Tag: woody

Friday fun!

It’s the holidays, but this pine tree is feeling anything but merry.  It was installed about a year ago.  While the upper foliage looks lush and green, the lower branches have no new needles and in fact the current needles are dropping:

This is a two part question:

1)  What might be directly responsible for the needle decline on the lower branches?  (Hint:  this is caused by the plant itself.)

2)  What might be the underlying stress causing the needle decline?  (Hint:  this is caused by by people.)

Additional photos on Monday will reveal all!

Let It Snow!

Here in Minnesota one of the things that we need to worry about is the cold.  Over the winter we can see temperatures down into the -30s (even the -40s in the Northern part of the state) and it can damage many of the plants that we grow.  The tops of the trees are usually able to handle these types of temperatures — though a good heavy snowfall can cause a limb to collapse now and again.

The bigger problem is with roots which aren’t able to handle the cold like the top of a plant can.  Once you get 10 degrees or so below freezing you’ve killed the roots of most plants.  Fortunately the ground is a great insulator and doesn’t get nearly as cold as you’d think.  Once you get two or three inches under the surface of the soil temperatures will hover right around freezing for most of the winter.  The plants that are most susceptible to cold are those that are in containers because their roots are above the soil’s surface.  Nursery growers usually protect containers from the cold by consolidating them (pushing them together as in the picture below).

These containers are then covered with a layer of polyethylene fabric, about 6 inches of straw, and then another layer of polyethylene fabric.  Temperatures under the fabric rarely go below 26 degrees or so — even when outside temperatures stay around -20.  Most plants come out fine — our biggest problem is that sometimes voles and mice will take up residence under the tarp and eat the plants — which isn’t a big deal unless its a research project — in those cases we will often use poisons or, more frequently, repellents.

The only thing better than this method is snow.  If we could count on snow every year we wouldn’t bother covering the plants at all.  Snow is the best insulator that we have.  Under snow temperatures rarely go below 29 degrees or so.  So, despite the traffic problems that snow causes, nurserymen and landscapers are always happy to see snow on the ground before the really low temperatures hit.

Inspecting nursery plants, part IV

(Note:  this is a really LONG post.  Not in text – but in photos!  Sorry for all the scrolling.)

I don’t know about you, but after spending three weeks on my hands and knees looking for trunk rots, surface roots, and suckers, I’m ready to become bipedal again.  So today let’s look at trunks – and what shouldn’t be missing on them.

Many young trees have numerous short branches along their trunk, as shown in the photo below:

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Unfortunately, many nurseries and gardeners think this looks scruffy, and respond by pruning these branches off, leaving a tree such as the one in this picture:

Personally, I think these trees look like lollipops, but aesthetics aside, this type of pruning can inadvertently damage young trees.  Their bark is often thin and sensitive to environmental stress – especially sunburn.  Without those short branches deflecting the sun from the bark surface, the living tissues under the bark can be killed, creating dead patches on the trunk:

How can you tell if the tree you’re considering has been improperly pruned?  Just look for those tell-tale pruning cuts, as a close examination of the lollipop tree reveal:

In time, these trees develop thicker bark, and the lower branches are gradually shaded out as the crown increases.  Be patient!  Let your trees be a little fuzzy when they’re young.  They’ll grow out of it.

I think about these things as I peer into my coffee cup…

This winter, we’re working on renovating part of the campus Hort Garden. We’re tossing around lots of ideas/themes, but I’m leaning towards a garden full of “Plants with a Purpose”. Edible, fiber-producing, medicinal…you get my drift.  Which brings me to today’s bloggerific topic: beverages.

Mankind has, throughout history, infused or fermented just about every species of flora in an effort to get either perked up or calmed down.  These plant potions are often classified anthropologically as, ahem, “ceremonial beverages”. The species that we currently rely on for our daily ups and downs are not native to North America.  But that’s not always been the case.

