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July
20, 2006
Hortiscope
Ronald C.
Smith, Horticulturist
NDSU Extension Service
Q: I have an oak tree
at my home in Ottertail, Minn. It has little, brown balls in clusters
on its branches. Dean's Landscaping in Wahpeton, N.D., told me the brown
balls are made by tiny wasps that won’t damage the tree. Do you
have any ideas? (e-mail reference)
A: Listen to Dean's
Landscaping! It is telling the truth and you have nothing to worry about.
Q: Our chokecherry
trees have worms. What should we do? Should the trees be sprayed? Should
the surrounding trees also be sprayed? These chokecherry trees are in
a windbreak. (Tappen, N.D.)
A: If these worms
are in tent sacs, there is little you can do that would be effective
at this time. You can spray Malathion for some control, but the most
effective treatment is dormant oil applied next spring, before the trees
leaf out. The dormant oil kills the eggs the adults lay. There is no
need to spray everything - just the species that are affected.
Q: I read something
on the Web that said you shouldn't plant strawberries and raspberries
together. Is this true? Is it because of verticillium wilt infection?
(e-mail reference)
A: What authority
did the site use for the statement? Verticillium wilt is a threat almost
anywhere, so that is nothing unusual. Of course, one shouldn't plant
where it was diagnosed. I have had a planting of these crops together
for years without problems. The rabbits and voles are the biggest headaches,
not disease!
Q: I have two three-year-old
gooseberry bushes that are healthy and full of leaves, but they have yet
to produce any fruit. What could be the problem? (e-mail reference)
A: It could be that
all the plants are male, which will not produce fruit.
Q: Squirrels are eating
my flower plants. How do I stop them? (e-mail reference)
A: You are not alone!
Use pepper spray or spray with Hinder, Ropel or Liquid Fence. Several
other products are on the market, but these are the most common.
Q: I planted six red
latham and six heritage raspberry plants. They started to get leaves and
some were getting suckers. One had six buds on it. Now the leaves are
turning brown and wilting. Some of the canes are now sticks. I did have
some foliage get eaten off some of the plants, but they have started to
grow leaves again. Are the plants that are wilting diseased or planted
too close to trees? Will the plants come back or do I need to replant?
Do rabbits or birds eat raspberry plant foliage? (Cavour, S.D.)
A: Raspberries need
full sun. The rabbits will girdle the stems during the winter months
unless you protect them. Squirrels will nibble on anything they can,
but this is the first I have heard of this happening with raspberry
plants. If you planted them in a former site that had other ornamentals,
flowers or vegetables in it, your berries could be slowly dying from
verticillium wilt, which is a soil-borne fungus. Deter varmints from
feeding with pepper spray, Liquid Fence or Hinder.
Q: We received two
honeycrisp apples as replacements for a tree taken out during a road construction
project. The trees were delivered in pots this week. Will they do OK if
we plant them now? I believe you are supposed to prune them by a third
when planting, but now is a bad time of year to prune. The trees are full
of blossoms. Do we remove the blossoms? We do not have other apple trees,
but there is a flowering crab about a block away. Do we need to plant
a pollinator or is the crab close enough? (e-mail reference)
A: Plant them now
and don't prune them during the first year. If you don't know how to
plant a containerized tree, hire a landscaper to do it for you. These
are very good apples for eating, making pies or storing. You can plant
another apple tree species or hope that the crabapple a block away will
do the trick, which it probably will. You will get much better fruit
set if there is a closer tree. I assume that is something you want!
Q: What do full sun,
partial sun and light shade really mean? If full sun is six hours of sunlight,
does that mean six continuous hours or could it be three hours of sun,
a period of shade and then more sun? Maybe I'm being too uptight about
the sun thing, but I don't want to plant something in the wrong spot and
have it not thrive. I'm starting new flower beds and would like to get
it right from the beginning. (e-mail reference)
A: Full sun means
a straight six hours or divided up as you state. However, experienced
gardeners know that not all sun is created equal. Morning sun is cooler
and less stressful on plants than midday or late afternoon sun. Also,
it is well known that reflective sunlight can be even more damaging
to plants. I would say you are being a little uptight about all of this.
You needn't be because gardening is not an exact science. Gardening
is a combination of science and art, which makes it enjoyable and exciting
to see how things turn out. In other words, there are many paths to
success! Use common sense and ask experienced gardeners what has worked
best for them on any plantings you question. I have yet to meet a gardener
who isn't anxious to share his or her knowledge!
Q: I have been told
that red maple is toxic to horses. Is crimson king also toxic? (e-mail
reference)
A: Red maple has
been confirmed to be toxic to horses. Until proven otherwise, all maples
should be considered potentially toxic. The crimson king is a cultivar
of the Norway maple.
