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Posted by Bill on October 13, 2008, 3:41 pm
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gardenSPAM-ME-NOT@paghat.com (paghat) wrote:
> Nice overview on causes of sudden rhody death for newly planted shrubs.
> I'd never heard that about voles being a possible threat to shrubs in the
> average garden, though I know of an orchard that had girdling by mice or
> voles of all the trees after the owner dynamited a winter rattlesnake den
> resulting in overpopulation and food shortage. Wouldn't've happened
> otherwise. So it served the guy right.
>
> If you turn this overview into a web article you might want to add one
> more thing: death by deep woodchip/shaving mulch. In the early days of the
> Rhody Species Foundation they used woodchip mulch and decades later
> they're still having to repair some of the soil sights because of that
> initial error. It held moisture above the soil so that shrubs didn't get
> proper moisture, and it smothered roots. When they moved the collection
> from Oregon to the Weyerhaueser site, the mulch was totally free because
> hey it was Weyhrhaueser. So hundreds of important specimens dried out &
> died due to the woodchip shavings. I've an ongoing landscaping job at a
> property that used woodchips four inches to a foot deep and I expect never
> to repair all that damage, it'd take a tractor and sacrificing everything
> that's managed to survive.
>
> -paggers
>
>
> >
> > > As an aside, I bought three rhodos early this spring, popped them in the
> > > ground. They flowered spectacularly, sprouted new growth, and today all
> > > three are flat-out dead. Perhaps planting them along my pine walk was a
> > > bad
> > > idea?
> >
> > Hi Dwight,
> >
> > Actually I got my SX10IS for photographing rhododendrons and travel
> > photography. Too bad your rhodies died.
> >
> > There are a number of possibilities:
> >
> > ROOT STRANGULATION: This is best prevented by proper root pruning when
> > planting. The roots need to be opened up. Whether the plant is
> > balled-and-burlaped or potted, make sure that the plant is getting wet.
> > Rhododendron guru Harold Greer noted: "Quite often a plant will get
> > completely dry and then no matter how much water you apply, the rootball
> > will just keep shedding it. The top of the soil may seem wet, and the
> > soil around the plant may even be very wet, but the actual rootball of
> > the plant is bone dry. This is especially true for newly planted
> > rhododendrons, and it is the major reason for failure, or at least less
> > than great success with that new plant. It is hard to believe that a
> > plant can be within mere inches of a sprinkler that has been running for
> > hours and still be dry, yet it can be SO TRUE!"
> >
> > DROUGHT: Drought can cause entire entire plants to die. We have had
> > several years of drought here and we observe that if rhododendrons and
> > azaleas are not watered during a drought some plants will die,
> > especially ones just planted. Never let the soil completely dry out'
> > it's best to keep the soil evenly moist. Too much water or poorly
> > drained soil might be another explanation of sudden rhododendron or
> > azalea death. Rhododendrons and azaleas have very fine, fibrous roots
> > that are easily damaged by waterlogging, even for short periods of time.
> >
> > VOLES: Voles, also known as meadow mice, may have chewed on the bark
> > and roots near the crown of the plant. Sometimes they chew all the way
> > around the trunk and kill the inner bark, resulting in death of the
> > whole plant. Keep mulch away from the trunk to discourage voles.
> >
> > JUGLONE POISONING: The roots of Black Walnut (Juglans nigra L.) and
> > Butternut (Juglans cinerea L.) produce a substance known as juglone
> > (5-hydroxy-alphanapthaquinone). Persian (English or Carpathian) walnut
> > trees are sometimes grafted onto black walnut rootstocks. Many plants
> > such as tomato, potato, blackberry, blueberry, azalea, mountain laurel,
> > rhododendron, red pine and apple may be injured or killed within one to
> > two months of growth within the root zone of these trees. The toxic zone
> > from a mature tree occurs on average in a 50 to 60 foot radius from the
> > trunk, but can be up to 80 feet. The area affected extends outward each
> > year as a tree enlarges. Young trees two to eight feet high can have a
> > root diameter twice the height of the top of the tree, with susceptible
> > plants dead within the root zone and dying at the margins. The juglone
> > toxin occurs in the leaves, bark and wood of walnut, but these contain
> > lower concentrations than in the roots. Juglone is poorly soluble in
> > water and does not move very far in the soil.
> >
> > ROOT ROT: Phytophthora Root Rot or wilt is the major killer of
> > rhododendrons and azaleas. It develops when roots are growing in wet
> > conditions. The rot is more prevalent in warm summer conditions. Plants
> > infected with crown rot caused by the fungi Phytophthora have roots
> > which become clogged with brown fungi internally. The roots get blocked
> > and the plant wilts and dies. There is not much of any cure for crown
> > rot. Some varieties of rhododendrons are vulnerable (Chionoides,
> > Catawbiense Album, Nova Zembla) and some are resistant (Roseum Elegans,
> > Scintillation, PJM). Sphagnum moss and bark dust combined with good
> > drainage seem to prevent crown rot, but do not cure it.
> >
> > There are two essential when growing rhododendrons:
> >
> > DRAINAGE: Because the fine roots of azaleas and rhododendrons are
> > easily blocked by fungi, excellent drainage is important. To test
> > drainage, dig a hole 6 inches deep in the bed and fill it with water. If
> > the water has not drained from the hole in four hours, install drainage
> > tile to carry away excess water, or build raised beds. Moist
> > well-drained soil is a must for most varieties. This sounds difficult,
> > but it means to not let the soil dry out completely but don't get it too
> > wet. Thoroughly water if necessary and then let it become almost dry.
> > Most gardeners do this by planting in a well-drained area and mulching
> > to hold the soil moisture in. Watering is seldom necessary except during
> > long dry periods.
> >
> > ACID SOIL: Most varieties require an acidic soil (pH 4.5-6). Powdered
> > sulfur is the best agent to acidify the soil. Holly-tone has this in it.
> > Your plants will get chlorotic if the soil is not acidic enough.
> > Chlorosis is easily identified; the leaves turn yellow with green veins.
Found this and thought mimicking the environment of Tibet may matter.
³There are altogether 400 species of rhododendron on the Tibetan
Plateau, which make up about 50 percent of the worldıs total species.
According to Wu and Feng (1992)²
From the exiled Government of Tibet
<http://www.tibet.com/eco/intro.html>
Think of all the plant hunters of the early 1900ıs and where they
collected plants. The name Weston comes to mind but I may be confused
with Edward Weston. Perhaps the camera reference led me astray.
Bill
--
Garden in shade zone 5 S Jersey USA
Fight TB http://xdrtb.org/
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