Ecology of Quaking Aspen in our Yard

The quaking aspen (Populus tremuloides) performs diverse and intricate ecological roles in our garden and might be the most important plant for wildlife in our yard. In the wild, quaking aspen occur in a wide variety of habitats ranging from riparian areas to dry hillsides, and in the garden, aspen can be planted in a variety of locations especially if it receives partial shade or water. In our yard, they thrive in the absence of supplemental water- in its place we planted them where they will receive some shade.

In the wild, quaking aspen provide important breeding, nesting and cover habitat, and forage for a variety of birds and mammals. Quaking aspen is host to a variety of insects, some of which are important foods for other animals including woodpeckers. Wildlife species consume nearly every part of aspen at one time of the year ranging from the roots, to shoots to bark and catkins. Because of this, in the wild, it is truly a keystone species in many habitats.

Quaking aspen are native to the Missoula area, though they are probably at the edge of their range. This location can cause stress and make them susceptible to a variety of pests.

Though a beautiful tree, quaking aspen are maligned by many urban foresters because of their tendency to sucker, and for their predisposition to borer beetle infestations. However, borers are just one of the many insects that use the aspen.

Here is how it often goes…In our yard, it might begin with the bald-faced hornet looking for nesting material. The hornets chew the aspen bark, and mix it with their saliva to create their papery nests. The holes they create in the aspen bark allow the aspen borer beetle (see photo above), to easily open up the cambium to deposit the eggs (more on this later…). Bald-faced hornets are big and mean looking, and often mistaken for yellow jackets. Bald-faced hornets are truly beneficial in your garden, and they even pollinate flowers as summer goes on. One of their main prey is yellow jackets and they even lie in wait for them near food sources. You have probably noticed the two species near a food source, but, watch closely, and you may see the bald-faced hornets ambush and kill yellow jackets. Frankly, I am not a huge fan of yellow jackets, so this is pretty neat and gratifying to see.

Back to the borers. Once the adult borer lays its eggs in the bark of the aspen (see photo above, and notice all the pock marks on the aspen bark from bald-face hornet gnawing), the cool stuff really starts to happen. The aspen borers are a type of long-horned beetle (named for the very long antennae in adults- not for horns, unfortunately), and the one we have in our yard is Saperda calcarata, (also called Poplar borer). Some of these insects may reach two inches long, and are very well camouflaged mimicking the texture and colors of aspen bark and fungi (see photo below). The entire life cycle (from egg to adult) takes about three years in our area.

The borer's eggs typically hatch within two weeks, and the newly emerged larvae chew through the bark, where they spend the first year. As the larvae grow, they eat and tunnel through the wood deeper into the heartwood and sapwood for two years. This tunneling produces the bulges and lumps you see in the trunk. All the while, they force coarse shavings, like sawdust out the holes. In the summer, you can literally watch this happen – just look for fresh sawdust at the base of an aspen at follow it up and you will see saw dust emerging from holes in the trunk. If you look closely enough, you may even see the larvae. The chewing and tunneling weakens the tree and allows the invasion of canker and fungi.

The accumulation of saw dust and borings beneath the aspen is home to the chrysalis of several moth species in our yard including the five-lined sphinx moth. Whereas butterfly caterpillars often pupate in a chrysalis that is suspended beneath a leaf or twig, sphinx moth caterpillars burrow into loose, dry duff to pupate. The loose, dry wood shavings the borer larvae produce is perfect for sphinx moth caterpillars to excavated and pupate within. The chrysalises are dark brown to almost black and look nearly dead. If you do find one when you are rooting around, if you watch carefully you might be able to see it move. Just place it back into the ground.

The five-lined sphinx moth, or commonly called a hummingbird moth, caterpillars are specific hosts of the Oenothera flava (yellow evening primrose) in our yard. The giant caterpillars have marking on them that mimic the shape of the narrow, serrated leaves- fantastically camouflaging the 4” caterpillars (see photo below).

