Author: Linda Chalker-Scott

Dr. Linda Chalker-Scott has a Ph.D. in Horticulture from Oregon State University and is an ISA certified arborist and an ASCA consulting arborist. She is WSU’s Extension Urban Horticulturist and a Professor in the Department of Horticulture, and holds two affiliate associate professor positions at University of Washington. She conducts research in applied plant and soil sciences, publishing the results in scientific articles and university Extension fact sheets. Linda also is the award-winning author of five books: the horticultural myth-busting The Informed Gardener (2008) and The Informed Gardener Blooms Again (2010) from the University of Washington Press and Sustainable Landscapes and Gardens: Good Science – Practical Application (2009) from GFG Publishing, Inc., and How Plants Work: The Science Behind the Amazing Things Plants Do from Timber Press (2015). Her latest effort is an update of Art Kruckeberg’s Gardening with Native Plants of the Pacific Northwest from UW Press (2019). In 2018 Linda was featured in a video series – The Science of Gardening – produced by The Great Courses. She also is one of the Garden Professors – a group of academic colleagues who educate and entertain through their blog and Facebook pages. Linda’s contribution to gardeners was recognized in 2017 by the Association for Garden Communicators as the first recipient of their Cynthia Westcott Scientific Writing Award. "The Garden Professors" Facebook page - www.facebook.com/TheGardenProfessors "The Garden Professors" Facebook group - www.facebook.com/groups/GardenProfessors Books: http://www.sustainablelandscapesandgardens.com

W.O.W. (aka Why oh why do nurseries sell this plant)?

Since we’re back on the alien train (spaceship?), I thought I’d bring up another of my least favorite shrubs – Scots broom – as our next installation of WOW (why oh why?).

Scots (or scotch) broom (Cytisus scoparius) is a much-reviled intruder in the western and eastern United States.  Originally introduced as a sturdy ornamental, this legume quickly invaded disturbed areas and is labeled as a noxious weed in several western states.  In Washington, it’s quarantined.  Research dollars have been dedicated to studying best methods of eradication.  So it doesn’t take a rocket scientist (or even a garden professor) to figure out that it’s probably not a wise addition to one’s landscape.

But apparently some nurseries either (1) haven’t paid attention or (2) don’t care.  In a quick look at the internet, I found nurseries in many states, including Oregon and California, that sell this species.  Many will argue that they are selling “less invasive” or “sterile” cultivars, which is a poor excuse in my opinion.  Readers of this blog know by now that cultivars often revert to wild type, and there’s no reason to assume that broom cultivars are exempt from this ability.  Furthermore, we know that plants have the ability to extend their ranges past what we think they are (hello kudzu?).


Just popping in to say hello

There are many ornamental alternatives to Scots broom that can easily be found online or in print.  I’d love to hear some rational arguments from nursery owners, landscape designers, or anyone else justifying the sale of this plant.

Freaky flower flummoxer

Finally, I’ve given a quiz that’s fooled everyone!

Believe it or not, this is a foxglove flower mutation:

Often, species with irregular flower will have flower which revert to a more primitive form.  In the case of foxglove, the bilaterally symmetrical flower reverts to the ancestral radial form – a phenomenon called peloria.  Apparently foxglove floral variations are pretty common and have been reported in the literature for many decades.

Friday’s freaky flower

Having now depressed my Michigan colleague with my earlier post, here’s a little lighthearted fun for the long weekend:

This photo is from Brandi at Fine Gardening.  Can you figure out (1) what it is and (2) why it looks like this?

Monday’s photo will reveal more, and we’ll discuss the second question in more detail.

Have a great holiday – enjoy yourselves!

Further decline of “public” education

“The Texas A&M University System is moving ahead with a controversial method of evaluating how much professors are worth, based on their salaries, how much research money they bring in, and how much money they generate from teaching, The Bryan-College Station Eagle reports. Under the proposal, officials will add the money generated by each professor and subtract that amount from his or her salary to get a bottom-line value for each, according to the article.”

This bodes ill for faculty like myself who have Extension appointments.  For those of you who aren’t familiar with how Extension works, Extension specialists educate citizens outside university classrooms.  But with declining state support for universities, their administrators in turn focus on income generation from grants and tuition.  Extension specialists do get grants, but for those of us in areas outside food and fiber research (which is what the USDA funds), there’s not much money available.

Bottom line?  According to this model I’m not just worth nothing – I’m worth less than nothing.  I’m not worried about my job (I have tenure after all), but for the direction that outreach education is heading.  What will happen is that Extension specialists will be pushed back into classroom teaching, leaving no time for educating the rest of the state citizens.  Outreach education will become little more than an afterthought.

