Agriculture Reference
In-Depth Information
pepo
) but not with a buttercup squash (
C. maxima
). Cross-pollination has its advantages and disad-
vantages: characteristics and traits that have been selected for over generations can quickly disappear
through cross-pollinating, yet interesting new varieties are also developed in just this way.
In order to be clear about what varieties will cross with what other varieties, you will need to know
to which
Cucurbita
species each squash you are growing belongs. If you are not using labeled original
seed from a reliable source, you will have to determine the species yourself. One method is to observe
the seeds;
C. ficifolia
seeds are black or gray;
C. moschata
seeds have a characteristic silvery golden
sheen and a rough surface, and so on. A much more reliable method for determining the species is to
observe the stem of the fruit:
• pepo squash: stems have five primary longitudinal ribs, sometimes with more secondary ribs in
between, and are somewhat prickly
• maxima squash: stems are woody, round, and 0.5-2.5 in. (1-6 cm) thick; fruits often slip (separate
from the vine on their own) when ripe
• moschata squash: stems are edged, sometimes starkly so, may be somewhat rough, and may have
small knobs; the base of the stem is either protruding or appears to rest atop the fruit
POLLINATION NOTES
Squash plants are monoecious; each plant produces male flowers and female
flowers. All squashes are insect-pollinated outcrossers, with honeybees and bumblebees being the
most important pollinators. Male and female flowers are each open for only one day. Female flowers
are easily identified by the large ovary, which often looks like a small version of the fruit, even before
pollination. Male flowers have much longer stems than female flowers; their stamens grow together to
form a single column, and they have on their surface an oily substance that helps their pollen grains
stick to visiting insects. Male flowers have pollen and nectar, female flowers only nectar; honeybees
appear to bathe in the base of yellow squash flowers, whether male or female, spending large amounts
of time there.
Since all squashes that belong to the same species can cross with one another, great isolation dis-
tances must be used between varieties of the same species (see previous table). Even in an ideal
garden, with diverse flowers and physical barriers like bushes, houses, and tall plants, varieties of the
same species should be grown at least 800 ft. (250 m) apart. (Remember to consider neighbors' gar-
dens as well.)
Squash can be kept from cross-pollinating by growing in an isolation cage or hoop house, though
this can be a challenge for large-growing varieties. Ideally, grow 12 (or at least six) plants, and use pol-
linator insects like honeybees, mason bees, or bumblebees. Flies can be used as a last resort, but they
do not pollinate as well.
HAND POLLINATION
Hand pollinating squash plants is time-consuming but fun—and a fairly certain
way of ensuring that cross-pollination does not occur. This method can also be used to intentionally
cross two varieties. Here is how it is done, and here is what you'll need before you start:
• six to 12 healthy plants
• at least two plants flowering at the same time
• at least one female flower
• at least three male flowers from another plant
