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

The ugly side of compost

In my part of the world we’re able to send most of our organic stuff through the green cycling program, where it ends up being made into compost.  Cedar Grove contracts with the City of Seattle to do this service.  As you might imagine, this requires huge, multiple facilities to handle all of the organic material that comes through the system.  And it’s not difficult to imagine that problems arise, especially in choosing locations for these sites.

I don’t know anyone who would welcome a large composting facility next to their neighborhood, and I sympathize with people who were living downwind of where these facilities were constructed.  (People who moved there afterwards should have known what they were getting into.)  But even worse is putting a facility in an environmentally sensitive area – like on an island.

On one hand, it might seem the perfect solution – put the facility on an uninhabited island to keep mainland neighbors happy.  On the other hand, it’s an ISLAND – runoff is going to be a problem.  So if such a site is chosen, then the company should be required to manage runoff and keep it out of the water.

Thus, I was most severely vexed to hear that Cedar Grove has asked to be exempted from the rules regulating phosphorus runoff into the adjacent slough. Unlimited amounts of phosphorus.  The facility routinely exceeds the legal limit of runoff of phosphorus and occasionally other nutrients set by the state Department of Ecology. Citations, fines, and out of court settlements are nothing new to this company.

According to their spokesperson, Cedar Grove "cannot find a treatment that would work" to manage phosphorus pollution and need a waiver from the requirements. Somehow this has become the public’s problem and we should just absolve Cedar Grove of any responsibility to be a good environmental steward.  

I don’t know what bugs me more: the fact that this corporation did not design an adequate facility to contain the runoff before it began operations, or that whatever governmental agency approved their plan didn’t require it.

Shut ’em down.

MossTiles – a really bad idea

A few months ago a colleague alerted me to MossTiles, which can be attached to walls to create interior vertical gardens. They look really cool, and I assumed they consisted of some tough little moss species rooted in a mesh-enclosed planting mix. But the more I read about them, the more confused I became. They don’t need light – or fertilizer – or water (though misting them occasionally is recommended). More investigation was in order.

It turns out that these aren’t made from moss at all, but lichens – specifically reindeer moss (Cladonia rangiferina). This slow-growing lichen is harvested in Scandinavia, "stabilized" in a salt solution, glued onto tiles with a resin, then dyed one of twelve different colors.

Come on. This isn’t a plant anymore. It might as well be made out of plastic. All the misting does is keeping them from drying out and crumbling to pieces.

Even worse, reindeer moss is a major food source for caribou and other large ruminants. It’s so slow growing that it’s a threatened (and protected) species in some parts of the world. Do we really need to have preserved plants hanging on our walls like some kind of botanical trophy?

If so, be sure you’ve got a fat wallet. Installation of MossTiles costs about $200 per tile.

Pest Alert for western Washington – late blight

I know most of you are not residents of western Washington, but this information might be of interest to gardeners everywhere.

Pest: Late blight (Phytophthora infestans)

Hosts at risk: Tomato and potato

Conditions of risk: cool, moist environment

Found: Images typical of late blight infection on tomato have been submitted from two Puget Sound area (King/Snohomish county) farms.   Growing conditions were plants in field soil where the area was covered with a plastic hoop structure.

Potential impact: Significant crop losses may occur if not managed properly.

What action should be taken: Scout for evidence of the pathogen on the foliage, stems of tomato or potato, as well as the fruits of tomato. Look for black discoloration to the foliage and a halo of sporulation around the edge of the damage if conditions are moist. Keep the foliage as dry as possible. Maintain good air circulation around plants. A variety of preventative fungicides (both organic and conventional options) is available – click on the links above for tomato and potato.

Information is also available on the PNW Plant Disease Management Handbook website.

Why I don’t like cardboard mulch

I’ve discussed my dislike of cardboard mulch before: like other sheet mulches it restricts water and gas transfer between the soil and atmosphere. In published comparison studies, other mulch choices generally outperform cardboard in terms of plant growth, weed control, etc. But there’s one area where cardboard is tops compared to every other mulch material tested.

Termites.

 

Termites LOVE cardboard. Did you know that termite researchers use cardboard feeding stations to lure termites? And cardboard is often used as the “control” in feeding studies, because termites will always eat it?

People seem to think that wood chips are termite magnets. Though termites can eat some types of wood, they prefer cardboard in taste testing. If they are given no choice and have only wood to eat, they will consume it but their survival rate decreases. Dead termites don’t reproduce.

To give termites a bit of a break, they are very useful in bringing life back to crusted, arid soils: studies have shown that just adding mulch and termites to these degraded soils is enough get biological processes going again.

But personally, I’m not providing a cardboard welcome mat for termites to the gardens surrounding my wooden house.  Hopefully you won’t either.

