What goes with chartreuse?

After the beautiful elms that lined our streets succumbed to Dutch elm disease in the mid-twentieth century, my town, like many others, thought they’d found great street trees to replace them: Norway maples (Acer platanoides). 

Surviving elms in New York's Central Park

After all, the maples were tough, adaptable growers that could survive the tight root space, thin, rocky topsoil, and plentiful road salt that our narrow curb strips offered.
    
    In one way, choosing these maples was a success. Almost all our streets are now lined with mature specimens. Over their lifetime they’ve rolled with the punches, putting up with limbs torn off by ice storms and passing trucks, finding water by pushing their roots under the sidewalks into lawns and garden beds, growing around holes gouged in their canopy by pruning around power lines.

Norway maple street tree-photo Famartin

    The problem with these nonnative trees is that they’re too successful. Each tree produces thousands of viable seeds every spring, packing pairs of them into the helicopter-like samaras that we see twirling to the ground. 

Winged seed pods of Norway maples

They lie in cracks in the sidewalk, in garden beds, and on any bare soil or pile of organic debris. It seems as if most of those seeds succeed in producing seedlings the following spring. 

    This is the time of year when gardeners like me become obsessed with weeding out those seedlings. We know that by next year, this season’s tender little sprout will have grown a woody stem and sent down a deep root. If we don’t catch them this year, they’ll be harder to pull with every passing year.

One-year-old Norway maple seedling, left, with this year's on right

    When we moved into our house, a dense thicket of Norway maples that soon reached 20 feet high grew behind the back fence, just because our neighbors had left some seedlings alone to grow. The trees make dense shade, their shallow roots crowd out competitors, and they exude allelopathic chemicals that keep other plants from thriving in their vicinity.

Norway maples shading the backyard in the mid-90s

Luckily for my garden, we were able to remove those trees. Their relatives have continued to colonize the city, though. 

    When the Norway maples flower at the end of April, my heart softens toward them, despite my struggle to curb their reproduction. I love the lacy silhouettes the flowers make against the street lights after dark. The rosettes of chartreuse flowers and tiny new leaves are a heartening sight when many trees haven’t yet put out any foliage. 

Norway maple in bloom

A cloud of yellow-green covers the whole city, reminding me of Robert Frost’s line, “Nature’s first green is gold.”

Norway maples paint the landscape a vibrant pale green

    In recent years, our city has gotten wise. Where street trees have died or been cut down, our urban forestry director now chooses to plant a range of resilient tree species—but no more Norway maples. Soon we’ll have a diverse mix of street trees that are less inclined toward world domination. Meanwhile, we should remind ourselves when choosing spring-blooming bulbs and shrubs that they’re going to flower against a chartreuse background. Whether we like it or not, those maples won’t disappear anytime soon.

Nesting time

It’s great to hear the dawn chorus of bird song at this time of year and see birds collecting material from the garden for nests. 

When magnolias bloom, it's time for birds to build nests

    I’ve put out mesh balls filled with feathers again to aid in the nest-building effort. An attractive ball made from bent twigs filled with fluffy raw cotton that I bought a few years ago from a catalog and hung from a branch drew no bird customers at all. I noticed that birds seemed more interested when the ball contained feathers. 

Feathers make more popular nesting material than a wad of raw cotton

    That’s when I started saving onion bags and ordered a big bag of goose feathers from a company that sells them for topping up feather comforters. I fill the bags with feathers, close them with twist ties, and hang them from branches like Christmas ornaments.

 

Onion bag feather ball hanging in a Norway spruce

It’s fun to see a bird hover or cling to the mesh to snag a feather or two and then fly off purposefully to where the building project is underway.

    The bad news is that many of the birds taking me up on this offer are nonnative house sparrows (Passer domesticus). 

European house sparrow

This highly adaptable species originated in Eurasia and North Africa and now lives on six continents, everywhere but polar areas. Flocks of house sparrows evict native birds from their nesting sites and hog the food supply.

    My goal is to foster a generous garden ecosystem where a diverse range of bird species can find the plants, insects, water, shelter, and nesting opportunities that they need. For that reason, I’ve tried to stop inviting these sparrows to my yard. Not filling birdfeeders during the growing season has made a big difference. Once the feather balls come down this summer, I won’t do anything else to encourage house sparrows to return. 

    I’m encouraged to see birds using some garden debris for building nests. That’s what I hoped would happen with the transition to intentionally bird-friendly gardening (Grow Native Massachusetts offers this guide to providing food and habitat for birds in your yard).

    This week I’ve noticed American robins (Turdus migratorius) busily flying back and forth and scolding when I get near certain trees. On Saturday I spotted faded hosta leaves hanging from a nest in a tall Japanese cedar (Cryptomeria japonica). 

