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

Mystery tongue identified

A few brave souls dared to take on Friday’s puzzle.  Here’s a more revealing photo; the "tongue" is actually the top of a pitcher plant: 

Kudos to Hap for correctly identifying the genus (Sarracenia) of this carnivorous plant.  This particular one is S. purpurea, which is distinctive in that it has dark red, open pitchers rather than hooded ones.  You can easily see the downward slanting hairs in the throat of the pitchers.  These hairs, as Diana pointed out, keep trapped insects from climbing back out of the pitcher. 

This pitcher plant is part of my nifty bog garden that we put together this year.  If any of them get big enough, I’ll have to try Hap’s unorthodox method of slug disposal.

Off with their heads!

About a year ago I posted my thoughts about the nursery production practice of heading young trees (“whips”) to stimulate lateral branching or columnar form or whatever.  (You can find this original column here.)  A healthy discussion ensued, much of which revolved around the need for appropriate follow-up pruning to ensure the development of a stable crown structure of headed trees.

Fast forward to last month, where a column I wrote for NPM (Nursery Production and Management) magazine hit the web.  And then the fan.

I made some people very unhappy with this article.  I had a lengthy and productive conversation with one such person last week, during which we agreed on many things, including (1) trees that are headed develop multiple leaders; (2) multiple leaders, however they’re created, need to be thinned to one central leader; and (3) uncontrolled multiple leaders can create hazardous conditions.  The bottom line, from a nursery production perspective, is that headed trees require regular pruning to create and maintain natural, structurally sound crowns.

And here’s my problem:  how many homeowners are going to perform this regular pruning?  Furthermore, how many homeowners KNOW how to perform corrective pruning?  We all know that number is going to be abysmally small.  Even for those situations where competent arborists could do this regular pruning, how many communities budget for this activity?

More troubling for me as a scientist is the lack of peer-reviewed scientific papers on this practice.  Though there are numerous papers documenting the effects of pruning, I can’t find any that specifically look at the long-term effect of heading trees during nursery production. You’ve heard all of us GP’s say it before – unless you can show us the data in a published and peer-reviewed format, we can’t regard anecdotes as anything but.

The nursery industry has invested a lot of time and money in a practice that leads to problems for which no one will claim responsibility.  Production nurseries wash their hands of the issue once the trees leave their facility.  Many retail nurseries don’t perform the necessary follow up pruning while the trees are in their care (do any retail nurseries do this?  Are they aware of the problem?).  Homeowners don’t receive information or training on how or why to perform corrective pruning.

What I’d really like to see the nursery production industry focus on is consumer education.  The metamorphosis of a sapling into a maturing tree is a wondrous thing.  Rather than interfere with the process, we need to cultivate patience as well as a respect for tree physiology.

Turf trickery

Now I feel a little guilty.  You tried to answer Friday’s puzzle so seriously, and I was taking liberties with photography:

I think this is the coolest garden stairway I’ve seen yet.  The buffalgrass tolerates moderate foot traffic, and it lends a fluid look to the otherwise hard edges of the steps.  And you can’t tell from looking, but it both felt and sounded silky.  Best of all, it doesn’t require mowing.  (This is the Rolston/Cohn garden, part of the garden tour put on by the GWA in Dallas last week.)

Sheet mulching – benefit or barrier?

Alert reader Matt Wood pointed out a recent article in the NY Times on mulching with newspaper and wondered about my take on the topic.

For use on landscapes, I do not like sheet mulches of any stripe.  They tend to hinder to air and water movement, most especially in unmanaged landscapes like restoration sites.  A classic example is the use of cardboard or newspaper covered with wood chips.  The chips are easily dislodged, exposing the sheet mulch which quickly dries out and becomes hydrophobic.  Thus, the roots of desirable trees and shrubs lose out on the water, while the weeds surrounding the edges of the mulch benefit from the runoff:

Published research on sheet mulching in landscape settings confirms the drawbacks of sheet mulching.  But the article in the NY Times is about vegetable gardens.  This is a different situation – more akin to agricultural production than to landscape horticulture.  Vegetable gardens are routinely managed during planting, thinning, weeding, and harvesting.  Newspaper sheet mulches in these situations rarely dry out and, when kept buried and moist, do break down quickly.

So – keep the sheets on the (vegetable garden) bed where they belong!

A freakin’ violet

Friday’s puzzle scared you off!  Matt was correct – this is an African violet (Saintpaulia spp.).  But unlike other African violets, this one never opens its flower buds (Sandy nailed it!).  Originally cultivated in Germany, these plants are marketed in the US by Optimara Violets.  That’s all I can tell you about this quirky little cultivar.

 

Friday puzzle – from Dallas!

I’m in Dallas for the next 4 days attending the GWA (Garden Writers Association) annual conference.  (I get to give a talk on Horticultural CSI on Sunday!)  Tonight we had a slew of vendors to explore, and among the offerings I found this plant:

So today’s question – what is this plant?  And what makes it so unusual?  The first question might be easy – the second one, not so much.

Answer and more info on Monday!

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.