Tag: woody

Friday quiz…better late than never!

As you know, I wanted to get something intriguing for this week’s puzzler from the NW Flower and Garden Show.  Alas, there was nothing that jumped out at me, so I’m digging into my photo archives.

Here is a recent photo from a parking lot tree.  About four feet up the trunk, I found this interesting growth.  No, I don’t know what the tree species is because (a) it wasn’t in leaf and (b) I’m a taxonomy klutz.  But I can assure you that the odd bark morphology has nothing to do with genetic identity.

I can also assure you that there is no foreign material under the bark that’s causing this phenomenon.  The question:  what DID cause it?

The answer – and a revealing photo – on Monday!

Odds ‘n Ends

Some odds and ends today that I either #1 was asked to post or #2 couldn’t resist posting.  First for the picture that I was asked to post.

This, as far as we can tell (we being myself, my technician, and our grounds department), is the American elm tree that was being planted in that picture from 1909 which I posted on January 21.  Dutch elm disease was devastating here in the mid 1900s as it was everywhere, but this region of the world was lucky and there were a number of escapes — and resistant trees (that’s an ongoing project of mine — working with DED resistant elms — I’ll probably post more about it this spring).  Anyway, the tree is a little smaller than I would normally expect for an elm of this age, but the proximity of the road and sidewalk could easily have stunted its growth.

Now for the stuff that I can’t resist posting — mostly having to do with Bert’s post on January 25.  Chad (my technician — if you follow the blog you’ll remember him, 6’4″ — etc.) was showing me a book titled Shade-Trees in Towns and Cites by William Solotaroff published in 1911 and it had this great shot of filling a tree cavity.  So here it is:

The book also had a great shot of what they did to a trees canopy before they planted:

This type of pruning isn’t necessary at all.  When trees are planted they adapt to the amount of roots which they have by producing fewer, or smaller leaves.

Update:

Here is a photo of the leaves of a freeman maple which was severely rootpruned right before planting and, below it, the leaves of a similar maple whose roots were left pretty much intact (both plants were container grown).

As you can see, trees have their own methods of dealing with root loss — no need for us to come in and clip their tops off.  Now, two years later, both of these trees (and all of the others in the research plot) look pretty much identical.

The evolution of tree care

I’m one of those people who can’t resist things that are free.  When you pass a yard that has a ‘FREE’ sign on a rusted-out lawn mower or an old piece of exercise equipment and wonder, “Who on earth would take that home?” Uh… that would be me.  Actually, I blame my dad.  The Old Man’s garage was crammed full with outboard motors missing pull-cords, mismatched lawn furniture, and all manner of secondhand tools in varying states of disrepair. So my defect is genetic.  Only my hyper-organized wife prevents my garage from suffering the same fate as my dad’s.  But, like a blind pig finds an acorn, sometimes a scavenger finds something interesting.  Recently a retiring professor in our building was cleaning out his office and put a stack of old books on a table by his door.  And there was the magic word: FREE.  I sifted through the stack and found my treasure; a 1948 edition of Maintenance of Shade and Ornamental Trees by Dr. P.P. Pirone.  Granted, I have ready access to several modern tree care texts plus an ocean of information on the International Society of Arboriculture (ISA) website, but after thumbing through a few pages I knew this one was a keeper.  The main reason the Pirone book interested me was to see how tree care has changed over the years and how things have stayed the same.


What’s changed?  The most obvious example of how tree care has changed in 60-plus years is that an entire chapter of the 1948 text is devoted to cavity filling.  For those not familiar with the process; cavity filling, as the name implies, is the practice of filling hollow areas in trees with concrete, just as a dentist fills a tooth cavity with amalgam or composite materials.  Filling cavities in trees was once a relatively common practice.  Today we recognize that filling does not stop decay and there is little value in the practice (and it certainly complicates removals).  If anything, we would replace this chapter with ‘hazard tree assessment’, seeking to determine if the tree has enough solid wood to be structurally sound.


Filling a tree cavity.


The finished job

What hasn’t changed?  I was surprised to see a fairly lengthy discussion of problems related to girdling roots from 60 years ago.  This actually causes me to eat a little crow.  I have sometimes questioned whether the current ‘epidemic’ of girdling roots is actually related to the fact that arborists and urban foresters are spending more time looking for them and have better tools (specifically air spades) for finding them.  Of course, Pirone’s text also suggests that girdling roots were an issue before the advent of evil nursery production systems such as container growing.  The discussion of treating girdling roots points out another change in practices.  In 1948 the arborist was advised to carefully dress the wound with paint or tar.  Today we generally advise against treating wounds except for situations which risk certain exposures such as if oak trees must be pruned when they are at risk for infection from oak wilt.


