High Tunnel Fruit and
Vegetable Production
LESSON FOUR: HIGH TUNNEL
MAINTENANCE
Maintenance
 Just like a vehicle needs to be maintained for
optimal performance, high tunnels must be
maintained as well.
 How
many things can you think of for vehicle
maintenance?
 Today we will discuss many different high tunnel
maintenance needs.
Objective
 Explain how temperature, humidity and
wind can be managed in a high tunnel.
Replacing the Cover
 Remove the plastic in reverse order.
 Replacing a cover depends on the age and wear
of the plastic, but should be done every three
years for tunnels in year round use.
 When not in use, multi-bay tunnel covers are
rolled and rest in the alleys where the bays
connect to keep them off of the ground.
 To protect them from sun exposure and
degradation, tunnel covers should be covered
with black plastic when rolled.
Regular Maintenance
 Plastic covers should be inspected regularly for
wear and tear.
 Rips should be immediately repaired with clear
tape.
 If the plastic remains on the tunnel for the
winter, periodic removal of snow load may be
needed to avoid structural weakening or
collapse.
 This is best done with a non-pointed object, such
as a long-handled floor broom head or
squeegee, before ice or a stiff crust forms.
Climate Variability
 The locations of plants in a high tunnel and the
plant canopy have an effect on temperature
variations.
 Some producers may expect high tunnels to
extend the production season in the fall by
protecting the crop from early frosts.
 However, the frost protection provided by the
high tunnels is minimal.
 In many areas, high tunnels are most often used
to facilitate early production rather than lateseason extension beyond the fall frost period.
Temperature Variability
Temperature
 High temperature can be as damaging to crops as
low temperatures. Excessively high temperatures
can cause flowers to fall off tomatoes and peppers
as well as reduce pollination, resulting in a lower
percentage of marketable fruit.
 Stress related to dehydration may be avoided
through careful attention to availability of soil
moisture.
 Shade cloth, and vents in the roof, end walls and
side walls are the most effective ways to moderate
temperature inside a high tunnel.
Shade Cloth
 Shade cloth is used to reduce light intensity,
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temperature, and plant exposure to wind.
In warm climates or during the summer, a shade
cloth can be used as the sole covering for a high
tunnel.
Black, white and various shades of green and brown
are available.
Shade cloth is rated by the percent of light blocked,
varying from 20 to 90 percent.
Seasonal and crop species requirements dictate
which percent shade cloth should be used.
A 50 percent white or black shade cloth is commonly
used.
Humidity
 Careful ventilation will help to keep relative humidity
at lower levels and to keep the foliage dry,
preventing disease outbreaks.
 Proper use of drip irrigation will also keep the
humidity low.
 High tunnel sides should be opened each morning
to dry the leaves that have collected condensate
during the night.
Wind
 Trees, shrubs and fabricated material like wood lath
can be used as a barrier to moderate and/or
redirect wind. Windbreaks could consist of woody
shrubs designed to be harvested for fruit or flowers.
 Windbreaks on the north side of a high tunnel
should be about 100 feet away, keeping snow drifts
away from the structure. The length of a windbreak
should be ten times longer than it is high.
Ventilation
 Regulate temperatures inside high tunnel by
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opening and closing tunnel sides, end doors and
peak vents.
Sides may be opened up fully or partially,
depending on outside temperatures.
Sides can remain open day & night during summer
Retain as much heat as possible inside tunnel
during night in spring and late fall
Tunnel sides should be closed in late afternoon or
sooner when outdoor temperatures cool off at night
Activity
 Find a partner!
 You will be assigned a season: Spring, Summer,
Fall or Winter.
 Describe a typical day for that season in regards
to maintenance for the high tunnel.
 Try to come up with as many maintenance
duties as possible.
 Present to the class.
Summary
 Maintenance is an important aspect to proper
utilization of the high tunnel.
 Without maintenance, the fruit and vegetable
production could decrease or the high tunnel
may fall into disrepair.
 A well maintained high tunnel will efficiently
produce quality fruit and vegetables and
therefore increase the yield and profit of
produce.