Are natives the answer? Revisited

I started to leave a comment on Linda’s Friday post regarding Seattle Public Utilities proposed building codes regarding “Healthy Landscapes” but decided I’d weigh in with a regular post.  Linda honed in on the 75% native requirement but there are lots of things to make one scratch their heads in the proposed codes.

Existing invasive plant species shall be removed and no invasive species planted.
No mention of how invasive plants shall be removed.  Heavy-duty herbicides? Armies of school children forced into slave labor? Slow-moving ground-fire? Goats?

75% of all new plantings will be native to Western Washington.
So where did 75% come from?  Sounds like a number that was pulled out of the air.  How is 75% defined?  75% of plants? 75% of the area?  And how does this foster “Healthy Landscapes”?  If I have a 2 acre landscape and plant an acre and half of salal or Oregon grape I’ve met the requirement of 75% but have I increased species diversity or structural diversity or contributed to a “Healthy Landscape”?

A vegetation plan must be submitted for review.
By whom?  What happens if they (whoever ‘they’ are) don’t like it?

Existing native plant species shall be protected whenever possible.
Sounds reasonable but what about existing non-invasive non-natives?  Could a homeowner be required to cut down a 40-year-old red maple?

And on and on we could go.  Let me state clearly, I’m not against native plants.  Quite the opposite – I grew up in western Washington and have a passion for PNW plants since my high school days.  Since moving to Michigan I’ve written articles and given talks promoting natives here as well.

Nonetheless, I think many in the native plant movement hurt their cause by parroting the same old lines without ever critically thinking about what they’re saying.  Repeating a lie often enough times does not make it the truth.

Let’s critically look at some of the reasons for planting natives according to the Washington State Native Plant Society:

Native plants are adapted to our climate of wet winters and dry summers.
True. But so are lots of non-natives.  Adaptedness is a function of the environment in which plants have evolved; whether it’s native or exotic.  There are many climates around the world that are similar to the PNW and can produce similarly adapted plants.

Require less water than most non-natives once they are established.
Once again, adaptations such as drought tolerance are a function of the climate under which plants evolved.  There are many exotic species that are more drought hardy than western Washington natives and likely to use less water.

Resist native pests and diseases better.
Sometimes. But unfortunately the days of worrying only about native pests are in the distant past.  Exotic pests are here and they are here to stay.  Dutch elm disease, white pine blister rust, emerald ash borer, chestnut blight, Japanese beetle, the list of exotic pests is long and getting longer.  Native does not mean pest-free.

Improve water quality by needing less fertilizer and no pesticides.
OK, here’s where I get confused.  The reasoning in Doug Tallamy’s book, Bringing Nature Home, is that native insects don’t feed on exotic plants, therefore if we plant exotics, native food pyramids will collapse and it will be the end of life as we know it.  So… if native insects won’t feed on exotic plants, why would exotics require more pesticide use?

Save resources and encourage a sense of Stewardship.
Ok, now maybe we’re getting somewhere.  Not sure why stewardship is capitalized here but if they mean a ‘sense of place’ or a ‘connection to the natural environment’ then I can buy it.  Many native activists, including Tallamy, run away from this argument – apparently it doesn’t sound scientific enough – but it’s one of the best we have.  Washington state has some of the most incredible plants anywhere.  They should be celebrated and promoted and planted.  In my mind, the biggest reason for planting natives – along with carefully selected non-natives – is to increase overall biodiversity.  When I mention biodiversity I am speaking broadly; species diversity, structural diversity, age-class diversity, and landscape diversity.  When we look to the future we have no idea what lies ahead. We don’t know what new, exotic diseases or insects are looming on the horizon. Most of us expect climate will change but no one can say with certainty how.  Plants cannot evolve as fast as climate will change or as fast as new pest will be introduced. The only way to deal with this uncertainly is to spread the risk through diversity – this includes natives, exotics, and even interspecific hybrids.

The natives debate continues…

Bert’s usually the one who posts on native plant news, but since he’s not in Seattle he will have missed this one.  So Bert, sit back and enjoy!

I just got an email from Seattle Public Utilities, who are having an open house to discuss “high efficiency landscapes” through their Green Code Provision Boards. One of the changes has to do with invasive species (a good thing). But these are the proposed changes:

Invasive Species and Native Vegetation (Regional Plan)

Who it Applies To:  For all new vegetated landscapes, or those being replaced


• Existing invasive plant species shall be removed and no invasive species planted.

• 75% of all new plantings will be native to Western Washington.

• A vegetation plan must be submitted for review.

