Want more bird visitors? Nonnative plants may be the answer

We’ve posted before about the native vs. nonnative conundrum, especially as it relates to invasive species.  So let’s complicate the issue a bit more by considering how birds are affected by our landscape choices.

About 10 years ago my UW colleague Sarah Reichard and I collaborated on a literature review on the interaction between birds and non-native plants.  While we know that invasive plants can displace native plants and create less biodiverse environments, the resulting impact on species like birds is not so cut and dried.  And what about noninvasive, nonnative plant species?  How do they affect bird populations?  Here are some of the practical bits of information that we found:

1)    Nonnative shrubs and trees are often chosen for their brightly colored fruits, especially those that produce them in a different season than native plants.  Winter color is highly valued by gardeners.

2)    Frugivorous birds (those that eat fruit) generally benefit from the introduction of fruiting species as an additional food source, even if the species is invasive.

3)    Birds tend to prefer fruits that are red and/or black, or that have red arils or pseudoarils.

4)    Birds tend to prefer fruits that offer the most pulp; interestingly, highly invasive plants species tend to have larger fruit displays and therefore higher bird usage than less invasive relatives.

5)    Additional food sources can allow frugivorous and omnivorous birds to expand their ranges and/or their breeding seasons.

6)    Nonnative shrubs and trees with structural features such as thorns and spikes can provide protection to small birds from predators.

It’s clear that birds are highly adaptive and will quickly learn to utilize new food resources – and in doing so, may contribute to their spread through seed dispersal.  It’s enough to make your head spin.

Here’s what I recommend for choosing bird-friendly trees, shrubs and vines:

1)     Use native species first if they are adaptable to your site conditions.  (Note:  many native species, especially those of forested environments, don’t like urban conditions.)

2)    Be sure to provide structural diversity in your landscapes – groundcovers, small dense shrubs, larger open shrubs and small trees, big trees, and vines – to provide shelter and nesting habitat.

3)    Before choosing nonnative species, check the web for information on invasiveness.  The USDA Plants Database (http://plants.usda.gov/) has information on invasive species.  If it’s invasive, please don’t plant it!

4)    Birds see best in the red end of the color spectrum, so select plants with fruits and flowers that will attract them. 


Water is the answer!

Wildlife week continues!  My humble experience with my own gardens past and present, as well as our campus garden, is that the presence of water virtually guarantees the presence of wildlife.  One of the National Wildlife Federation’s top requirements for becoming a  Certified Wildlife Habitat is “supply water” (another requirement: "$20 fee").   Water is, of course, the beverage of choice for most animals (though I did hear of a squirrel that preferred beer). And some creatures require it as a substrate in which to reproduce (that sounded a bit clinical).  Unfortunately, the popularity of water gardening, according to garden trend surveys and such, peaked in the late 1990’s and has decreased since.  I’d imagine this goes hand in hand with the desire for “no maintenance” landscapes. Whatever. I will not have a garden without moving water in it.  

Our first pond-building experience. Dig 11′ x 16 hole with concentric steps. Place excess soil behind pond to create stream/falls/unintended volcano. Line, add river stone and gravel. Add water and LOTS of plants to disguise said volcano


True story that has nothing to do with wildlife*: We put this house up for sale one spring when the garden was kickin’. Within 10 minutes of the Realtor putting the sign out front, a truck drove up. The couple walked straight to the pond (at this point outfitted with a spiffy patio) and said "We’ll take it."  I said "don’t you want to see the inside of the house?" and the young woman responded "Sure, I guess we need to."  Sold it at 99% of asking price. Never underestimate the value of landscaping!!!

Back on topic…The sound of moving water is an essential part of the experience for me. Makes pulling weeds in the vicinity almost pleasant. Fish, tadpoles, snails, and salamanders populate our wee pond.


Watching the birds bath on the shallow gravel beach is delightful. The pump runs all winter, keeping the water moving and mostly open.  I’m pretty sure that in the dead of winter, it’s the only unfrozen water source for quite a distance, judging from the multitude of critter tracks in the snow.

Water makes a garden more pleasant, adds value to our home, and increases the odds of survival for the wildlife during the toughest times of drought and cold.  Now get digging.

