May 2019 - 14

WINTER
CONTINUED FROM PAGE 12
to 10-day intervals. This helps allow
for a more drawn out harvest. It also
reduces the risk of planting date
variabilities in weather and the risk of
crop failures over winter.
Using transplants can get your crops
a head start. " I really recommend you
use transplants for the crops you'd
grow from seed, like spinach, " Heflick
said. " We sacrificed some space to use
transplants so we could stay on our
planting schedule. "
The days of growth time as a
transplant must be added in when
counting back the days from the
last 10 hour day. " Adjust for your
transplant time in your planting dates, "
Heflick said.
Crops that overwinter for harvest
next spring, like radishes, can also be
planted in the fall based on the last 10
hour day. The plants will establish in
the fall, be dormant over winter and be
ready for a fast start the next spring.
" They'll start growing again when
you get to your 10 hours of daylight in
the spring, " Heflick said. Days lengthen
quickly in the spring. Plants should be
ready so daylight is not wasted.
Planting crops for overwintering
until next spring is especially
important when targeting earlyseason
markets, but growers should
be cautious with the strategy. The
wide fluctuations in temperature in
the spring - from late winter lows to
sunny day highs - are a challenge.
Warming up
Adequate ventilation, minimizing
temperature fluctuations and managing
soil moisture are all management
considerations in winter production.
Keeping the hoop house warm isn't as
important as minimizing temperature
fluctuation. " Ventilation is very
important, " Heflick said. " It can be cold,
but on a sunny day, temperatures could
spike up to 85 degrees and that's pretty
stressful on plants. The plants are used
to 20 to 30 degrees, so you want about
40 degrees, maximum. You want to
minimize temperature fluctuation as
much as possible. "
Maintaining adequate air flow is
an issue since diseases and insects can
build up in the hoop house when the
temperature gets too high. Scouting
and promptly removing any diseased
plants are essential. Wider row
spacings can help, too.
" You want to be really
creative about extending
the summer season while
also getting your winter
plants up to size. "
− Kate Heflick,
Michigan State University
Redefining the C.E.A. industry
Soil moisture must be brought up to
the right level before winter. You want
the plants to have enough moisture
between planting and reaching the
goal of at least 75 percent mature by
the Persephone Period. Most crops,
however, don't use much water over
winter. This makes it easy to water too
much or too little.
When you do water, you don't want
to leave any water on the leaves when
temperatures are falling toward freezing.
" We only water on sunny days, " Heflick
said, and only between 11 a.m. and 2
p.m. With crops like head lettuce, only
the area between the rows is watered
to avoid getting water in the head and
causing disease or quality problems.
MSU's Student Organic Farm is only
using supplemental heat in one hoop
house starting in late January when
transplants are being established.
Under cover
Various types of internal covers are
used to add a layer of warmth and
protection to the crops.
Row cover fabric and old hoop
house plastic have both been used as
internal covers. Some are draped over
the rows on low hoop frames or on
wire supports. This allows smaller,
more manageable sizes of cover to be
used.
Frames and supports are hard to
work around. Removing them also
adds one more step to get ready for
spring planting.
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of plastic to cover the width of the
hoop house. " It's hard for one person
to remove, " Heflick said. " It can be a
good option - especially if you have
two workers all of the time. "
Overwinter production is a
complicated system. One strategy
will not work for every situation. The
Persephone Period for your area gives
you a set date, but you still must have
some flexibility.
" Go on either side of that date.
Leave yourself some room to
make adjustments, " Heflick said.
" Sometimes growing in the winter
works out well, sometimes it doesn't.
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May 2019

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