Q: Three-fourths of
the top of my plum tree is dead, so I cut all the dead material off and
rounded it on May 21. It looks like fall is here and my wife can't stand
to look at it all summer. Will the tree come back or will I have to replace
it? (e-mail reference)
A: You haven't been
married too long, have you? When your wife is not happy, do something
immediately and apologize for having to be told that she isn't happy
with a situation. In other words, replace the tree, but probably not
with another plum tree!
Q: I have tried to
find some information about broadleaf control in raspberry plants, but
haven’t had much luck. What options do we have? (Arthur, N.D.)
A: About the only
thing I can suggest is very careful spraying with Roundup. The stuff
that is approved for commercial plantings is not available to homeowners.
Q: Can you tell me
where I can get help with our black ash tree? We’ve had the tree
for about five years. Last year it did not leaf out properly because many
of the leaves shriveled and died. This year the same thing happened. I
have noticed other black ash in our neighborhood seem to have similar
problems. Can you recommend anything that we should do or someone we can
contact to examine the tree? We love this tree and don't want it to die.
(Fargo, N.D.)
A: The black ash
plantings up and down the valley have been dying off the past few years.
We don't have a clear understanding as to why. All the tree experts
in the area are stumped and our specialists at the university are working
on trying to determine the reason for this decline. I'm sorry, but we
can’t offer any help at this time. If your tree should pull out
of this or if you know of any black ash trees that are looking good
at this stage with none of the die-back symptoms, please let me know.
As soon as we know something about what is causing the problem, we'll
let everyone know!
Q: We have two small
American lindens on our boulevard. The leaves are covered with raised
green pods and some of the leaves are starting to look tough. Is this
an insect or a disease problem? Is there anything we can spray on the
trees? (Fargo, N.D.)
A: The trees in
the boulevard are the responsibility of the Fargo Forestry Department,
which you are charged for each month. Contact it for an evaluation of
what is going on with your trees. It may be something that is cosmetic
and not lethal.
Q: We planted a lilac
and a climbing rose two years ago. They both look healthy, but haven’t
produced any blooms. What is the time frame for flowers to bloom? I was
reading about pruning lilacs in the spring after blooming. If there are
no blooms, when should we prune? Should I be cutting back the climbing
rose so it will climb? I fertilize the rose with Miracle-Gro. Should I
use another product? (e-mail reference)
A: If the plants
are in full sun and not overfertilized, then they should bloom. Try
driving a spade into the soil around the base of the plants to cut off
some of the roots, but not all. This will cause the plants to be shocked
into flowering the following season, at least the lilacs. Roses bloom
on the current season's growth, so you might get a reaction this growing
season.
Q: I have a sample
of a Hanson hedge rose that appears to have cankerworms on the leaves.
It's green in color with a dark head. It does not loop as a normal cankerworm
does. There also is a large, brown gall along the side of the rose. The
gall appears to be attached to a stem. Also, what are the miniature flies
called that I've seen on this and other indoor plants? (e-mail reference)
A: There are two
types of galls that typically form on rose bushes. One is a wasp gall
and the other is a bacterium gall. The difference is fairly easy to
tell. The wasp gall is thin-skinned, while the bacterium has a corky
growth. Both galls can be removed or left alone. The plant will survive
with them in most cases. The larvae could be a species of sawfly, which
is easily controlled by spraying with Orthene or another insecticide.
The miniature flies are fungus gnats or fruit flies. They are controlled
by using a knock-down insecticide spray.
Q: My son has fairy
rings in his lawn. Is there a way of controlling them by spraying? (Napoleon,
N.D.)
A: There is no practical
cure for fairy rings. They will respond to frequent core aeration (one
or two times a year), regular watering and keeping the fertility of
the lawn at optimal levels. This means fertilizing two to three times
a year.
Q: We planted a Cortland
apple tree several years ago. Although it has flourished, this year is
the first time it has blossomed, but only a few of the blossoms have set.
Should we also have other apple species growing nearby to assure pollination?
I would appreciate your comments. (Dent, Minn.)
A: Some apples,
such as the Cortland, are self-fruiting, but will set fruit better if
there is another tree nearby. Any species will do or plant a crabapple.
Q: I regularly read
your tips in the paper and find them very helpful. I have two problems
I am hoping you can help me with. I have a lilac tree that bloomed the
first two years, but not this year. Also, my cotoneaster hedge has grown
too tall. I am wondering if it could be trimmed back about 12 inches.
If so, when is the best time to trim? (Moorhead, Minn.)
A: If you trimmed
the lilac after mid-July last year, that could be the reason why the
lilac didn't bloom this year. For the cotoneaster, you can prune at
this time of year, but the best time is while it is dormant in the spring.
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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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