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November
23, 2005
Hortiscope
Ronald C.
Smith, Horticulturist
NDSU Extension Service
Q: In the fall, is
there a rule of thumb as to what plants, such as tea or shrub roses, mums,
hydrangea, hibiscus or strawberries, to trim back or cut to the ground?
(e-mail reference)
A: Don’t get
too anxious! Wait until a good, hard frost renders them dormant for
the season. Then, the cultured roses and peonies, along with the hydrangeas,
can be cut back. The latter two can be cut off at ground level, while
the cultured roses should be cut back to about 6- to 8-inch stubs and
tipped and buried or heavily mulched and covered with soil before the
seriously cold weather arrives.
Q: I have three variegated
dogwood bushes on the north side of my house that are looking shaggy.
Will it hurt to prune them this time of year? I have heard that you need
to take special precautions when pruning because they are very susceptible
to disease after pruning. What do I need to do? (e-mail reference)
A: Cut them back
hard early next spring while they are still dormant.
Q: Do you have any
advice for identifying the differences between nightshade and garden huckleberry?
I have planted garden huckleberry for the past two years, but I think
I also have nightshade growing in the same area. Please help! (e-mail
reference)
A: Garden huckleberry
plants resemble pepper plants. Huckleberry is bushy and erect. The flowers,
appearing in clusters in July, are small and white. Each plant will
bear hundreds of half- to three-quarter-inch berries, ripening from
green to deep black. One plant should produce enough berries for a single
pie. The fruits are not edible until fully ripe and cooked. They are
toxic if eaten unripe and the raw fruit is bitter. The berries are ready
to harvest about two weeks after they turn black, the skin has changed
from shiny to dull and the flesh is very soft. The interior pulp will
turn from greenish to purple when ripe. The flavor of the berries will
improve if you allow the berries to remain on the plant until after
the first frost. The plants have some cold tolerance and may continue
to ripen after light frosts. If there are any plants in your garden
that do not strongly resemble a pepper plant, don’t eat! This
is as far as I can go on this. If there are “weedy” looking
plants growing, they are likely nightshades. This is an unusual crop
for a home gardener to cultivate.
Q: We have 13 Miss
Canada lilacs that were planted in 2004. They did bloom this summer and
last, but they have shriveled up/dead tips on them instead of new growth.
The stems are alive and the leaves are fine, but the tips of each stem
are dead except for a few on two of the plants. They are not overwatered
and get full sun. They were mulched with rock and have landscape fabric
underneath. Any suggestions as to why they aren’t growing much?
Thanks! (e-mail reference)
A: The rock over
landscape fabric is a problem. It likely has created anaerobic conditions
for the root zone. This could account for the reduced growth and possibly
lead to the death of the plants.
Remove the rock
and fabric, replace it with organic mulch or allow the soil to remain
bare.
Q: What plants can
replace purple loosestrife, if homeowners want to get rid of it and replace
it with something that looks like purple loosestrife? I know you have
written about it, but I can’t get my hands on that information.
(e-mail reference)
A: No problem, I
do that all the time! Several plants can be used as substitutes and
in many ways are better than the non-native loosestrife. They are: blazing
star or gay feather, Liatris spp; bugbane or black Snakeroot, Cimicfuga
racemosa; (I’m growing this one and love it!) cardinal flower,
Lobelia cardinalis; lupine, Lupinus spp; penstemon, Penstemon spp; Russian
sage, Perovskia artriplicifolia; salvia, Salvia X suberba and S. sylverstris;
and spike speedwell, Veronica spicata. Any of these would be worthy
replacements!
Q: Four of us work
in a tiny office without much ventilation (fresh air). We also lack any
source of outdoor light. What would be the best plant to place in our
office (and how many plants) to generate some oxygen? (e-mail reference)
A: Good question!
There are a number of plants that can fill the bill, such as Norfolk
Island pine, spider plant, wandering Jew, pothos (“Devil’s
Ivy”), peace lily (Spathiphyllum), and Dallas or Boston fern.
The Dallas fern is the tougher of the two, if the plant is neglected.
Q: Five years ago
I planted about 75 native plum trees in a tree row. They are doing very
well. They bloomed the last two years, but haven’t produced any
fruit. Is there a reason for this? (Minot, N.D.)
A: It could be that
it was too windy at the time the pollen was mature, too rainy, cold
or a lack of pollinators. That about covers the ballpark of reasons!
Q: I am looking for
help with an African violet problem. The plant is healthy, but the violets
are becoming overgrown, overcrowded and hard to the touch in the crown.
The new leaves and blooms can’t force their way out of that tough,
hard-leaf overgrowth. What’s wrong? (e-mail reference)
A: The poor thing
needs dividing! African violets, in spite of the popular myth that they
are delicate houseplants that need fussing over, are almost weedlike
in their native environment. To divide the plant, allow the soil to
dry slightly, then tap the plant from the container and place it on
a workbench or open newspaper. Separate as much of the soil from the
root mass as possible, then cut through the crown with a knife, scissors
or small pruner. Take the divisions and plant them in a premoistened
soil mixture. Keep the soil moist for a few days. Then allow the soil
to remain slightly dry for the next couple of weeks so the plant can
recover from the shock of division and transplanting. If you have a
multicrown plant, divide the multiple crowns by hand and repot.