• Existing native plant species shall be protected whenever possible.

I really don’t like the second bullet point.  75% natives?  Many of our Western Washington natives are understory plants adapted to the cool, moist coniferous forests that in no way resemble urban developments.   The few species that are able to tolerate hot, sunny, dry conditions won’t make for a very interesting or diverse palette. And we already know that a biologically diverse landscape is better than otherwise.

What’s wrong with using well-chosen nonnative plants that will tolerated urban conditions, support wildlife, and add some aesthetic interest?

Injecting Gels Into The Soil — Good Idea?

It recently came to my attention that the Sierra Club published an article on a new system for reducing watering in lawns.  You can read it here.  Basically what the company, AquaCents, does is inject a polyacrylamide gel into the landscape and then the gel supposedly collects irrigation and/or rain water and releases it for plants to take up as the landscape dries.

I think it’s a good concept, but I’m highly skeptical that this is a good product for two reasons.  The first is that I’ve used polyacrylamide gels to hold water for plants before and have found no benefit.  In fact, most papers out there on the topic show either no benefit or marginal benefit from using these gels in terms of increasing the amount of water available to plants – though I must admit that results are variable.

Please note that I didn’t say I was skeptical that the polymer will hold lots of water – I’m not.  It will hold lots of water.

Which leads us to an important question.  If we know that the gel will hold water, and this company has done testing which shows reduced watering is required in lawns that use this technology, then why am I skeptical?

Based on what I have read and the experiments I’ve done, I think the company’s testing isn’t telling the whole story.

As far as I can tell, what they’re doing to test this product is injecting it into lawns and then allowing a moisture detector in the lawn to trigger sprinklers to go on when soil moisture falls below a certain level.  If you test one lawn with the polymer side by side against another lawn without the polymer, then the lawn with the polymer will use less sprinkler water because the gel holds more water than the surrounding soil – meaning that it stays more moist. So at this point it sure seems like the gel is a good idea — right?

No, because this experiment asked the wrong question.  It looked at how much water was in the lawn, NOT HOW MUCH WATER WAS GETTING TO THE PLANT.  And that’s what we need to know – how much water gathered up in that gel will actually get to the plant.  What I’ve found in my work is that having water in the gel is not the same as getting water to the plant.  The gel seems to hold the water too tightly for the plant to get it.  It’s a little like having an impenetrable safe filled with five million dollars in gold.  Sure, the gold is there, but if you can’t get to it, who cares?

So, why does the grass seem to be growing more roots when the gel is used?  My best guess is that the lawns were overwatered in the first place and the gel just provided a way for homeowners to decrease their watering.  Let’s face the facts, overwatering of lawns is rampant.

But I mentioned that there were two reasons why I didn’t like the gel.  I named the first, so what’s the second?  It’s something that I saw on one of Linda’s sites a few years ago and then looked into a little further.  Polyacrylamide gel, while relatively safe in and of itself, may break down into more toxic substances.  See Linda’s article here.

Finally – and this is just a thought — there are plenty of other absorbent materials out there that might be injected into the ground, including some made of starch – I have tried gels made of starch and have found them to be as effective as those made of polyacrylamide (though I know that’s not saying a lot).  Or…maybe we should just water more judiciously.  Like I said, just a thought.

Hey Kids! Check This Out!

I recently spotted this in the window of a toy shop:

Recommended for ages 10 and up. My youth was apparently misspent with Hot Wheels and model horses (and collisions thereof).  I could have been getting a step up on grad school.

"See genetic material with your
own eyes as you isolate the DNA from a tomato in a test tube."
(This is actually fun and easy and you don’t need a kit to do it.)

"Learn about dominant and recessive genes and play inheritance
games to determine how traits will be expressed."
  Then you can blame the correct parent for your near-sightedness, flat feet, etc.

"Breed your own bacteria colony to experiment with survival of
the fittest."
  Now, we’re talking!!!  I would have loved this.  My mother, however, would have argued that the disgusting storage space under my bed was, in fact, a giant petri dish.

It’s Meeting Season

Just flew in from Miami and boy are my arms tired – rim shot.  Seriously, I just returned for the annual meeting of the American Society for Horticultural Science (ASHS) in Miami.  Always good to wander the halls and renew old acquaintances and take in the latest in Hort science.  Judging by the posters and talks here are some of the hot topics at this year’s ASHS meeting.