Groundcovers for gaps

I promised on last week’s post that I’d mention some other low-input methods of keeping weeds out of the gaps between paving stones.  Here are a few photos of my own yard, where we’ve been installing flagstone pathways and terraces.  (Money-saving hint: check out craigslist and/or freecycle for free pavers and other types of stone.  We got all of ours free – just had to pick them up.)

We bought flats of groundcovers, such as woolly thyme, Irish moss, and blue star creeper.  In sunny areas, these plants thrive and spread quickly. But in shadier, moister areas they haven’t done so well.  Instead, we’ve allowed nature to fill the gaps for us.  Naturally occurring mosses, ferns, and other small plants keep out annoying weeds yet are small and attractive in their own right.

You can jumpstart the process by making a moss “milkshake” to spread between pavers.  There are recipes on the web, so I won’t bother repeating them here.  I prefer to let nature take its course (or maybe I’m just lazy).

Hot new method of weed control?

There’s a new report out from University of Copenhagen on killing weeds between paving stones. What they recommend is burning or steaming the weeds lightly and repeatedly. Boiling water, steam, even flamers can be used to wilt the leaves over the course of several treatments (six was recommended). This process damages the leaves beyond repair, slowly starving the roots to death.

I’m not sure exactly how I feel about this study (which is getting a lot of attention on the internet). On one hand, it is a chemical-free way to kill weeds…but on the other hand, it’s pretty labor intensive and requires energy inputs for generating heat. Moreover, what does one do once those weeds are gone? Those bare patches of sterilized soil are just going to be recolonized by new weeds.

Several years ago I had a Master’s student look at different methods of killing English ivy. She also tried the steam treatment.  Ivy laughs at steam. Aggressive perennial weeds like English ivy or blackberry or Japanese knotweed are unlikely to be much affected by blanching, and certainly not by half a dozen treatments.

But most of us probably don’t have big, woody-rooted weeds amongst our paving stones.  In my own garden, it’s a mixture of species that fill these gaps and some of them – like mosses and some smaller ferns – I actually enjoy.  So I pull out the things I don’t like, leaving the desirable species to fill in the gaps.  It’s simple and requires no special equipment.

Am I missing something here, or is this really much ado about nothing?

The Pop-n-Drop method of planting shrubs

One of the planting practices that severely vexes me is the Pop-n-Drop (TM) method, where plants are popped out of the container and dropped into a hole roughly the same size.  When I’m lucky enough to find such installations in progress, I try to take as many photos as possible for later comparisons.  Here’s one such landscape that was installed in this manner:


A row of Pop-n-Drops in 2002

And here’s the same landscape 10 years later:


Two rows of Pop-n-Drops in 2012

Some of the shrubs survived, some did not, and certainly none of them are thriving.  You can see that the shrubs have remained about the same height after a decade of “growth.” Yet this practice continues to be SOP for many landscaping companies all in the name of shaving off a few minutes of labor and making a few more $$.

We GPs can (and do!) disagree about how much root preparation is needed before planting containerized and B&B trees and shrubs.  But I don’t think any of us would recommend NO root preparation.

(Additional note:  the “before” photo is the side of the landscape that faces west.  Those shrubs are gone.  The “after” photo is facing south (this is a corner lot).  All of the landscapes were put in at the same time, in the same fashion.  Unfortunately I didn’t take photos of the south facing landscape when it was put in, and the one that failed on the west was replaced before I knew it had died.  Sorry for not including this explanation initially.)

And here is the 2012 landscape from a closer viewpoint; note the dead shrub on the left end of the lower row.  The others are all failing, in both this row and the upper row:

Podcast: Subarctic Gardening

Earlier this spring I spoke to the Alaska Master Gardeners at their annual meeting in Anchorage.  I’d not been to Alaska before this, so I was on a steep learning curve most of the time.  It was fantastic.

In any case, I thought it would be fun to do a podcast on gardens and landscapes at high latitudes.  And if you’ve ever wondered what, exactly, you can grow at 51N latitude, you’ll find out

Pest Alert: Red Lily Leaf Beetle

One of the things this blog can do is alert gardeners to the presence of new problems.  This is one such instance.

WSU produces Pest Alerts, and recently the Red lily leaf beetle has been found in the Seattle area.  The state is monitoring the spread of this nonnative pest, so those of you living in Washington please read this and pass it on to your gardening friends.  New Englanders have been dealing with this pest for a while, but any of you outside this region may want to keep your eyes peeled.

Please comment here if you see this insect!

Podcast – Better living through chemistry

One of the coolest things about plants is their unlimited ability to manufacture some of the most amazing biochemicals.  This week’s podcast will brief you on some of these phytochemicals in the news – they’re good for you as well as for plants!  We’ll also explore whether natural organic compounds are really all that much safer than synthetic chemicals.  (You can probably already guess the answer to that one.)

Enjoy!