Tag: woody

Why bother having trees?

Sorry to be late with my post this week – I was away reviewing grant proposals.  It was interesting and useful work, but really drains your brain.  So with that being said, my post is long on pictures and short on words.

One of the things that bugs us GP types is poor plant placement.  Why bother planting a tree if you’re not going to allow it to grow naturally?  Here are some photos to mull over the weekend.  While I have lots of bad pruning pictures, these ones are chosen specifically because the trees were obviously poor choices for either site usage or size.

Because my sense of humor seems to have been left at the grant reviewing venue, I can’t think of amusing captions for these pictures.  But I’ll bet you can!  Just submit them in the comments sections, and I’ll repost the photos later next week with your contributions.

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Friday quiz: The case of the bumpy maples

 

OK, this Friday’s quiz is the real deal: everyone gets to play “Extension Specialist for a Day”.  I am stumped on this and so are my colleagues here at MSU.  I used to work for a guy who liked to say, “None of us is as smart as all of us”.  Let’s put it to the test.

The photos below come from a nursery here in Michigan.  The trees are container-grown Red sunset maples.  Pretty routine crop around here.  The trees look fine: good color, full crowns, growing well.  The only problem is that nearly all of the trees have bumps along the bottom 8” or so of the trunks.  The grower is concerned, and rightly so, about consumer acceptance of the trees.  The trees have been examined by a highly qualified pathologist – no evidence of fungal disease; and by a highly qualified entomologist – no evidence of insect activity.   The grower is sitting on several hundred of these trees.  What should I tell him?


NOTE: The name of the nursery is confidential – they just used the calipers from Schumacher’s in the photo.

The importance of knowing your plants

One of the first courses a horticulture student takes is plant materials, or, in the case of a forestry student, dendrology.  Why?  Pretty simple; it’s hard to select plants if you don’t know what they are and what they’ll do in the landscape. Of course, the classic example is a large tree or shrub planted in a tight spot that eventually devours an entire house.  But we usually don’t have to look too far to find situations where a homeowner or landscaper clearly had no idea what plant he or she was dealing with.  To wit, a couple of recent examples of poor plant choices (maybe this can be our next series after “Why do nurseries still grow THAT?”)

I spotted the first example wandering through downtown in my hometown of Olympia, WA.  At first glace it looks like an ordinary hedge; boxy to by sure, but nothing remarkable.

As I passed by though I noticed the hedge was actually a weeping Norway spruce (Picea abies ‘pendula’ – actually it could have been an ‘inversa’ – the repeated butchering made it hard to tell).  Either way, what could have otherwise been a fairly interesting plant had been reduced to a squared-off blob of blech.  The other side, of course, is that if a squared off blob of blech is truly desired there are cheaper and easier ways to achieve the effect.

The other example of the perils of not knowing your plant material comes from northern Michigan.   This case represents that other extreme of trees that grow too large for their space.  Here the homeowner wanted to screen his house (on the left but out of camera range to protect the guilty!) from the railroad track on the right of the photo.  Solution: Plant some conifers! Sounds like a good idea to me.

Only problem – the owner chose to plant the screen with dwarf Alberta spruces!  As with the blob of blech, the property owner could have achieved the desired screen in a couple of years and at a small fraction of the cost with seedlings from their local conservation district or seedling nursery.  In any event, we’ll check back in about 40 years and see how it’s working out for them…

 

What’s old is new again

While the Emerald Ash Borer (EAB) continues to expand in the upper Midwest (see http://www.emeraldashborer.info/files/MultiState_EABpos.pdf  for a current infestation map), EAB is old news here in Michigan, especially in the southeastern part of the state.  Efforts to restore urban and community forest canopy lost to EAB will continue, however, for the foreseeable future. In 2003 we established an Ash Alternative Arboretum MSU Tollgate Education Center in Novi, MI – which is near ‘Ground Zero’ for the EAB infestation in North America.

