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Ron Smith answers readers' questions about the world of plants and gardening.

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I have a question about controlling weeds in my garden. I
have grass sprouting up all over the place in a bed of pinks
and blue star creeper. Is there a spray for getting rid of the
grass without hurting the flowers? I have tried pulling up the
grass, but the runners have crept under the plants. I am a
12-year-old amateur gardener. (e-mail reference)

A: There is a product known as Vantage that is good at
controlling grass in a garden setting. See if your parents can
locate some at a local garden store or a national chain and
have them apply it following label directions. It should do
the job for you.

Q: I have a cotoneaster hedge that is infected with
fireblight. I need to know if I have to cut off the infected
branches before I spray or if I can just spray (I purchased
streptomycin sulfate) to stop the blight from spreading. (
Kulm, N.D.)

A: Generally, spraying now will do little good except to make
you feel better. The active pathogen already is there, so
streptomycin cannot do anything at this point. The infected
branches can be cut back late this fall or early next spring
before leafing out begins. Spraying with a bactericide should
take place at blossom time to prevent infection. Repeating
applications as new growth takes place is strongly suggested
through the summer, especially if there is a hailstorm.
Cutting now only would open new wounds for the pathogen to
enter and possibly stimulate new growth. If you have other
members of the rose family, such as crabapples and hawthorns,
they can be sprayed with the bactericide to prevent the
disease from becoming established. Be sure to follow label
directions. Try to avoid anything that will cause succulent
growth, such as fertilization or watering, because this type
of growth is more susceptible to the pathogen than hardened
woody tissue.

Q: I saw one question about where to get ornamental rhubarb.
There is a list at (e-mail

A: Thank you for the listing. Our readers will appreciate
having this source of information.

Q: I have planted a row of bare-rooted, old-fashioned lilacs.
I want to use the lilacs as a border and a wind and snow
fence, so I planted them around the edge of my yard. I have a
huge yard and I am in the middle of nowhere. Where my yard is,
I have a good feeling as to how the pioneers felt! (I hardly
have any trees in my yard, so the winters are a bear.) The
lilacs only are a foot or so tall. I have read they are a
moderate growing plant and should reach 20 feet in maturity.
About how many years will it take them to reach a decent
height for blocking wind? How fast growing is moderate? Will
they be a good size 40 years from now when I won't be able to
enjoy them? Any tips on getting them to grow fast and thick?
(Kennedy, Minn.)

A: Barring any calamity, they should be their full size of 20
feet or more in much less than the 40 years you have to
retirement! Moderate means anywhere from a foot to a foot and
a half a year.

Q: We have a very old and large chokecherry. What are the
pruning guidelines? Can it or should it be thinned out? If so,
when is the best time? (e-mail reference)

A: Pruning is best done in March when the tree still is
dormant and the spread of disease is minimized. It also
facilitates healing of the pruning cuts faster with spring
growth coming on.

Prune to open the crown, but never leave any stubs. Always cut
back to a lateral branch or bud while attempting to maintain a
natural size. Survey the tree first before making any pruning
cuts so you will know when you have arrived at the last cut.
In other words, know what you want the finished product to
look like before starting. Also, don't prune off more than a
third of the total canopy at one time and don't expect
something that looks like a sow's ear to become a silk purse
the first year.

Q: I have a newly constructed home with an existing hackberry
tree on the property. To match grade, the tree's base was
covered with 18 inches of black dirt. Will this kill the tree
or do I need to dig down and build a small retaining wall
around the tree base? (e-mail reference)

A: There is almost a 100 percent guarantee that you will
slowly kill the tree over the next three to five years. Dig
down to the original grade and out at least to the drip line.
That should help save the tree. Someday housing contractors
and horticulturists or arborists will get together and
communicate that covering tree roots above grade is akin to
tying a plastic bag over one's head.

Q: I planted some hydrangeas that are supposed to be hardy for
my area. Should I do anything special to them before winter
arrives? (e-mail reference)

A: Yes, cut the hydrangeas back to the ground. I do that to my
hydrangeas every fall using an old power mower. Do it after
the hydrangeas have been frosted several times, but before
winter closes in. In your case, you probably can use a chain
saw or long-handled loppers to do the job.

Q: We just moved into a house that has blueberry and raspberry
bushes. When is a good time to transplant the raspberry
bushes? They are in the middle of a patch that we need to
rototill. How should I move them? Is it safe to transplant
them close to a building? Can I plant the raspberry and
blueberry bushes together? How long before the blueberry
bushes provide fruit? What is the best way to maintain these
bushes? (e-mail reference)

A: Don't worry about your raspberry bushes that are in the
way. Dig up the bushes and, if you want to try now, replant
them where you want, but they likely will die at this time of
year. Raspberries are very generous at multiplying. In the
spring before they leaf out, dig up a crown and divide it and
then plant where you want. Always cut back the canes that bore
fruit the previous year. Cut the canes to the ground, if it
wasn't done the fall before. It's a bad idea to mix the two
species of plants because they have different requirements and
growth habits. Blueberries require soil acidification on a
regular basis with aluminum sulfate and lots of sphagnum peat
moss. It wouldn't hurt the raspberries, but I'm afraid that
they would simply take advantage of the extra care and grow
like Jack's beanstalk! They are challenging enough to control
without giving them extra encouragement.