The ironic thing about this trend is that Extension is one of the biggest bargains states get from their land grant universities.  Extension education includes Master Gardeners as well as other programs tailored to local state and county needs.

It’s sad that Texas A&M puts so little value on outreach education.  What’s even sadder is that this economic approach will undoubtedly be adopted by other state universities.

Rubber mulch – the discussion continues

Almost a year ago I posted my complaints about rubber mulch (you can find the posting here).  This week I was contacted by Jesse, a purveyor of rubber mulches.  We’ve had a very civil discussion about the topic, and he asked me to review his fact sheet.

Which leads me to today’s assignment. I have no personal experience with rubber mulch, so I’d like to hear from you about your experiences with this product.  Specifically:

1) Have you seen fungi growing on rubber mulch?

2) Have you had issues with the heat captured by the product – either to your feet or to your plants?

3) Does the mulch continue to smell, especially when hot?

4) How quickly do you notice degradation of the product?

Obviously this is anecdotal, not scientific, evidence.  But the scientific literature regarding rubber mulch is thin, and anecdotal evidence can often indicate directions that science should explore.  Perhaps this can be the beginning of such a study.

Why won’t landscapers use mulch?

A few weeks ago I was in Olympia (it misses you Bert!) reviewing grant applications.  As I tend to do whenever I have time and my camera, I set out in search of gardening goofs that evening.  Here’s the edge of a relatively new commercial site I discovered:

OK, not too bad so far.  We’ve got a nice stone mulch next to the curb, then a lovely groundcover, in flower, that also functions as a living mulch.  But what’s that we see in the upper half of the photo?

Yes, it’s Canada thistle (Cirsium arvense), an aggressive perennial weed that spreads by stolons and can make dense monocultures of prickly nastiness.  In fact, the front is already advancing on our little groundcover:

Had the landscapers continued with mulching the soil rather than leaving it bare, these thistle seeds might not have germinated.  But for whatever reason, the bulk of the landscape was left bare:

I’m sorry, but this just looks ridiculous.  There was some obvious care in laying the stone mulch and groundcover, but then the landscaper seems to have run out of time and/or money and just plopped in some bulbs and corms.  It reminds me of a birthday cake.

I don’t understand the rationale behind this.  Was this a real design?  Did the client run out of money?  Or (as the more cynical side of me wonders) was this done deliberately to create a high maintenance landscape requiring lots of weeding in the future?

Thoughts?

Dying dogwood diagnosis

Lots of good, thoughtful answers from you over the weekend about these trees.  Here’s another photo from a bit farther away:

As Laura pointed out, there’s a relatively new parking lot here.  The creation of the parking lot both compacted the surrounding root zone, then covered it with impermeable surface.  The dogwoods are huddled on their little island, which is unirrigated, unmulched, and indeed hot in the summer as Daniel said.  All of these environmental insults, in addition to the mature age of these trees, have led to what we call a “mortality spiral”:  trees are environmentally stressed and then become more susceptible to opportunistic pests and diseases.  Jon and Wes both did a nice job of discussing this.

There’s a couple of take-home messages here:

1)  If you must disturb a significant portion of an existing tree’s root zone, you should both protect the zone from undue compaction during construction, and then follow up with heavy-duty aftercare of irrigation and mulching.

2)  If you can’t follow point #1, then for heaven’s sake just remove the trees when they start their inevitable failure.  “Lingering death” is not an attractive landscape theme.

A ground cover I just love

I’m a particular fan of ground covers, especially those that replace bare soil or synthetic mulches (plastics, fabrics, and the sciency-sounding “geotextiles”).  That enthusiasm is tempered, however, by those invasive species, like members of Hedera, that seem to take over the world (or at least my little corner of it).  So while logic might dictate a preference for native species, I can’t help but love Rubus hayata-koidzumii (often mislabeled as Rubus calycinoides), and commonly called creeping raspberry.

When it comes to ground covers, I prefer species that stay on the ground; I like them low, tough, and dense enough to keep weeds out.  Of course they need to have attractive foliage and/or flowers.  But the icing on the cake, quite literally, is when they have edible fruits.

That’s why I love Rubus hayata-koidzumii, a high-elevation species native to Taiwan.  This USDA Zone 7 plant prefers sun to part shade (as you can see in the photo above), thriving in hot, dry conditions.  Not only does it do yeoman’s work in covering and protecting slopes, it bears abundant white flowers which morph into tasty fruits that practically beg to be baked into a cobbler or crisp.

But have I let my heart overrule my head?  Are there places where this species has become a problem?  I haven’t found anything in the literature to suggest it’s invasive, but am curious to hear from others.

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.

Photo #1

Photo #2

Photo #3

Photo #4

Photo #5