Hanging hosta leaves make this robin's nest noticeable

The penny dropped: that’s why last year’s hosta leaves are migrating around the yard and showing up draped over low branches. 

The robins are picking them up to carry to their chosen nest spots, dropping some along the way. Even wilted and dried out, those large leaves must make a heavy load for a 3-ounce robin. 

I noticed hosta leaves woven into another nest located on a downspout under the eaves of the house. Saving the garden clean-up for later this spring has allowed nest-building robins to make use of last year’s leaves, stalks and twigs.

    True, hostas are Asian imports, not native to New England. If they’re useful to the robins, though, I feel their inclusion in the garden is sustainable enough. That’s fortunate, because they’re pretty too. 

Nonnative hostas and flowering astilbes in July

 

Stalking invasives--in moderation

At this time of year, every morning there’s something new happening in the garden. This weekend daffodils and magnolia blossoms opened. 

 

Star magnolia and Magnolia 'Leonard Messel' popped into bloom overnight

Also burgeoning: invasive plants. These super-survivors start early and finish late, sprinting out of the starting blocks while competitors are still dormant.

My arch-nemesis, Norway maple, gets a jump on the season

    Before everything else leafs out, providing camouflage, it’s relatively easy to spot the nonnative problem plants. Now is also I time when I’m not dizzily spinning from task to task, as I will be in May.

    First on the list, I need to check on Japanese knotweed (Fallopia japonica) that’s surfaced along the south fence line. This could be the year I stick to my plan to foil this potentially powerful land grab. I’m sure you’ve seen Japanese knotweed, because it lines highway shoulders and any other areas where soil is disturbed and then left uncovered. 

Japanese knotweed seizes any open ground

Once it starts growing, it’s almost immortal. Like many invasives, it makes lots of seeds. The underground part of the plant is the real menace, though. To eradicate stands of Japanese knotweed, the Massachusetts Department of Transportation has to remove all soil down to 3 feet and burn it. That’s because if even a nubbin of root is left, the plant will grow back. My strategy for Japanese knotweed is to cut it to the ground every two weeks. Eventually if it can’t make energy through photosynthesis, it should dwindle and die. At least that’s the theory.

Last fall I tagged this sprig of Japanese knotweed so I won't miss it

    Garlic mustard (Alliaria petiolata) is another rapid spreader in our area. It’s easy to uproot. I need to catch it all before it flowers and sets seed in its second year, though, or it’ll take over. Garlic mustard emits allelopathic chemicals that suppress other species’ growth. This is one of the few invasive plants in North America that thrives in a shady forest habitat, such as what prevails in much of my yard.

Garlic mustard impersonating an early perennial

    When I pull or cut down these plants, I can’t throw them on the compost pile. If I did, I’d be spreading the unwanted plants whenever I distribute compost. It goes against the grain to bag invasives and throw them in the regular trash, but adding them to the yard waste would pass them on to someone else’s garden.

Volunteer pulling garlic mustard at Cuyahoga Valley National Park-photo NPS/Arrye Rosser

    Of course, officially recognized invasives aren’t the only plants growing aggressively in my garden. Lots of plants I chose myself, including native smooth Solomon’s seal (Polygonatum biflorum), have turned out to be thugs that I have to beat back every year.

Smooth Solomon's seal shooting up from the leaf litter this week

    I don’t like to get too hysterical about invasive plants. They’re mostly responding to human alterations of plant habitat, diving in to pioneer newly disturbed soil. The nonnative invasives in my yard didn’t parachute in from abroad, they just made it under the fence from adjoining properties where people are less interested in policing the landscape. Spending some gardening time keeping them at bay does seem worthwhile, though. The more garden space they claim, the less there’ll be for a diverse landscape that includes native plants.

With help, I hope native inkberry will grow instead of  Japanese knotweed

   

Appetizers

It barely feels like spring to us, but there are already pollinators out foraging for pollen and nectar. Early spring is a lean time for animals, and these insects are no exception. What’s on the menu? 

    Snowdrops (Galanthus nivalis) were the first flowers to bloom in my yard in late February. 

Snowdrops undeterred by ice

These little plants originated in Europe. Their early show is so popular that people have spread them all around the world. Tiny but tough, the flowers emerge unharmed from drifts of snow dropped by late snowstorms, offering pollen for intrepid bees and flies. 

    Next the witch hazel trees (Hamamelis x intermedia) opened their spidery yellow blooms. 

Witch hazel perfumes the yard while waiting for shivering moths

I have two, both spring-blooming nonnatives, hybrids between Chinese and Japanese species. Their bright flowers and sweet scent indicate that they’re advertising for insect pollinators, but they can’t count on bees to do the job reliably this early in the year. They’re pollinated by owlet moths of the genus Eupsilia. These moths cope with March’s cold temperatures by using an adaptation unusual among insects: they warm themselves by shivering.

