Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
7/12/99
Contacts:
Jeff Iles, Department of Horticulture, (515) 294-0029,
iles@iastate.edu
Elaine Edwards, Extension Communication Systems, (515)
294-5168, eedwards@iastate.edu
Cool Off with the Plant Guy
Jeff Iles
Extension horticulturist
Iowa State University Extension
Hey, Plant Guy:
I need your help to settle a small wager. You see, one of my
wisenheimer golfing buddies says you can still purchase
bare-root nursery stock this time of year. C'mon, I'm no
Plant Guy, but I do know that garden centers only sell
bare-root plants early in the spring season. Selling
bare-root trees and shrubs in the heat of summer makes about
as much sense as wearing your golf shoes to bed. Excuse the
golf reference Plant Guy, but I think you know what I mean.
Anyway, give me the straight answer so I can collect my
winnings.
Confident in Clive
Dear Confident:
Sorry Confident, but your ball is in the sand trap on this
one. Thanks to a fairly new technique called "gravel
culture," it is possible for retail garden centers to sell
bare-root nursery stock in the middle of July. This is how
it works. At the end of the bare-root season (usually
sometime in early April) left over plants are "lined out" in
above-ground beds filled with pea gravel. As you might
guess, irrigation is key. If the gravel is kept wet, it
becomes an ideal medium for root growth. And speaking of
root growth--you wouldn't believe the mass of vigorous,
healthy roots that develop in the wet gravel. But what about
harvesting these plants on a 90° F day? Actually, they
can be transported and transplanted quite successfully as
long as you keep the roots moist, out of direct sunlight,
and don't stop to play a round of golf on the way home from
the nursery.
Hey, Plant Guy:
About a year ago we learned we were coming to West Des
Moines, Iowa, to play in a golf tournament. No trees, no
hills, just golfing amidst the corn, cows and soybeans. Yes
sir, it was going to be a cakewalk. Well Plant Guy, we fly
into town last week and from the air all we see is an ocean
of trees. Then, we get to the golf course and there's more
trees...and they're big. So much for playing birdie-golf and
breaking the course record. Anyway, a group of us are
standing near this big evergreen right before we tee off
when my friend Arnie notices the cones on this thing are
standing straight up. We've played golf in lots of places,
and all of us have seen evergreens with cones that hang
down, but never have we seen anything like this. Now
contrary to what you might think, most of us actually like
trees. In fact, my other close friend, Chi Chi, claims he
can identify a tree from 150 yards away, but even he
couldn't come up with a name for this one. What kind of tree
were we looking at Plant Guy?
Arnie, Chi Chi, and Hale from the Senior Tour
Gentlemen:
Hmmm...an evergreen with cones held in an upright
position? Undoubtedly, you were in the company of a fir (all
of them have upright, barrel-shaped cones) and most likely
you were standing next to one of our best conifers, Abies
concolor (white or concolor fir). Concolor fir is best known
for its soft-to-the-touch, blue-gray foliage. But getting a
glimpse of the cones of concolor fir is about as rare as
getting a mulligan on the Senior Tour. You see, cones are
borne only in the uppermost branches of mature and sometimes
very old trees, and usually go unnoticed by most of the
golfing and gardening public. From a distance, concolor fir
are often mistaken for Colorado spruce (both are conical in
outline), but spruce have pendulous cones and very sharp
needles. Say, next time you fellas are in town, give me a
ring. There's nothing I enjoy more than talking trees and
playing golf.
Hey, Plant Guy:
Last winter, my wife and I bought our first home. It was
constructed back in the mid-1970s, but for the most part,
the house was in great shape. Plumbing and heating systems
were solid, there was a nice fireplace in the basement and
even the landscape looked functional and well-maintained.
Besides, what could go wrong with a few trees and shrubs
anyway? Well Plant Guy, never was the statement, "hindsight
is 20/20," more true. In fact, there were plenty of warning
signs--yellow wallpaper in the master bedroom and that silly
yellow mailbox next to the street. How did we miss their
significance? Apparently, the previous owners had "a thing"
for yellow because, in addition to the wallpaper and the
mailbox, we are now saddled with an "all yellow" landscape.
That's right, scattered throughout the property are
yellow-leaved river birch, pin oak, red maple, baldcypress,
shingle oak and something called 'Sunburst' honeylocust. I
guess the honeylocust is supposed to be yellow, but the
others should have green leaves. Everyone experiences some
"buyers remorse," but this is ridiculous. Is there anything
I can feed these trees to turn them green again?
Sickly in Spillville
Dear Sickly:
Looks like you hit the jackpot, Sickly. We'll never know if
the previous owners intentionally planted trees that would
turn yellow, but it does seem suspicious that so many of
them would end up in the same yard. Yellow (chlorotic)
leaves on trees that are supposed to be green are indicators
of poor tree health. Chlorosis may be caused by a mineral
element deficiency, root damage, temperature extremes,
herbicide misapplication, too much light, too much or too
little water, insects and/or plant pathogens.
In your case, however, I'm quite sure the problem is mineral element deficiency brought about by high soil pH. You see, most shade trees prefer their soil a bit on the acid side (pH in the range of 5.0 to 6.5). In this range, most essential mineral elements are easily harvested from the soil by plant roots. But when the soil pH creeps above 6.5 (pH above 7.0 are common in Iowa) certain elements become unavailable. In essence, these alkaline soils hold on to certain mineral elements so tightly that they can't be taken up by plant roots. Iron (Fe) probably is the element most commonly deficient in trees like pin oak and river birch. Remember, iron is not necessarily deficient in the soil, but is in an unavailable form due to the alkaline soil conditions. In the case of red maple, manganese (Mn) is usually the deficient element.
Now, is there anything you can do to rectify the problem? Well, for starters, you might try lowering the soil pH with elemental sulfur (2-4 lb/100 sq ft). But don't get your hopes up too high. Lowering soil pH into the acceptable range, and then keeping it low, is extremely difficult, especially when your goal is to alter the soil chemistry of your entire front yard! Instead of addressing the cause, some people opt out for treating the symptoms with special fertilizers that contain readily available forms of the deficient element (for example, iron chelates or ferrous sulphate). These products can be applied as a liquid-drench over the root-zone of trees or in holes drilled beneath the tree canopy. Injecting or implanting these same kinds of products directly into the trunk of the tree is another option, but even tree-care practitioners wonder aloud about the long-term consequences of such an invasive technique. The final option, of course, is tree removal. This may seem radical until you begin tabulating the number of hours and amount of money you might have to invest to re-green your trees. You did mention you had a fireplace in the basement, didn't you?
ml: isugarden
Extension programs are available to all without regard to race, color, national origin, religion, sex, age, or disability.