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October
20, 2005
Hortiscope
Ronald C.
Smith, Horticulturist
NDSU Extension Service
Q: I have a problem
with my tomatoes. The tomatoes get small, dark brown spots on the leaves.
After that, the leaves turn yellow and the brown spots grow together.
I’m worried I’m going to lose my tomatoes because it seems
to spread fast. What do I need to do? (e-mail reference)
A: You have blight,
but I can’t tell which one. Here is a laundry list of what you
can do to prevent it from spreading. Pick off all infected leaves. Don’t
water overhead because the splash is an excellent conveyor of the disease
spores. Don’t overfertilize. Dig out the badly infected plants,
but don’t hoe, weed or otherwise work the garden when dew is present
on the foliage. If you believe there is a need, get the appropriate
garden fungicide for vegetable crops and apply according to directions.
Typical fungicides include mancozeb, benomyl and chlorothalonil.
Q: We are having problems
with mushrooms coming up in our lawn. The largest group is where we had
to have an elm tree removed because of storm damage. The tree was removed
at least three years ago, but the mushrooms still keep coming up. We had
an underground sprinkling system installed last year, so the top layer
of the sod and soil was removed and reseeded, but that did not solve the
problem. Is there anything we could use to get rid of the mushrooms? (Mobridge,
S.D.)
A: Not really. The
mushrooms need to run their course, which is digesting the decaying
organic matter from the old tree that was taken out years ago. If you
back off on the watering somewhat, that will stop or at least slow down
the showing of the mushrooms.
Q: You specifically
say not to fertilize trees and shrubs. My husband says the card that came
with the bushes says to use Miracle-Gro Quick Start, and to drive Miracle-Gro
Tree and Shrub Spikes into the ground around the tree. I believe you 100
percent, but I need a little “ammunition” to dissuade my husband
from using any fertilizer or spikes. (e-mail reference)
A: Fertilizing trees
and shrubs is not needed in 99 percent of the situations at planting
time. In the old days when I was doing fieldwork as a landscape contractor,
such fertilization was standard operating procedure. Then research was
conducted at various universities around the country, most notably in
Oklahoma and Virginia, plus others as well. It was found that such treatment
had little positive effects on the plants when compared with no treatment.
Fertilizers simply added to the expense. While a “shot”
of Miracle-Gro Quick Start will not hurt anything and may lessen some
transplanting shock (during the months of active growth) without adding
significantly to the cost of planting, the use of spikes are a waste
of good money. Have him take you out to dinner tonight or sometime soon
because it will do the trees as much good. Spikes are not needed because
they concentrate the nutrients in specific, tight locations, so the
roots will spread randomly following the path of least resistance and
mine the nutrients that already exist in the soil. Adding more nutrients
blindly is like taking three vitamin pills when a qualified physician
recommends just one. If a little is good, more must be better, which
of course is wrong. Even in sterile soil, spikes still would be the
wrong choice because the nutrients in the spikes would serve the plant
much better evenly distributed throughout the backfill soil, plus the
cost per unit of nutrient is the highest on the market. Everybody is
marketing these darn things because the consumer is purchasing them,
so why wouldn’t they recommend them? They do contain fertilizer
and they can be driven right into the ground around the base of the
trees, but the simple fact is they are not needed. It is like putting
high-test gasoline in your car when regular will do the job, so why
waste the money? This doesn’t make the companies that sell these
products “bad companies” because they are simply responding
to what the customers think they want. The companies are reading their
market, responding to it and attempting to get a piece of that market
for themselves. I can’t blame them for their business action,
but it is my job to point out whether or not such action will benefit
the consumer.
Q: I purchased a blooming
African violet more than a year ago. I kept it on my desk at work under
fluorescent lighting. It never bloomed after that initial blooming. Was
there something I should have done to get it to continue blooming? I didn’t
give it any food and used purified water. (e-mail reference)
A: You did nothing
wrong based on what you have told me. African violets will flower when
they have enough energy. They get that energy from light. You might
think about adding a plant grow light to give it a little more of a
boost. If you are patient enough, the plant eventually will bloom under
the fluorescent lights. If it has been more than a year since you made
the purchase and are using purified water, you may want to consider
a small shot of African violet plant fertilizer to help it along.
Q: I am writing about
my radishes. The last couple of years all I get is tops. I planted white
globe, cherry and the red and white varieties. I planted some early in
April and more in May. They all turned out the same. Out of three packages,
I got four radishes. I was talking to some friends and they had the same
problem. I used to have bowls of radishes to give away. (e-mail reference)
A: All top and little
or no bulb growth is commonly caused by too much shade, seeding too
thickly or planting in soils that have too much nitrogen and too little
potassium. Radish plants need just the opposite, which is low nitrogen
and high potassium.