*Actually, there was a wildlife-related incident…when the buyer’s Realtor took them down the exterior steps to inspect the cellar, he reached inside the door and put his hand on a 5′ long black snake wrapped around the light switch. That was almost a deal-breaker.  Point being…if you create a wildlife-friendly yard, they will  come.  All of them.

The Garden Professors Go Wild!

It’s ‘Wildlife week’ on the Garden Professors.  One of the most common questions that we get when speaking to garden groups is, “What can I do around my home to promote wildlife?”   My stock answer used to be, “Throw a party!”, but only a handful of people ever got it so I’ve backed off of that one.  Anyway, since the subject of gardening and wildlife comes up so often we’ve decided to dedicate a week to the topic.

Questions about wildlife (the animal kind) always take me back to my undergraduate forestry days at Washington State University and Dr. Zamora’s Wildlife Management course.  Even though I’ve always been more of a plant person than and an animal person, I found this to be a fascinating course.  In fact, assembling the winter browse twig ID collection was one of my proudest undergraduate achievements.  Doesn’t seem like much; but try wandering the Palouse hills in the dead of winter and see if you can indentify 50 browse species without the benefit of leaves, you’d be proud too!  In addtion to a notebook full of mounted twigs and a mild case of frostbite, I took away from the course several key principles of wildlife management that have stayed with me over the years.

What do wildlife need? In general, all wildlife need four basic elements: food, cover, water, and space.  The specific types and amounts of these elements, of course, will depend on the type of wildlife you wish at attract.  Homeowners can provide or enhance these elements through plants or through other, non-living means.   Important non-living components include feeders, bird-baths or other water features, piles of rocks or sticks (provide cover for small animals), salt, and standing or fallen dead trees (provide habitat for cavity-nesting birds and mammals).  Plants can provide both food and cover.  Important plant components in designing for wildlife include evergreen conifers for cover, summer fruits and berries, fall fruits and seeds, winter fruits and seeds, flowers that provide nectar, and trees that provide nuts and acorns.

At this point the questions often turn to the importance natives versus exotics.  In light of Doug Tallamy’s book, Bringing Nature Home, many people assume that only native plants can serve these functions.  But there are several factors to consider here.  First, Tallamy’s discussion is largely focused on co-evolutionary relationships between native plants and native insects, and even here some of the reasoning is stretched thin (see Linda’s Feb. 12 post).  There is more to supporting wildlife on a broad scale than insect/herbivore interactions.  Non-invasive exotic conifers, for example, can certainly contribute winter cover, vertical structure, and edge effects.  And, while some animals have evolved very specific diets (think koalas and eucalyptus), many herbivores are generalists and in some cases even prefer to feed on exotics.  So, in thinking about wildlife it’s important to consider function and providing the elements animals need than to simply fixate on whether plants are native or exotic.  This is especially true on tough, disturbed sites where natives may be poorly adapted and unable to survive.  Habitat provided by an exotic will be preferable to no habitat at all.

Lastly, another factor to consider is whether attracting wildlife around your home is always a good idea.  Along with the wildlife we’d like to see, improving habitat may increase the likelihood of running into critters (skunks, raccoons, possums) that we’d rather not encounter on the way to take the trash out late at night. Also, in many parts of the country, people and their pets are encountering large predators such as cougars and bears with increasing frequency.  Obviously a lot of this is due to human encroachment into the predators’ habitat, but it may be prudent to consider a ‘defensible space’ strategy as we do for wildfires. Keep the elements that are likely to attract larger animals a safe distance from the house.  Stay tuned for more as ‘Wildlife week continues’.

NOTE: Thanks to my high school choir-mate and college soccer team-mate, Tim Schlender for the timely wildlife habitat cartoon.

Mysterious glowing object identified!

Ed, Wes and Paul all correctly identified Friday’s flower as a morning glory, probably an Ipomoea spp.  (They also made me feel rather soiled for pedaling flower porn.  Sheesh.)

