When Trees Don’t Know They’re Dead.

Last week a neighbor of mine called me up to ask how likely it was that their 4 year old (or so) crab apple tree was dead.  Sometime over the course of the winter cute fuzzy bunnies had decided that the tree’s bark was tasty and decided to eat it.  Naturally they ate it all the way around the circumference of the tree with the exception of a strip about an inch wide.  At this point you’re probably asking yourself why the neighbors suspected the tree might be alive.  The reason they were calling me was that the tree was leafing out–  so they figured that maybe the tree would make it — that maybe, just maybe, it wasn’t as bad as it looked.  My answer — Sorry, the tree is dead, it just doesn’t know it yet.  As a rule of thumb you can have up to a third of the circumference of a young tree girdled and the tree has a decent chance of growing out of it.  More than that and, though the tree might live for a few years, you’re dealing with so much damage to the vascular tissue that you’re just putting off the inevitable by not cutting it down.  A tree with as much damage as my neighbors tree had was just going through the motions.

When bark is eaten what is destroyed is the phloem — the tissue which carries the carbohydrates made by the leaves down the plant’s stem.  The cambium — which creates new phloem and xylem — is also destroyed.  But the xylem — the innermost tissue which transports water and nutrients up the stem — is left largely intact.  So girdled trees will flush out in the spring (using resources provided by the xylem), perhaps even two springs, but ultimately the tree will succumb.

But there is an up-side!  Girdled trees will be under a lot of stress.  Stressed trees tend to flower heavily — so enjoy the show first, then cut down the tree.

A rant about urban farming

(I know this one will get me into trouble…but hey, if I don’t tick someone off I’m not doing my job.)

I have mixed feelings about the increased popularity of urban farming. On one hand, I love the idea that people are becoming more involved in producing their own food. But on the other hand, the naivety of many urban farmers is scary – because they assume that home-grown food is safer and/or healthier than what they can buy at the market.

I give a lot of seminars every year, on a lot of different topics. At the end I usually have a room full of happy people, asking lots of questions and eager to go apply the new knowledge that they’ve gained. But one talk I’ve done has exactly the opposite effect. It’s the seminar I give on vegetable gardens and heavy metal contamination of urban soils. The audiences are subdued and worried. It doesn’t make me feel very good, but on the other hand I know I’ve got people thinking.

Heavy metal contamination of soils is insidious.  Like the iocane powder in The Princess Bride, these compounds can be odorless and tasteless…and deadly. Lead, arsenic, cadmium, and a handful of other heavy metals are the legacy of centuries of “civilized” living. Mining, smelting, manufacturing, and driving all contribute to localized toxic hot spots. Unlike organic contaminants, heavy metals are elemental. They don’t break down and go away. The lead from gasoline fumes of the past is still found along roadsides; the arsenic from early pesticides still lingers in soil used for field and orchard crops. Many plants not only take up heavy metals, but accumulate them in their tissues.

It’s easy to avoid heavy metal problems: soil tests are the logical first step. If soils are contaminated, you can build raised beds or use containers with clean, imported topsoil or other growing media for vegetable gardens. Likewise, you might want to take care in buying produce from farmer’s markets – ask questions about possible soil contamination.

So by all means, grow your own vegetables – save money and take satisfaction in producing your own food. But be careful out there.

Tuesday Quiz!

I think I’ll stay on the invasive species track. And in honor of finals week, here’s a wee quiz for you.

1) What do we have here?*

hint – it’s a naughty plant

2) Why can’t federal/state designations be somewhat uniform?**

Exempli gratia:

“[This plant] is listed by the U.S. federal government or a state…" – USDA Plants Database

Connecticut: Invasive, banned

Massachusetts:   Prohibited

Montana:  Category 3 noxious weed

New Hampshire: Prohibited invasive Species

Oregon: "B" designated weed; Quarantine

Washington: Class C noxious weed

*scroll down for answers…




[a bit more]

* Iris pseudacorus. Yellow flag iris. Loves wetlands. Spreads like crazy via rhizomes and seeds. Possible inspiration for the fleur-de-lis.

** I don’t know. It’s very confusing. "Banned" seems more alarming than "prohibited",  I suppose.  Is "B designated" less a concern than "Class C"? Feel free to weigh in.