Girdling root removed and wound dressed.

So there you go, another book to clutter my shelf and another example of one man’s trash turning into another man’s treasure.  I think Dad would have been proud.

Blue Spruce Blues

One of the roles I’ve evolved into over the past decade as an extension specialist at MSU is that of ‘the Conifer Guy’.  Conifers are great and fascinating plants.  The oldest trees in the world are conifers, the largest trees in the world are conifers, and some of the most interesting (at least to me) landscape plants are conifers.  Unfortunately, for a variety of reasons, in the Upper Midwest we have gravitated to Colorado blue spruce more than just about any other conifer.  Part of this over-reliance on blue spruce in the landscape is driven by production (see, Linda, I’m not always an apologist for nurseries).  Growers want to grow what they know and what’s easy to grow.  As a nursery tree, blue spruce is a reliable performer that is well adapted to a relatively wide range of site conditions.  Of course, growers also want to grow what they can sell, and there always seems to be a steady demand for blue spruce.  In many neighborhoods it appears that there is an ordinance that every other tree has to be a blue spruce.  So what’s the issue?  In the Great Lakes region, blue spruce often look pretty good when young.  However, as trees age they become susceptible to several major pests, especially cytospora canker and gall adelgid.  So all those shapely blue Christmas trees that were planted 10 or 15 years ago are now a bunch of ratty-looking messes.  So what’s the solution for blue spruce burn-out?  Clearly landscapers and homeowners need to think beyond blue spruce and look for a greater variety of choices.  Here are three to consider.

– Serbian spruce Picea omorika  Whenever I’m asked to suggest a conifer, Serbian spruce is usually one of the first trees in the conversation.  While the color may not be as striking as a blue spruce, Serbian spruce still has impressive needles in its own right – bi-color with dark green on the upper side and silver below.  Adding to Serbian’s charm is its graceful weeping habit.

– Swiss stone pine Pinus cembra The late, great conifer expert Chub Harper used to remark, “I never met a cembra I didn’t like.”  Chub’s fondness for Swiss stone pine was well founded.  Here is an understated, consistent landscape performer.  Few pests, dark green needles and stately upright form.

– Korean fir Abies koreana  It would be a stretch to consider Korean fir an alternative to blue spruce.  While Korean fir is more broadly adapted than many of its pantywaist cousins in the genus Abies, it will still do best on the Holy Grail of moist, well-drained slightly acidic soils.  Nevertheless, Korean is tougher than the average fir and is a conifer with some character and worth a shot.  Korean firs are often heavy cone producers, which can add an interesting element of color.

And now for something completely different…

From this week’s e-mail file…

“Dear Dr. Cregg:

As I’ve done for many year, this year I harvested my “wild” Christmas  tree from the Huron-Manistee National Forest. I cut the tree at ground level. Soon after I brought it home, it started sprouting new light green clumps of needles at the tips of many branches. Is the tree actually growing? It doesn’t seem possible that it’s still alive, but it seems to be thriving and I hate to toss the tree to the curb if it’s fighting for life. I am tempted to leave it in the tree stand to see what happens….”

Pat M.

Midland, MI

 

Dear Pat:
The tree is dead, it just doesn’t know it yet.  Depending of the species, some Christmas trees will break bud and begin to grow once they are brought indoors.  The tree is still alive in the sense that its needles are still carrying out photosynthesis and water is still moving up the trunk to the needles.  But since the tree has no roots and no way to produce any new roots, it has no prospect for long-term survival.  The phenomenon you’re observing is common in some spruces and other conifers adapted to cold regions.  Before you cut the tree, the buds were exposed to enough cold to meet their chilling requirement to overcome dormancy – the only thing that keeps trees in wild from growing at this point are cold temperatures.  Once you brought it indoors, the tree ‘thought’ is was spring and started to grow.  If you or a family member want to do a little science project you could keep the cut end in water and see how long the tree lasts.  Eventually, however, the conducting elements at the cut end will begin to plug with resins and the tree won’t be able to move enough water to meet its needs and will expire.

Regards,
Bert Cregg

 

Do landscape trees need nitrogen fertilization?

