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June
17, 2004
Hortiscope
Ronald C.
Smith, Horticulturist
NDSU Extension Service
NOTE: Ron
Smith is on vacation for two weeks and the following responses are from
Joe Zeleznik, Extension forester and Todd Weinmann, Cass County Extension
agent.
Q: We planted a row
of cottonwoods and a row of blue spruce trees at one end of what was once
a cattle barnyard. The area has been planted to crops for the past 20
years. The land must be quite fertile because the crops were heavy and
tended to lodge. The trees were planted about five years ago. Each year
we had to replace some of the blue spruce. Some of the damage is by deer
and a hail storm we had, but some of the trees do not seem to be able
to survive no matter what care we give them. The trees get yellow and
dry up. It has been suggested that perhaps the soil is too fertile. If
this is the case, what trees would you recommend to replace them? (Valley
City, N.D.)
A: This is a common
problem with areas that have been cattle feedlots. Trees simply don't
do well in these areas. No one is sure of the exact cause, but it seems
that excess nitrogen (as nitrate) in the soil is common. As you said,
the crops that are grown in this area seem to grow well, but lodging
can be a problem if there is too much nitrogen in the soil. A second
idea that comes to mind is using a herbicide called Casoron. This is
a pre-emergent herbicide used for control of perennial weeds such as
Canada thistle or leafy spurge. For whatever reason, spruce trees are
very sensitive to this herbicide. It causes the needles to turn a bright
yellow and fall off. The trees eventually lose all their needles and
die. There is not a whole lot you can do if you have a nitrate problem.
Most trees won't survive. If Casoron is your problem, you have a lot
of options. Most other trees or shrubs do not have a problem with this
herbicide.
Q: We are moving to
a location that does not have trees. What is the fastest growing shade
tree? (Pelican Rapids, Minn.)
A: The fastest growing
trees in this area are hybrid and other poplars. Your local nursery
should have a good idea about what is available. Fast-growing also usually
means short-lived. For example, the Lombardy poplar (a variety from
Europe) grows very fast and straight and then dies in about 20 to 25
years. At that point, you're stuck with a tall (40 to 50 feet) dead
tree in your yard that needs to be removed. If it is not close to anything
such as a house or powerline, then it is easy to cut down. If there
are obstructions, it will be difficult and expensive to remove. Remember
this when you are determining plant locations. Having said that, I still
think hybrid poplars are great for a quick, temporary shelter. You may
want to consider planting poplars in combination with other trees that
are slower-growing. The poplars will provide quick shelter while the
other trees get established. Think of poplars as disposable.
Q: I’ve had
a French purple lilac for about four years. I keep it in a big pot because
we are moving around a lot right now. It gets nice small green leaves
on it each year, but it has never bloomed. Could it be root bound or should
I not have it in a pot? (e-mail reference)
A: There are several
possibilities why your lilac has not bloomed. The flower buds may have
been killed during the winter (flower buds are more sensitive to freezing
temperatures than vegetative buds are). The flower buds may have been
pruned off. You may have the wrong soil pH; lilacs don't like acid soil.
Lilacs do best in full or almost full sun, so your plant may not be
getting enough sunlight. The bush may still be adjusting to living in
a pot so it isn't able to fully spread roots and develop. Your plant
may also be getting too much nitrogen fertilizer. Nitrogen encourages
vegetative growth at the expense of reproductive growth (flowers). Ideally,
lilacs should be planted outside. If you decide to keep it in a pot,
remember that it will be slightly stressed and may not get enough of
what it needs to thrive.
Q: When is the best
time to try to eradicate dandelions? Do I have to spray more than once
a year? What is the best weed killer to use? Is it harmful to birds and
animals? I notice that birds, especially goldfinches, like to feed on
the seed heads. Any other do's and don'ts would be appreciated. (Cooperstown,
N.D.)
A: Fall is the best
time for controlling dandelions. The plants are going through an assimilative
type of growth that will be more receptive to herbicide application.
The plants are typically not in flower then, so the birds that feed
on the seeds will not be affected. There are many broadleaf herbicides
on the market. I suggest shopping around to see which herbicides are
specific for dandelion control. Apply herbicide in the early morning
hours because the drying sun will help to get the herbicide translocated
into the plant tissue more effectively.
Q: A co-worker has
a ficus and rubber tree that they put outside. Do they need to take it
inside on chilly evenings? I would think that a temperature below 50 degrees
is not good for the plants. (e-mail reference)
A: Temperatures
below 50 degrees are not good for tropical plants. Even though it is
a pain, they need to be brought inside. In our area, I wouldn't move
them outside until after Memorial Day!
Q: I just purchased
a Pocahontas lilac. It is dark purple and very fragrant. It has four or
five flower stalks on it, but we want to have more next year. Is there
anything I can do to the stalks that don't have flowers to encourage them
to flower next spring? Also, we have a Donald Wyman lilac which blooms
later than traditional lilacs, but I see only one flower bud. I think
I pruned it last fall. Did this remove the flower buds for this year?
