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April
1, 2004
Hortiscope
Ronald C.
Smith, Horticulturist
NDSU Extension Service
Q: My mother had a
Christmas cactus for about 40 years. She had Alzheimer's and forgot to
water it for six months. I rescued it and even though it was hanging and
had paper thin leaves, it came back after about three months. I've had
it hanging from my ceiling on the east side of my house for three years.
I water it once a week. It looked great until about two months ago. The
leaves are drooping and look dehydrated. Should I repot it? (E-mail reference)
A: Give it a rest
period for about six weeks. We learned from your mother the plant can
survive. During that period, water it only enough to keep the soil from
drying out completely. It could also have a disease. Take cuttings right
away and get them to root in case the disease has advanced to the point
of being lethal.
Q: What do you recommend
in place of diazinon for wireworm control in garden potatoes? (E-mail
reference)
A: Set up a trap
by scooping out a couple of low areas in the soil and placing some pieces
of potato in the hole. Cover the holes with a board to collect swarms
of wireworms. Collect the infested potatoes and dump them in a pail
of soapy water. Another tactic is to improve your drainage because wireworms
tend to gravitate toward moist soil. As a final alternative, get some
granular Sevin and place it in the soil as the potatoes are planted.
Plant some buckwheat as a cover crop after the harvest and turn it the
following spring. The buckwheat will act as an insect repellent and
soil conditioner.
Q: I have an oak tree
in my front yard that seems to be growing an odd bunch of dark green colored
leaves. It reminds me of a holly plant. What should I do about it? Will
it damage the tree? I’m going to have it cut out but is there any
way to prevent it from returning? (E-mail reference)
A: It’s probably
mistletoe not holly. There’s not a lot you can do but it shouldn’t
hurt the tree. I suggest leaving it where it is. Birds eat the fruit
and spread the seed which sometimes lands on an oak branch. This is
a good example of a symbiotic relationship between two plants and could
be a "teachable moment" for a youngster.
Q: We have some emerald
green arborvitaes standing by themselves at several corners of our home.
We planted them about five or six years ago when they were four to five
feet tall. They are now about seven feet tall and have filled out nicely.
We have never trimmed them but probably should. This winter we had some
heavy snowfalls. During one storm, the weight of the snow caused the branches
to separate so they now flop to the side. Needless to say, they are not
holding the tall slender shape they previously did. I used twist-tie wires
to pull the branches back together with the hope they will strengthen
and hold their previous shape. Did I do the right thing? Is there something
more I should do to correct the problem? (E-mail reference)
A: You did the right
thing. Eventually they will pull themselves up again provided the wood
is not broken. You can also trim them lightly to lessen some of the
weight.
Q: You suggested we
remove our Lombardy poplar trees in order to rid the yard of new trees
that pop up, sometimes yards away from the mother tree. We took your advice
and cut down nine huge trees. The company that cut down the trees removed
the stumps and applied some type of chemical to supposedly kill all the
roots and trailers. Do you believe removing the trees and using chemicals
will take care of the problem or will we have to tear up our yard in order
to get rid of new growth? I'm having a hard time believing that new trailers
don't already have a good start and will keep growing on their own. Any
suggestion on new trees to plant in their place? We are looking for some
fast growing trees. (E-mail reference)
A: You are right
to be a skeptic but, don't despair. Treat the suckers that will be coming
up with a broadleaf weed killer. Trimec, applied two or three times
this season, should take care of the problem. If you want the same tree
form as the Lombardy, you might try the upright European Aspen. It has
fewer disease problems and grows rapidly. Botanically, it is known as
populus tremula 'Erecta'. It is a native of Sweden.
Q: I have a hibiscus
that I thought died last summer due to the heat. I cut it back last fall
just to see if it would come back. During the winter months it started
getting leaves. It was doing great until yesterday. I watered it the previous
evening and the next morning all the leaves were drooping. (E-mail reference)
A: If it was doing
fine until you watered it, then you have nothing to worry about. Hibiscus
can be a fickle plant to grow. It can give the owner fits over its health.
When all is considered lost, it sometimes re-leafs and blooms! So don’t
give up, even if it drops its leaves.
Q: I need to get rid
of a quaking aspen in my front yard. I understand that just cutting the
tree does not work. (E-mail reference)
A: Have an International
Society of Arboriculture certified arborist do the work for you. They
can treat the stump, roots and anything else that comes up with a herbicide
like Trimec.
Q: I have a large
oak in my yard that has some exposed roots. I want to make a flowerbed
around the tree and add some potting soil to accommodate the plants. Someone
told me the tree will die if I cover the roots with soil. Is that true?