Way before the joys of coffee hit these shores, there was the Yaupon holly (and I am partial to hollies). This thicket-forming evergreen shrub likes “wet feet” and is usually found in marshy areas in the piedmont and coastal plains of the southeast.  Translucent red berries grace the female plants in winter – hollies are dioecious, meaning male and female flowers reside on separate plants.  The fact that Yaupon is one of few native plants to contain caffeine was picked up on very early by Native Americans – a potent tea brewed from the leaves was called the black drink.  Though the scientific name Ilex vomitoria might indicate some unpleasant side effects, it only exhibits emetic properties when a ridiculous amount is consumed.

Sassafras (Sassafras albidum) has been used as both a flavoring and as the main ingredient in teas and soda.  The sassafras is a sweet little understory tree, with oddly and variably shaped leaves – with one, two, or three lobes – Dr. Dirr at UGA pointed out to us that they often resemble “racoon mittens”  Native throughout the Appalachians, the tree roots were dug up in early spring before while still loaded with sap (where’d ya think they got the name “root beer” from?!).  Safrole is the  phenolic compound that produces the characteristic flavor.  However, safrole is now considered a carcinogen and the FDA banned the sale of sassafras for human consumption in 1976.  Extracts used in food and beverages have to be “safrole free” – produced through a commercial process. It’s also a psychoactive compound.  This may explain Yosemite Sam’s obsessive-compulsive tendencies and Saturday morning profanity (and I quote)  “Rassan, sassan, sassafrasan…”.

Last in today’s line-up of stuff from the woods: Humulus lupulus (the vowel-heavy name for hops).  Mmmmm, hops.  Here ye, the one or two people that may not know this, that from hops cometh the essential oil that maketh beer yummy. Speaking of oils, get close enough to hop vines on a really warm day and you’ll get a whiff of why it’s in the family Cannabaceae.  This perennial vine is native to most of the Northern Hemisphere.  The European beer-making strains have naturalized – that is, has spread from plants brought over by colonists in the mid 1600’s.  Hops are also dioecious – the female flowers are papery cones about the size of a quarter and the source of all hoppiness (the male flowers are basically useless and just sit around with their feet on the coffee table).  The leaves are sandpapery and most have three lobes – sort of reminiscent of a grape leaf.  Not only useful to make ceremonial beverages, the vigorous leafy vines provide an excellent screen and can quickly cover up an unsightly fence, shed, or family member.  Now that’s a useful plant!


I spent so much time writing this I ran out of time to hunt for plant photos. So here you go: My traveling T.Rex enjoys a nice, hoppy Virgin Islands Pale Ale on a lovely beach in St. John.

Salt solutions

Hopefully everyone got their filling of turkey and dressing over the long Thanksgiving weekend.  I used our unusually mild weather on Saturday to celebrate a time-honored tradition around the Cregg farm: The annual cursing of the tangled Christmas lights.

Turning the calendar over to December in Michigan means another Midwest tradition is just around the corner as well: The annual dumping of the road salt.  Although totals vary, at least one source estimates that road crews pour 8 million tons of salt on roads in the US each year.  The effects of this sodium chloride are readily apparent on our vehicles – in Michigan it’s rare to see a vehicle more than 10 years old on the road – and drivers of those older cars that remain can usually see the road pass under them through a rusted-out floorboard.  Of course all this road salt has profound implications for landscape plants as well.  Sodium chloride can damage plants in several ways.  Both sodium and chloride can cause direct toxicity, particularly from salt-laden spray drift from highways.  Salt in soils can cause osmotic stress resulting in drought injury.  Sodium in soils can displace potassium, magnesium, and other essential plant elements.  High levels of chloride in plant tissue can reduce cold hardiness and make plants more susceptible to freezing injury.  Suffice to say that salt is bad for plants.

So what’s a plant lover to do?  In general I advise a two-phase strategy of Selection and Protection for homeowners and landscapers that have to deal with heavily salted roads.  By Selection I am referring to planting salt tolerant plants (or at least avoiding salt sensitive ones).  The poster child for a poor choice in Michigan is eastern white pine, which is extremely intolerant of road salt.  Witness this planting at a rest area along I-96 between Lansing and Detroit.

