Winter!
Be smart in the fall or work hard in the winter to make
a jasmine bloom
Dear Janet,
For Valentine's Day last year my husband gave me a pink
flowering jasmine (Jasminum polyanthum). I would like to
get this plant to flower again, although I am very much a beginner
when it comes to gardening. So if it's too complicated I have
decided it's okay to buy a new one, beautifully in
bloom.
One website I read suggested this plant needs an 18
degree temperature drop to flower. Is it true?
Well, if it is true, I found a cool closet in my home
that's around 50 degrees. Do I put her in only at night, or all day
with lights? Gradually, or start tomorrow? How many days or weeks
is necessary for her to get flower buds?
D.C.
Dear D.C.,
Many plants of temperate regions need to experience a change of
weather and daylength to "know" that a new growing season is
coming. Because of cooler air and longer nights at that change of
season, different chemical reactions take place in the plants'
cells. When the chemicals that are the by-products of those
reactions reach adequate levels, flower buds form.
Jasminum polyanthum is such a species. It can't take
Michigan's frigid winters but it does "expect" a season that's at
least 18 degrees cooler on average than the summer. So it might
flower as well in Louisiana or southern California as it does in
its native southeast China, but not in Miami where temperatures are
too steady all year. In Michigan you can induce bloom if you leave
it out in fall as nights cool toward 40 degrees. Although we must
bring it indoors before its foliage is frosted or its roots killed
back, it may get enough weeks of good growing at lower temperatures
to set buds.
How many weeks depends on how well the plant is growing and how
mature it was before it began being chilled. Authorities won't name
a number, only say that once it begins to set flower buds, then you
can stop the special treatment. Those buds will ripen and open as
long as the plant continues to have very good light and steady
moisture.
It's possible that cool nights alone may do the trick, but I
can't find any data to support it. Growers in a position to work
with statistically valid numbers of jasmine don't move them each
day. They do the simpler thing, dropping the temperature of the
greenhouse overall, all day and night.
So it's not complicated, just challenging, to induce another
round of bloom in your jasmine once that natural opportunity in
fall has passed. To simulate those long nights and cool weather,
you might set the plant under grow lights in your cool closet. Use
fluorescent lights, to avoid warming the closet. Put them on a
timer for twelve hours on, twelve off. Check your plant regularly
to keep it watered. Four to six weeks of that may bring out the
bloom.
Or you can try the nights-only treatment. If you do, let us know
how it comes out.
Dear Janet,
I have a 55 year old silver maple in a bed of Baltic
ivy. The ivy has grown up the tree and is very attractive, but a
couple of my children are insisting that the ivy will kill the tree
if I don't remove it. Is this true? It took several years to get
the ivy established and I'm fond of the effect.
J.D.
Dear J.D.,
Evergreen ivy (Hedera helix) won't hurt a tree's trunk
or main limbs. It's not a strangler, like bittersweet vine. Its
roots don't penetrate the bark to put the sensitive cambium at
risk. In fact, evergreen ivy provides an extra layer of protection
from cold and attract small birds that while sheltering there may
put a dent in your insect population.
Do your children garden in milder climates? In the Southeastern
U.S. or California, their advice may be sound. There, unlike in
Michigan where winter kill works in our favor, ivy can bridge the
gaps between trunk and limb, and scramble right out to the branch
tips.
Ivy crossing between limbs turns the tree into a huge sail. That
tree catches more wind and water than it should, and may topple.
Meanwhile, ivy growing out to and over the tips of the branches can
shade out the host tree's foliage and kill it.
Here in Michigan, rest easy if you have ivy on a tree and like
the look. It will stay on the trunk and main limbs, unable to
survive the exposure it gets in winter in the open areas between
limbs and out toward the small branches.
Stumper
Some problems have no solution. I can't provide much help to
those who pose a "stumper" such as:
Why is it that a plant described by knowledgeable authorities as
reaching "ten to twenty feet" will stop growing at ten feet if I
wanted 20, but will top 20 if I chose it to grow in a restricted
ten-foot space?
Green thumbs up
to Groundhog Day, the turning point of winter. It should be a
day of thumbs up and relieved smiles between gardeners.
Green thumbs down
to neglecting the birds during big snows. You benefit even in
winter from the nit-picking they do that helps you control insects
in your yard. So keep the birds alive. Shovel out that feeder and
keep it filled.
Originallly published 1/29/05