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December
2, 2004
Hortiscope
Ronald C.
Smith, Horticulturist
NDSU Extension Service
Q: I have a caragana
hedge that has a white powder on the leaves. I think it is powdery mildew.
How do I treat this problem? (e-mail reference)
A: It is powdery
mildew. There are a number of fungicides on the market that will control
it. I suggest doing an application at your earliest convenience. Next
year apply it as a preventative before the mildew shows up. It is more
effective preventing powdery mildew than curing it.
Q: I have a little
leaf linden that is doing great, but I have a problem with wasps. I’m
sure it’s because of the nectar on the top and edge of the leaves.
For the last few years there have been swarms of wasps flying from leaf
to leaf. Is there something I can do to limit or completely stop them
from bugging us? (e-mail reference)
A: I would suggest
pheromone or nectar traps. The traps are sold at retail outlets that
handle garden products. That way, no deadly pesticide has to be used
and no one gets stung!
Q: My grandparents
bought the house I live in back in 1925. A patch of rhubarb was there
when they bought it. My grandmother, mother and now I have made many pies
and rhubarb soup from this wonderful plant. I will soon be moving and
want to take the rhubarb with me, but I have never transplanted anything.
I have to mention that I will be moving to a pond area where I can only
use certain types of fertilizer so I don’t pollute the pond. Do
you have any suggestions? (e-mail reference)
A: It would be best
if you could wait until after there has been a killing frost. If you
can’t wait that long, then cut it back hard, divide the crown
with a sharp spade and move it to the new location as soon as possible.
Water it in well and use compost as your source of nutrients that will
become slowly available and not leach into the pond water.
Q: I have a question
about Bermuda grass. Will cold weather kill it or will it just freeze
the exposed parts and grow back next spring? Will it grow from seed? How
common are sod webworms? (e-mail reference)
A: Bermuda grass
should be completely killed by our winter weather. If it goes to seed
before winter, that seed could survive and sprout next year. I doubt
Bermuda grass can produce mature seed because of our short warm seasons.
Sod webworms are quite common. It is the adult that is seen just about
every time a lawn is mowed. It is the zig-zagging moth that flies out
of the turf just ahead of the mower. The larvae feed in the thatch layer,
nibbling on grass leaves from a silken tunnel they’ve built. The
female sod webworm is a good mother because she usually raises her young
in the best of lawns. Those lawns can usually tolerate the feeding without
damage.
Q: We moved into a
house a few years ago that has two apple trees. One is very round, thick
and full of apples. The other tree is much smaller. It has nice large
apples on it, but there are very few branches. The branches it does have
are long and droopy. Is there something wrong with it? Can you give me
some information on pruning the trees? I know absolutely nothing about
apple trees. (e-mail reference)
A: Note the limbs
that are in bad shape and prune them back next spring while the tree
is still dormant. Cut it back to a side branch or to just outside the
collar on the main trunk. Don’t leave a stub and don’t cut
into the bark of the main trunk.
Q: This summer my
corn had a white and yellowish foamy substance shooting out of the plant.
Some sections looked like the “insulation foam in the can”
you get from your local hardware store. Some of the plants fell over and
at least half of my sweet corn was infected. What is the disease? (e-mail
reference)
A: You had corn
smut (Ustilago maydis), a common fungus disease of sweet corn, popcorn
and field corn. In Mexico, it is considered a culinary treat. If you
have any Mexican restaurants in your area, you might contact them to
see if they would be interested in purchasing some. You could make more
money selling it for ethnic cuisine than as straight sweet corn. No
sprays are available to alleviate the problem, so try to find varieties/cultivars
that are bred for resistance and clean up the garden.
Q: I have a question
about an old flowering crab tree. Each year, including this year, it has
bloomed beautifully. The past few years we have noticed the bark is peeling,
and after it blooms, the leaves begin to dry up and turn yellow. The tree
drops about half or more of its leaves. It had a tremendous crop of berries
the last two years, but only a few this year. I`m afraid it is old and
dying. What do you think? (Lake Park , Minn.)
A: Old crabapple
trees can have any number of pathogens or insects that cause the symptoms
you describe. If the tree is important to you, I would suggest contacting
a local International Society of Arboriculture certified arborist to
make an accurate diagnosis and discuss a possible remedy.
Q: I have a client
who is wondering about the possibility of propagating hybrid roses. Is
this possible? Do you need a root starter? Should you put the clippings
in water or directly into soil to root? If this works, how long would
it take until a new rose plant would be ready to plant in the garden?
(Cando, N.D.)
A: Hybrid roses
are usually protected by a patent number. If this is the case, then
any propagation would be considered illegal. If they are not protected
or the patent has run out, then stem cuttings are the easiest way to
go. Semi-hardwood cuttings root easily in a sand/peat mixture. There
is a downside to using this method. The rootstock may lose hardiness,
dwarfness or disease resistance.
Q: I have a question
about the raspberry patch I have. The patch is basically in a large square
and is so thick I was considering transplanting them into more defined
rows. Weed control would be easier and we could gather fruit from all
the plants. Should I transplant before I kill the weeds or after? When
should I do the transplant? (e-mail reference)
A: I would suggest
mowing over the plants and then digging out the new growth as it emerges
next spring. I am all for accomplishing tasks the easiest and most effective
way possible.
