Doug Tallamy on "Biological Corridors: Networks for Life"

The first time I heard entomologist Doug Tallamy speak was at a Master Gardener training day. It was, I think, six years ago, and it was a real “aha” moment for me. I hadn’t had a yard of my own for that long, but I was already an enthusiastic grower of native plants.  I understood some of the benefits of growing plants native to the local area: they were less likely to require a lot of maintenance once established, less likely to become invasive, helped establish a sense of place, helped support wildlife, etc. What hadn’t occurred to me, or to a lot of other people, I think, was the critical importance of native plants as a food source for native insects.

In that talk, and in his subsequently published book Bringing Nature Home:How Native Plants Sustain Wildlife in Our Gardens, Tallamy explained that most native insects have evolved to feed on only a small number of native plants. Without these specific plants, the insects can't survive. This in turn impacts the species that depend on insects for food; for example, the vast majority of migratory birds raise their young on insects.

Other animals also rely on insects for some part of their diet. Without native insects, a huge food source disappears; non-native plants are far less productive of insect biomass. These insects, in other words, are a critical part of the food webs on which life depends. The lawns and non-native plants of suburban lawns and gardens do not provide food for native insects – they are basically food deserts. Tallamy thus built a quite compelling case for homeowners and gardeners to incorporate native plants into their yards and as much as possible.

Last week I heard Tallamy speak again at a Master Gardener training day. This time his focus was broader: on the need for biological corridors, which, he said, are not just corridors for animals to pass through, but habitats in themselves. At this point, he maintained, biodiversity cannot be sustained by parks and preserves alone. We must restore land between existing landscape fragments, everywhere. Obvious places to do so are along roadways and power lines. Roadways can be planted with trees; power lines, as they pass through the landscape, are usually mowed and can be good edge habitat. Beyond that, if we turned half of all existing lawn into habitat we would be creating a "Homegrown National Park" of over 20 million acres, which would go a long way toward protecting future biodiversity.

We gardeners are lucky, I think. We can hear and understand the message about loss of biodiversity, which is pretty dire. At the same time, we’re in a position to contribute to a solution, simply by doing something we love, gardening, with  nature instead of in opposition to her. “The landscape challenge of our time,” says Douglas Tallamy, “is, more plants!” That’s something to make any true gardener’s heart beat faster!

Early summer perennials

I love how the perennial garden is constantly changing. There are seasonal changes, of course, but also changes from year to year, as plants manage to redistribute themselves within a particular bed - more of this, less of that.

My early summer garden this year has acquired an abundance of Asian lilies, mixed in with the natives and cultivars. Although native plants are my passion, I like the way the lilies look mixed in with the red of the bee balm, the orange butterfly weed, and the white swamp milkweed cultivar, 'Ice Princess.' 

I've decided not to begrudge the lilies their place in the yard as long as they don't become too prolific. The lilies won't last much longer anyway, and then I'll cut their thick stems back.  And I'll have my eye on them next year!

Bottle gentian and bees

The bottle gentian, Gentiana clausa, is a fall-blooming plant; the deep blue flowers provide a welcome splash of color as the summer-blooming plants die back  Also known as closed gentian, the mature flower looks like it is about to open but never does.

I wondered how such a flower was pollinated, and read that it is done by bumblebees, the only pollinators strong enough to force open the flowers. So I started watching. I had assumed that the bees would force the flower open from the top. But from what I observed, the bees clasp the bottom of the flower, facing downward to get pollen from the base. Fascinating!

The garden at mid-summer

It's been a very hot and dry summer here in Maryland, but a few replenishing rains recently have helped. The front garden, a mix of native and non-native, is doing well. Now that my rain barrel is full again, I can give the plants supplemental water without guilt.