Creating a sense of place

As many GP readers know I’m originally from Olympia, WA.  Once a week or so I troll through the on-line version of my hometown newspaper, the Daily Olympian (“the Daily ‘O’” for short or, more commonly, “the Daily Zero”) to keep up with latest happenings back home and to see if any of my high school classmates are on their way to jail.  While none of the Olympia High Class of ’78 made the news recently, my interest was piqued the other day by the headline “Saving the world – from weeds”.  The article described the Earth day efforts of local grade-schoolers to eradicate Scotch broom from a local nature trail.



For those that are not familiar, Scotch broom is an exotic shrub that commonly invades disturbed areas throughout the Northwest.  It’s been a problem for years and, even as a kid 40 years ago, I remember every cutbank around town covered with the nasty yellow blossoms.  In doing a little trolling on the internet I was surprised (stunned is probably a better word) to learn that there are parts of the country where Scotch broom is still sold as an ornamental shrub – named cultivars and all.  There are commercial cultivars of dandelion after all, so why not?


As we’ve noted here on the GP blog, there are lots of layers of complexity to the native/non-native discussion.  In many cases I think native advocates have over-sold the ecological side to the argument.  But the Daily O article got my dander up; not because 4th graders were pulling up Scotch broom – good riddance and keep up the good work kids – but because the Scotch broom was replaced with trees and shrubs that were all exotics in that part of the Northwest.


Native plant advocates often downplay the ‘sense of place’ argument in promoting natives.  I suppose they feel the ecological arguments are based on ‘harder science’ and therefore more convincing.  While it can be argued that native plants have adapted to the environment in which they evolved; it’s not always a given that the native conditions still exists, particularly in the built environment.  What’s beyond argument, however, is that trees and other plants provide a connection to the natural world around us and, for lack of a better term, do give us a sense of place.  From my personal experience, I have a visceral reaction to the sight of Scotch broom or English ivy in the Northwest where I’m native.  Here in Michigan, on the other hand, I’m less bothered by exotics – even some that may be considered invasive.  I suspect many native-born Michiganders have the opposite reaction.


I’m sure part of my connection to all things Washington stems from lessons learned in school (I still know all the lyrics to ‘Washington my Home’ and my plant collection form Mr. Chance’s high school Botany class is still somewhere in the attic of my parent’s house).  Which is why I was flummoxed by the schoolkids planting tulip poplars and sequoias instead of big leaf maples and western redcedars. Wouldn’t this exercise have been a great opportunity to teach these young people about the great trees and shrubs that are native to the Northwest and to give these kids a sense of place?

Solution to Friday’s flower fuddlement

Ed and Gayle correctly pointed out that short day plants (those that bloom in the spring or the fall) can sometimes do both.  The asters probably experienced some transplant shock in the fall, which would have suspended floral bud development.  This phenomenon could also be due to mild winter conditions (as Ed and Gayle also mentioned), which could have spared flower buds normally killed by freezing temperatures.

In any case, as spring daylengths approached those found in the fall, flower development continued and voila!  Asters in the spring!  Likewise, there are a number of spring bloomers that sometimes have a second (usually reduced) floral display in the fall.

Thanks again to Ginny for sharing her photographs and information!

Floral fuddlement

Gardeners love asters as part of their autumn floral palette.  Yet these native asters are blooming now – in the spring!

These specimens were purchased last summer and planted in the fall in Florida. Why might they be blooming out of season?

Reader Ginny Stibolt contributed today’s puzzle.  If you’d like to be a guest inquisitor on our blog, send photos and explanatory text to Linda Chalker-Scott.

This ‘n That

Grading finals, looking at roots, and planting seeds is consuming my time this spring, but I have just a few things to share today which might be interesting.

So, as those of you who follow this blog know, I love peanuts.  This year we’re planting out a bunch of new varieties, a few of which are extremely interesting.  Believe it or not there are not only red and pink peanuts but also black, white, and mottled peanuts.  We have these on order — when they come in I’ll post a picture.  When we introduce Minnesota Boiled Peanuts at the State Fair in a few years (that’s the goal anyway) the plan is to introduce a wide variety of really unique looking peanuts.  Fingers crossed they can live here!

Here, at the University of Minnesota, we do a really great job of telling people that, when they fertilize their grass, they should keep the fertilizer on the grass and not on the sidewalk — SO WHY CAN’T THE UNIVERSITY TEACH THE KIDS WHO APPLY THE FERTILIZER TO THE UNIVERSITY’S LAWNS TO KEEP THE DARN FERTILIZER OFF OF THE PAVEMENT?!?  Last week as I walked in I heard a crunching sound coming from my feet.  When I looked down there was a little pile of fertilizer on the sidewalk.