Owlet moth Eupsilia tristigmata-photo willapalens

    Crocuses opening in mid-March were greeted by bees who were ready to go, climbing in to grab some sustenance. 

A bee visits my favorite Dutch crocus variety, 'Pickwick'

Larger-flowered Dutch crocuses (Crocus vernus) in white and purple seem to be more popular with the bees than smaller snow crocuses (C. chrysanthus and tommasinianus) that are spreading around the front yard. All of these come from Greece, Turkey and the Balkans. 

Snow crocuses are smaller and more modest

    By the end of March, dusky purple hellebore flowers (Helleborus cultivars) are starting to open. 

Hellebores have captured gardeners' imagination with early blooms in subtle shades

You’ll have spotted a trend—these too are nonnatives. So far I hadn’t offered a single native flower for those early foragers. I’m always looking to extend the garden’s season of bloom at both ends. I’d like to offer native flowers as food for pollinators consistently from earliest spring until snow starts to fall in December.

    Lots of natives are about to start flowering. As I trundled my wheelbarrow back and forth in the warm sun this weekend, bloodroot (Sanguinaria canadensis) leaves unfurled and flowers opened before my eyes. 

Bloodroot flowers come wrapped in grayish green first leaves

Emerging leaves of yellow trout lily (Erythronium americanum) presaged the arrival of its pendant trumpet-shaped blooms. 

Trout lilies don't bloom for long, but while they do they're sublime

These are two spring ephemerals, native woodland plants that take advantage of the sunlight that reaches the ground before trees leaf out. They’re among New England’s earliest bloomers.

    When May comes, there’ll be a banquet of flowers for pollinators to sample. In my yard, the crabapple (Malus ‘Donald Wyman’) and white-blooming redbud (Cercis canadensis f. alba) will cover themselves in glory. 

I prefer the white flowers of this redbud to the more common magenta

Native shrubs will add to the show, from venerable highbush blueberries (Vaccinium corymbosum) to newer additions: black elderberry (Sambucus canadensis), Carolina allspice (Calycanthus floridus), and spicebush (Lindera benzoin). 

Carolina allspice, also called sweetshrub, has unexpectedly dark red flowers

But in February and March, it’s up to the nonnatives to provide the first meals for hungry bees.

Sheet composting begun

Blood meal came in the mail (sounds ominous, doesn’t it?), enabling my grand-dog Felix and me to start the sheet composting project. As you’ll remember, this is a technique for converting some lawn to expand a planting bed. We’d be applying layers of compostable materials to smother the grass and make rich soil for new native plants.

Purple coneflowers will be able to spread into the enlarged bed

    The first step was to mark off the grass section for execution. I did this using short stakes and some stretchy orange plastic surveyor’s tape. I can re-use the tape when this project is finished.

    After moving the stakes around to see how the edge of the new bed would look, I settled on a straight edge parallel to the nearby rectangular vegetable bed and 10 feet from the rabbit fence that protects that area. The ends of the new bed would curve into existing planting areas.

Orange tape marks the edge of the future planting area

    Next I sprinkled a dusting of blood meal on the grass and followed it with layers of newspaper. To pile them several sheets thick, I had to combine sections of the paper, overlapping them so no grass was showing. I avoided glossy supplements that might contain problematic inks. The paper wanted to blow around in the spring breeze but subsided with a generous sprinkling from the watering can. I laid down newspaper in three stages, weighing it down with the next materials before moving on so that the paper wouldn’t dry out and blow away.

I watered the newspaper to keep it from blowing away

    On top of the newspaper I spread a layer of composted cow manure. I had two bags left over from last fall, both open. Some of the contents were frozen, and I couldn’t break them up. I stood the icy parts in the sun to melt. 

Cow manure popsicle warming in the sun against the rabbit fence

In all, it took most of four 50-pound bags to cover the 120 square foot area with an inch of cow manure. I was treating the sheet composting recipe more like instructions for a stir fry than a fine pastry—just adding what looked about right.

A section of newspaper covered with cow manure

    Admonishing Felix not to dig through the manure-covered newspapers, which seemed to be an alluring possibility, I next turned to hauling wood chips from the big heap in the driveway. After many wheelbarrow trips, I’d dumped an 8-inch layer on top of the newspaper. 

Wood chip layer

I added a few inches of fall leaves that I raked from nearby beds, anchoring them down with more wood chips. That’s where the project stands as of Saturday afternoon: a long foot-tall mound of compostable layers, widest in the middle and tapered at both ends.

It doesn't look like much now. Give it two years.

    The next stage will be to pile on a layer of compost, which will boost the population of soil organisms to start the decomposition. The icing on the cake will be a topping of weed-free straw.

    Moving the wood chips wore me out, but the initial investment of time and energy seems like a small price to pay for what should become an area of great soil in a couple of years.