Plant Talk - Johnsons Nursery

Plant Talk
M AY 2 0 1 4
T
by Michael Yanny
What Happened to the Evergreens?
he last three weeks I have been on assignment.
I am leading an important investigation
for Johnson’s Nursery on what happened to the
evergreens. Why are they brown??? Who or what
caused the death of foliage? How did this happen?
What was involved? Was there in fact wrong doing in
this case? Was there intent to kill or be killed? Did the
sun, snow, and cold temperatures conspire to destroy
life? This Plant Talk will be a report of my findings
based on the use of the latest forensics methods that I
know of, namely looking at the plants from my truck
window and then jumping out and closely inspecting
the victims.
I first began noticing something was wrong in midMarch. The yews were brown. Little did I know
that a month later other casualties would show up.
Chamacyparis, Scots Pine, Vanderwolf’s Pyramid
Pine, Douglas Fir, Concolor Fir, ‘Mucronuta’ Norway
Spruce, Alberta Spruce, and more. The last plants
Concolor Fir were severaly burned here, at Johnson’s Nursery.
CSI Investigator Yanny hard at work.
to reveal their damage were the Junipers. Various
cultivars of Upright Junipers were scorched. Even
the native ones along the sides of the roads showed
damage.
I have been a CSI plant evaluator for over 34 years.
This year’s damage to evergreens is the most extensive
I have ever seen in our area. In order to make a
determination of cause of death or damage I must
analyze the evidence.
I scanned the weather records for our area, starting in
September and going through the winter. The weather
can have a profound affect on the condition of plants
going into winter. So what happened? In September,
it was dry. We had one half the normal precipitation.
This lead to a later than normal shutdown for
numerous plants because above average rains in
October kept certain plants active. Warm temperatures
and good moisture levels in early November didn’t
help matters. In late November and December we had
a quick onset of cold that quickly stopped any active
plant processes and was shortly followed by below
zero temperatures just after Christmas. Some of the
evergreens were perfectly set up to be hurt. They
hadn’t hardened sufficiently. In addition, the winter
was very dry. We didn’t have the typical heavy wet
snows usually associated with Wisconsin. Almost all
the snowfalls were light fluffy ones, demonstrating
the drier, colder condition we had. We had an above
normal snowfall measurement with below normal
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2014
What Happened to the Evergreens? cont.
precipitation. This means that the snow, when melted
into water, yielded less water than a typical year. I
wonder whether the fact that the snow was so dry with
few melting events gave plants less of an opportunity
to absorb moisture through their foliage like they
would in a normal winter. I haven’t ever heard of this
method of water absorption discussed as it relates to
winter desiccation (water lost from the foliage) of
evergreens. I suspect it does occur.
In any investigation the victims themselves provide a
wealth of evidence as to what happened to them. Let’s
look at the specific groups of plants that had some
severe damage.
Japanese Yews - Taxus
These are perhaps the most noticeable of the landscape
plants that were hurt this winter. It seems that the
south and southwest sides of most Japanese yews in
our area were brown this spring. In fact, I have seen
plants on other exposures looking bad as well though
most plants that were sited on north or east exposures
suffered minimal damage in comparison. My
explanation for this is that the sun hits the south side
of the plant for the longest period of time. It warms
the foliage and along with the wind draws water from
the plant into the air. The warmer the temperature of
the foliage the more water is lost. In addition, the drier
the air the more prone to drying the plant is. When the
ground is frozen a plant can no longer replenish its
water resource in its foliage via the vascular system
including the roots. Everything is frozen both in the
ground and the plant itself. So the foliage that is most
exposed to these conditions dies. That would be the
outermost leaves on the outsides of the plants where
the conditions are the worst—the south and southwest
sides.
A planting in our display beds showed browning on
its east side but not the west even though it is shaded
by a building. The browning in this case is due to the
overhang from the roof keeping the damaged side too
dry. The needles had less water in them than on the
other side so when the drying occurred in the winter
that part of the plant was the most severely affected. I
also noticed some plants in our nursery that were not
damaged to any great extent even though they were
grown in full sun.
The overhang from building caused a water deficit on the side of
the plants nearest the building. That side burned.
I have noticed profound differences between cultivars
as relates to their resistance to the ‘burn’ or browning
caused by the winter’s desiccating conditions.
Exposure played a big role in how much damage plants incurred.
Above is a spreading yew hedge with an east exposure to the left
and a south exposure to the right.
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The cultivars ‘Taunton’ and ‘Everlow’ showed
minimal winter damage while the cultivars ‘Hicks’ and
‘Densiformis’ were fried. ‘Taunton’ and ‘Everlow’ are
certainly two cultivars to remember for future use.
Vol. 3 No. 2
What Happened to the Evergreens? cont.
Cultivar differences in burn resistance were quite evident at
Johnson’s Nursery. ‘Everlow’ Yew is on the left and ‘Densiformis’
Yew is on the right.
The depth of which the burn affected Yews varied from plant
to plant. Check the level of burn inset and shear back to green
foliage as illustrated below.
So what can be done with the yews that were
damaged? Will they recover?