Don’t you love to see your tax dollars at work?  Even a cursory look at a list of salt sensitive plants would have been a tip-off that that white pines and highways are a bad mix.  Most blog readers should be able to come up with a list of salt tolerant or salt sensitive plants for their area by Googling their way around the internet.  A couple caveats about these lists:  First, many are based on anecdotal experience, not hard data, so you may see inconsistencies between lists.  If possible, try to consult several sources and look for a consensus opinion about the plants you’re interested in.  Second, many recommendations are dated and include plants that may be considered invasive or no longer recommended for planting.  One list I just looked at included Russian olive (invasive) and green ash (no longer planted in the Midwest due to Emerald ash borer).

Another approach to reducing salt damage to plants is Protection.  Here I am referring to erecting a physical barrier to block salt spray or salt splash from reaching plants.  The most typical form of barrier around here is a wooden frame or fence covered with burlap or canvas.  Some people will actually wrap their evergreen trees or shrubs with burlap.  This may help against winter desiccation but does little for salt since the salt-saturated burlap will still be in contact with the foliage.  Obviously aesthetics go out the window with the protection approach but I’m noticing more and more people are willing to put up with a couple of months of looking at burlap to keep their plants looking thrifty the rest of the year.  In northern Europe some road systems will line their roads with pre-formed plastic barriers to reduce salt splash to adjacent vegetation.

What about alternative deicers?  This is a question I get frequently when I speak about salt and plants.  There are several things to consider about alternative (i.e., not sodium chloride) deicers.  First is the cost. All alternative deicers are more expensive than salt, some by a factor of 10 times or more.  This often limits their widespread use for highway departments.  Many road crews will use alternative products around bridges and other sensitive areas where they want to limit corrosive damage.  Alternative products may also be useful for smaller scale operations such as parking lots and walkways.  Secondly, many alternative deicers contain calcium and/or magnesium chloride.  These may even be marketed as ‘plant safe’ since they contain calcium and magnesium, which are essential plant elements.  The problem is the chloride.  Chloride is a plant nutrient but is only needed in minute amounts (a few parts per million). At higher levels it becomes toxic.

A study in Colorado found tree damage due to chloride near roads which were treated with calcium and magnesium chloride for dust abatement.   For safer alternative deicers consider chloride-free products such as calcium magnesium acetate.

In the meantime here’s hoping for a mild winter for everyone.

Advice Requested!

Greetings, all!

I am not a tree-care expert, having invested most of my mental capital into herbaceous plant stuff.  But I know enough to be dangerous: spiraling/strangling roots and narrow crotch angles are bad news. But at what point do they become “unfixable”? So I’m asking my illustrious colleagues and diligent readers (a.k.a “all y’all) for advice.

We have a lovely specimen in our campus Horticulture Garden…Acer ‘White Tigress’ – a hybrid between A. davidii and A. tegmentosum – also known as snake-bark maple.  Probably been in the ground for 18 years or so. Lovely buttery fall color, gorgeous stripey bark.

This tree, as we say in Georgia, “has more problems than a show dog.”

Scroll on down…


Bit of constriction there, mid-way up.


Some interesting crotch angles, too…

But here’s the kicker (I can hear Linda hooting it up from here…)

This poor gal is obviously a “what not to do” teaching tool.

But the question is:
Can this tree be saved? Discuss.

Friday puzzler addendum

OK, I know we gave you a tough assignment for the weekend, so I want to post something fun as well.  (Think of this as dessert after your healthy meal!)  Take a look at the photos below:

This hedge is regularly sheared and no one part of it has been maintained any differently than another part.  Both sections of the hedge face east, and the damage is anywhere from 2 to 4 feet from the ground.  What do you think has caused the damage?

Explanatory photos reveal all on Monday!