I’m in Grand Rapids this week attending the Michigan Nursery and Landscape Association/Michigan Turf Foundation Great Lakes Trade EXPO.  The topic for my talk today was Landscape Tree Fertilization.  That might not sound like a subject that would generate controversy, but as with most things, there are camps emerging.  There is a rising chorus of folks that suggest that landscape trees should not be fertilized with nitrogen.  There are a couple of lines of evidence that bolster this point of view.  First, many systematic studies on the growth response of street trees or landscape trees often do not show a response.  There are numerous examples of this, for example, in Arboriculture and Urban Forestry (formerly J. of Arboriculture).  The second line of evidence for not fertilizing landscape trees relates to the relationship between tree nutrition and susceptibility to insect pests.  This argument relies on the ‘growth vs. defense’ hypothesis and suggests that fertilization promotes growth at the expense of defense compounds; essentially making fertilized trees tastier to insect pests.

So, in light of this, why do I suggest that landscape trees should receive 1-2 lbs of N per 1000 sq ft. every 2-3 years?  First, we need to understand that nitrogen is constantly lost from landscape systems.  In forests, trees take up nutrients from the soil, translocate them to leaves, shed the leaves, and the nutrients are ultimately returned to the soil in a cyclic process.  In landscapes, leaves are usually raked or blown and removed from the cycle.  Soil nitrogen is also lost due to nitrate leaching.  Additionally there are often key weaknesses in some of the papers that purport to show no response to fertilization.  For example, Ferinni and Baietto (Arb & UF 32:93-99) found no response of sweetgum trees to two levels of fertilization.  However, the data show that the control trees, which were not fertilized, had similar (and fairly high) foliar N levels as the fertilized trees.  This pattern can be found in several similar studies.  The more appropriate conclusion for these papers should be “Trees that are not nutrient deficient do not respond to fertilization”.  Similar issues pervade studies related to the growth vs. defense hypothesis.  Why would one presume that a nutrient deficient plant would be better able defend itself against insects attack than a tree that has adequate nutrition?  Ideally, fertilization decisions should be based on visual symptoms and soil and foliar samples.  Nevertheless, low rates of N from either organic or inorganic sources will make up for losses from the N cycle and maintain tree vigor.

It should be noted that the rates I’m suggesting are considerable lower than those that are found in some older extension literature, which recommend rates of N up to 6 lbs for 1000 sq ft.  As a point of comparison, Midwestern farmers apply 150-200 lbs/acre to grow a crop a corn.  The 6 lb rate for landscape trees works out to around 260 lbs per acre!

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O Tannenbaum!

Twas the blog before Christmas…  My last chance to post about Christmas trees for another year.  I’m always surprised when I troll around the web or do interviews how many myths about Christmas trees still abound.  So in the spirit of the season, a little Christmas tree myth-busting.


“Good grief.  I’ve killed it.”

Using a real tree hurts the environment
Here’s a real post from the e-how.com website:

“Its so not fair to cut down all those baby trees, use them for a few weeks and then toss them by the curb for garbage removal. Everytime, i pass by a house and i see those poor trees just shoved out like that it breaks my heart. they belong in the forest or backyard where they were meant to be, growing old and improving the air and atmosphere. i used to like real Christmas trees but not anymore.”

Yes, Virginia, there are still people out there that think Christmas trees are cut from forests. The U.S Forest Service and some state forestry departments do offer permits to cut Christmas trees but this is a tiny fraction of the trees used in the U.S.  Virtually all Christmas trees sold at tree lots and stores are grown on Christmas tree farms for that purpose.  For each tree cut, growers plant two or three more.   Moreover, many communities have programs for re-cycling Christmas trees into mulch or compost.

Christmas trees are a fire hazard.
The key here is water.  Fresh Christmas trees that are properly watered are not a fire hazard.  Trees that are allowed to dry can be a fire hazard.  These are the ones your local TV station uses for their annual dramatic Christmas tree fire video.

Fire retardant sprays make Christmas trees safer.
Research by Dr. Gary Chastagner, a colleague of Linda’s at WSU-Puyallup, has shown that some fire retardants can actually increase tree moisture loss.  Maintaining tree moisture is the key to making trees safer and improving needle retention.  Making sure the tree stand never dries out is much more important than a fire retardant spray.

Injecting water directly into the stem is the best way to maintain tree moisture content.
This is a case where a little knowledge can be a dangerous thing.  Since water moves up the tree through the xylem elements in the stem, wouldn’t injecting water right into the stem be the best way to water?  That’s the logic behind the Tree I.V.  As the name implies, this device is like an I.V. drip for your tree.  Drill some holes in the trunk, attach some tubes to a jug a water, and voilà, a self-watering tree!  We can thank Gary Chastagner again for busting this myth.  He and some colleagues found that displaying a tree in a regular tree-stand with water maintained higher tree moisture levels that the I.V. technique.