The big stories of the moment - hummingbirds and tomatoes. On Sunday as we were getting out of the car I saw that the cardinal flowers in the front garden were starting to bloom, and I wondered when the hummingbirds would show up.  No sooner did I have the thought than two appeared, one hovering over the cardinal flowers, the other perusing the purple blossoms of the chaste tree. Last year I had a female virtually living in the yard for much of the summer -- I wonder if she is one of the two? So now, the quest for a really good photo of a hummingbird begins anew.

The tomatoes have puzzled me for awhile. All have had clusters of green tomatoes for weeks, and none seemed to be ripening, although now the Brown Berry, the Yellow Pear, and the Costaluto Genovese have begun. But the Brandywines and other large tomatoes remain resolutely green. I googled "tomatoes not ripening" and came up with 3 pieces of advice: 1) be patient, 2) cut back on water, and 3) fertilize. It had never occurred to me that it would be possible to water a potted tomato too much, and I'm still not sure about this, but I am cutting back just a bit. I sure want those big green softballs to fulfill their delicious potential.

More bees

It did indeed prove too late for the bee tubes I set out. I brought them inside so they'll be fresh for next year. I'll plan to set them out early next spring - March, I guess.

In  the meantime I've turned into a bee watcher. I don't see many butterflies in my yard, but I have lots of bees!  When my Penstemon digitalis started blooming I began to notice that there were always bumblebees hovering over the white tube-like flowers. I began watching more closely, and saw bees disappearing into the flowers, emerging a few seconds later to fly on to the next flower. It became a sight that delighted me: the glove-like fit between the flower and the bee, the idea that each is benefiting from the bee's visit.

Of course, I wanted to get the perfect picture, of a bee just about to enter a flower. This proved to be about as challenging as my attempt last summer to get a really good hummingbird picture. After many tries I've gotten a few that I like, but the quest continues.

Native groundcovers for the Mid-Atlantic

I've been trying various groundcovers, mostly those native to the mid-Atlantic region, for different parts of my yard. One of the tough spots is on a slope under a large silver maple. It gets some eastern sun in the morning, but is mostly dry shade. The Pennsylvania sedge (Carex pensylvanica) I planted a couple of years ago is doing well and starting to spread. It is a pretty little grass-like plant that grows about six inches tall.

Last year I added Sedum ternatum, also native around here, and it has come through the winter well.

At the native plant sale at the National Arboretum, I picked up some Pachysandra procumbens after one of the vendors told me her sister had good success growing it under a large tree. I believe it is native a little further south than where I live in Maryland, but it will sure beat the non-native pachysandra, which I have plenty of in other parts of the yard. It's still dormant right now, so I'll have to see how it does.

Lahr Symposium on native plants

The annual Lahr Symposium on native plants was held this past Saturday at the National Arboretum in Washington DC. I've gone for the last couple of years, and for more years than that to the native plant sale that accompanies it. It's a great event, and it's held at a great time of year - when spring is just getting underway. I always look forward to seeing the massive cherries in bloom at the Arboretum. Yes, I know they're not native, but aren't they magnificent?

This year two of the speakers, Darell Morrison and Bill Cullina, spoke about aspects of designing with native plants. Morrison, a Fellow of the American Society of Landscape Architects, talked about some of the large-scale projects he has designed using natives. Cullina talked about different botanical features of plants such as color, form, leaf variegation etc. can be used to advantage in the garden.

The third speaker, Kim Winter, talked about attracting wildlife to the garden. It was particularly interesting to me that she mentioned solitary bees. I had just recently read a short article about using small cardboard tubes as nesting cavities for these bees, and so it was already on my mind. She gave a link to a website I'll be exploring: pollinator.org.

I also got to go on a guided wildflower walk at the Arboretum's newly renovated Fern Hill wildflower garden. It was a chilly but sunny day, and many things were just starting to poke out of the ground, while a few things were already blooming, including Dutchman's breeches, trillium (the red one, I think commonly known as wake-robin), and one of my favorite shrubs, spicebush (Lindera benzoin) which has little yellow flowers and emits a spicy smell when the bark is scratched. Wish I had a place in the yard for one of these guys!