Growing Onions in the Tropics
There
are two main types of onions, based on the daylight hours required for bulbs to
form. Short-day varieties start forming a bulb when days are about 13 hours of
sunlight; long-day varieties don't form a bulb until days are 14-16 hours long.
For both types, bulb growth is slowed or stopped during hot, freezing or dry
weather. Near the equator, where days are 12-13 hours long throughout the year,
long-day onions will never form a bulb; and in Canada, where days are 14-20 hours
long during the growing season, short-day onions will not be successful. The seeds you find in the southern United States
will be short day varieties. Seeds in Haiti
are questionable since well-meaning missionaries carry in all sorts of seed,
many which will not grow in the tropics.
Short day onions tend to be milder in taste but will not store as long
as the long day variety. The Vidalia
onion is a short day variety.
Short
day onions almost always must be started from seed. Seed should be started in December/January
and then transplanted in February/ March to the garden. I have found that
planting the seeds in trays or beds inside the shade house to be equally
successful. If you use a tray, don’t use
an insert just fill with planting soil and sow the seeds in the tray. Scatter the seed and cover them with about ¼
“of soil and water liberally. After the
plants reach 3 to 4 inches in height, they can be transplanted to beds either
in the shade house or outside beds. Extreme hot temperatures and drought will
prevent good heads forming. The beds
should be loose soil and the onions plants should be set about 4 inches apart,
onions don’t like close company. Don’t
keep the beds damp but water a couple of times per week. If for some reason the heads do not develop
or are small, don’t worry, green onions also taste great.
If you
can get onion sets, which are long day onions, into Haiti they make wonderful green
onions in a very short period. They
will not make large heads but as green onions they are a wonderful addition to
Haitian cooking.
Hours
of day light for Port au Prince will reach 13 hours about May 15, reach a peak
of 13 hours and 15 minutes June 20 and decline again to 13 hours at the end of
July.