As a result of the larvae boring though the tree, the holes “bleed” or produce sap you can see running down the sides of the aspen. This sap is a great food source for a variety of insects, including butterflies. In our yard, the mourning cloak (Nymphalis antiopa, the Montanan state butterfly) is especially fond of it, and sap is its primary food. The mourning cloak only lays its eggs on twigs or in the shallow cavities of the quaking aspen, or related species, where the adults and caterpillars feed. In addition to butterflies, the sap attracts a variety of other insects from ants to yellow jackets and ultimately bald-faced hornets, which prey on the insects, and the cycle continues.

The presence of the aspen borer in the tree further weakens the aspen making it susceptible to more invasions of aspen beetles. These stresses on the tree also cause it to sucker- which is good because at this point the aspen is on its way to dying (though it make take 6-20 years for the initial trunk to truly die and by then a sucker is there to replace it). Quaking aspen seldom occur individually, and having a cluster of them is not only more natural and more beautiful looking, but it is also a way to provide for its longevity and succession.

In the fall, after about two years of growth, the larvae will move shallower- just beneath the bark, where they pupate during the winter. In February, in our yard, downy woodpeckers will drill into the bark looking for these pupae. In doing so, the woodpeckers drill holes that will create small cavities for insects to hide, lay eggs and even for adult aspen borers to deposit the eggs of a new generation. Once fully developed, the adult aspen borer beetles emerge through a hole in the bark, and spends its adult life mating, and dispersing is eggs to host quaking aspen.

The cavities and holes left by the borers create wonderful places for a variety of insects and spiders to raise their young. In turn, insect eating birds, like warblers, chickadees and others scour the aspens gleaning insects, spider eggs and others from the trunk, crevices and cavities of the aspen.

All this can happen around a quaking aspen in your yard, or, you could use a few types of insecticide and kill the borers.

Essentials for your pollinator garden: sap, moths and beetles.

This time of the year, the best thing you can have in your pollinator garden is sap.  There are probably lots of ways to come up with a sap feeder, but the easiest one is to let borer beetles and clearwing moths do their job- more on this in a minute.

Adult popular clearwing moth (Sesia tibialis), a yellowjacket mimic

In my garden, butterflies often owe their early spring survival to some unlikely sources- the larvae of aspen borer beetles and poplar clearwing moths.

Adult aspen borer (Saperda calcarata)

These larvae tunnel through quaking aspen (Populus tremuloides), which kills the trees, but the journey provides so much along the way (I've written a lot about this relationship- click here for more information).  As one response to the attacking insects, aspen force sap out of the tunnels.

Larvae of the aspen borer beetle (Saperda calcarata)

Over the last couple of weeks we've had several butterflies in the garden including a few Milbert's  Tortoiseshell (Aglais milberti) and even a Mourning Cloak (Nymphalis antiopa, our state butterfly) yesterday afternoon.  Judging from local blogs, Facebook, and actual interpersonal communications with people, other "out and about"  Missoulians are noticing them, too.

You may be wondering what they the butterflies ares eating, because if you have been looking around for the last few weekend, you'll have noticed that not much is flowering yet.  As a result, this is one of the most critical times of the year to support butterflies in your garden (or at least attract butterflies to your yard).On warm March days you can see the sap running (slowly) out of the holes in the trees, and when the first butterflies emerge this is where they go to eat.

An adult Lorrquin's admiral (Limenitis lorquini) feeds on sap on our aspen .

What butterflies need is a food source timed for their survival.  When many of our overwintering butterflies emerge from their hibernacula they are hungry.  With not much of anything flowing now the best food source is sap.

If you want pollinators, plant a lot of native plants and get out of the way!

and the story continues...

I could hear their chewing from across the yard. Granted, we have a small yard, but they are small animals, too. The chewing I heard was the female aspen or poplar borer beetle (Saperda calcarata) enlarging a hole in the bark of one of our quaking aspen (Populus tremuloides) to lay eggs of a new generation of long horn beetles. Over the last couple of weeks, the adult borer beetles have been mating in our yard, and the females have been laying eggs. One of our aspen, one we planted about nine-years ago is finally starting to succumb to the damage the borers are causing, and I am totally fine with this. Aspen are some of the most interesting and important trees in our yard, not because of the trees themselves but rather for the complex role they play in wildlife in our garden (read here).