What I find fascinating about these flowers is the unearthly glow at the center.  They’re pollinated by bumblebees among other species, and bees see best in the blue-violet-ultraviolet range.  If we were able to see this flower under UV light, you’d see those white areas become completely dark, creating a bullseye for bee approach.

Here’s why the white areas turn dark.  The pigments in a white flower are flavonoids, which absorb UV radiation and reflect visible light.  We don’t see into the UV range, so to us they look white (all that visible light bouncing back).  But bees and some other insects do see UV light, and these flavonoid pigments create patterns to help them find nectar and pollen.

Glowing mystery

Here’s a snippet of a photo I shot this summer:

What is this mysterious glowing object?  (I did not manipulate this photo in any way other than to crop it) Answer Monday!

By the way, Lynn asked if we could do a posting on how to make our landscapes more wildlife friendly.  We’re doing even better than a posting – we’re doing a whole week’s worth of blogs on the topic!  Thanks for the suggestion – and the rest of you feel free to suggest topics as well.

Big Trees for Crime Reduction

Like Linda, I believe that we don’t plant enough bare-root trees.  Trees that are harvested and sold bare root tend to establish better and recover faster from transplant shock than trees sold in containers or as B&B (balled and burlapped) stock.  But, in general, trees that are purchased in as bare-root stock are smaller than the other two styles, with B&B generally being the production method which yields the largest trees.

I disagree with Linda that, as a general rule, B&B stock should have its roots washed off prior to transplanting — I’ve done it and I’ve lost trees.  Most of the B&B trees that I know of where root washing has been successful have been small, relatively easily transplanted stock.  Once we have a few nice, big, long term studies that shows that B&B trees with their roots washed perform comparably to, or better than, normal B&B trees I’ll start to believe.  (I will note that, as a rule, it looks like B&B stock is dug and cared for much better here in Minnesota than Washington!)

I’m not going to go into the nuances of the arguments here — we’ve done it before if you want to check the archives.  But what I am going to point out is that a new study in Oregon has shown that bigger trees might help to deter crime.  Yet another reason for the people of this country to demand larger stock.

Despite what all of the research shows (that it’s better to plant smaller trees — preferably bare-root) people want big trees — they want an instant landscape.  They want it because to them it looks nice — and now its a way to protect your family too.

Historically this big stock comes B&B and is very expensive, cumbersome, and not the easiest things to successfully plant.  We need a new, cheaper way to grow large stock.  A number of researchers are working on different methods to produce large stock (special containers, bare root from a gravel bed) but nothing has worked out perfectly yet.  It’s going to be interesting to see how all of this shakes out in the future — especially with the loss of ash trees in the Midwest.

Newsflash: trees will die if their roots can’t establish

I’ve blogged before about the importance of getting tree roots in contact with the landscape soil during transplanting (you can find those posts here, here, here, here, and here). My advice to bareroot woody species upon installation is often ignored in favor of the quick-n-easy methods so often showcased on HGTV (“A complete landscape makeover in a weekend!”). And of course everything looks great…for a while. Let’s see what happens after a few years.

Below are photos of a pine tree, several of which were installed in 2007 at my children’s school (The Bush School in Seattle):


Not only is this pine tree planted too deeply (you can’t see the root flare, so it’s too deep), but the twine and burlap were not removed, leaving the roots encased in clay.  Furthermore, we’re not sure how great a root system this tree has since we can’t see it.  Even more horrific, the orange nylon twine is beginning to girdle the trunk.  What’s been planted is a big ball o’ trouble.

I sent these photos and my concerns to the administration and advised them to have the installers (low bid, of course) redo the planting before the one year warranty expired.  My advice was ignored, and here we are three years later:

This particular tree has declined to the point that the foliage is chlorotic and the uppermost needles are dead.  It’s symptomatic of a root system that has failed to establish, which is what I predicted would happen.  But it’s long past the warranty period, so if this tree is replaced the school will have to pay for it…again.  (Though it’s hard to see in this compressed photo, the pine next to this one also has top dieback, and I’ll continue to follow its decline.)

Many professionals, including some of my fellow GPs, disagree with the bare-root approach.  But based on this evidence, how could one argue that bare-rooting would not have been preferable to decline and death?