Q: We recently let
our ficus get too dry (maybe 10 days without water). It has lost tons
of leaves. The branches that have lost leaves are dry and brittle. One
nursery told us the branches would re-sprout leaves over time. What is
the best way to save the tree? Do I need to simply water it correctly
and be patient or do I need to remove all the dry branches? How long will
it take to come back? (e-mail reference)
A: Be patient and
prune out the branches that obviously are dead. Dead branches will not
send out new growth. Establish a regular watering regime based on season
of the year and rate of visible growth. As to the length of time it
will take to recover, I have no idea and neither does anyone else. It
all depends on the care it gets, its location and the vigor within the
plant.
Q: We were with a
friend who wondered how the Bing cherry got its name. Please share the
answer with us. I’ll see her next weekend and definitely will let
her know and about seven others! (e-mail reference)
A: Seth Luelling
was a skilled horticulturist. In the late 1860s, Seth cultivated the
Bing variety notable for its large, firm fruit and sweet flavor. He
named it Bing after his 6-foot-tall Manchurian foreman and close friend.
Bing worked with Seth for 35 years until his contract was fulfilled
and he returned to China. Bing cherries continue to this day to be the
preferred fresh market cherry. If anybody is baking pies using Bing
cherries, I’ll be glad to take one and sample it.
Q: I received a very
large, full peace lily in April. I repotted it because it looked potbound.
Since that time the leaves have been wilting and turning brown. I used
Miracle-Gro potting soil and a slightly larger pot. I have two cats. I
thought they were hurting the plant by rubbing against the leaves. I put
it on a stand, but it hasn’t helped. I have it in a south patio
window, but also have a large tree outside this window, so the light is
not harsh. This plant has a lot of meaning to me and I have never had
this problem with houseplants before. Could you please help me? (Hillsboro,
N.D.)
A: About the only
thing I can advise you to do is try misting the plant on a regular basis
and setting the pot on a tray of pebbles filled with water. They thrive
in high humidity and moisture. I’m assuming the plant is in a
free-draining container and that you dump off excessive water within
30 minutes of watering.
Q: I have had my aloe
vera plant for a few months. When I bought it, it was malnourished. I
thought I could help it recover, so I started watering it once a week.
A couple of weeks ago I noticed one of the leaves had turned brown at
the stalk, so I removed it. Then all the leaves began to grow outward.
I thought the leaves were growing outward because it needed to be replanted.
As I began to replant it, I noticed that another leaf had turned brown,
so I pulled it off. When I did, half of the bottom stalk came off with
it because it was rotten. In essence, my leaves are growing outward horizontally
and the bottom half of the stalk has fallen off. Is there any way to save
my plant? It is very near and dear to my heart. (e-mail reference)
A: Overwatering
is the culprit, so back off. It will not reverse the rot that has taken
place, but you can pick off the leaves from the stem and allow them
to cure for a day and then repot in pasteurized, well-drained soil.
Q: I (stupidly) forgot
to water my dad’s hydrangea Sargentiana. It was sitting in the sun
all day yesterday, so the leaves have wilted. My dad will be back tomorrow.
He is a landscape gardener, so he will be mad! If you could tell me the
best thing to do for the plant, I would be eternally grateful! (e-mail
reference)
A: Soak it in distilled
water. The plant will take up the water and respond quicker than any
other water with a salt content. If anything, it will rehydrate the
plant quickly. Of course, get it out of direct sunlight as well.
Q: I have an approximately
25- to 30-year-old snake plant that I inherited from my mother. I am not
sure what species it is, but it does not have the yellow rim around its
leaves. My question is about the yellowing that has occurred in the last
few days at the core of the stalk. The inner 5 inches of stalks are yellowing
while the rest of the stalks are green and healthy looking. I am wondering
about root damage or other problems. I have to admit, I never have been
that great at watering it regularly. It has sometimes gone weeks to a
month without being watered. I never have had problems with this plant
before. I am wondering if the pot is too small or if there is a problem
with the soil or drainage. I definitely do not want this plant to die.
It has been around as long as I have. (e-mail reference)
A: You probably
have some root rot taking place in a plant that old. Remove it from
the pot and divide the crown. Get rid of anything that looks like it
might even have a little rot. Take a couple of cuttings as well. The
cuttings should be about 8 or 9 inches long. Stick them in a sand/peat
mix and keep moist. In two months, a new plant will appear from the
base and the cutting leaf itself eventually will deteriorate, which
you can then dispose of. This gives you a little backup insurance in
case something happens to the mother plant. Like any houseplant, don’t
overwater, keep it in a container that is free-draining, and after watering,
dump out the excess water.
Q: I have a low area
that has collected too much water this year and killed my four lilacs.
Are there any flowering bushes that would do well in a bed that will stay
wet in future years? (e-mail reference)
A: Yes, pussy willow
or any of the willow species.
Q: I have a hosta
question. Every year my hosta has increased in size, but this year it
is half the size of the year before. The plants are not being eaten by
slugs (yet) or any other insect. The leaves look fine. Would there be
a reason for this? (e-mail reference)
A: Usually, half
the size means that something is wrong in the root system. It is often
the start of root rot. If you are game, dig up one of the plants in
question and inspect the crown and roots. If it appears healthy, then
my next best guess is that the foliage was damaged or removed early
last year and not enough carbohydrates were stored to produce the typical
foliage.
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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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