Spider mites, also known
as two-spotted mites, become a particular problem for
the gardener through the winter. Normally, they hibernate
in ground litter or under the bark of trees or shrubs.
However, if they stowaway onto a plant being brought
indoors, the artificial lights, and warm, dry, conditions
of most heated homes will allow them to keep infecting
spider mite, Tetranychus urticae, is a tiny,
8-legged pest related to the spider & tick. Adults
are normally green or yellow but turn red when the day
lengths shorten in the autumn. They attack plants by
stabbing the underside of the leaves and sucking out
the sap. This damage causes a distinctive stippling
effect due to the loss of chlorophyll. As their numbers
increase, the number of white speckles on the leaf increases
and the leaf eventually dies. Once the spider mites
begin reproduction, a distinctive “webbing” forms, usually
under the leaf and then at the growing tip of the plant.
What makes this pest truly
difficult to control is its rate of reproduction. Each
female will lay up to 12 eggs per day. Mating is not
required for egg production. At 21ºC, these eggs will
hatch in as few as 3 days and will develop into adults
in only 14 days. If left unchecked, 10 spider mites
in May will become 100,000 by July!
Spider mites have been
found in greenhouses across North America and Europe
and are known to attack over 200 species of plants including
azalea, camellia, citrus, evergreens, hollies, ligustrum,
pittosporum, pyracantha, rose, and viburnum; fruit crops
such as blackberries, blueberries and strawberries;
vegetables including tomatoes, squash, eggplant, cucumber;
and trees such as maple, elm, ash, black locust, and
The Predatory Mite
the spider mite, the predatory mite, Phytoseiulus
persimilis, is a welcome insect in the garden &
greenhouse. It is a fast moving insect with an orange
teardrop-shaped body. The species is a specialized predator
the two-spotted spider mite and feeds on all stages
of its prey, from egg to adult.
The adult P. persimilis
is a voracious eater, eating between 5-20 prey per day.
It uses its sense of smell to find plants infected by
spider mites. As soon as it comes into contact with
spider mite webbing, it will intensify its search.
P. persimilis can
be purchased from many biological control companies.
Often it is shipped in a glass vial or on trays of bean
leaves. The easiest method of application is to sprinkle
about 20 adults on each plant. These predatory mites
prefer to work their way up a plant, searching for food
so try to introduce them as low down as you can. In
addition, if many of your plants are infected, keep
them close together with their leaves touching so that
these predators will be able to easily move from one
plant to another.
Unlike the spider mite, P. persimilis prefers humid conditions and misting
will not only help it multiply, but will keep down the
numbers of the spider mite. A relative humidity of 70%
is ideal for P. persimilis. Once its food supply
is exhausted, the numbers of P. persimilis will
Other cultural controls
As previously mentioned,
misting plants at least twice a day will keep spider
mite numbers down. Mite populations can also be reduced
by spraying the underside of the leaves with a jet of
water to break up the webs and wash the mites off.
Soap sprays are also very
effective at controlling spider mites. The active ingredient,
potassium or sodium salts of fatty acids, is not toxic
and can safely be used indoors. A homemade spray can
also be prepared using ordinary dishwashing detergent.
Mix 5 tablespoons of detergent in 1 gallon of water
and spray the plants, especially the underside of the
Viva Organics – a source of P. persimilis
University of Florida Dept of Entomology – life cycle
of the spider mite
Cornell University Biological Control – A guide to P. persimilis, the predatory mite
Hamir is an agronomist and President of Terra Viva
Organics. When she’s not planting peas or picking zucchini,
she answers questions about organic gardening at: firstname.lastname@example.org. You
can also read her gardening articles on Vegetable Gardening
Did you know that 80 %
of the plants that were available at the turn of the century
are no longer available to us?
a child I remember sitting with my grandfather on the
back porch eating tomato sandwiches. The tomatoes were
huge and the air was filled with a tangy, tart smell
that tickled your taste buds long before your first
bite. As an adult I remember ordering a BLT, in a charming
restaurant in Charleston, SC. When my sandwich arrived
I gawked at the tomato that was the size of a slice
of bread and as I inhaled I could almost hear my grandfather
laughing as that tangy, tart smell reached my nostrils.
I looked at the waiter and said “These tomatoes . .
.” He replied, “Oh, yes ma’am we only use heirloom vegetables
and herbs here.” And just like that, a whole new world
of gardening opened up for me.
To be considered an heirloom,
the plant itself (be it vegetable, fruit, herb etc .
. .) must be open-pollinated, or able to produce seeds
that will come back true year after year. You will find
as you delve deeper into the world of heirloom gardening
that many heirloom plants come with humorous names and
usually a touch of folklore such as the “Mortgage Lifter”
tomato or the beautiful flower named “Kiss Me Over the
There are 4 different
classifications of heirlooms:
– the most common and well known. These are seeds
that have been passed down from generation to generation.
– the open pollinated varieties that were offered
commercially until approximately the 1940’s.
Created heirlooms – the result of the deliberate crossing of 2 known
hybrids or an heirloom and a hybrid.
– result of the natural crossing between 2 heirlooms
where only 1 parent is known.
The past few years we have seen a renewed interest in
the plants that our ancestors held so dear, and rightly
so, but why? There are several different theories. The
first being that the resurgence of gourmet foods and restaurants
have been able to bring a new appreciation to the strong
flavors and wide array of colors and textures available
in these older varieties.
