Burlap often dominates the 45 mph garden in late fall...
...So sad to see a pretty scene spoiled by unnecessary
screening.
In this case, the tall perennial grasses (switch grass,
Panicum virgatum) are themselves a very effective screen
against salt and wind.
This fact was something of an accidental discovery made when
shrubs and trees along highway shoulders started showing less
damage wherever ornamental grasses became part of the scene between
cars and the woody verge.
Road de-icing salt goes airborne from spinning car wheels -- it
can spray 200 feet from 45mph tires. It's true it could coat,
dehydrate and defoliate these spruces, but it won't because it is
caught first in the blades of the switch grass. Cut that grass down
in late winter, cart it away and with it goes the salt that would
have damaged the plants and the soil, too.
Below: Switch grass (Panicum virgatum) is beautiful
and a de-icing saltbuster, too.
Screen raised because salt damage misunderstood?
Maybe the reason the bed is burlapped is because someone has
blamed road salt for current problems there. If that's the case,
we're pretty sure the diagnosis is wrong.
What we see behind the screen are salt-resistant junipers and
blackeye Susan (Rudbeckia fulgida variety), the latter
suffering from leaf spot (more about this in What's
Coming Up 51, page 2; the inset image in the photo below,
right is from that newsletter issue). As for the spruces, they are
weak (we noted the scrawny top growth and dull bronze cast) and
have dieback that's almost certainly the result of having been
planted too deep.
Branches arising from the deep?!
It's hard to help you see details among dead twigs cluttering
the view, but those defoliated branches go into the soil
before they join the trunk. Given that angle, we figure the root
ball is probably at least 4 inches too low.
Being buried in moist soil decayed the bark on those branches.
Then, pathogens entered, killed the cambium and girdled those
limbs. The same thing is happening to the trunk, so the remaining
limbs have off-color, undernourished, thinning foliage.
When roots are set too deep
Meanwhile, the roots are struggling because four inches of extra
soil means more pressure and too little oxygen is available to
them. Roots can't grow up to better conditions, only outward if
conditions are good. Set too deep they deteriorate and die,
starving foliage so it discolors and thins, and branches die. The
tree hangs on, growing little if at all, until it has too little
foliage left to sustain the woody parts. Then it dies.
For a look at how trees end up too deep and a real life example
of correcting this problem, see Growing
Concerns 488.
If the spruces were salt-burned there would be more damage on
the top and side facing the road. The Rudbeckia would
emerge weakly and die, not grow, develop spots and turn black in
summer.
How to avoid planting deep
Follow the directions and photos in Oaks got flare. Pay prticular
attention to this step: 