Back to the dying aspen, ... I am actually looking forward to this aspen trunk dying (it is one of the largest trees in our yard) and becoming a standing snag (read here for more info). The diameter of this aspen is such that a black-capped chickadee or red-breasted nuthtacth could excavate a nest in its trunk, and there is already some progress to that end. As a result of the aspen borer life cycle, downy woodpeckers excavate the larvae in the late winter/ early spring when the larvae are close to the surface. The holes that the small woodpeckers create later become the beginnings of a cavity that chickadees and nuthatches will enlarge and excavate.

Even though this trunk is dying, this one has suckered and spread (a response to stress) and before long, a new aspen (or several will take its place). So by letting the borers do the work, we get several new aspen, a new snag, a lot of entertainment and wildlife habitat.

winter in the wildlife garden

It is cold and getting colder. Temps are predicted to be around -20 degrees F (not including wind) and highs are forecasted to be in the low single digits for the next few days. And, on top of that, there is the wind. It is below zero now, and it is only getting colder. This is an important time to think about wildlife in the garden.

While working in my woodworking shop yesterday (where it was very warm, by the way), I spent a lot of time watching birds and what they were up to in the garden. It was a lot of fun and gratifying to see the wildlife garden in action. I even braved the cold and -20 degree wind-chill to take some pictures (maybe “brave” is too strong of a word).

Winter roosts
The northern flicker in the photo above has been spending the night in the nest box to escape the cold. This is the same male that excavated the nest box this past spring and raised a clutch in our yard (he has a distinguishable nape crest). Although it is important to clean and fill nest boxes annually, especially ones that you fill with nesting material (see here for information), it is important to leave these boxes empty for the winter and not refill them until February.

Brush piles, bird nesting boxes, snags and rock piles are such important features for a variety of wildlife species in the garden. These elements allow birds and other animals to escape conditions that would otherwise be inhospitable and unavailable in a "clean" yard- that is a yard with only a manicured lawn and some nicely pruned specimen trees.

Feeding
We don't feed very much, even in the winter by most standards (click here for more information). Our primary feeder is our garden- the seeds, berries, insects and others results of our garden design. For example, downy woodpeckers are spending a lot of time drilling our aspens looking for borers (click here for the fascinating, never ending borer story), and flickers are emboldened by the cold to excavate our anthill in search of cold weary (and defenseless) ant. These are the most reliable and most diverse feeders we have.

Pictured above is a song sparrow sitting on one of our fallen snags eating seeds from an aster. We do feed suet in the winter (click here for directions to build an easy one), and black sunflower seeds though not the latter for some time. Just having suet available for winter birds, seems to attract the fewest pest species.

Knowing what species are likely to visit your feeders is important in determining what to set out as food. Generic “bird food” usually end s up unused or wasted, or attracted non-native or pest species (like eastern squirrel species, European starling, house sparrows or house finches). In our yard, the primary winter birds include black capped chickadees, red breasted nuthatches, northern flickers, dark eyed juncos, downy woodpeckers, and others.

One unconventional feeder that is really effective is a natural suet feeder. Though this might look a little odd to some, a deer, elk or antelope carcass is just what lots of birds love, including chickadees, nuthatches and magpies. This is what store-bought, conventional suet feeders try to imitate. After butchering game, I will usually hang a ribcage in the backyard for birds to peck at and feed on. Yesterday as I watched, the chickadees and nuthatches never went to a typical suet feeder, but rather spent all their time feeding on the deer ribcage. Consider hanging your ribcage for the birds, or if you don’t hunt, and you are interested in adding a conversation piece/ feeder to your yard, stop by a wild game butcher, I am sure they will give you a ribcage.

A new chapter in the quaking aspen and longhorn beetle story

The longhorn beetles aka aspen or poplar borers (Saperda calcarata) have hatched and lots of animals are after the larvae before they burrow deep into the quaking aspen (Populus tremuloides). This is just another chapter in the fascination ecology of quaking aspen and longhorn beetles. In order to determine how long it takes for the eggs to hatch, I labeled the places where female aspen borers laid their eggs (click here for more information), and I have been periodically checking back in on the egg masses (yes, this is the kind of thing I wonder about).