Q: My husband was given a flowering crab by his students when
he retired last June. It appears to be growing well, but has
not blossomed. Is there a period they must grow before
blossoming or could there be a problem with this tree? (e-mail

A: Be patient and give it another year or two. It will flower,
so don't worry.

Q: I usually put about two drops of Liquid Miracle-Gro plant
food in the water before I water my plants. I am afraid of
overwatering. When I bought a new bottle, it didn't say that
it had chelated iron. Is this something important for the
plant? My new bottle doesn't have it. (e-mail reference)

A: Miracle-Gro fertilizer tends to acidify the soil somewhat,
which makes the iron available to the plant. Most potting soil
brands have enough iron within to sustain most houseplants. If
the plant needs iron, it will tell you with interveinal
chlorosis on the most recent growth. It easily is corrected at
that time.

Q: We recently planted a weeping birch in our front yard. It's
been in the ground for more than two months and was doing very
well until a couple of weeks ago. I noticed that some of the
leaves were turning yellow. I watered the tree thoroughly. We
returned home after the long weekend to notice that there were
more yellow leaves than when we left. I think I may have
overwatered the tree. There has been very little rainfall in
our immediate area, so I thought it could do with a couple of
real good waterings. Do you think I've overdone it? If so,
what should I do to help it along? It's a beautiful young tree
and we don't want to lose it. (e-mail reference)

A: I'm willing to bet that you have the tree planted too
deeply. The crown (where the stem meets the rootball mass)
should be at ground level, not lower. As little as 6 inches
deeper can cause what you describe. Heavy watering only
exacerbates the problem. Pull some of the soil from the
rootball back to the surrounding soil level. If this is not
the problem, then I am at a loss to help you.

Q: How can I get rid of potato bugs? No matter what kind of
spray I use, I can't get rid of them. The bugs I have (I
think) are called Colorado potato beetles. (e-mail reference)

A: The larval stage of the potato beetle will be the most
vulnerable to Bt, which is an organically approved material.
When sprayed on the foliage and eaten, it will cause the
insect, at this stage, to become sick and die. This will
interrupt the reproductive cycle. Application after a rain
event is necessary and any new growth would require a
reapplication. Reapplication is needed throughout the season
as the bacterial material breaks down in the sunlight. I have
found that the combination of hand picking and spraying with
Bt formulations is the most effective at controlling this

Q: Last year we planted an endless summer hydrangea on the
north side of our house. It was a very nice, healthy plant,
but no blooms. We decided to wait until this summer to see if
it would bloom. To date, it's a nice looking plant, but no
sign of flower buds. The Annabelles next to it are doing fine.
Does the endless summer need more sunlight? Does it bloom on
new wood like the Annabelles? Any tips would be appreciated.
Thanks! (Baudette, Minn.)

A: Endless summer has the advantage of being able to bloom on
old and new wood, so pruning is not a problem. My guess is
that it needs a little more time to mature and then bloom. I
hope you are not fertilizing it with a high nitrogen material
because that could inhibit blooming somewhat. Be patient. It
will get around to flowering for you.

Q: Our sump pump drains water in our backyard. How much damage
does drainage water do to lawns? The other option is to have
it run out the front, but then we have water in front of the
driveway. Any ideas? We just moved, so moving is not an
option! (e-mail reference)

A: Turfgrass is a very tolerant to sump water, so simply move
the hose around to keep one spot from getting all the water.
Whatever you do, don't have the water go down the front of
your driveway. It looks tacky and encourages algae growth,
which is slippery and unattractive. You live in too nice a
neighborhood and you are too cultured to do such a base thing
as discharging sump water down the front of your driveway!
Future generations of homeowners, I am sure, will view our
unsophisticated handling of sump water with disgust - perhaps
in the same manner we view the old European method of
discharging garbage and sewage into the streets.

Q: Someone told me that silver maples are notorious for
clogging septic drain fields. Is that true? How close is too
close? Should I move a couple of silver maples that are within
about 20 feet of my drain field? Any recommendations for
better trees near a drain field? (Grand Forks, N.D.)

A: Silver maples get a bad rap for too many problems. What
tree wouldn't invade a septic drain field with its roots? It
is like putting freshly baked chocolate chip cookies in front
of a kid (or salivating adult) and saying "don't touch!"
Definitely move them to about double the distance. Another
solution is to install a biobarrier around the drain field to
keep roots from penetrating. Don't give up on your silver
maples yet because they grow fast, which everybody wants. They
also have nice fall color and are handsome trees, if allowed
to mature with proper care and pruning.


NDSU Agriculture Communication

:Source: Ron Smith, (701) 231-8161,
:Editor: Rich Mattern, (701) 231-6136,

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