Believe it or not, judiciously fertilizing your grass actually helps prevent fertilizer run-off.  That’s because grass with a weak root system (as occurs in the typical lawn when you don’t fertilize at all) won’t be able to hold the soil as well — so you get more erosion.  So do fertilize your lawn, just don’t go nuts.

About that whole tree in the lung thing which I posted last week?  Yeah — It’s BS.  How do we know it’s BS?  No obvious roots on the tree and the tree’s needles were green (you don’t get green plants without sunlight). Personally I think this is some kind of odd cry for attention, but I guess it’s possible that the guy swallowed a cutting while he was shearing/pruning trees.  HOWEVER, there are documented cases where seeds will germinate in a persons lung — Usually the person has a compromised immune system.

A word about GMOs from our visiting GP

I gave a talk to a group of gardeners last year about vegetable and community gardening.  There was a wide variety of gardening experience represented, but one statement from a seasoned gardener bothered me a bit.  And I think my response bothered him a bit too.  I haven’t thought much about it until recently, when a high school English teacher I know told me a student expressed similar ideas in her class.  The erroneous idea from my audience member was this: our tomatoes are being poisoned with ‘germetically modinified’…something something.  The arguments have lost me beyond that (because there aren’t any).  And really, there hasn’t been much talk about sex on this blog recently, so that should be remedied too.  Therefore, I would like to take the platform offered by the Garden Professors to talk about plant breeding.



Fig. 1: Jaune flammee, which has at least one gene from at least one of its parents that causes the fruit to have very little lycopene.

Conventional” breeding is when a plant breeder selects parents and offspring and tests them for desirable characteristics (traits).  It works the same way as breeding works in nature, except that we humans have a goal we’re working toward.  Firm, 5-oz, disease-resistant, crack-resistant tomatoes, for example.  In nature, the offspring that survive and reproduce the best in a given environment are ‘blindly’ selected and tend to stick around (Darwin, 1859).  Male (sperm) cells are transferred to female (egg) cells by a plant breeder, or a bee, or the wind, or a beetle, or a fly or bird or bat or moth (etc.).  The sperm and egg fuse to form an embryo, which grows to become what we’d call a plant.  In both natural and artificial selection of tomatoes, no non-tomato DNA has been added, and no tomato DNA has been removed.  By the classical definition of ‘genetic modification’, there has been none.  I suppose this paragraph was only incidentally about sex, and probably a disappointment to some.  Sorry.

Fig. 2.  Tainan, a tiny heirloom

The confusion of the issue may lie with the Flavr Savr tomato.  This was developed (yes, genetically modified) in the mid-90’s to resist softening during ripening.  It has a couple bits of manufactured DNA in it to make this possible.  The Flavr Savr is no longer grown or sold in the marketplace (that was SO 1990’s), and to my knowledge, no other transgenic tomatoes are either.


Fig. 3.  Rutgers, historically much-cultivated and like all other tomatoes we can buy, bred conventionally.

Confusion may also lie with the plant hormone ethylene.  Ethylene is made from incomplete combustion of fossil fuels, but it’s also made by plants.  Keep your bananas away from your carnations, right?  Bananas make ethylene gas, which causes carnations and snapdragons to senesce (die).  Tomatoes make ethylene as they ripen.  If you harvest tomatoes a bit early, but not too early, they are hard enough to ship but will still turn red later.  If you expose these pre-ripened tomatoes to ethylene gas, they will ripen more quickly and uniformly.  That’s what happens to a lot of the tomatoes in our stores.  They are not genetically modified, they are treated with a plant hormone.  That’s not unusual at all.  Ethylene is used to ripen bananas, and to help make cucumber seeds (by eliminating male flowers from female parents).  It’s used in growing ornamental plants quite a bit too (but not as much as many other hormones, and especially hormone inhibitors).

So please, if you are someone who tells anybody who will listen that the tomatoes in the store are GMOs, stop it.  They’re not.

I’d be happy to answer any questions you might have…

Patience: A minor form of despair, disguised as a virtue.
– Ambrose Bierce

We just completed our annual student/hort garden spring plant sale.  I spent the better part of three days encouraging, suggesting, wheeling, dealing, and dispersing information, most of it sound, and all for a good cause. Generally enjoyed my legitimate excuse to sell some plants and also stay away from my ridiculous desk/computer.  My “Ornamental Plant Production and Marketing” seniors have a unique interest, as they not only grow plants for the sale, the last bit of the semester has been spent discussing cost accounting and (much more fun) marketing, including garden center management.  Through the hort club sale, they get to deal with real people with real questions.