My advice to those that have experienced this burning
on yews is to be patient. Wait for your plants to show
their buds. Once you see these buds beginning to pop,
you will know how far back into the plant there is live
tissue. Then you can prune them back to that point and
let the new growth cover up the damage. As the season
moves on, the plant will shed the remaining brown
foliage or it can be shaken off with little effort.
Correctly pruned yew after winter burn.
Spruce - Picea
An over-reaction to winter burn on Japanese Yew. They would
have recovered!
Not all spruce were damaged but some were. Alberta
Spruce, Picea glauca ‘Conica’ probably took the
biggest hit. Similar to the yews, the south and
southwest sides of plants were damaged the most
severely and for the same reasons that the yews were
hurt. However, one thing I find very interesting is
that most other spruce were not damaged. I saw a
couple of Alberta Spruce plants in a cemetery in
Milwaukee (us CSI investigators spend inordinate
amounts of time in cemeteries) that had reversions
that hadn’t burned while all the normal foliage around
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2014
What Happened to the Evergreens? cont.
the reversions was toast. A reversion is just a branch
sport, a mutation from a bud that reverts to a slightly
different form. I find reversions fascinating! Anyway,
I was thinking about why the reversion had not burned
even though the plant it reverted from was fried.
Dwarf Alberta Spruce, Picea glauca ‘Conica’ were severely
burned. Notice that the reversion on the burnt side was not
affected. Why?
I asked my friend, Bill Reichenbach, another CSI
investigator, what he thought the difference could
be between the Alberta Spruce and its reversion. He
thought the needles were different. He has noticed that
the foliage on the reversions is usually thicker and may
have a broader layer of cuticle on the leaf that lessens
the amount of water loss compared to the mother
Alberta Spruce foliage on the left (much thinner!) Needles from
the reversion growth on right (thicker!)
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Alberta plant. I think that the mass of the leaf itself
would allow it to preserve more of its water resource
as well. It is certainly interesting to think about.
We must always remember in this kind of
investigation, it is a combination of all elements
that causes the result - the weather, the other
environmental conditions (soil, grade, sun exposure,
salt exposure) and the condition of the plant itself
(its genetics, its physiological condition, and its age).
Few other spruce were damaged during the winter in
the nursery with the exception of some ‘Mucronuta’
Norway spruce and sporadic burning on the south
sides of some other Norway and Serbian Spruce
seedlings. This damage wasn’t major. I expect the
brown needles will drop off, but the buds on the
burned shoots are still viable. They should grow out
of it. The Alberta Spruce plants on the other hand
look like they not only have lost foliage but the buds
on the burnt branches are dead. I’m afraid the entire
sides of plants will not regenerate new foliage thus
disfiguring the plants for a long time. They could be
ugly for five to ten years or more depending on the
severity of the burn. Replacement may be appropriate
for many of these plants. If you are unsure as to the
extent of the damage just wait to see how they bud
out before cutting on them.
Alberta Spruce buds close up. Healthy Alberta Spruce buds from
the north side of the plant; Dead Alberta Sprice buds from the
south side of the plant.
Vol. 3 No. 2
What Happened to the Evergreens? cont.
Pine- Pinus & Fir- Abies, Psuedotsuga
Relatively few Pines were damaged this past winter
but some were. Lessons can be learned from these
occurrences. New plantings that were put in late in
the fall were particularly punished. I’ve observed
numerous landscapes that were installed late that have
severely damaged Pines. The common practice in
our industry is to install Pines, Spruce and Firs early
in the fall or late summer for best establishment. At
our company we don’t recommend planting most
B&B conifers after October 15th and prefer to get
them in before October 1st. The absolute best time
for planting these materials is between August 15th
and September 15th. Normally this is the time when
summer temperatures have started to moderate and
the ground is good and warm. Conifers planted then
will have enough time to readily root in before cold
temperatures halt growth. It gives the plants the ability
to maintain its water resource right up until the ground
freezes. This is why watering evergreens right up until
freeze up is so important.
I noticed burn on White Pine in isolated areas other
than new plantings. Most susceptible seemed to be
plants along roadways that were planted on the top
of retaining walls or berms. It seemed to me that
these plants probably lost access to water earlier than
those planted at flat grades where the frost would
likely have driven in considerably later. In addition,
locations along roadways usually get salt spray from
the splash-up by cars. This likely affects the water
balance in the cells of the plants as well, and as my
wife Lori said to me when we were discussing this,
“It adds insalt to injury”.
Concolor Fir, Abies concolor (left), and Douglas Fir (right),
quickly lost their brown needles this April. Their buds looked
plump and alive!
The various Firs in the nursery were browned out
rather severely. Some individual plants were spared
but most had some damage on them. Douglas Fir was
quite erratic with some plants being totally defoliated
when I observed them in late April while other
individuals had some browning on the outside of the
south and southwest sides but were OK otherwise.
Concolor Firs had similar symptoms, though they
still had their brown needles. When I looked at the
Concolor Firs up close and touched them to see if the
wood looked alive, the needles dropped into my hand.