So, if arborists can use trunk injection to apply pesticides and fertilizers to trees, why wouldn’t the Tree I.V. work?  Actually, the tree I.V. does work in the sense that the tree will take up water from the jug.  The problem is that the tree may not take up enough to meet its total water need.  In a normal stand, the entire stem cross section is exposed to water.  With the tree I.V. only a portion of the stem will be translocating water.  Plus, conifers contain resin ducts which clog injection ports.  This is one of the reasons why arborist’s trunk injections don’t work as well as on conifers as they do on most hardwoods.

Bottom-line, keeping your Christmas tree hydrated is the key to retaining needles and keeping the tree safe.  A good rule of thumb is that a stand should hold a quart of water for each inch of tree caliper at the base.  For most trees this means a stand that will hold at least a gallon of water.   Check water in the stand daily and never let the tree go dry.

Have a very merry Christmas!

Friday quiz

Thought we’d take a break from the invasive discussion (I have some throughts I’ll weigh in with on Mon.)  In the meantime, here’s a photo of dwarf Alberta spruce not too far from my boyhood home in Olympia, WA.  I get 2 or 3 of these calls each year; usually with a homehowner exclaiming, “I’ve got a tree growing out of my tree!”.

Growing a greener Christmas tree

Among the many hats I wear, one of the most enjoyable is that of an Extension Specialist working with Christmas tree growers here in Michigan and surrounding states.  I suppose part of the satisfaction stems from the fact that my first real job was shearing Christmas trees in southwest Washington during my high school summers.  To give you an idea how long ago this was, the minimum wage when I started the summer between my sophomore and junior years was $2.20 per hour.

Today I’m involved in a variety of projects related to improving sustainability of Christmas tree production, particular water and nutrient management.  One of our major focus areas has been the development of container production systems for living Christmas trees.  For those not familiar with the concept, living Christmas trees are conifers that are sold with their roots intact as opposed to a cut Christmas tree.  Living Christmas trees serve a niche market for people that think cutting a Christmas tree is wasteful or even harmful to the environment (never mind that virtually every Christmas tree cut in the US was grown on a plantation for that express purpose).  Many Christmas tree growers have sold living trees by digging trees from their fields and selling them balled and burlapped or placing them in containers.  In our current work we’ve focused on growing several species of conifers as container stock with the end goal as living Christmas trees.  Container growing imparts a couple of advantage over the B&B method.  First, container-growing eliminates loss of roots associated with field digging.  Second container-grown trees are much lighter weight for consumers to handle than field-dug trees. Also, we have found the container-grown trees survive post-holiday storage and transplanting better than field-dug trees.


My former grad student, Wendy Klooster, shows off one on the Fraser firs she grew as part of her MS project on nutrient management.

If you’re considering a living Christmas tree here are some things to keep in mind.

  • If your ultimate goal is to plant the tree in your landscape, make sure the tree is a species that’s hardy in your location.  There are several types of container-grown conifers such as Italian stone pine (Pinus pinea) sold in big box stores and super markets that are hardy in only the warmest parts of the country.
  • Limit display of living trees to 10 days to two weeks.  Most conifers will begin to lose dormancy shortly after being brought indoors.  We’ve observed that some, such as Black hills spruce (Picea glauca var. densata), will break bud if the weather has been cold and they’ve had sufficient chilling.
  • After the holidays, place the living tree in a protected but unheated space such as a garage or enclosed porch or patio.  The key here is that the tree needs some exposure to light – but avoid direct sun.

As with just about everything these days, the environmental friendliness of Christmas tree production is receiving increasing scrutiny.  One way to have the ‘greenest’ tree on the block is to bring home a tree that keeps on giving.

Friday puzzle solved!

Great discussion over the weekend, with some very astute observations.  If you looked at the brown needles under the tree in Friday’s picture, you may have noticed that some of them weren’t needles:

Not only was this tree planted too deeply, as several of you pointed out, but the burlap and twine were left intact.  It appears the nylon twine has already started to girdle the trunk, based on the trunk swelling just above where the twine is wrapped.

I’ve ranted about this practice already, so I’ll just sigh and move on to the first question – what directly caused the needle drop from the lower part of the tree?  It’s a young tree facing west so the lower half gets plenty of sunlight.  And though needle drop is normal with all conifers, the upper portion of the tree does not show the same drop with its interior needles.  My guess is that ethylene gas is responsible.

Plant roots under stress often release ethylene, a natural plant growth regulator more commonly associated with fruit ripening.  It also induces leaf drop, so as it percolates out of the soil it affects the lower leaves, but dissipates before it reaches leaves higher in the crown.  It’s a common phenomenon with over-watered house plants.

Thanks to all of you who participated in the diagnosis discussion – this is more fun than my 20 years of college teaching!