 

The planting offers some insights into selecting alternative landscape trees to replace ashes.  A couple of elm cultivars, in particular, have emerged as shining stars in the demonstration planting that includes five specimens of 37 different species and varieties.  All trees were planted as 1½”-2” bareroot liners by Tollgate volunteers.  Tollgate farm manager Roy Prentice has overseen the maintenance of the planting.

 


Accolade elm (Ulmus japonica × wilsoniana ‘Morton’)  Compared to most of the other selections planted in the arboretum at Tollgate, Accolade elm looks like a man among boys.  Growth of these trees has been outstanding – the trunks of the trees have grown fast enough that they have split off their plastic rabbit guards (see photo).  Like Triumph elm, Accolade elm has dark green glossy leaves and develops into a large tree.  Although elms are often thought of ‘ugly ducklings’, both Triumph and Accolade are quickly developing well-formed vase-like crowns.

 


Triumph elm (Ulmus ‘Morton Glossy’) has also done very well at the Tollgate planting.  This elm develops a vase-like crown with age and has dark green, glossy leaves.  A large tree to 55’.

 

The elms are part of series of elm cultivars that have been developed with high tolerance of Dutch elm disease.  Most of the new elms are hybrid crosses with Asian and European elm species, though selections of American elm that are tolerant of Dutch elm disease are also available in the nursery trade.  The irony in all of this, of course, is that native American elms were devastated by another introduced exotic pest, Dutch elm disease.  As elm trees were rapidly lost during the 1950’s, 60’s, and 70’s, ash trees became a popular replacement due to their ease of transplanting, growth rate, broad site tolerance and pest resistance (yet another irony).  Now we’re promoting elms to replace ashes.

 


Street scene before and after Dutch Elm Disease.  Photo: theprincetonelm.com

The moral of the Dutch Elm Disease and Emerald Ash Borer stories is that it’s critical to avoid over-reliance on one species or even one genus – even a native one.  In Michigan some of our urban and community forests are over 50% maple.  As global trade increases and the potential for destructive pests to hitch-hike around the world rises, the best hedge against catastrophic tree loss is to plant a broad and diverse array of adapted trees.

Riding the storm out

This past weekend marked our first real bout with severe thunderstorms here in Mid-Michigan.  Several lines of storms moved through the mid and southern part of the state and northern Ohio.  The storms in southern Michigan and Ohio also spawned some tornadoes.  Around here, storm damage was confined mainly to downed trees causing power outrages and some damage to homes and buildings.

Severe weather outbreaks provide some opportunities to observe tree failures and gain insights into how they can be prevented.  Or, as Yogi Berra put it, “You can observe a lot just by watching”. I was at a little disadvantage in scouting out tree damage from out most recent storm because we were traveling over the weekend and  I wasn’t able to get out and about to survey damage until Monday evening.  As it turns out the area most heavily affected by the storm is also fairly affluent.  Folks in these neighborhoods don’t tolerate downed trees lying around very long.  Nevertheless, I did make a couple of interesting finds.

 


A common sight after a storm in this area is wind-throw in shallow-rooted species, such as spruce and pines. We didn’t see a lot after the current storm, which was probably due to the fact that the storm moved through quickly – most of the high winds lasted only a few minutes – and the storm was not preceded by prolonged heavy rains.

I don’t have any specific data but I have seen several cases where wind-throw was occurred on trees in which mulch was underlain with landscape fabric.  Perhaps coincidence, but another strike against the stuff in my mind.

 


This maple provided one of the best (or worst) examples I have seen of planting too deep.  The tree snapped off about 6” below ground line.

Note that there are plenty of pretty stout roots that look like structural roots near the surface, but none of these originated near the current ground line.  The tree was on private property and time constraints prevented me from getting permission to do an excavation, nevertheless, it would be interesting to try to find the original root flare.