Inspecting nursery plants, part ll

Well, I’m recovering from this simply horrific chest cold or whatever it is and feeling brain function returning.  The last time we were at our virtual nursery, we were looking for root flare and inspecting the trunk for damage from improper bagging.  Since we’re already down on our hands and knees, let’s consider roots.  In general, you really don’t want to SEE roots, except where they meet the trunk (the root flare).  The presence of coyly crossed “knees” in this photo is a clear indicator of a plant that wasn’t potted up quickly enough:

Likewise, while the fused, circling woody root mass in this next photo might be aesthetically interesting, it sure doesn’t make a functional root system:

It’s pretty easy to avoid these types of plants, because you can see the root problems before purchasing.  The hidden root problems, such as those I’ve shown in earlier posts, are tough to find until (or if) you take all the extraneous stuff off of the root ball.

Finally, there is a new production practice that really fries my potatoes.  What really makes me angry is that these trees had absolutely LOVELY roots – a nice flare, woody roots spreading radially – and then they were butchered – and left unprotected:

 

I can think of no legitimate reason for this practice.  I’ll be curious to hear my colleagues’ thoughts, as well as those from the blogosphere.

What Makes Growers Change?

Over the last few weeks I’ve said a lot of complimentary things about the Minnesota Nursery Industry and how they’re careful to avoid situations where trees are planted too deeply.  What I haven’t mentioned is that there is a reason for this.  During the 1980s and early ’90s trees were usually planted deeply with lots of soil over the uppermost roots.  It was just common practice.  Unfortunately this practice led to roots growing across the trees stems and, when those roots cross the stem, the roots always win  (as you saw in Linda’s quiz last week)!  Many, many trees planted in that era have trunks which enter the ground looking like the picture below.  You can clearly see the roots strangling the tree.  This photo was actually taken last year on this campus!

This tree is one of the lucky ones.  These girdling roots were removed, the layer of soil over the crown was removed, the crown of the tree was inspected, and it was determined that this tree could survive.  Many others planted during the 80s and 90s are not so lucky — in fact, many are suffering or dead.

An outcry over the last dozen years or so, mostly from cities (St. Paul and Minneapolis), led to changes in harvest by the nursery industry, and by the landscapers who install the trees.  Yesterday I received a plan for planting trees up and down a major highway here in St. Paul to review.  The specs were very specific — and similar to the specs that we see now across the Twin Cities and most of Minnesota.  Root flare must be at, or even above, the surface of the soil.

I don’t want anyone to get the wrong idea.  There are still those who sell nursery stock with the root flare buried deep under soil in the ball, and there are landscapers who dig a hole twice as deep as the depth of the ball before planting, but it’s becoming less and less of an issue as, in general, we seemed to have learned from past mistakes.

Inspecting nursery plants, part 1

I’m frequently asked to give seminars on selecting healthy plants at the nursery, especially trees and shrubs which can run hundreds of dollars.  (Nobody seems to want a seminar on how to pick out a flat of petunias.)  I routinely visit nurseries with my camera so I can record examples of good and not-so-good choices.  What better forum to share these than on our blog?   I’m also curious whether the problems we see in the Pacific NW are found elsewhere in the country, or in the world for that matter.  So today we’ll hunker down on our hands and knees and inspect root flares.

The root flare (or root crown) is the point where the trunk meets the roots and should be wider than the rest of the trunk.   The photo below shows this clearly:

In balled and burlapped trees and shrubs, you might not be able to find the root flare as soil and/or burlap cover the root flare.  The tree below is burlapped far above its root flare:

Over time, many trees and shrubs buried too deeply will develop trunk rot.  You can inspect for rot by gently peeling back the burlap from the trunk and looking for damage.  Don’t worry, this doesn’t hurt the root ball or the trunk:

The tree in the above example already has some red flags – the presence of weeds on the soil surface suggests that it’s been in this pot for a long time.  (And no, you don’t want to buy this tree.)
The most dramatic example of the problems that can occur is this weeping larch, which has been completely girdled by the rot induced by the burlap and twine around the trunk:

Lesson:  It’s cheaper to wash your now-dirty pants than it is to buy (and eventually replace) a poor quality plant.