Bird Food Grows on Trees!

Spring is here, and love is in the air for our backyard birds! After a long winter of subsisting on seeds and berries, birds need a new menu in spring. Soon they will be mating, nesting, laying and hatching eggs, and hunting from sunrise to sunset to feed their newborn chicks. That takes a lot of energy, and it requires a special diet.

Baby birds can’t eat seeds or berries. They need the protein and other nutrition found only in insects. And, though baby birds will eat a variety of insects, their favorite food is caterpillars, the larvae of moths and butterflies. Caterpillars are soft, easily digested, and loaded with nutrients. Bird parents need thousands of caterpillars to raise even a single clutch of babies. Where are all those caterpillars to be found?

 A pair of chickadees needs 7,000 to 9,000 caterpillars to raise 3 baby chicks
Photo: Doug Tallamy

Caterpillars, quite literally, grow on trees – but only on native trees! For example, not one species of caterpillar has been observed growing to maturity (to become a moth or butterfly) on Norway Maple, a non-native tree. A bird searching for caterpillars on a Norway Maple will find nothing to feed her babies. In contrast, many native trees are hosts for hundreds of different species of caterpillars, so they produce lots of bird food.

Among native trees, some species are much more productive hosts than others. Recent studies have ranked native tree species for their ability to host caterpillars. So, which are the best trees to have around if you want to feed the birds?


The undisputed MVP of caterpillar-producing trees is the native Oak (Quercus spp.). You cannot go wrong planting a White Oak (Quercus alba), Red Oak (Quercus rubra), Scarlet Oak (Quercus coccinea), Pin Oak (Quercus palustris), Bur Oak (Quercus macrocarpa), or any other Oak tree native to our region. Oaks are host plants for over 550 species of caterpillars! Think of Oaks as the grocery store for bird families.

Though this White Oak likely holds thousands of caterpillars, it is not at all disfigured by their munching!


Second only to Oaks as caterpillar factories are the small trees in the Willow family. Pussy Willow (Salix discolor) is a great garden plant and hosts over 450 species of caterpillars. (The familiar weeping willow tree, however, is not native to North America and is not a host plant.) Our recent blog post found here is full of information about Pussy Willow.

Pussy Willow is a small multi-trunked tree great for smaller gardens
Pussy Willow in bloom supports native bees

Black Cherry

Our native Black Cherry tree (Prunus serotina) and the closely related shrub, American Plum (Prunus americana), are essentially tied with Willows as caterpillar producers, with over 450 known species using their leaves as hosts. Both also produce fruit that adult birds enjoy in the summer. Black Cherry is not often planted, but if you have one in your yard, take good care of it, and the birds will thank you. American Plum has beautiful flowers, can form a dense thicket, and is a great shrub for a privacy screen if you have some space.

Wild Black Cherry is incredibly valuable to birds
Bees, butterflies, and birds all flock to American Plum


Native birches are next in line as caterpillar producers, hosting just over 400 species of moths and butterflies. River Birch (Betula nigra) is a favorite as a landscape plant, and its crazy bark holds a variety of insects that attract woodpeckers all winter. Chickadees, warblers, wrens, and many other songbirds hunt and find caterpillars in the leaves of birch trees.

River birches make lovely landscape plants
Photo: Mia Edwards
The bark of River Birch adds winter interest


Malus, the apple tree family, hosts over 300 species of caterpillars and includes the lovely crabapples that bloom so profusely in late spring. Crabapple is another caterpillar host that is of equal value to native bees because of the pollen and nectar provided by its flowers.

Crabapple in bloom


Our native Red Maples (Acer rubrum) and Sugar Maples (Acer saccharum) host 285 species of caterpillars and are gorgeous shade trees. But be sure to choose one of these natives rather than a Japanese Maple or the invasive Norway Maple, which do not host native insect species at all.

Native red maples are stunning in the Fall

White Pine

It may surprise you to know that even our native White Pine (Pinus strobus) is an impressive larval host to moths and butterflies. Over 200 species of caterpillars develop on the needles of native pines, and many of them over-winter on the tree. If you watch carefully, you may spot birds combing the branches of pines and making trips back to their nests with juicy caterpillars for their babies.

Pine trees are also caterpillar hosts

It is often said that trees are essential to life. They pull carbon dioxide from the air and store it for years. They produce oxygen, manage storm water, improve soil, provide shade, and shelter so many animals. It is easy to forget, however, that their leaves also feed the little wiggly creatures that make life possible for all of our beloved birds. Our choices – which trees to plant, which to take down, and which to care for – have a huge impact on the world around us. Choose wisely!

