Noel Kingsbury, writing
in June/July 2001 issue of 'The English Garden,' takes up the idea of
self-sown plants (see "Last Year's Garden
this Year" elsewhere), but deals with biennials and short-lived
perennials that thrive in the temperate climate of his garden. He remembers
the charms and the frustration of seedling appearances in unpredictable
places, and has had the experience, that we must all have shared, of
the irresistible attraction that gravel and a crack between paving stones
seems to exercise for these wanderers.
While the main attraction
for him lies in the semi-wild or cottage garden look that self-sown
plants can give, he also values the changes in populations that develop
season by season as some of the highly bred garden plants self-pollinate
and cross to give a kaleidoscope of forms. A planting of a few colours
of aquilegia will, season by season, give new colours, and the same
is true of hellebores and astrantia. As they flower, the least desirable
forms should be discarded so that only the best are thrown back into
the crossing game. Some very interesting plants have been developed
and selected in this way.
Some of the most
reliable self-seeders for Mr. Kingsbury are : Alchemilla mollis,
Dipsacus fullonum (teasel), Digitaria (foxglove), Eryngium
giganteum, Foeniculum vulgare (fennel), Helleborus
foetidus, Linaria spp. (toadflax), Lychnis coronaria,
Oenothera spp. (evening primrose), Onopordon acanthium
(Scotch thistle), Salvia pratensis, Silybum marianum,
Stipa arundinacea, Stipa tenuissima, Verbascum
spp., Verbena bonariensis.
pesticides with Biological Control Agents
The efficiency and
ease of use of chemical controls makes them the first choice of most
nurseries and greenhouses, but the advantages of biological pest controls
is winning a place for them as well. Dr. Kevin Heinz of Texas A.&
M. University, writing in the July 2001 Greenhouse Business, discusses
the difficulties in combining the two systems of control, and suggests
The problem, of course,
is that chemical pesticides are not often specific enough in their targeting
to distinguish between friend and foe. With careful planning, the natural
control organisms may be kept away from the chemicals in time or space.
Releasing the natural control at an interval after the final application
of a short residual pesticide may be effective, as may the use of such
a pesticide when the control organism is in a resistant stage of its
is possible if pesticide use can be made only to very restricted areas
in the nursery so that the bulk of a control organism population is
not exposed to the chemical.
There is some hope
for the future development of pesticide-resistant natural controls,
and extensive testing is under way to discover compatible chemicals
for specific controls or for whole control programs He cites examples
for particular crop problems and their controls, and is encouraging
about the possibilities of incorporating both chemical and biological
control into an integrated pest management program.
final report on the grant from American Floral Endowment that was the
partial funding for this work, is on-line at http://www.endowment.org/pr/heinz_finalreport.htm
The small dark flies
that alarm homeowners when they appear around their plants are more
than just a nuisance to greenhouse operators.Greenhouse Product News,
June 2001 issue has an article by Drs. Raymond Cloyd and Edmond Zaborski
(of the University of Illinois and the Illinois Natural History Survey
Center for Economic Entomology respectively) that reports work just
beginning on controls for this insect.
Adults are found
on the surface of the soil or resting under leaves. They live 7-10 days,
and the females lay 100-200 eggs into crevices in the potting medium.
Moist conditions that favor fungal growth on organic materials in the
soil provide food for the developing larvae, but in the absence of fungal
strands they will attack plant roots. The larvae are about 1/4"
long, white with a shiny black head cap, and are most common in the
upper 2'' of the medium.
Control is usually
done with common greenhouse insecticides, but since some of these may
be lost to the industry, biological controls have been tried with some
success. A nematode, Steinernema feltiae, and a predatory mite,
Hypoaspes miles appear promising. For the homeowwner, some control
is possible with insecticieds, and the flies are also discouraged if
the top layers of the soil can remain dry most of the time, to discourage
The authors are planning
work that includes new techniques of assessing populations in order
to evaluate the new combinations of control methods which they will
News has a web-site with a searchable archive of articles from back
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