I’m sure they have all shed by now. The buds looked
alive. So those of you with Firs, please be patient. I
think the buds will pop new growth this spring. The
plants will look goofy for a couple of years, with
bald interiors and just twigs of new growth on the
extremities. They should fully recover after three
years.
South facing White Pine, Pinus strobus, along a busy road with
heavy exposure to salt spray.
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Vol. 3 No. 2
What Happened to the Evergreens? cont.
not as severe as the cultivars I have mentioned. Young
plants that weren’t under the snow were particularly
hard hit. They are often the last to stop growing and
don’t have as deep of roots as the big guys. At least
that’s what I think explains the difference in burning.
Junipers - Juniperus
Canaertii Juniper, Juniperus virginiana ‘Canaertii’ burned
severely at Johnson’s Nursery while Juniperus virginiana ‘Hillii’
to its right was untouched.
Of all of the plants that were damaged this winter, this
is the group that most surprised me. I have never seen
damage as extensive as this to Junipers in my 35 years
of observing woody plants. It is very unusual to see
these tough durable plants being winter damaged.
Since Junipers are one of the latest growing conifers,
if not the latest growing conifer in our area, they
were prone to damage this past season. My theory
is that the dry September in combination with the
warm moist October and November, followed by
the quick, dramatic freeze up in late November and
early December caught many of the Junipers before
they could get fully prepared for winter. I think this is
why we see many plants with brown tips on them this
spring. The foliage wasn’t completely hardened when
the winter hammer came down.
There were considerable differences between cultivars
in our nursery. We only field grow Upright Junipers
so those are the ones I assessed most extensively.
The cultivars which were most severely burned
were: J. virginiana ‘Burkii’, J. virginana ‘JN Select
Green’- Emerald Feather™ Juniper, J. virginiana
‘Cupressifolia’, J. chinensis ‘Hook’s #6’,
J. virginiana ‘Glauca’, and J. virgiana ‘Canaertii’.
Some others at the nursery had spotty tip die-back but
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In landscapes around the Milwaukee area, I noticed
extensive burn on: J. virginiana. ‘Canertii’, J. sabina
‘Sea Green’- Mint Julep Juniper, J. chin. ‘Pfitzer
Compacta’, J. chin. ‘Pfitzer Glauca’, Golden forms
of Juniperus chinenesis and several other cultivars I
couldn’t identify. I suspect a lot of this damage had
to do with the locations of the plants or late pruning
because I also saw specimens of these plants that had
little to no burn.
The native Juniperus virginiana, Eastern Red Cedar
growing along roadways throughout Southeast
Wisconsin were impacted to various degrees by
the winter. I observed plants that were burned
completely on their outer extremities while others in
close proximity were just fine with little to no burn.
I suspect there is genetic variability among seedling
J. virginiana in their ability to withstand such a
winter. Salt spray also likely played a large role in the
damage on these roadside plants.
It looks like the junipers were just damaged on the
outsides of the plants and can be easily fixed up by
shearing off the burnt foliage.
Canaertii Juniper foliage burned. It is best to let the burnt
Junipers start to push growth before deciding how far back to
shear.
Vol. 3 No. 2
What Happened to the Evergreens? cont.
Thuja - Arborvitae
Thuja x ‘Green Giant’ suffered severe burn in the fields at
Johnson’s Nursery
Thuja plicata ‘U.W.’ are the green plants to the front and right.
In the back of the first row is Thuja plicata ‘Excelsa’ with severe
burn.
Arborvitae held up surprisingly well this winter with
a few exceptions. Some plants of Thuja occidentalis,
Eastern Arborvitae in extremely exposed locations
burned on the southwest sides of the plants. I saw
minimal burn in our nursery on the Eastern Arborvitae.
Some cultivars derived from the Western species,
Thuja plicata had some major burn; ‘Excelsa’ and
‘Green Giant’ were severely damaged on the south and
southwest sides of the plants. I had seen burning on
small plants of these cultivars several times in recent
years but never on plants 3’ and up. This year all sizes
were severely damaged in the nursery. Most interesting
to me was the fact that the Thuja plicata ‘Fastigiata’
and Thuja plicata ‘U.W.’ planted right next to the
burned cultivars were unscathed.
My investigation of this year’s tragic set of events
involving evergreen plants has been intriguing. I
have come up with the usual set of guilty parties in
association with this caper, namely; the sun, the cold,
the wind, unfortunate sitings of plants, salt spray,
and inferior genetics. It was definitely a conspiracy!
What I have found to be the most interesting thing
of all from my CSI investigation is that the plants
themselves are the greatest teachers of horticulture
out there. Their relationship to each other and their
environment provide all the important clues for one to
understand their strengths and weaknesses and which
are best suited to our challenging world.
I am not sure whether the damaged cultivars of Thuja
plicata will recover. I will wait to see where the new
growth comes from to make a determination if they are
salvageable.
Plant Talk Available Online
Each Plant Talk article is available online on the Johnson’s Nursery
website under the Contractor Sales section. Feel free to comment,
ask questions or begin new topics! As always, Mike Yanny can be
reached by e-mail: [email protected]
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Vol. 3 No. 2