The second theory, the
new millennium evoked such a mistrust towards future
food supply within the public as a whole, more and more
interest came to the plants that could provide seed
that would come up true year after year, without interference
from us or commercial nurseries etc.
The third theory, after
many years of dealing with mass crops of corn, soybeans,
potatoes being wiped out by a single blight or bacteria,
we have finally begun to understand the importance of
genetic diversity. Jennifer Heer, a good friend of mine,
is a Genetic Research Assistant at North Carolina State
University. I posed the question to her as to why she
felt so strongly towards maintaining heirloom plants,
and this was her response:
Anytime I think about
heirloom ANYTHING, I think about genetic diversity (of
course). There are all these genes in a plant, and some
you like and some you don’t and some you have no idea
what they do because they are “quietly” important. Important
in ways we don’t know. If we let some herbs “fall out
of favor” and push them to the side or even go EXTINCT,
we are losing something that we can’t find again and
LATER it might be important, medicinally, for drought
tolerance, for pest tolerance, etc. It’s like fighting
to save the world’s endangered species, only it’s not
species, it’s GENES and we can’t even describe them
yet so that makes it even harder.
I, on the other hand,
sadly, am not that complex. My reasoning for getting
so involved in heirloom gardening is the simple reason
that I cannot imagine not having these plants in this
world. I want my children to be able to experience what
it is like to go into the garden and find a delightful
“Moon and Stars” watermelon, painstakingly gather the
seed after delighting in the sweet taste, and saving
those seed to plant next year.
My grandfather grew luffa
for years. I remember walking with him on the cold days
of October and November and checking the luffa to see
if they were dry enough to harvest yet and then watching
in absolute amazement when he peeled the skin back and
there was a sponge! I thought that these seed had died
with him. As I was chatting with a neighbor of mine
I mentioned this story and he replied, “Oh, your granddaddy
gave me some of those about 10 years ago. I still grow
them, want some?” He went out into his garage and came
back with a dried luffa just ready for me to collect
the seed and replant! Wonderful.
Whatever your reasons
may be to want to save these plants, whether it is maintaining
genetic diversity, bringing a touch of nostalgia into
your garden, or to be able to pass part of your garden
on to others, you will be greatly rewarded with the
Savers Exchange: a great organization that is assisting
in the cultivation of heirloom plants by growing some
of them themselves but also teaching others about the
importance as well as the how-to’s of heirlooming.
Land: wonderful website containing much information
on organic growing and the beauty of heirlooming.
Elizabeth Harwick is an
avid gardener specializing in the historical, medicinal,
and therapeutic properties of herbs and other little
known “wayside” plants. “To maintain a garden you must
also maintain a sense of humor.” All questions or comments
are welcome : email@example.com
Gardeners practiced the concept of the three R’s: Reduce,
Reuse, Recycle, long before it became trendy. People who
grow things have a special relationship with the land
and they naturally take steps to take care of it. Take
composting for example, they have always known that recycled
plant material was beneficial to the soil. Nothing from
my grandmother’s garden or kitchen was ever wasted. Using
manure in the garden was an accepted fact. These are just
some of the recycling practices which have been around
for a long time.
Reducing has also been
widely practiced among the garden folk. Mulching to
conserve water and reduce watering has been standard
practice among many. Water caught in a rain barrel was
and is a good way to get water for the garden taking
the strain off the household water supply. Using that
compost so carefully acquired reduces the chemicals
that have to be added to the soil.
But, I don’t think that
any other group shows as much imagination when it come
to reusing. All of our modern conveniences have created
a wealth of discarded materials that have challenged
the gardener. What self-respecting gardener has not
found some use for clear plastic pop bottles? From plant
covers to scoops to bird feeders, these containers have
been a gardener’s friend. Panty hose quickly became
a staple to tomato growers for holding up their tender
kinds of containers have been used for starting seeds
most notably: foam cups or egg cartons, either foam
or fibre. The rigid plastic packs that baked goods come
in make great mini greenhouses for starting plants.
Even plastic bags are useful to cover a pot of cuttings
or a tray of seeds.
Popsicle sticks are useful
in any household but to a gardener they become plant
markers or even small stakes for seedlings that have
become leggy. Pill bottles or film canisters make excellent
storage containers for seeds.
is a great temptation for a true gardener to put a plant
or two in any discarded container. Tea pots, wash tubs,
cooking pots, old boots, buckets, any empty container
that can hold some soil is likely to become a planter
or a liner for a planter. And a plastic bucket, especially
if it has a lid, is a real find.
Ask any gardener what
makes the best tomato stakes. Broken hockey sticks are
the number one choice. But any long stick will do so
don’t leave any scrap pieces of wood where any gardeners
can get their hands on it.
A patch of fruit is not
complete without a few foil plates strung up to scare
away the birds. And what better use for old clothes
than to clothe the distinguished friend of the garden:
Old sheets, blankets,
towels or any good sized piece of fabric should never
be thrown out – they all come out to adorn the gardenscape
on nights when frost threatens. On those nights the
garden takes on an eerie appearance all decked out in
See what happens when
an inventive group of people takes advantage of the
discards of our modern living. I am proud to associate
myself with this illustrious group of caring and imaginative
people. You all deserve a big thank you and a hearty
Elaine is a horticulturist,
landscape designer and free lance writer