One of these real people accosted one of my students late in the day Friday. Off in the distance, I saw an animated exchange as he nervously pointed her in my direction (ask Dr. Holly!)

“Is this a cultivar?” the rather intense lady barked (yipped, actually) as she marched over and shoved a quart pot of Allegheny spurge (Pachysandra procumbens) up to my face.  Close enough that I could read the big ol’ label quite clearly – which did not list a cultivar name.

“Doesn’t seem to be,” I deduced, rather brilliantly.  Did I mention it’s perilously close to beer:30.

I processed for another moment, and then noted “I don’t think I’ve ever seen a named selection of this.”

“Are you sure?! Because I don’t want any cultivars, you know, things that have been MESSED WITH!”

Here we go. 

“Ma’am, many of our perennial and woody plant cultivars are simply selections identified by some eagle-eyed and knowledgeable plantsperson as perhaps more compact, or more floriferous, more vigorous, maybe a different color, etc.  Nature, in many cases, has already done the work.”  Working under a suspicious glare, I go on that plenty of named cultivars are virtually indistinguishable from the straight species or botanical variety; for better or worse; it’s mostly just a marketing thing. Echinacea purpurea var. alba just doesn’t sing like Echinacea ‘White Swan’.  Though there are (obviously) plant breeders out there working to create new/superior/weird stuff (usually patented), but really, the historical bulk of what we have in our gardens is the stuff of perspicacious serendipity.

Said species, courtesy of NPIN.

She pursed her lips, stared hard at the tag, and repeated “But how do I know this hasn’t been MESSED WITH? And when it says native – that means to here, right?” 

*Pop* goes yet another can of worms.

I guess I could have said “Yep.”  Pachysandra procumbens appears on everyone’s “native groundcovers” list east of the Mississippi.  However, it is not native to Southwest Virginia, despite our location on the eastern edge of the Alleghany Mountains. It’s fairly rare, mostly found in the Cumberland Plateau of Tennessee and assorted limestone-y bits of Georgia, Alabama, and Kentucky. I take a deep breath and commence with the disclaimers.

I thought I was doing pretty well; then behind me I hear a familiar voice – Dr. Stephen Sheckler, lauded botany professor emeritus, poobah in the Linnaean society, and loyal plant sale shopper. He stepped in with an “I couldn’t help but overhear” and proceeded to explain the effects of glacial episodes on native flora distribution a mere twenty thousand years ago and Pachysandra may have indeed been native here if you look at the broader picture etc. etc. etc. Five minutes later, he was explaining why we have similar ecotypes to the Yunnan Provence, and I excused myself and wandered off to sell a Japanese maple. We’d both tried to answer her questions to the best of our ability. My utmost respect and admiration goes out to those of you in retail who do this on a daily basis.

My student was pleased to reported that she went back and bought the entire tray.

These are a few of my (least) favorite things…

Spring clean-up came in earnest this weekend at Daisy Hill farm.  Everything will be downhill from here as my least favorite yard chore; cutting back our ornamental grasses, is done for the year.  I know, I know, there are all kinds of shortcuts and tricks for this job including lassoing grasses for the last round-up (see Holly’s March 8 post), duct-taping them, and cutting them down with hedge-trimmers or a chainsaw.  Unfortunately, between our winter snow beating them down and our dogs using them as their own personal jungle playground, standing the grasses up neatly to await a trim just isn’t an option.  So I dive in and do it the old-fashion way; armed with a set of hand-loppers, every piece of  personal protective equipment I can find, and the entire repertoire of swear words my Army sergeant Old Man taught me.  Between hacking, cussing, and hauling it’s a two afternoon job.  On the plus side, it did give me time to ponder my top five list of least favorite yard jobs.  See how it compares with your list…


  1. Cutting back ornamental grasses
  2. Picking up black walnuts (this is to Fall what no. 1 is to spring)
  3. Weeding (the only redeeming factor is instant gratification)
  4. Deadheading (yeah, it’s not the hard but you know you’ll have to turn right around and do it again (and again and again…)
  5. Leaf raking (Actually, this wouldn’t be so bad but I went out and bought a chipper-shredder a couple years ago and feel compelled to use it.  Works like a champ – shreds leaves as fast as I can feed them in.  Too bad the bag needs to be emptied approximately every 43 seconds…)