Watering smarter

On warm days this week, I’ve resumed one of summer’s tasks: watering. Back when my garden was young and all the plants were new, I was grateful to have a computerized irrigation system to keep them lush. Over the years, though, I’ve become increasingly conscious of using too much water. 

Automatic sprinkler watering the lawn and nearby beds

One of the environmental downsides to using purified drinking water in the garden, as I do, is its energy cost. Water utilities consume 3 percent of the energy generated in the United States. By cutting back on automatic irrigation, I can make a small contribution to the fight against global warming.

Clean drinking water comes with a carbon cost

Our sprinkler irrigation system was typical for our area when it was installed in 1997. It divides the yard into twelve watering zones, and it’s controlled by a computer in the basement. An attached rain gauge prevents watering after a storm. In retrospect, I could have saved a lot of water by choosing drip irrigation instead of sprinklers. 

Drip irrigation in an almond orchard. Emitters deliver water only to the trees' root zones

A drip system for trees and shrubs would direct water to exactly where it’s needed. Sprinklers inevitably lose water to evaporation. I cringe a bit when I see sprinklers in the neighborhood running in the middle of the day. To minimize that evaporative loss, I program the sprinklers to run after midnight, when it's dark and cool. That’s still less efficient than drip emitters would be. 

Another wasteful feature: our system’s watering zones were laid out when the garden was new. Sprinkler heads placed to water sections of lawn now cover a mix of grass and young and old shrubs and perennials. I don’t have the flexibility to target just the new plantings within a zone. 

Some environmentally-minded gardeners water only by hand, even in the relatively wet Northeast. A lovely garden I visited last summer is maintained without an irrigation system. The homeowner and garden designer explained that most of her garden gets no supplemental watering. When she needs to water new plants, she fills a bucket or watering can from one of her rain barrels.

Water from barrels at downspouts is sufficient for Joanne's native plant garden

At this stage, most of my garden is comprised of established trees, shrubs and perennials. They’ve spread their roots far and wide to find water when soil is dry. New England plants have adapted to survive our summer dry spells, even without the kind of Xeriscaping that’s appropriate to arid parts of the country. A lot of the irrigation I’ve been doing is probably unnecessary at this point.

It's pretty in May, but sweet woodruff is taking over, maybe because of steady moisture from irrigation.

The bold move would be to cut off irrigation to those older plants, at least until I see that they’re really suffering from drought. New plants will still need two years of watering to get established. That’s where watering cans and hose wands come in.

Ready for summer

Hand watering has its pleasures, especially in summer’s soft morning and evening light. That’s often when I truly see these new arrivals to the garden. I notice the unique patterns of new leaves and register the weeds emerging alongside. I’m looking forward to observing more closely this summer.

 

Striking a balance

There’s a tension built into welcoming native insects. I want to host native leaf-eaters, because they’re the base of the food web for the garden ecosystem. They turn the sun’s energy, embodied in plant tissues through photosynthesis, into food for carnivorous animals, including birds and beneficial insects such as ladybugs. But unchecked, they can also defoliate plants and cause an unsightly mess.

Ladybug eating an aphid

    Worldwide, herbivorous insects make up 37 percent of all animal species. If you’re like me, you don’t spot most of them at work. A leaf-eater has to be big and unmissable, like a Japanese beetle (Popillia japonica) or a tomato hornworm (Manduca quinquemaculata), for me to notice it. But although I don’t see them, they’re out there chewing.

Japanese beetle

    In a healthy garden ecosystem, their population is controlled by predators, including birds, reptiles, amphibians, small mammals, and especially other insects. That’s a reason to avoid pesticides. If I kill their prey, insect predators won’t stay in my yard.

     Problems happen when a nonnative insect with no local predators enters the system. In Japan, for example, Japanese beetles aren’t a problem. When they came to North America in 1916, they left behind the insect predators that kept their numbers under control. Nice for the beetles; less pleasant for rosarians. This story repeats with increasing frequency as global trade expands. In my area, we’re seeing native hemlocks (Tsuga canadensis) devastated by hemlock woolly adelgid (Adelges tsugae), another inadvertently imported nonnative insect.

Adelgid egg cases on a hemlock twig

     I’m trying to keep leaf-eater populations in balance by supporting a broad range of insects in the garden. I tolerate some leaf damage and hope it won’t become too obvious. Research into what’s termed “aesthetic tolerance” indicates that 10 percent of the leaves in a yard can be chewed before the average gardener even notices. 

     This spring as hosta leaves poke up and unfurl in shady spots, I’m noticing that several seem to emerge with notches or tears in the leaf margins. Did some insect get to them as they developed underground, or is this just a result of careless steps before their location showed? To me, the hosta leaves are still glorious. I don’t think I’ll be bothered by a few flaws.

Hosta leaves will still be dramatic with a few holes

     Theoretically, native plants should be even more attractive to native herbivorous insects than imports such as hostas. That was certainly my experience when I planted a native maple leaf viburnum (Viburnum acerifolium) in view of the window over the kitchen sink. Within a few weeks, I saw it completely defoliated. 

I’d chosen to add this shrub to the back of a bed to provide food and shelter for native insects. Well, they’d certainly made use of it. I decided to consider this a victory. Interestingly, that shrub was never stripped by hungry insects again. It seems to have settled into its niche, sustaining a few chewed leaves but thriving. So far, that seems to be typical.

