August 16, 2004: Greenhouse production of vegetables and fruits
is one approach to season extension in temperate climates.
Although greenhouses are effective in this regard, they are
often quite expensive. Putting row covers over field transplants
is an intermediate strategy between greenhouse and open field
production. This method can accelerate early season growth
and prevent late frost damage on summer crops at much reduced
capital costs to farmers compared to greenhouse production.
Penn State researcher Mike Orzolek reports on his results
this year with zucchini under row covers. Early zucchini yield
was 10 days earlier under row covers compared to open planting.
All plants were transplanted to the field on May 27; covers
were installed the same day and were removed on June 16. In
the first 7 harvests, 14 varieties of zucchini that had been
covered yielded double than those without row covers. Overall,
zucchini under covers yielded 25 percent more than exposed
This spring was cooler than normal in State College but these
preliminary tests indicate that row covers have potential
not only as a good insurance of avoiding late frosts but also
a way of stimulating early harvests, which generally get best
market prices. Organic, sustainable, and conventional farmers
should consider looking at this option as a potential alternative
in their cropping system. We suggest farmers get information
on how this works from your own small on-farm trial and then
run return-on-investment numbers before moving to the system
In addition to controlling temperature, row covers can serve
as insect barriers. Insect avoidance would be especially important
for organic production systems under some conditions.
As you make up your plans for next year, consider trying
some covered rows—and let us know what your experience
is with this developing method.
Organic Swiss chard keeps better than conventional
Increasing vegetable storage life holds huge advantages for
farmers and consumers alike. Farmers want to sell and consumers
want to buy fresh products. Highly perishable products such
as chard and other greens can degrade before or shortly after
arriving in the marketplace, disappointing both producers
A group of Argentinean scientists have shown that Swiss chard
grown organically can store better than conventional chard.
In blind studies, organically produced chard was rated firmer
and maintained brighter colors longer than conventionally
produced chard. In both conventional and organic chard, the
rate of deterioration was indexed at 0.057 per day; however,
start of deterioration was at 3 days for conventional chard
and 10 days for organic chard.
No significant differences between conventional and organic
chards were found for yeast, mold, population levels of assorted
bacteria, rate of vitamin degradation, water content, chlorophyll
content, or acidity.
Orzolek, Mike. 2004. “Row Covers: Do They Work?”
Pennsylvania State University Department of Horticulture,
The Small Fruit and Vegetable Gazette 8(7). http://hortweb.cas.psu.edu/extension/vegcrops/vegetable_gazette/2004/august2004.htm#covers
Moreira, M. del R., Roura, S. I. and Del Valle, C. E. 2003.
Quality of Swiss chard produced by conventional and organic
methods. Lebensmittel-Wissenschaft und -Technologie 36(1):135-141.
Paul Reed Hepperly, Ph.D., is research and training manager
at The Rodale Institute.