Should I prune it in the spring or just let it go until next year? (e-mail
reference)
A: The lilac will
set flower buds later this summer. Don't do any late summer or fall
pruning, as you will remove the flower buds for the next season.
Q: My lilacs are in
full bloom. I notice when I cut the blossoms they only last a day or two
and shrivel quickly. When they are professionally cut by a florist, I've
seen them last a week or more. I read that there is a special technique
to cutting lilacs to prolong their bloom as a cut flower. I cannot recall
what the technique was. Do you have any insight to this mystery? (e-mail
reference)
A: The trick to
getting lilacs to hold their bloom longer is to cut them as some are
just starting to bloom and doing it in the early morning while the tissue
is full of water. Remove most of the foliage from the stems. If you
want leaves, include those as a separate cutting. Take eight ounces
of tepid water, eight ounces of a soda drink such as 7-Up, a teaspoon
of bleach and then stick the cuttings into this alchemists mix! The
mix provides carbohydrates and water, and the bleach stops bacteria
from forming, which clogs the stem and prevents water from being taken
up.
Q: My son just planted
several thousand strawberry plants. The temperature is supposed to get
down to 26 degrees tonight. Will they be okay or are they in danger? (Pembina
County, N.D.)
A: Usually they
are, as long as they are not in flower at the time.
Q: Do you have any
information on male ash trees? I need your eloquent words to let a homeowner
know that his ash tree has some strange growth because it is a male. (Forman,
N.D.)
A: How about this
simple, factual statement: Ash flower galls result in the abnormal development
of male flowers on white and green ash species lasting throughout the
winter and are caused by a mite. If that doesn't do it, I don't know
what else to say.
Q: I have an aloe
vera plant that I want to propagate. According to some literature, buds
are present in the plant which will develop as plantlets. The only buds
I can find come from the flowering stem. (e-mail reference)
A: The aloe is propagated
via small offsets that are found at the base of the mother plant. The
new rosettes are often attached to the parent by a short underground
stem (stolon) and may already have some roots, which should be retained
for propagation. Make sure the leaves have opened before detaching them
from the mother plant to facilitate their rooting and further development.
Q: I've had a ficus
for about four years. It was doing fine until about a year ago. I am starting
to notice a lot of scale on the outer limbs. It appears like brown scale/tiny
bumps. I've heard about using Volk or Neem oil on the entire tree, but
I wanted to investigate further. I heard I should trim back the infected
areas, but what should I use to get rid of the bugs? (e-mail reference)
A: It will have
to be treated with Neem or Volk oil. You can do it by dabbing the scale
with cotton dipped in the oil or simply by spraying it on. I would suggest
the dipping method because using too much oil may cause a toxic reaction.
If the scale are isolated to just a few branches and they can be removed
without destroying the shape of the tree, then do so, but keep a vigil
on the remaining branches for any future outbreaks.
Q: The leaves of my
peace lily plant turned brown around the edges. What is wrong with it?
How do you take care of a peace lily and a Chinese evergreen? (e-mail
reference)
A: It might be signaling
you that the salts in the water are too high or that they have accumulated
as a result of frequent fertilization. It could also be a sign that
it needs to be divided and repotted. Both plant species do well in indirect
light and should never be exposed to direct sunlight for any length
of time. Both should be kept in temperatures above 60 degrees and fertilized
only when active growth is evident. With the Chinese evergreen, you
can allow the soil to dry a little before watering again. Never allow
the soil of your peace lily to dry completely, but reduce it somewhat
in winter.
Q: I have seven global
arborvitae shrubs growing in my yard. Half of them are about 20 years
old. The shrubs have gotten really shabby looking in the last few years.
I water them in the summer. I used fertilizer spikes last spring and this
spring, but there doesn't seem to be much growth. I trimmed the shrubs
two years ago. Now the bottoms look very thin. A snow plow broke the top
off one plant two years ago. It has never grown back. Is there any hope
for these shrubs or should I dig them up and replant? What do you suggest
for fertilizer and winter support against ice and snow? (e-mail reference)
A: Never use fertilizer
spikes on any plants. Spikes are a waste of money and don't do the job.
There are better and more economical ways to fertilize plants. Fertilizing
should be done if needed, during the beginning phase of active growth
using a product like Miracle-Gro. Based on what you have told me, it
doesn't sound too good for the trees. If they don't respond to basic
care and they are not complimenting your property, get rid of them.
For winter protection, use a strong oak stake tied in to keep the tops
from being crushed under a heavy snow load.
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:
Joe Zeleznik, (701) 231-8143, joseph.zeleznik@ndsu.nodak.edu
Source: Todd Weinmann, (701) 241-5707, tweinman@ndsuext.nodak.edu
Editor: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu
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