It turns out, it takes about 2.5 weeks for the larvae to hatch (which is consistent with the literature). I first noticed they hatched when I saw ants congregating around the egg mass locations, pulling the newly hatched larvae out (see photo below).All this activity on the aspen did not go unnoticed. Soon, bald-faced hornets moved in, displacing the ants, feeding on the larvae. And, if you recall, this is where the whole story began, with bald faced hornets chewing bark to mix saliva to make their nests.

It did not take long before any of the surviving larvae burrowed deeper into the cambium, protected from ants or bald-faced hornets. However, still shallow in the trunk or branches of the aspen, they are easy prey for woodpeckers. Last night a hairy woodpecker showed up. You can see in the photo at the beginning of the post and below this male hairy quickly drilled a hole into the aspen and spent the evening eating the borer larvae.

The ecology of yellow evening primrose in our backyard

There have been several great blog posts about pollinator plants and pollinator gardening, calling attention to both the good and the bad. (the latter post very articulately describes the problems with pollinator gardens). A while back I wrote about my disdain for the trend that was pollinator gardening. OK, disdain is way too strong, but you get the idea.

In honor of national pollinator week (June 21- 27), Kelly Senser from the National Wildlife Federation compiled favorite pollinator plants from gardeners from across the country (click here for the story). In this, I wrote about one of my favorite plants in our garden, the yellow evening primrose, (Oenethera flava). Tonight my wife and I watched as one of our yellow evening primroses opened- click here for a video of it happening (the action really picks up at 55 seconds).

Though the flower is gorgeous, large and showy, the real reason I like it so much is it offers a wonderful microcosm of wildlife gardening. In short, the primrose is moth pollinated, because it flowers at night. That is pretty cool in an of itself, and probably not that typical in the run of the mill pollinator garden. However, the neat thing is this is the host plant for a moth that does not feed on its nectar, since it is a daytime flyer: the five- line Sphinx moth, also known as a hummingbird moth. And where this whole story gets more interesting, and typifies the intricate plant/ insect relation ship is that even though the eggs and larvae are tied to the primrose, it needs something else to complete its life cycle- soft duff or sawdust.

In our yard it finds fresh, loose sawdust at the base of our aspen (Populus tremuloides)trees. The reason for this accumulation of saw dust is that the trees are invaded by the larvae of a long horned beetle- the aspen borer (Saperda calcarata). As the larvae tunnel through the aspen they force out sawdust that collects around the base. Also, as a defence, the aspen pushes sap out these wounds. The sap is a critical food source in the early spring for many species of butterflies that overwinter as adults like the mourning cloak or Lourquin's admiral (shown below feeding ion the sap of an aspen).

So, from this one example you can see how interesting and intimate the association of plants and pollinators are. Furthermore, you can also tell how unrelated some of these plants and animals are. Provide native species, and diverse assemblages and you will be rewarded with much more productive "pollinator" gardens than if you tried to plant a garden for pollinators.

Quaking aspen, longhorn beetles, and the wildlife that love them

Based on searches directing people to this blog, adult aspen borers (Saperda calcarata) are very active in people's yards and on their quaking aspen (Populus tremuloides) trees right now. The insects themselves are fascinating, beautiful and downright crazy-looking. And although I love the intrinsic value of having the borers using the trees in our yard to complete their life-cycle, the complexity of their relationship to other species is enormous. As I have mentioned, aspen are probably the most important plant species in our yard for attracting and providing the needs for diverse species of insects and birds.

The photo above is of an adult Lorquin's Admiral (Limenitis lorquini) in the picture it is feeding on the sap from the damage the larval borers cause. Likely it is also drawn to the aspen to lay eggs; Populus species are the host plant for Lorquin's Admiral caterpillars.
Adult borer activity probably peaked in our yard a week or so ago, but a few adults (see below)can still be found mating and gravid females laying eggs (like the one above). I have received some wonderful comments from people (some on some blog posts and some via email), that are finding a new appreciation for these animals.