Q: My mother-in-law
has an ash tree close to her house. We have been told it is dying, but
it will be a couple of years before it is cut down. She is worried about
the roots damaging the foundation. How long can the roots get? The tree
is approximately 15 to 20 feet from the house. (e-mail reference)
A: My colleague,
Joe Zeleznik, NDSU urban forester, showed me an example of a tree that
had “volunteered” near the foundation of a house. The owner
cut the aerial growth back each year, not giving a thought to what was
going on underground. When the roots and crown were dug up, it was interesting
to see that the roots had grown against the wall and were following
it down the side, exerting pressure on it. The root was only following
the route of the percolating water, but the potential for foundation
damage was there if it was at all weak. She does have room to breathe
because the tree is 15 to 20 feet from the house. She might want to
have a barrier trench put in between her house and the tree if she is
really worried. If she has a good overhang on the roof and the weather
is not prevailing on that side of the house, the soil immediately adjacent
likely stays dry most of the time. Roots will not grow where there is
no water.
Q: We have been clearing
a wooded lot to build a house on next spring. We would like to know what
we can safely use around the base of trees to kill the remaining poison
ivy. An article I read said to use Roundup, but we don’t know if
there is a specific kind to use. Also, the ground where the poison ivy
was growing will be worked up in order to plant grass. Do we have to worry
about it growing back? Is there something we can do to make sure it doesn’t?
(e-mail reference)
A: Roundup, or the
many formulations of Glyphosate, will control poison ivy as long as
it is in leaf and the overspray doesn’t hit any of the desired
green vegetation. Getting it on the bark or in the soil will not be
a problem because it becomes deactivated immediately. It is only effective
on the foliage, where it is taken in and translocated to the roots for
an effective kill. Monitor the area for the next couple of years after
you have carefully removed all visible signs of the poison ivy. Birds
relish the fruit, so the seed may be deposited around the site, waiting
for the opportunity to germinate. A selective herbicide, such as Trimec,
will effectively control any emerging seedlings or shoots from remaining
root pieces.
Q: I have creeping
Jenny in my azala, rose and hydranga beds. It seems to suffocate the roses.
Do I need to worry about it suffocating any other plants? (e-mail reference)
A: Creeping Jenny
has one of the most extensive root systems on Earth and will smother
everything near it. I’d do something to get it out of your landscape
beds if they are of value to you, even if it means hiring a landscape
maintenance company to come in and do the work.
Q: We have an expanding
wet spot at the base of our elm tree. It is below a seam or crack in the
tree that appears to go toward the center of the tree, right where the
roots go into the ground. It never seems to dry up and grass won’t
grow in it. It doesn’t have an offensive smell, but it has us worried.
It is in our parkway and some people believe it may be the water line
for the house that has sprung a slight leak, but I don’t know exactly
where the line runs. I found another tree a few blocks away with the same
problem, but the water line is not close to the tree. Any ideas? (e-mail
reference)
A: The only thing
that is not usual about this is the lack of an offensive odor. Everything
else fits. Perhaps the feeding fungi, bacteria and insects haven’t
found it yet!
Q: Friday mornings
are not the same without my Master Gardener class. I really enjoyed it,
learned a lot and have so much more to learn. My question is about activities
that would qualify for community service volunteer hours. I work at the
Veteran’s Administration hospital, which sends out a monthly employee
newsletter. I would like to start a little gardening column based on what
I learned through our classes, the reading material or other Master Gardener
classes. I would not tout myself as a Certified Master Gardener (at least
until it is so) and wouldn’t answer questions unless that is acceptable.
I would provide set information. I might also do a couple of presentations
during our National Hospital Week in May. Would these activities count
toward my 40 hours of volunteer work? I’m thinking an hour per article.
It also is a way to get interested people information about NDSU’s
Master Gardening class. Thanks! (e-mail reference)
A: You are right,
Friday mornings are not the same, which has different meanings for different
folks! My wife and our two office staff, who also took the course, have
bugged me about not continuing it through the fall season! I am glad
you gained something from the classes and enjoyed it in the process.
Yes, you certainly can do the information column. Beware, once you start
something like that, it is bound to catch on and people will not allow
you to quit! Feel free to answer questions as long as you have a university-based
or some other science-based authority that you can use as a reference.
Certainly nothing from Jerry Baker, “America’s Master Gardener!”
Once you complete your 40 hours, you may officially refer to yourself
as a Master Gardener. If Mr. Baker can do it without ever taking any
university classes in Michigan or Florida, you certainly can after eight
weeks of classes and 40 hours of volunteer work! In the meantime, feel
free to refer to yourself as a Master Gardener student. The term Master
Gardener is a misnomer for us because no one can live long enough to
master all there is about horticulture. It is an information pit that
is bottomless and continuing to expand with every passing year as more
and more is learned. One last plug, if at all possible: Try to attend
the Minnesota Green Expo Jan. 5-7 in the Twin Cities. Simply log onto
www.minnesotagreenexpo.com
for registration and program information. There will be an overwhelming
amount of information on everything to do with horticulture.
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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