Q: I have a double
problem. I cut down an old lilac bush. Underground bees now have made
their home in the stump. I started working on the edge of the stump and
was greeted by a small cloud of bees or wasps. I am not sure what they
are. I did gradually back away, so they quieted down and went back underground.
How do I get rid of these insects and can I use something that will get
rid of the insects and work on rotting the stump at the same time? I would
prefer something natural, but I am open to something that will not be
a major problem to the environment. (e-mail reference)
A: They are probably
wasps. You need to get rid of them before you do any digging again.
There are wasp insecticides in pressure dispensers that are effective
in eliminating them. You need to hit the nest in the evening or early
morning (best) while the temperatures are cool and they are in the nest.
Stand back, make sure the nozzle is pointed in the right direction and
let it fly for eight to 10 seconds. If none fly out after you or you
don’t see any buzzing around when you return to work on the stump,
you have been successful. For the stump, get a material called, of all
things, Stump Remover! A saltpeter concoction works slowly to decompose
the stump. Follow directions on the container.
Q: I have a maple
seedling growing in my flowerbed next to the garage. The seedling is near
the corner where the garage meets the sidewalk and near the gutter. This
area always ices over each winter, so I don’t think the seedling
will survive the winter. It’s a nice tree and I do want it to survive.
Do I transplant it to where I want the tree to be in the backyard? One
of my friends suggested I put it in a pot for the winter. (Fargo, N.D.)
A: You need to make
a decision after the tree loses its leaves. Give it plenty of protection
with a rose cone over it just before permanent freeze-up occurs or dig
it out and transplant it to the permanent location. If you choose to
protect it through the winter, then do the transplanting the following
spring before leaf-out takes place.
Q: I just got a call
about bitter lettuce in a garden. What causes it and can anything be done
about it? (e-mail reference)
A: Lettuce can become
bitter in taste when it is subject to hot weather and seed stalks form.
Wash the leaves well and store in the crisper in the fridge. The bitterness
should disappear.
Q: We recently purchased
a Linden tree. The leaves started dropping off in less than a week, so
we watered the tree, but the leaves kept dropping. I used a root feeder
to water the tree outside of the soil line. It did not help and the leaves
kept falling. There are about 10 leaves left on the tree. Will this tree
survive? Could the roots have been damaged because it was 92 degrees the
day we planted the tree? My neighbor said I should not use a root feeder
for a new planting. Is that correct? (e-mail reference)
A: The tree is going
through transplant shock. Your neighbor is correct, the root feeder
creates a hole where the water comes out and could contribute to the
drying of the roots. Surface watering is more than adequate. Going into
the fall, I would keep it moist, but not soggy. Chances are good the
tree will leaf out nicely for you next spring.
Q: This summer we
had a destructive windstorm that came through, took several of our older
evergreen tops off and uprooted numerous green ashes. I am wondering what
the fate of these evergreens will be. The wind also sheared many needles
off. We are going to move some green ash trees from our shelterbelt. What
is a good time of the year to move them and how large can the trunk be?
I am also thinking of moving some variegated dogwood shrubs. Will I be
successful? Lastly, what can I do about creeping Charlie? My lawn is full
of it! (Esmond, N.D.)
A: The evergreens
probably will be all right, just misshapen. The best time to move any
woody plant material is early spring, while the plant is still dormant.
This includes green ash and dogwoods. Smaller stock always has a better
chance of surviving a move than larger stock. If given a choice, go
smaller rather than larger. If the creeping Charlie is growing in dense
shade from trees, I would suggest allowing it to stay as your ground
cover. If it is growing in open turf, then apply Trimec in early September
to bring it under control. It will take repeat applications and the
material stays soil active, which means it could migrate to the tree
roots, causing some decline, and eventually even death. If the weed
is everywhere, then an application of Roundup is suggested where everything
in the lawn is killed. You then can replant with the appropriate grass
seed.
Q: I transplanted
about 10 evergreen trees four to five years ago. They are now about 10
to 12 feet tall. They get watered at least three times a week. A few weeks
ago, I noticed a tree was turning brown and appears to be dying. It does
have some green needles, but I would guess 85 percent of the tree is dead.
What would cause this and can the tree be saved? (e-mail reference)
A: Evergreens as
tall as yours come nowhere close to needing water three times a week.
I’m surprised that more of them are not dying. Shut the water
off and allow the roots to forage for the water themselves. The best
I can do is guess about a tree that is 85 percent dead. I’d say
the answer is no, it will not survive. I suspect that root rot has set
in and is causing the decline.
Q: Why do all the
sunflowers I see face east? I thought sunflowers were supposed to follow
the sun or is that just a “rural myth”? (e-mail reference)
A: It is not a rural
myth. Sunflowers turn their heads to follow the sun while they are developing.
Once developed, they lock into facing east.
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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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