Seasonal Gardening: Cacti and Succulents, Controlling Greenhouse Whiteflies and Soil Disease

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British expert Roy Mottram says that although people associate succulents with harsh alkaline soils, their soil pH should be slightly acidic-ideally, 5.5.

The Seasons of the Garden column shares seasonal gardening information and tips with MOTHER EARTH NEWS readers.

Seasonal Gardening 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

Succulents can tolerate fairly high levels of soluble
salts-if the pH isn’t too high but 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 of MOTHER EARTH NEWS NO. 102),
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 degrees Fahrenheit.

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 plants especially 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.

Soaking troubles?
Many gardeners pre soak some crop seeds
(such as okra) to speed germination. But USDA plant
physiologist Stephen Spaeth says presoaking can create
lifelong problems for crops. An unsoaked seed remains
essentially intact until its root tip pokes out, but a
soaked one takes up water so quickly it cracks. Sugars,
proteins, and amino acids can then leak out into
surrounding soil and nourish pathogenic fungi — which
infect the seed. The fungi may stress plants their entire
lives. Spaeth also considers leakage a problem for seeds
germinating in very wet soil — such as farm grains and
legumes planted just before heavy spring rains.

Pesticide facts. Cornell professor David
Pimental and graduate student Lois Levitan recently noted
in BioScience that the U.S. uses about a
billion pounds of pesticides a year (120 million
pounds in and around homes). About 16 % of the country’s
land area is treated yearly, with an average of three
pounds of pesticide per acre (12 pounds near household
areas!). Environmental and social costs of pesticide use
amount to about $1 billion yearly (direct costs are about
$3 billion), while pest control benefits are worth roughly
$12 billion.

Sadly, less than 1% of applied pesticides typically affect
their target populations. Improved application
technology — even just spraying close to
crops — could reduce pesticide use considerably
without decreasing effectiveness.

Easy on the N, please. Egyptian
researchers found that fertilizing spinach heavily with
soluble nitrogen increases the plants’ content of poisonous
oxalic acid and active oxalates. Winter-produced and young
spinach also had generally higher oxalic acid levels than
spring and mature plants.

Don’t prune. Just what we like: a plant
that yields more fruit when it isn’t pruned. New
Zealand trials with Magnus black currants showed that
unpruned currants bore nearly twice as heavily as pruned


The booklet “Marketing for the Small Farmer: Direct
Marketing and Quality Control” covers vegetable harvesting,
packaging, and handling and is available free from The
Small Farm Center, University of California, Davis, CA. The U.S. Forest Service guidebook “Managing
Urban Woodlands for a Variety of Birds” provides details on
creating bird habitats in parks and suburban backyards
throughout the East. Write for a free copy of Bulletin
NE-INF-6385 from Information Services, Northeastern Forest
Experiment Station, Broomall, PA.; Finally, the USDA has set up an Alternative Farming
Systems Information Center (National Agricultural Library,
Beltsville, MD) to provide
access to publications that emphasize low-input,
resource-conserving farming and gardening. The summer
’86 issue of Growers’ Review Quarterly ($3
postpaid from Florists’ Review Publishing Co., Chicago, IL) includes a
well-illustrated article on using a homemade conduit bender
to make inexpensive hoop-framed greenhouses. Author John
Senne built eight 80 inch by 50 feet greenhouses for his flower
business from standard 10 foot conduit. The herbal insect,
slug, and snail repellent “Green Ban” — recently
imported from Australia — contains eucalyptus oil,
Norwegian kelp, sage, garlic, and English ivy. Preliminary
tests show it particularly useful against aphids. Order an
eight-ounce bottle for $8.25 postpaid from Smith &
Hawken (Mill Valley, CA).
Send $1 to Lesco, Inc. (Grass Seed Issue, Rocky River, OH) for a quite useful booklet on
turfgrass and wildflower seed.

Greg and Pat Williams raise most of their own food on a
small farm and publish HortIdeas, a fine newsletter on
gardening research and products (available for $10 a year
from G. & P. Williams, Gravel Switch,