Maple leaf viburnum-photo

Joshua Mayer

Sustainable enough

I just listened to an informative interview with Uli Lorimer, director of horticulture at Native Plant Trust, our local native plant society in Framingham, Massachusetts. Uli was a guest on garden writer Thomas Christopher’s weekly radio show and podcast, Growing Greener. Thomas focused the interview on native and locally adapted plants.

Monarch on New England aster

    Together, the two men proposed a type of garden that’s designed to serve the interests of as many living things as possible, not just humans. Instead of choosing plants because they’re pretty, you’d select what performs the most useful functions for your garden ecosystem. You’d put aside neatness as a top aesthetic priority.

Goldenrod is a key player in this meadow ecosystem in Maine

    This is the path I want to follow, but I argue that we don’t all have to arrive right away. Uli pointed out that much important information about native plants hasn’t yet been ascertained, and the rest hasn’t spread past native plant enthusiasts. As a start, he suggested, growers should be using plant labels to tell where plants came from and how they were propagated.

A plant label that lists the seed source and nursery location

    Native Plant Trust advocates growing plants that evolved in the local ecoregion, the area with the same environmental conditions they'll find in your garden. In addition, they value genetic diversity within each species, meaning plants that are grown from seed, not cloned through cuttings or divisions to be genetically identical. 

    A genetically diverse, locally adapted plant population will be well-equipped to deal with shifts in its environment, including rapidly changing climate. But so far, conventional growers haven’t figured out how growing from seed could be scaled up to their volume of production in a financially viable way. In addition, we consumers have been trained to want reliably uniform plants, which is what you get with clones. Seed-grown plants are variable. 

Mass produced plants are genetically identical and uniform

    Native Plant Trust sells about 300 species of locally adapted native plants at their garden shop. They’re grown from ethically collected wild seed of known New England provenance. But what if the shop doesn’t offer a native plant you’d like to buy? Is it wrong to buy plants that don’t meet their high standards?

    This brings me to my point. I think becoming a sustainable gardener, and a native plant gardener, can be a process. You don’t have to change everything all at once. After 35 years, my garden is full of nonnative plants I’ve chosen over the years. Many of the ones that have survived are plants I love and wouldn’t dream of removing. We have a history together.

They'll have to pry my nonnative white bleeding heart from my cold dead trowel

    Every year as I learn more about native plants, I add more of them to the garden. I adjust my gardening approach to accommodate their needs and welcome a richer population of wildlife, especially insects. Is it still OK to buy nonnative plants because you like them, or North American native plants even if they’re not local, they’re “improved” cultivars of native species, or they’ve been propagated asexually? I think it is. If we’re thinking about these issues, we’re moving toward full sustainability, even if we’re not there yet.

Newly planted mountain mint from NPT--native, locally grown and adapted

 

Thanks, decomposers

With the May Day spotlight on under-valued workers, I’m grateful for the work of decomposers in the garden. Last fall I lamented my depleted compost supply. Now I’m rejoicing to see lots of fresh compost in my bins. This strengthens my impression that compost is like sourdough starter, full of what’s needed to reproduce itself. Once you’ve got the process going, it gets easier and quicker over time.

Under a layer of fall leaves in the bin, I found new compost

    That’s despite my lazy woman’s composting approach. I just pile on the garden waste as it comes. I don’t turn the piles or bother balancing the amount of “brown” high carbon and “green” high nitrogen materials. Compost still happens.

Adding fall leaves to a bin I emptied last fall

    Composting is central to my garden. With a renewed supply of compost, I’m ready to add some oomph to the perennial beds by improving soil from above—no need to dig in that extra organic material, because soil organisms will incorporate it.

Things go better with compost

    I’ll also save some compost for making homemade potting mix. By mixing it with coir, or coconut fiber, I make peat-free potting mix that works just as well as the bagged stuff I used to use for container plants.

Peat-free potting mix: because harvesting peat contributes to climate change

    In 2011, I had my compost tested for biological activity by Soil Food Web, a lab in New York. I highly recommend this experience. The lab reported the populations of the types of organisms in my compost sample: bacteria, fungi, protozoa, and nematodes. They calculated the ratio of fungal to bacterial biomass and observed that the compost was mature, bacterial-dominated, and becoming more fungal. 

     I even got a note, “One of the better compost samples I’ve seen in a while. Keep up the good work.” The only caveat: “Need to work on nematode diversity a bit more.” To that end, they recommended inoculating the pile with forest duff, the mix of half-decomposed material that lies on the forest floor. You can bet I did that right away.

Beneficial nematodes thrive on the forest floor

    Looking out at the thick layer of fall leaves I left on the beds last fall, I recognize that the whole garden depends on the same work these small organisms do in the compost pile. It’s often said that without the work of detritivores--animals such as earthworms that take in, break up, and digest dead stuff—and decomposers--bacteria and fungi that absorb nutrients from dead materials--we’d be living on top of huge piles of dead animals and plants.

    I don’t just count on these small organisms in the compost bins. They’re also hard at work building soil and turning fallen leaves into leaf mold. The wood chips that I spread on paths and around trees and shrubs last a long time, but they too are broken down, predominantly by fungi that can digest lignin, the polymer that makes wood rigid and resists rot. Without those fungi, I’d have everlasting mulch, but it would do a lot less for the underlying soil.

Wood chips would be around forever without decomposing fungi

    Composting is just a half-domesticated way of speeding up what’s happening all around us, thanks to those unseen workers.

As soil organisms break down fall leaves, they make good soil for spring flowers