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Happy Pollinator Month!

June is here — the bees are buzzing, the butterflies are fluttering, and everybody is excited about summer flowers. It’s National Pollinator Month!

At the Nature Center, we are also celebrating the first anniversary of our newest Pollinator Garden. It is astonishing to see how lush, diverse, and colorful our garden has grown in just one year!

Want to know how we did it?

The “Before” photo

Right next to our big open lawn, in a very visible spot near the beehives, there was a messy patch of weeds. The soil was poor and dry, and there was very little shade. So…the perfect spot for a pollinator garden! The first task, done by Guy Pardee of Suburban Natives LLC, was to clear the area, getting rid of all the weedy invasive plants. Then, the ground was covered with leaves and left for the winter.

After the first clearing

The following spring, we cleared it again and prepared to plant.

Ready for planting, May 2021

A good friend to the Nature Center, Bill Boyce of Biosphere Landscape Architects, came up with a great idea for the garden. We would make a literal “pollinator pathway” wandering through the blooming flowers, with signs along the way identifying pollinators. Bill did a “back-of-the-envelope” concept sketch for us on site.

The idea in formation

We roughed out the lines in the dirt, and then defined the path with mulch.

The idea emerges
Pathway lined with mulch

Then it was time to plant. We chose tough native plants — species that evolved in our region growing in open dry meadows, able to survive without fertilizer, pesticide, or supplemental water. And though we planned to water and weed the garden for a season or two until the plants were established, we wanted a garden that eventually would need little maintenance. We also needed plants that would not be attractive to deer, rabbits, or woodchucks. We made a plant list, scoured the nurseries, and bought about 450 plants in containers (with funds contributed by multiple donors).

If you would like to know which plants we selected, click on the link below.

We started in the middle, planting the “spine” of the garden with tall, deep-rooted Switch Grasses that would support the tallest flowers in the center of the garden.

The center “spine” of the Pollinator Garden

We then worked outward, planting clusters of flowering species arranged in descending height. Shorter native grasses and ground covers were added along the edges to fill in and provide texture. We planted densely, aiming to have the plants grow together to occupy all soil areas within 2 seasons, thereby reducing available space for weeds.

Plants are spaced 12 – 18 inches apart

We decided not to mulch after planting, for a few reasons. Some of the invasive plants removed from the area were deep-rooted and would re-appear soon, with or without mulch. Weeds would be easier to see and remove promptly if we did not mulch. We also hoped our new plants would quickly grow together, expanding to occupy the entire ground space, and reseed themselves freely in the garden. Mulch would inhibit those natural growth processes. Finally, mulch would prevent the pollinators we are trying to attract from nesting in the ground, as many of them want to do. We want to support pollinators through their entire life-cycles.

We finished planting the Pollinator Garden on June 2, 2021. By August 2, it was in full bloom and alive with pollinators.

Two months after planting, August 2021

As we had hoped, this spring the garden came back full and lush. Weeding is ongoing, but not as difficult as we had anticipated.

The Pollinator Garden this week, June 2022
Photo: Nick Macaluso

So, please come celebrate Pollinator Month with a walk on our new pathway, and let the pollinators give you a tour!


Click the picture below to get more ideas on how to plan and plant your very own pollinator garden.

The Trouble With Double

One beautiful spring morning, we stood under our Kwanzan cherry tree and noticed that something was missing: pollinators! Not one bee or butterfly was visiting the tree, even though it was loaded with flowers. Not far away, a blooming crabapple tree was literally humming with pollinators!  What accounted for the difference?

We realized that the cherry tree has “double blossoms.” Its flowers have been modified by humans to replace all of its pollen-bearing stamens with flower petals. The flowers are beautiful – but only to people. There is no pollen or nectar for bees or butterflies. The flowers of the crabapple, on the other hand, were loaded with pollen and nectar. And the pollinators were all there for breakfast!

The stamens are missing completely in these sterile double blossoms
The stamens in these flowers are ready for pollinators

Flowers are the reproductive organs of plants. Pollen contains the genetic material that must be transferred from the (male) stamens to the (female) pistil for pollination (fertilization) to occur. In most flowers, the petals form an outer ring and the stamens are just inside, forming a second ring around the pistil. The flower’s colorful petals, its fragrance, and the sweet juice called nectar all are designed to attract pollinators. As pollinators sip the nectar located at the base of stamens, and collect pollen to feed their offspring, they “accidentally” transfer pollen from flower to flower and deposit it on the pistil where pollination happens. Successful pollination results in seeds, which then grow to produce more plants.

