Be careful what you wish for

          One gardener’s ideal plant is another gardener’s nightmare. 

          More times than I’d like to admit, I’ve planted what I thought would be a useful groundcover and found it taking over. Two examples are sweet woodruff, Galium odoratum, and smooth Solomon’s seal, Polygonatum biflorum. I planted them because my yard is shady, and they promised to thrive in shade.  Thrive they did.  Smooth Solomon’s seal is native to the eastern US. I found it quite pretty, with its arching stems and modest white flowers hanging below shiny leaves.  

Smooth Solomon's seal

 Perhaps its description as “rhizomatous” should have warned me. Actually I didn’t do any research, just scooped it up from the shade plant section at a local garden center. At first its spreading pleased me, and I gave away divisions to neighbors. Pretty soon I realized it was popping up all over the garden. 

            Sweet woodruff, a European import, took longer to start to move. The little plants looked so delicate when I bought them from a mail order nursery that I wondered if they’d survive. The whorls of little pale green leaves were adorable, and that May I was delighted with the starry white flowers held above the foliage. 

Sweet woodruff

 Later I found a warning that sweet woodruff could be aggressive in the right growing environment. For years it spread gradually, until suddenly I looked up and realized it had taken off in all directions. 

          That’s the catch.  Something about my yard in particular makes an ideal home for smooth Solomon’s seal and sweet woodruff, but a few houses down, they might be well-behaved, useful groundcovers for shade. You can’t always know from other people’s experience, and it can take years before a seemingly innocent little thing shows its colors. Conservation biology confirms this phenomenon: a species has to build a colony of significant size before its population suddenly surges. It’s one reason we get suckered by exciting new imports.

          But let’s face it, the whole groundcover idea involves playing with fire. We’re looking for a plant that spreads willingly, but we also think it should stop when we want it to. Vigor is good, until it shades over into aggression. Invasiveness is really a spectrum, not a bright line.

        If I’m lucky, I’ll end up with a varied tapestry of groundcovers with different leaf forms, colors and textures. If I’m unlucky or inattentive, I’m likely to cover my whole garden with one of the strongest growers, which will look boring and be very frustrating to try to change. I tend to feel superior when I walk by neighboring front yards where shrubs are surrounded by oceans of mulch where nothing grows. What a wasted opportunity! And to me, it’s a sad look. But the joke could be on me—in twenty years, their shrubs may have widened enough to touch shoulders, while I’ll be trying to dig ever-so-native smooth Solomon’s seal out of my beds.

 

Welcome visitors

Today is a banner day for my garden. A hummingbird appeared outside my kitchen window this morning, feeding at a tall stand of yellow Oriental lilies and even perching on one briefly before darting away. Because of her subdued coloring, I’m guessing she was an immature female of our region’s ruby-throated hummingbird; she wasn’t sporting the bright greens or reds of the adults pictured on the website of the Cornell Lab of Ornithology.

            I rarely spot hummingbirds, and I’m going to credit this visit to my efforts this year to provide more plants that will attract wildlife. In addition to squeezing in native plants where I can in my already crowded landscape, I started an insectary garden this May to provide food and lodging for native insects. 

May 19, before the plants went in

It began with a few seedlings of cosmos and black-eyed Susans and some native perennials I chose because they were recommended by Jessica Walliser in her wonderful book Attracting Beneficial Bugs to Your Garden. For more about beneficials, check out Jessica's bug blog. 

Insectary bed July 25

           

 Thanks to her advice, I’ve now got a bed bursting with flowers and buzzing with new insect visitors. 

I can’t identify the bugs yet, but I’m optimistic that they’re contributing to a healthy balance in my garden’s insect population while also helping to pollinate my vegetables. 

Along with the swamp milkweed, yarrow, phlox and purple coneflower, I included a few zinnias and some sweet alyssum that insects like even though they’re not native to the Northeast. Today’s hummingbird visitor underscores Jessica’s point that some nonnative plants can provide services to wildlife. The Oriental lilies come from China, but their trumpet-shaped flowers apparently gave the hummingbird some nectar she needed. The new bed for insects has brought me a lot of fun, in addition to attracting hungry guests.

It’s been great to watch the new plants shooting up, making buds and opening their flowers. Besides encouraging beneficial insect predators, I also aim with this bed to provide food and shelter for native herbivorous insects near the base of my garden’s food web. When leaves are chewed, instead of worrying, I can count it as progress toward my goal.