Horticultural applications of Light Emitting Diodes (LED) are receiving a lot of attention these days.  There are a couple of reasons for this. One, costs of LEDs are decreasing as manufacturing becomes more efficient.  Two, LED’s can be built to generate specific wavelengths of lights.  As many folks learned in biology, plants only use specific wavelengths during photosynthesis.  Therefore LED’s can be used to only produce the light energy that plants need for photosynthesis – this can greatly increase energy efficiency.  Aslo, incandescent light bulbs are being phased out of production.  Old fashioned bulbs are not very efficient (they yield about 10% of energy used as light) but the light they do produce is effective for things like phot- period lighting (i.e., daylight extension for greenhouse crops).  Since LED’s can be designed to reproduce the same wavelengths using much less energy, they may ultimately be a good substitute for incandescent bulbs.

High tunnels

Lots of interest these days in ‘high tunnels’ for fruit and vegetable production.  These are not full-blown greenhouses but simply tall hoop-house structures big enough to grow fruit trees inside.  One of the main benefits is season extension; allowing fruit or vegetable harvests earlier or later in the season than would be possible otherwise.  This is especially important when we consider the local food movement for colder climates.  There are also other, less obvious, benefits such as eliminating cracking of cherries due to rainfall.

Sensor-based irrigation systems

A hot topic, especially for the nursery crowd.  There have been rapid advances in the reliability of capacitance probes and while costs are decreasing.  In addition, there have been advances in wireless control systems.  There are still challenges for nursery growers that have to deal with a diverse array of crop types and container sizes but researchers are definitely on the path of developing sensor-based systems that will automatically turn irrigation on and off in response to real-time soil moisture measurements.  This will help to optimize plant growth while minimizing potential leaching of nutrients and chemicals.   

New and/or interesting plants/stuff

Worst post title, ever. Sorry. 

Attended the bazillionth annual OFA "The Association For Horticulture Professionals" Short Course in Columbus, Ohio last week. It’s a huge 1500-booth trade show with educational session featuring 150+ speakers. Of which I was one.  The focus used to be strictly floriculture, but has expanded to include some woodies plus lots of garden center items and marketing options. This a "wholesale" show – attendees are mostly growers who purchase propagative materials to grow on and sell to consumers.  It’s always interesting to see what’s out there…here’s a few things that caught my attention:

Sedum ‘Maestro’ from Proven Winners. They’re expanding their perennial offerings a bit, and this looks yummy.  Dark foliage and very intriguing bud/flower color combo:

Every company has loads of petunia and calibrachoa in every shade imaginable. Some new introductions are notable for their subtle, almost vintage shades.  All of these would be fun for combination planters:

‘Glow Mocca’ from the Dutch firm Florensis, now a partner with Ball Horticulture. Closest thing to a black and white petunia (or any flower, for that matter) I’ve seen.  So new it’s not in a catalog. This little photo doesn’t do them justice.

‘Suncatcher Vintage Rose’ from Ball FloraPlant.  I’m not a pink petunia person (certainly wouldn’t admit to it, anyway) but the soft rose shades and neat, small flowers were lovely.

Weird lighting in their booth makes this Ball introduction ‘Pink Suncatcher’ much more yellow than it really is – more of a straw yellow with pinkish margins.

Enough with the subtle:

This new Ecke/Dummen poinsettia didn’t catch my eyes as much as claw them out.  ‘Luv U Pink’ is indeed screaming pink, which sounds gross but actually looked pretty cool with some of lime green decor around it (kind of preppy). The distinctive small overlapping bracts are because it’s not a straight-up poinsettia, rather a hybrid with some other Euphorbia species (secret recipe!).

This fluffy ornamental kale ‘Glamour Red’ is from American Takii – an AAS award winner, grown from seed. You  just want to grab it and floof the foliage with both hands. Or maybe that was just me.  Proof that kale can be both glamorous AND delicious…

More floofiness: Dianthus ‘Green Ball.’  From Ball, of course.  An apetalous mutant for every garden!

In the "stuff" department, saw the usual assortment of greenhouse equipment, garden center supplies, etc. with one notable exception: the infiltrations of Fairies. Fairy Garden decor was everywhere.  I must have missed this memo:

Hardscaping including pavers and fences; patio furniture, trellises, etc. At least you don’t need a truckload of gravel and an entire weekend to lay a fairy patio.

Fairy plants. Especially selected for…teensyness? There really was no rhyme or reason. Just a different (and named) fairy on each tag (collect ’em all!).  My Little Pony meets Horticulture.

Here’s a completed fairy garden. That’s a container of Fairy Dust on the table. I think it’s the same as stripper glitter, just in a much smaller jar.  Missing from this tableaux? Two tiny martini glasses.

Hope you enjoyed your brief whirl through the tradeshow!