Build a Mason Bee House in 5 Minutes

It is National Pollinator Week, and I figured a way to commemorate this was to build a mason bee nest box (more on this in a little bit). For Missoulians, a great way to celebrate this is at Thursday night's native plant sale with information about pollinators- including mason bees.

Unlike non-native honey bees that nest in hives with many others, native mason bees are solitary and each female builds her own nest. I think it's cute that although these are "solitary" bees they all nest right next to each other in communities, but evidently they have it worked out so they maintain their own identity. Anyway, they nest in cavities in logs, snags and decadent trees from woodpecker or wood boring insect holes. They also nest in hollow reeds and canes (like raspberries). As a result of the loss of native plants, removal of dead or dying trees, etc... many suspect that they are nesting site limited and by providing artificial nest sites (houses) we can help their populations.

Mason bee houses have been around for a while but I’ve been reluctant to build a house for them. Maybe it’s because I liken these houses to butterfly houses (that don’t work and cater toward yellow jackets). Or maybe it was because I thought by providing snags in the yard and or borer hole-filled aspen; we were providing more natural places for mason or other solitary nesting bees. So I did some research and in addition to a surprising amount of literature on the topic, I came across a great literature review that evaluated the efficacy of intervention (people trying to help out bees) on bee conservation: Bee Conservation: evidence for the effects of interventions Lynn V. Dicks, David A. Showler & William J. Sutherland Based on evidence captured at www.conservationevidence.com.

Here is a brief summary:
Yes, mason bees do use the nest boxes (so they have a leg up on butterfly houses). However, in one study in California, introduced European earwigs and introduced European leafcutter bee species used the boxes, and in one instance these introduced species were more common in the houses than native bees.

What about plastic nest cavities or using plastic straws?
Nest boxes with plastic‐lined, plastic or paper tubes were worse for bees than houses with simpled bored wood nest holes. The main reason was mold and even increases rates of parasitism. This is not surprising that just drilling out wood holes more naturally mimics a natural hole in wood. Don’t use plastic or straws.

But the big question: Does this help populations on a larger scale, that is does it boost local populations? In reviewing several studies, the answer is unfortunately not really. The results were mixed, in some studies it seemed to help for a while in other studies there did not seem to be an effect. Kind of disappointing.

Despite the less than exciting results, I decided to go ahead and build some and see for myself. If nothing else, they are pretty fun to have in the garden and I am looking forward to checking on them and learning more about mason bees. But really, the thing that I think put me over the edge is I learned that these make great flicker feeders. I figured this out inadvertently since all the descriptions I read about making mason bee houses involved a phrase like “cover with chicken wire to keep birds out”. At first I was puzzled, since I knew no birds could get into the 5/16” diameter hole. But then I figured out what keeping birds out really meant.

This is the second installment of building things for your wildlife garden in 5 minutes (click here for the first- a suet feeder). This bee house is a great project to do with kids or just with the kid inside yourself. This is also a great project to make out of scraps you have on hand already, or a great use for recycled materials commonly found at Home ReSource.

Materials:

• 1/4” peg board*
• 4"x4"x 12” or so
• 1"x6"x18”*
• 5/16” drill bit
• Drill
• Saw
• Screws
• clamps*

*optional

Step one
Cut 4x4 to size, cut the top at an angle to help shed water

Step 2

Use pegboard as a template for holes, align on 4x4, and drill 5/16” holes, about 3" deep (if you are using a 4x4- just don't drill all the way through the wood). The bees really don’t care if the holes are nicely arranged, and really you could skip this step of putting on a template, but I think it looks nicer.

Now, if you want, you are done. But, there is more if you are interested.

Step 3

Install top and back with screws- having the back on this allow for easy mounting on walls or posts. Now, you are done (again). All that is left is to install, and here are some tips:

• Place 3-5 feet off the ground
• Place east or south-east facing in a place where you can easily observe it
• East is best so the little fellas can get all warmed up quickly by the morning sun
• Once you install them, don’t move them until the winter
• You can place several in various locations in your yard or give to neighbors for their yards
• Try to place near a source of mud