           

Let the feast continue!

The fence delusion

Where I live, a lot of yards are fenced. We found a cedar stockade fence enclosing our fifth of an acre lot when we moved in. Now that we have a small fish pond, we’re legally obligated to maintain the fence to keep people from drowning. That fence can sometimes fool me into thinking my garden is separate from the rest of the neighborhood. The enclosed yard feels like a separate ecosystem, even though it’s not.

            The tendency to put faith in fences reminds me of the day when we first brought our dog Nadia home from the shelter. We opened the hatchback and let her jump into the far back of our station wagon, imagining she’d know to stay there. Of course she quickly jumped over the back seat and landed in our laps, happily oblivious to our idea that the seats were for humans.

            Only humans recognize our property rights. Like Nadia jumping into the front seat, the wild animals in my yard don’t let artificial boundaries deter them from roaming free. To a raccoon, the fence is probably like any other geographical feature, less interesting than a tree or a pond. When male chickadees maintain and defend territory with their song, they don’t set boundaries by my fences. And fences don’t keep wind-borne seeds from leaving my yard.

            In suburbia, good fences don’t make particularly good plant neighbors. If I grow invasive plants, imagining that I can keep them under control, it’s unrealistic to think they’re going to stop at the fence line. I’m growing a silk tree (Albizia julibrissin), a species from the Middle East and Asia listed as invasive in the Southeast US but so far not in my home state of Massachusetts. I’m attached to that tree because I grew it from a seed that I got at a propagation course. It’s at the edge of its hardiness here, but it has grown steadily, and a few years ago it added bottlebrush pink summer flowers to its attractive feathery foliage.  

Silk tree--the view from below

It also started producing lots of seed pods, and I started pulling its seedlings. 
            With climate zones creeping northward, I may be acting as my neighborhood’s Johnny Appleseed for silk trees. I can say I’ll track the seedlings and pull them all out. I can actually do that in my garden, but local custom doesn’t permit me to barge into my neighbors’ yards even for purportedly neighborly weed pulling. And if I dropped dead tomorrow, the silk tree would have reproductive free rein.

            So it probably doesn’t make sense to keep the silk tree. Right now, my goal is to add native plants to my garden and invite in native insects and birds. The nonnative silk tree is a beautiful zero in that regard. Eventually it may have to give way to a native. This could be my chance to try growing a persimmon tree.

Waste not, want not

California’s drastic drought has me thinking about the way I use water in my ornamental garden in Massachusetts. Someday I may be forced to change my profligate ways. I’m starting to think sooner would be better than later.

            My earliest gardens were small enough to water with a big watering can or a hose and watering wand.  When I cultivated more ground, I switched to rotating sprinklers.

The biggest negative to that approach was the operator—me. I hate to think how many hundreds of gallons I wasted by forgetting the sprinkler was running. 

            Finally my garden got so big that I moved up to an automatic sprinkler irrigation system controlled by a computer in the basement. The computer doesn’t forget to turn the water off.  It’s programmed to start watering at 3 AM, when the air is cool, but some of the water still evaporates. In retrospect, drip irrigation would have been a more water-saving approach for trees, shrubs, and perennial beds.

            The sprinkler irrigation system uses a lot of water. Comparing water bills before and after we installed it brought me up sharp. I’d tripled our household’s summer water use. I started paring down the water allotted to each irrigation zone, especially the lawn areas, letting the grass turn brown in August.

            We in the eastern US have skewed assumptions about water availability. We’re used to thinking of water as cheap and unlimited, almost like air. That's because the twentieth century was one of our wettest on record. In the future we may be forced to manage with a limited water supply. Using drinking water to irrigate an ornamental garden like mine may become prohibitively expensive or just impossible.

            I wish I’d planted with water conservation in mind, grouping thirsty plants together. Since I didn’t, I’m working on paying more attention to which plants really need supplemental watering. A rain gauge attached to the irrigation system is supposed to prevent automatic watering when rainfall is sufficient. I’d been relying on that and a fixed watering schedule to determine how much water each zone gets every week in the growing season. Established trees and shrubs may not need any extra water, whereas my vegetable garden, annual flowers, and newly planted shrubs and perennials do need regular watering. 

            My plan is to poke a finger in the soil periodically, find out whether it’s actually dry, and see whether plants are drooping. This should allow me to devise a less wasteful watering schedule.

            To this, residents of the Southwest probably say, “Duh!” I’ll catch up eventually.