 


By far the most common problem in this storm, and most of our typical thunderstorms, was large limb breakage associated with narrow crotches.  This occurred in a variety of species; oaks, maples, elms, pines.  Narrow branch angles often form from multiple leaders, which results in weak branch attachment as included bark forms and gradually reduce the proportion of wood attaching the branch to the tree.  The encouraging thing, or maybe discouraging depending on your point of view, is that this is one of the most easily preventable tree defects.  Pruning double leaders or multiple leaders back to single leaders and eliminating other poor branch angles when small can easily prevent this type of breakage.  For most of our garden-variety thunderstorms, eliminating narrow crotches would probably eliminate 50% or more of our tree-related storm damage.

Good to the last drop

As part of our discussion of the relative merits of fall planting, Linda mentioned an article in Arboriculture and Urban Forestry that suggests that frequent, light irrigation might be better for landscape trees then the usual recommendation of infrequent soakings.  While I will withhold final judgment until I see the article (I did a scan of the last two year’s table of contents for A&UF but missed the article in question), here’s my rational for following the standard recommendation.

 

First, the context.  In discussing landscape tree irrigation I am talking about watering trees during establishment, typically during the first year after planting and maybe the second if the tree is lucky.  The goal of watering in this case is ensuring survival.  The questions are whether deep soakings are more likely to encourage deeper rooting where water availability is less variable than near the surface after irrigation ceases and whether infrequent watering increases drought tolerance over more frequent irrigation.

 

Roots follow resources
As my Woody Plant Phys students quickly learn, we avoid the teleological ‘roots seek out water’; nevertheless, roots do proliferate where resources are available.  A couple of illustrations.  As a Tree Physiology Project Leader with International Paper I supervised a 25 acre hardwood fertigation trial.   Trees were watered daily via drip irrigation system with emitters spaced every 3’ down a row.  As part of the study we did periodic root harvests.  My technicians quickly learned it was an easy job: just look for the drip emitters – every three feet there was a mop of roots right next to the drippers.  The notion of roots following resources is also widely reported in the ecology literature on tree utilization of ‘patchy resources’ (e.g. Gloser et al. 2008 Tree Phys 28:37-44 ).  Other factors being equal deeper watering should result in deeper rooting.

 

Trees habituate to frequent irrigation
Another short rotation forestry example.  In eastern Washington and Oregon forestry companies Potlatch and Boise Cascade operated intensively managed ‘fiber farms’ which grew 70’ tall, 7” diameter hybrid poplars on a 7 year rotation.  To maintain these growth rates, trees were irrigated daily.  But there was a downside: If one day’s irrigation was missed the leaders to the trees would start to wilt.  Three days without water would result in leaf drop. The daily irrigation was great for growth but it turned the trees into physiological wusses.

 

Periodic water stress improves drought tolerance and survival
A common adaptation for trees to tolerate drought is osmotic adjustment, which is an active accumulation of solutes that enables plant cells to maintain turgor pressure during dehydration.  Plants that have acclimated to stress via osmotic adjustments and other physiological adjustments are able to survive better during prolonged drought than plants that have not been pre-conditioned.  For example ponderosa pine seedlings that had been subjected to brief drought events survived a terminal dry-down two weeks longer than seedlings that had been watered 3 times a week before the final dry-down (Cregg 1994 Tree Phys. 14:883-898.

 

What would it take to change my mind?
Obviously some of my examples here are anecdotal (though there’s plenty of hard data on osmotic adjustment and other drought conditioning effects on trees).  To recommend frequent (2 or 3 times a week), shallow irrigation I would need to see: a well designed and executed experiment that compared frequent irrigation to periodic (once every 7-10 days) applying the same amount of water weekly (0.5 to 1” per week) for the first year and then documented improved survival of the trees after irrigation had been discontinued.  I’m not saying it’s not possible but it goes against my personal observations with irrigated trees in a variety of settings and relevant data with which I’m familiar.

