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News Release -
Floyd County
Extending the Growing
Season with Plastics
February 27, 2002
Home and market gardeners alike are aware of the climatic
limitations and uncertainties afforded by the Ohio River Valley. Farmers
who try to derive part of their income by growing vegetables for local
markets appreciate the importance of extending the growing season to secure
a premium price and establish an early market "presence". Home
gardeners on the other hand often seek ways to begin gardening activities
earlier not only to extend their harvest of fresh produce but also to
improve their chances for "bragging rights" for the earliest
or largest vegetables in the neighborhood.
Regardless of the gardener's motivation for sheltering
tender plants from cold spring (or fall) conditions, there are significant
benefits for extending the growing season and nearly as many tools and
techniques to help them do so.
The use of modern horticultural plastics -often referred
to as Plasticulture- makes possible the production of warm season crops
(tomatoes, squash, peppers etc) up to a month earlier in the spring (or
later into the fall) or of growing cool season greens on nearly a year-around
basis. The choice of which season extension system is most appropriate
depends not only on the crop but also on the amount of time, energy and
money that one cares to invest in the venture.
The continuum of basic season extending systems –from
the simplest to the most complex- might look like this:
What each of these systems has in common today is the potential
of using inexpensive plastic products to make them successful.
Horticultural plastic have evolved from the translucent,
impervious sheet goods that readily deteriorated in sun and wind to a
diverse array of products that vary in color, light transmission, durability
and porosity (ability to "breath"). Gardeners will quickly realize
that there is no one best system or product and that each will have its
own merits for different applications.
Cloches and
Hot Caps
Evolved from bell-shaped glass jars once placed over individual plants,
modern cloches may look more like a wax paper cone or a water filled plastic
tee-pee (Wall of Water TM). In some cases they may cover an entire row
when a sheet of semi-rigid fiberglass is bent into an arch and fastened
to the ground on two sides. A less expensive cloche may be made by simply
cutting away the bottom of a common milk jug to be placed over a single
plant in the garden. To avoid overheating through the day the cap may
be removed to create a vent.
Low Tunnels
and Floating Row Covers
These systems employ a spun bond polyester fabric which is laid over an
entire row or rows of a crop and sealed along the edges to trap heat and
avoid its loss to the wind. Often used in conjunction with a plastic mulch
and drip irrigation, these systems differ only in that the "tunnels"
in the low tunnel system are created with the use of wire hoops to avoid
contact of the fabric with plant foliage. Both can offer 4-5 degrees of
frost protection and have the added benefits of screening damaging insects
and diseases so that yields are not only earlier and larger but often
of better quality. For those crops that are sensitive to heat or require
pollination care must be taken to remove these in a timely manner.
Cold Frames
and Hot Beds
Also referred to as "sun boxes" or "solar pods" these
rather simple structures provide a favorable growing environment, for
some crops, well into the winter months. These can be large and elaborate
like a small greenhouse (hotbeds) or quite simple with the only source
of heat being the sun (cold frame). Either can be permanent or mobile
to satisfy changing needs. Newer designs incorporate a means of passive
collection of solar heat through the day to be released as needed at night
when temperatures plunge.
These systems excel as a place to start young seedlings
for later transplanting or for starting sweet potato "slips".
Either may be covered with a single or double layer of polyethylene or
fiberglass.
High Tunnels
Also referred to as "hoop houses" by commercial growers, high tunnels are a compromise between the unheated
low tunnel or row cover and the conventional heated greenhouse. While
they are large enough to walk into with a roto-tiller they typically are
unheated except on extremely cold nights and are narrow enough to ventilate
naturally through roll up sides. In their simplest of designs high tunnels
are constructed of PVC or light metal bows and are covered with one or
2 sheets of polyethylene. They can yield high quality, clean, and disease
free tomatoes up to a month early but will require twice daily care to
ventilate even on cool sunny days.
Greenhouses
There is an almost overwhelming selection of types and styles of greenhouses
from the inexpensive but functional to the expensive elaborate and ornate.
It is important to note that from a garden plant’s
perspective (if I may speak for the plants) there is probably little significant
difference between them provided that heat and ventilation needs are addressed
in a timely manner. Coverings may range from "inexpensive" and
relatively short-lived polyethylene to the more expensive and rigid polycarbonate
sheets or glass.
Care must be taken when deciding whether these structures
should be free standing or attached to the home. In either case, a properly
managed greenhouse might be expected to require a similar level of care
and commitment as one might allow for a new child in the home. Delays
in watering, or providing for adequate and timely heat, ventilation or
pest control will most surely lead to disappointing results. Obviously
the more technology one can afford to invest in, the lower the level of
daily care that may be required.
There are many ways to (at least on a small intensive scale)
extend the growing season in the Ohio River Valley though none are without
expense. Each type will require significant planning and preparation and
each will be most successful where they are complimented by proper site
selection and soil drainage, windbreaks and appropriate variety selection.
Plasticulture should be viewed as an integrated system
that includes plastic mulch, appropriate structures and coverings and
drip irrigation.
If you are considering ways to extend your growing season
at home or on the farm, you can contact the Floyd County Office of the
Purdue Cooperative Extension Service at 812-948-5470 for help in choosing
the system that is right for you.
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