(E-mail reference)
A: A four to six
inch covering around the base of the tree using typical potting soil
which is well-drained will not cause a problem. That amount of soil
should be more than enough to grow flowers in. The nutrient or air-absorbing
parts of the roots are at or beyond the drip line. You might have problems
if you covered that part of the root system. Keep about three to four
inches around the trunk free of soil. It helps keep disease problems
from developing. You can do that easily by using poly-edging. Adjust
the edging as the tree increases in caliper.
Q: My friend has a
lipstick plant that she split in three but is not blooming. Can this plant
be split and still bloom? (E-mail reference)
A: Yes, but you
have to be patient.
Q: We built a new
house last summer and will need to seed a couple acres of lawn because
80 percent of it was destroyed. My kids are in college and I don't want
the work of mowing a bluegrass lawn every four days. I’m looking
for a slow growing lawn that doesn't need any watering after it’s
established and doesn’t need a lot of attention. It would be nice
if we could mix types to keep it fairly green from spring through fall,
including the heat of summer. I did some research and thought buffalo
grass would be the way to go, but someone said we'd be happier with a
fescue blend. It was suggested we use a blend of 25 percent sheep fescue,
25 percent Salem fine fescue (replaces Cindy- tolerates dry), 25 percent
south point chewing fescue and 25 percent Warwick hard fescue (replaces
Ruby). How much topsoil will we need over the clay? Will the fescue blend
stay green during the cool spring, hot summer and into the fall? If not,
what's the answer? Should we mix the blend with some annual rye to get
it started? When should we plant? (Lidgerwood, ND)
A: It looks like
a good blend of fescues. The blend will green up nicely in the early
spring and will be relatively drought and heat tolerant through the
summer. It will not stay apple green when heat and drought are highest
in late July and August. During that period it will go dormant, turn
brown and then turn green again during the cool and damp fall season.
There is no grass that I know of that will stay green through the hottest
part of the summer without supplemental irrigation. If you are finishing
your moving and soil prep in June, you are better off to throw some
annual rye or (I would prefer) perennial ryegrass down and then over-seed
in mid August with your blend of fescues. The ryegrass will germinate
quickly and compete with the weeds. It will give you a chance to get
the weed population under control before your late summer or early fall
seeding. When it is time to plant the fescues, scalp mow the ryegrass,
then power rake or run a drag mat over the area to rough up the soil
surface. Seed at a rate of four to five pounds per 1000 square feet
and run over it again with a drag mat to mix the seed into the soil.
From that point on, either irrigate or hope for a series of reasonable
rain events. You should use at least four inches of topsoil.
Q: I just received
my first indoor ivy plant. I would like to know a watering schedule that
will keep it as beautiful as it is now. (E-mail reference)
A: There are about
six ivy plants that I know of, so I don’t know which one you are
referencing. Generally speaking, allow the soil to dry between waterings,
then water thoroughly. Allow the water to accumulate in the saucer for
not more than 20 to 30 minutes before dumping it.
Q: Last fall you recommended
that I use a pre-emergence chemical to control forsythia that has infested
my lawn. What is a good chemical and can it be purchased as a dry application?
When would be the proper time to apply it? (Portland, N.D.)
A: You have a better
memory than I have! A post-emergent would be better. I was wrong if
I said to use a pre-emergent herbicide. Being a woody plant, the forsythia
sprouts would be vulnerable to a treatment or two of Trimec. The Trimec
goes to the roots and kills them. Apply the chemical when they are actively
growing. Be sure to follow label directions.
Q: A single cotoneaster
at the front of our house has had a bark problem for many years. The bark
is extremely rough and discolored. It's obviously unhealthy. We cut it
down to six inches last fall hoping the new growth would be normal. Should
the new growth be sprayed? What should we spray it with? Should we dig
up the entire shrub? (Moorhead, Minn.)
A: I suspect that
what you are referring to as rough bark is really a scale infestation.
Cotoneaster is subject to scale attacks. The adult can cause a sooty
mold to develop over the branching system that will cover the insect
giving the bark a rough, dark appearance. You did the right thing by
cutting the plant. Before new growth breaks out this spring, spray the
stub with dormant oil spray to make sure there are no lingering adults
on the lower branches. Keep in mind that scale insects will die from
such treatment, but not drop off. They have effectively built a "house"
over themselves. The oil kills them by cutting off their air supply.
I suggest that you also treat any other plants on your property that
are deciduous.
Do you have a gardening
or houseplant question? Write to Hortiscope, Box 5051, NDSU Extension
Service, Fargo, ND 58105 or e-mail to Ron Smith at ronsmith@ndsuext.nodak.edu.
Note to e-mail correspondents: please identify your location (city and
state) for most accurate recommendations.
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Source: Ron
Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu
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