But sometimes nature makes little mistakes. Sometimes a plant will develop extra flower petals where the stamens should be. This is not a good thing for the flower, because with fewer stamens there is less pollen, which reduces the chances of pollination and, therefore, reproduction. In nature, plants that continue to develop too many petals instead of stamens eventually would fail to reproduce.

For hundreds of years, however, horticulturists have been fascinated by this “mistake” of nature. Humans enjoy flowers, and we tend to think bigger and fuller flowers are better. So, when horticulturists discover a flower that has extra petals where stamens should be, they can select that plant for special treatment. They can propagate the plants with extra petals and, eventually, even develop plants with so many extra petals they have no stamens (or pollen) at all! Without stamens, of course, those plants are sterile. They cannot develop fruit or seeds or reproduce themselves.

Roses are a good example. Natural roses have 5 petals surrounding a circle of many stamens carrying pollen.

A simple rose with 5 petals, stamens with pollen, and pistil in the center

Roses frequently make the “mistake” of trading stamens for extra petals.

Note the under-developed petals in the ring of stamens

Over centuries, horticulturists have selected these “mistakes” for intentional manipulation to create roses that are more interesting to people.

In fully double roses, extra petals replace virtually all of the flower’s stamens and pollen is scarce or non-existant

Today we have thousands of flowering trees, shrubs, perennials, and annuals that are popular specifically because they have double blossoms. But this comes with a cost to pollinators. Butterflies need nectar. Bees need nectar and pollen to feed their offspring. Butterfly and bee populations are declining under pressure from loss of habitat, pesticide, and limited food sources. We can help with our garden choices.

Double peony with no stamens, pollen, or nectar
Double trillium with no stamens or available pollen
Double sunflower – native, but not useful for pollinators
Single peony with stamens and pollinator
Single trillium open for breakfast
Single sunflower and happy bumbles

We humans love our double blossoms, but if you’re making a choice, think about providing a big variety of native single-blossom flowers for our pollinator friends!

A buffet for pollinators in the Nature Center’s meadow

It’s Complicated…

You may already know that monarch butterflies need milkweed. But did you know that milkweed does not need monarchs? Milkweed is not pollinated by monarch butterflies!

Monarchs have long skinny legs, and even longer skinny tongues. They have learned, over eons of co-evolution with milkweed, to avoid the dangerous sticky sap of milkweed by carefully alighting on the sides of the flowers and lowering their long “tongues” (proboscises) into the flower to reach the sweet nectar.

Monarch sips nectar while perching on the sides of milkweed flowers

As they drink, monarchs are careful to not put their feet down inside the flowers where they might get stuck. Unfortunately for the milkweed, this means that monarchs don’t pick up milkweed pollen! The pollen is held in specialized structures inside the upper portion of the flower called “pollinia.” For pollination to occur, pollen from the pollinia has to reach the flower’s stigma, deeper inside the flower. Without successful pollination, no seeds develop, and milkweed does not reproduce.

Microscopic view of milkweed flower — pollen is held on the two yellow leaf-like parts on the right, called “pollinia”
Graphic: Rick Darke

So, if not monarchs, who pollinates milkweed? It’s not any of the other butterfly species that also visit milkweed flowers without picking up pollen. Honeybees can’t do it. They are native to Europe where milkweed isn’t native, and they are too small to be strong fliers. If they go deep enough into milkweed blossoms to reach the pollen, they can be trapped, which is not good for either the bee or the milkweed.

Milkweed needs a strong flier, with stout hairy legs that will go down into the flower, catch the sticky pollinia, and carry pollen from one flower to the next. Luckily, nature has provided just the right insect for the job: carpenter bees!

Carpenter bee with its feet in milkweed blossoms
Photo: Pixabay

Carpenter bees (Xylocopa spp.) are the most important pollinators of milkweed. Their legs are heavy and hairy, so they can step right into the flower and come out covered with sticky pollinia. They are strong fliers, so they do not get trapped, and they can carry the excess baggage. As the carpenter bee goes from flower to flower, pollen is dispersed, flowers are pollinated, seeds form, and milkweed is reproduced.

Pollinia, shaped like little yellow leaves, cling to the hairy legs of the bee
Photo: Polinizador’s Blog

Recently, friends who were developing a new pollinator garden for a historic property commented on the trouble they were having with carpenter bees burrowing into the eaves of the historic building. They said that exterminators had tried several applications of pesticide over the years, but the bees were nesting once again in the wooden structure.

