 144 sq inch for each plant.
Normally 16 plants is stated as the minimum quantity for pollination,
more is better. Poor pollination results in half filled cobs. Lack of
nutients results in only one cob per plant. Sweetcorn are heavy
feeders. There has been at least one field trial showing that the
roots of broad beans improve the nutrient take up of sweet corn if
that helps in your planning.

Hope this helps

Nigel




* unless one is bi-colour or white and the other is yellow. Then some
grains will be the other's colour.



On Sun, 12 Oct 2008 19:14:46 +0100, "Mel"
wrote:

I'm starting to plan ahead for next year's allotment crop and I'm looking at
sweet corn. I know that some varieties have to be grown apart from other
varieties, but I'm confused between tendersweet, extra sweet, supersweet,
sugar sweet, etc.

Could someone enlighten me as to which varieties have to be grown apart, and
which varieties can be grown close to each other?

Many thanks.