In this issue:
Arican violet dislikes cold
Secret to jade plant's bloom
Protect poinsettia between store and
Snow shoveling: Shapely gardener, smashed
When winter winds blow
tropical houseplants suffer
I received an African violet as a gift. It seems to be a
gift magnet. Since I got it everyone wants to give me advice how to
Many of the tips have to do with watering. Is it really
so important how I water it? - M.M. -
They're very popular so there are many people with African
violet experience. Yet the fact that they grow well for so many
people is testimony to this species' ability to deal with varying
conditions. So there's more than one right way!
It is important that water you pour on the soil or into the
saucer to be drawn up into the pot is room temperature, not cold
water. This plant is native to Tanzania, where temperatures rarely
fall below 60 degrees F. Cold rain and cold soil just don't happen
in Tanzania. So the species never developed any ability to deal
African violet roots bathed in cold soil or sitting on a chilly
windowsill often die and then rot.
Cold water is not good for the leaves, either. Where it touches
a leaf, a white spot is likely to develop.
For illustrations and more on
diagnosing cold damage, see What's Up 192: Jade cold cut
It's not true that African violet foliage must stay dry. They're
"watered" by rain from above all the time in their natural setting.
So you can water from above or below. It's also accepted practice
to clean the leaves during non-blooming periods by inverting the
pot over a dish of mildly soapy water, dipping the leaves and
swishing them clean.
(Just how cold must water be, to
actually damage a plant?
Sponsor us and Growing Concerns 751 can
jump to the head of the line to be posted.
That issue explodes myths as it
explores irrigation water temperature.)
For more about cold and houseplants'
low temperature limits,
see Growing Concerns
Jade surprises her with flowers
I've had a jade plant about 10 to 15 years. I put it
outside in the sun every summer and it's very large now. I was
amazed this fall when I brought it inside it started flowering
after a few weeks. Is that quite uncommon? - S.M. -
No, not uncommon for someone who leaves a jades out long enough
in fall that the plant feels decidedly cool temperatures and
lengthening nights for a few weeks.
It's all chemistry. While it's in the light, a plant uses carbon
dioxide and releases oxygen. At night, it burns oxygen to convert
the sugars it made during the day into energy to fuel basic life
processes. Different chemical reactions occur at night than during
the day. In fall night reations happen for longer hours at lower
temperatures, so the by-products are different. Given enough time,
those cool, night-formed chemicals build up and the plant is
spurred to produce flowers.
Our jade flowers pretty regularly after coming indoors in
fall. One year we were delighted to see that it flowered on one
side but not the other. Delighted, because we're teachers and saw
it as a perfect teaching example.
This jade sits on an open-sided but covered porch. It is very
large, and that year had gotten even larger than normal so that one
side, facing out, had "bellied out" so far that it was not under
the roof that sheltered the rest of the plant. That fall, it was
warmer than usual, so the part of the plant under the roof didn't
experience enough cools nights to spur flower production. (A roof,
even over a wall-less area, bounces heat back to the ground that
would otherwise radiate away each night.) But the outer portion of
the jade that was exposed to more cold, for more nights, did form
For more about this effect, and other long night plants, see What's Up 191: When long
nights spur bloom
please" when you buy a poinsettia.
Right: See how to wrap in What's Coming
Up 192: Jade cold cut back.
Photo © 2012 Ray Wiegand's Nursery
Don't let an uninformed salesperson ruin your poinsettia
or other holiday plants. Such plants must be protected from the
change in temperature as you take them home and should be wrapped
in paper to face the weather.
Insist that the plant be wrapped, to trap some insulating warm
air around it. Don't accept a plastic wrapping, as moisture can
condense on the inside of plastic and that water can cool very
quickly, damaging leaves and flowers.
The same is true for almost all houseplants, which are tropical
species without any tolerance for cold.
Green thumbs up
to snow shoveling as a way to stay in shape for
next spring's gardening.
Green thumbs down
to tossing big loads of heavy, wet snow onto the brittle
branches of shrubs such as bluestar juniper.
Originally published 12/18/04