Is Fall Really a Great Time to Plant Trees?

One of the joys of working on a university campus is that construction never seems to end.  As near as I can tell there are about 3,000 orange construction barrels that permanently reside on the MSU campus that simply get shuffled from one end of campus to the other every few months.  Along with all the construction comes a never ending series of new landscape projects.  Driving by one of the most recent projects the other day got me to thinking about the myth of Fall planting.  In numerous extension bulletins and certainly in nursery sales advertising we hear that “fall is the perfect time to plant trees”.


Photo: Dana Ellison

The recent fall planting job on our campus gave me pause to think about this.  I haven’t had a chance to completely survey the carnage but I suspect about a third of the trees will need to be replaced.  Obviously there are lots of things that may have gone wrong here, irrespective of when the trees were planted and one exception doesn’t prove the rule.  Nevertheless when I look back on the planting disasters I’ve been called in to inspect over the years a disproportional share (I’d say by a factor of two or three to one) are fall planting jobs.

 

What gives?  Well, the notion that fall is a great time for planting is built in a faulty premise, at least for this part of the country.  Probably the most commonly cited reason for fall planting is that trees grow a lot of roots in the fall.  This assumes that since there’s no shoot growth occurring, trees automatically shift reserves below-ground.   There is certainly a ‘pecking order’ of carbohydrate distribution within a tree based on relatively strengths of sources and sinks.  But there’s one factor that trumps all others: temperature.  Soil temperature is the biggest driver of root growth.  Measurements of new root growth in a cottonwood plantation in Wisconsin provide a classic example.  As temperatures decline in the fall, new root growth essentially ceases.  For trees that are well established, this is no problem.  For trees that have just been transplanted and need to re-establish root-soil contact this is a tough row to hoe.  Throw in a tough Michigan or Wisconsin winter and the tree’s facing an uphill climb.

 


New root growth of eastern cottonwood (top) and soil temperature (bottom). Source: Kern et al. 2004. Tree Phys. 24:651-660.

Again, most planting failures have multiple causal factors.  Even if the trees on this site had been planted in the spring, they may have still experienced problems.  My point is that a more accurate statement is “Fall is an OK time to plant trees”; not the ‘best’ time or even a ‘great’ time.  I think these statements are often driven by the fact the fall is a slow time for nurseries and landscapers.  When homeowners or landscapers ask me about fall planting the first thing I ask is if there is any reason why they can’t wait until spring, the real ‘best’ time for planting.

Building a Better Container

As most of you know, roots circling around a container isn’t considered a good thing.  And so people try various things to control circling roots.  One of the more creative horticultural minds out there, Carl Whitcomb, a guy why basically got sick of academia and went into private industry (and, as far as I can tell, loathes peer review and the whole process of publication), decided to see what he could do about making containers that don’t encourage circling roots.  He came up with a number of designs, but my favorite is the RootTrapper.  The container is made of a flexible cloth which roots get lodged in, preventing them from circling.  Not that I’ve never seen a circling root in a RootTrapper, it’s just that these circling roots are extremely rare.


A row of elms in RootTrappers


A cut open RootTrapper

This is one of those innovative products that really works and it surprises me that so few people use this growing system.  Yes, it’s a bit more expensive than standard containers, and yes, it does take a little more effort to take the tree out of this container than a smooth sided one.  But man, I’ve never seen a better root system come out of a container than those which you get out of these.

Spruce brown-out solved

Gall adelgids are certainly a problem in these parts, especially on blue spruce.  But the ‘problem’ in this case is not a pest.  This year, as in several recent years, spruces are developing copious amounts of pollen cones.  Once the pollen is shed, the cones dry up and turn brown.  Many homeowners mistake these for insect galls or sign of some other pest activity.
In many conifers, pollen cones occur on the lower portion of the crown while seed cones occur in the upper third as an evolutionary adaptation to reduce selfing.