A recent thread on heirloom tomatoes showed that there is quite some
confusion about this subject. Also there is a tendency to take up positions
on the topic that are not necessarily supported by fact. To start with
heirloom and hybrid are not two mutually exclusive categories that together
describe all edible cultivars. It may be useful to speak of commercial and
home varieties but in this we should distinguish between the situations
where seeds are selected for either commercial or home growing and seeds
that are supplied commercially or saved at home.

To me 'heirloom' means an old open pollinated (true breeding) variety. It
often also carries the connotation of being handed down through personal
contact, that is being passed around. There are also many commercially
produced lines which are open pollinated. Since the commercial lines all
had heirlooms as ancestors and since true breeding commercial lines get
grown for seed and subsequently passed around, often without acknowledgment
of their origin, the distinction is not that useful. Of course there are
companies that specialise in selling heirloom seeds but the idea of passing
them around amongst friends seems to be important to some people. To me a
better distinction is to consider the reason why the cultivar was bred and
what characteristics were enhanced or reduced.

A hybrid is a cross between species (horse + donkey = mule) or between
cultivars. For edible plant growing we usually mean the latter. Hybrid
cultivars often are fertile and true breeding. Hybridisation can be, and
often is, used as an adjunct to selective breeding. Selective breeding has
been going on since agriculture was invented (say10,000 years) it is the
major force that has produced all the edible cultivars that know today from
ancestral types that were in many cases barely edible and much less
productive. Selection has improved yield, flavour and size, reduced disease
susceptibility and many other benefits. Hybridisation also can have
benefits whether it is simply combining the good features of two different
lines or generating hybrid vigour. The latter effect is an improvement that
can be observed when crossing two lines. Not all hybrids show this vigour
and it is not always very significant.

Some hybrids are called F1 hybrids. The 'F' stands for filial, that is
child. So an F1 is the first child generation, an F2 is the second child
generation etc. F1s *may* have a special property of being heterozygous
depending on how they are bred. Of course in any breeding situation you can
call the first generation the F1, it doesn't need to be a hybrid.

Greatly summarised plants (and us) have two copies of each gene (we get one
from each parent) there may be many versions of each gene in the gene pool
and in general all possible pairwise combinations are present in the
population. So you cannot be sure which characteristics an individual has
unless you have bred out all the alternatives, that is you have reduced the
scope of the genepool so that only one gene is available for the
characteristic, the one you want. If for a given characteristic the two
copies are different genes then that is heterozygous, if the two copies are
the same it is homozygous. The true breeding cultivar would be homozygous
for that characteristic, so each parent necessarily passes on that gene and
so the offspring will necessarily have the same gene.

However if instead of breeding the same homozygous line with itself you
breed two lines each of which is homozygous but different the F1 will
necessarily get one of each type from each parent and be heterozygous and so
not true breeding. This is the situation with commercial lines that are
sold as F1 hybrids. There are some good reasons for doing this from the
point of view of the consumer, some F1 hybrids are superior in some ways.
There is also a reason for doing it from the point of view of the breeder,
the grower is tied into buying their seed every year as seed saving is
useless because the F2, f3 etc can not be the same as the F1.

So what are differences between commercial and home varieties? The
difference is mainly in the selection of characteristics that have been used
in their breeding. People shop by appearance. In the supermarket large
will be bought before small, good colour before poor colour, clean before
blemished and flavour very often has nothing to do with it. So what have
plant breeders done for the supermarket growers? They have produced lines
of edibles that are good looking and durable. You can add into the equation
that in some cases produce is machine picked then they have also bred into
those lines the property of bearing abundantly over a short period of time.
The commercial grower wants to get rid of stoop labour going along the rows
selecting the produce that is ready by hand, when the beans are ready the
picking machine goes along and harvests all of them in one go. Sadly in
selecting for supermarket qualities taste has been relegated to a secondary
consideration, this is not an evil plot by dark forces but a continuation of
selective breeding that has been going on for centuries constrained by
modern marketing and transport.

The home grower may want quite different characteristics. When you grow
your own you can select for taste and you would probably prefer a cultivar
that bears over a long period of time rather than have a glut and you don't
care much if the produce is durable because you are not sending it 1000km to
market but taking it into the kitchen. The home grower is also interested
in suitability to their conditions and variety. Some grow 6 kinds of
tomatoes because some are better for salad or bottling or paste and it's
nice to have a choice of size, shape, colour and taste.

So what should you grow heirloom or hybrid? It's a meaningless question,
they are not strict alternatives. What you should grow is the cultivars
that suit you, the ones that have the characteristics that you want for your
situation. These may be available from friends or seed companies and they
may be "heirloom" in the sense of being identifiably old strains that have
been around for centuries or they may be new varieties. If you particularly
want certain F1 hybrid characteristics you might be happy to buy your seed
each year, if you don't really want that or even know what it means then
save your seeds and your money. It is better to be eclectic instead of
religious about growing.

David