Only later, when we learned of the connection between carpenter bees and milkweed, did we realize the contradiction! If we plant milkweed for monarchs in a pollinator garden, but then try to kill the carpenter bees nesting in the eaves of the house, we are pulling a thread in the complex web of life that can unravel the whole thing! If we kill carpenter bees, milkweed disappears. If milkweed disappears, so do monarchs.

When we try to pick out anything by itself, we find it hitched to everything else in the universe.

John Muir, Naturalist

So, what to do about carpenter bees? Well, they prefer to move into holes or cracks that are already established. They apparently don’t like the smell of citrus, and they don’t care for white paint. So, instead of pesticide, try filling existing holes and cracks or replacing weak structures. Apply citrus oil, or maybe re-paint. But killing them? They are definitely hitched to everything else in the universe.

Carpenter bees are very efficient pollinators of many other flowers as well

So, it is complicated. Nature is complicated. The more we learn, the better we understand the profound relationships among living things that co-evolved over millennia.

But that doesn’t mean it is difficult to do the right thing. If we simply start with the maxim “do no harm,” we can make better choices. Before we kill a “pest,” let’s understand that creature’s role in the world. Let’s avoid pesticide, apply fewer chemicals, plant native plants, plant more plants, allow a little mess for habitat, live and let live.

For more information on the complex relationship between milkweed and the insect world, see the post “ Marvelous Milkweed-Not Just for Monarchs!” linked here.


Feed That Hungry Caterpillar!

This week in Around the Grounds, we recommend two great plants for attracting beautiful butterflies to your garden.

Ah, butterflies…the “winged blossoms” of the garden! Let’s talk about a couple of our favorite plants for butterflies.

If you want more butterflies in your garden (and don’t we all?), you have to feed their caterpillars. True, adult butterflies will visit just about any flower with nectar. So yes, if you have a butterfly bush (Buddleia spp.), or other non-native flowers, you may attract adult butterflies. But you won’t be making more butterflies unless you provide what their caterpillars need.

 Not one species of native caterpillar can survive on “butterfly bush” (Buddleia spp), a non-native plant that is also invasive in many areas

Even very hungry caterpillars won’t eat just anything. They are “specialist” insects, and can only eat certain “host” plants. If butterflies can’t find that host plant, and happen to lay their eggs on whatever is around, the caterpillars will die. So, pollinator and butterfly gardens should include host plants.

In recent posts, we’ve talked about planting Milkweed for Monarchs, and Switch Grass for Skippers. Both are essential hosts for their particular butterfly friends. Here are two more important host plants:

Zizia flowering in May

Zizia (Zizia aurea), sometimes called “Golden Alexander,” is the native host plant for Black Swallowtail butterflies. Maybe you’ve seen Swallowtail caterpillars on parsley, dill, or carrot plants? Although those plants are not native to the US, they are in the same plant family (Apiaceae) as Zizia, and genetically so closely related that Black Swallowtail caterpillars accept them as hosts, and do indeed eat them. 

Black Swallowtail caterpillar on parsley
Black Swallowtail adult on Zizia

Zizia is a lovely garden plant. It likes full sun, as do most pollinator-friendly plants, and is easy to grow. It blooms in early summer and often reblooms later in the season. Its flowers are loaded with nectar, so it attracts plenty of pollinators in addition to Black Swallowtails. It prefers moist conditions, but will do fine in average garden soil.  Zizia works well near the front of the border where it typically stays under 3 feet tall.

Zizia in the garden

Another excellent host plant is Antennaria neglecta, which has the curious common name “Field Pussytoes.” Maybe the fuzzy white flowers do vaguely resemble a cat’s paw? Antennaria should be used much more than it is. It’s a great ground cover along sunny walkways or at the edge of pavement. It holds up to summer heat, and actually prefers shallow gritty soil, so it’s happy where paving has left gravel in adjacent areas. It does not do well in rich or moist soil.

Antennaria blooming in a driveway bed

Antennaria is the host plant for the beautiful American Painted Lady butterfly. We found this exhausted Painted Lady laying her eggs on Antennaria, and it looked like she was very grateful to finally have found her host plant. It shouldn’t be so hard to find!

American Painted Lady laying her eggs on Pussytoes
American Painted Lady eggs and baby caterpillars
Developing Painted Lady caterpillar

Antennaria is semi-evergreen and survives even where snow plows bury it. In the spring, new leaves come up through the old foliage, and then it starts blooming in April.

Antennaria emerging in spring

Antennaria, or Field Pussytoes, is an underused plant in our landscapes. It is a great garden plant that should be found everywhere — because we really do need to feed those hungry caterpillars!