Seasons of the Garden
News briefs on pesticide facts, controlling greenhouse whitefiles, metallic blight, controlling soil disease, pruning and more.
by Greg and Pat Williams
RELATED CONTENT
Research Briefs
Suffering succulents!If your indoor cacti and other
succulents suffered from neglect during the gardening
season, now's the time to make amends. British expert Roy
Mottram says that although people associate succulents with
harsh alkaline soils, their soil pH should be slightly
acidic-ideally, 5.5. So check your tap water for alkalinity
if your plants seem unhealthy. Mottram also recommends
giving succulents weak doses (1:1:2) of N-P-K fertilizer
and adding organic matter or sterile soil for trace
elements.
Succulents can tolerate fairly high levels of soluble
salts-if the pH isn't too highbut extreme salinity kills
roots. So water occasionally but thoroughly to wash out
accumulated salts, and repot any plants that seem to be
either waterlogged or difficult to wet; they're most likely
full. of salts.
Control greenhouse whiteflies. Yellow
sticky boards control greenhouse whiteflies [EDITOR'S
NOTE: See "Getting the Most From Your Solar Greenhouse" on
page 74], but according to Japanese horticulturists,
their effective range is only one yard. So space them no
farther than three feet from plants and from each other.
Their efficiency also drops sharply when daily highs are
under 80°F.
Beware metallic blight! Some landscapers
and homeowners don't remove the soilballing wire mesh from
trees and shrubs when transplanting, because they think the
wire will break down quickly in the soil. Not so! Dr. James
Feucht of the Colorado Extension Service found that mesh
buried for 15 years can restrict root growth and
even kill formerly healthy plantsespecially during a
drought. (The size of the mesh openings doesn't matter.)
The moral? Remove wire from root balls when planting.
More on controlling soil disease. In our
May/June column, we reported on soil amendments developed
in Taiwan to control soil-borne disease. Plant pathologists
in Hawaii now claim they controlled damping off of cucumber
seedlings (caused by the Pythium splendens fungus)
by adding 0.6 % calcium and 1 % alfalfa meal, by weight, to
infested soil. (Calcium carbonate, hydroxide, and sulfate
were all used—the last does not increase pH.) Perhaps
a bit of calcium and organic matter can provide good
insurance against many soil-borne plant diseases.
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