Dying to be reborn

The autumnal equinox has passed, and leaves are starting to turn yellow, curl up, and brown at the edges, beginning the process that will end in their dropping off. Are shorter days and colder nights killing them? Yes and no.

Bleeding heart (Dicentra spectabilis) winding down

    Right in front of my kitchen window, a large pot of cucumber vines was burgeoning until two weeks ago, opening new yellow flowers and forming perfect little fruits that grew into delicious cucumbers much tastier than the waxed, store-bought versions.

July: cucumber vine flowering

Last week the leaves started to shrivel. One morning I looked out and saw the plants had turned completely brown. Was it because of a night temperature in the 40s, or was it just time? How do plants know when to die?

September: the season for cucumbers has ended

    Like us, plants need to maximize their utility, acquiring as much as they can of life’s necessities—in their case, water, sunlight, nutrients, and space to grow. They can’t chase after these things. But unlike us, they can add to their bodies, growing new roots and shoots all their lives. Plants don’t just grow randomly. To respond to surrounding conditions, they make adjustments to their growth mediated by hormones carrying chemical messages from roots to leaves and back. 

    Each plant makes unsentimental decisions minute to minute about which parts will get more resources and which have to go. The plant is continuously gathering feedback from its extremities and expecting each unit to pull its weight. It needs each root to bring in enough water and nutrients to make it worth “paying for” with sugars made through photosynthesis in the leaves. Similarly, it needs each leaf to produce enough of those carbohydrates to support the roots in their mission.

One cranesbill leaf too many

    I learned that there are two kinds of plant senescence, the ways plant tissues die. There’s stress-related senescence. That's what happens when I forget to water a container plant and some leaves turn yellow and die because the plant didn’t have enough water to support them. Those leaves became too expensive to support in drought conditions.

Elephant ear leaf saying, "Why didn't you water me?"

    The other way of plant death is pre-programmed for the end of the growing season. My cucumber vines (Cucumis sativus) are annuals, born to die about 70 days from planting, soon after they finish producing fruit. This strategy allows an annual species to put all its energy into preserving genetic diversity. As leaves get ready to drop, the plant pulls back nutrients they held and uses those nutrients to produce lots of seeds, each with a mix of genes from its parents. 

    Shrubs, trees, and perennials such as bloodroot (Sanguinaria canadensis) have chosen another option. 

Yellowing bloodroot leaves sending resources back to the roots

They store nutrients in roots and stems to use later. That gives them a jump on the annuals when spring comes. They’re poised to send up new shoots, push out new leaves and roots, and get the most from the early spring sunlight.

 

Bloodroot leaves and flowers opening in April

    I hate to see winter coming and the garden season ending, but it’s great to picture the plants laying up stores for next spring.

Fungi at work

Although we can’t see it, we live in a microbial soup. I just learned that there may be a Milky Way of viruses that floats on air currents around the globe and that trillions fall to earth every day. We know our guts are inhabited by billions of bacteria that we can’t get along without. A teaspoonful of soil contains up to a billion bacteria.

    Some of the most important players in this microscopic world are fungi. This summer has produced a particularly handsome crop of mushrooms and other fungal growths in woods and shady gardens in my area.  Walking woodland paths this month, I can’t resist stopping to snap photos of new, colorful fungal growths that seem to pop up almost every day.

Wet, rotting wood displaying a fungal bonanza

    The mushrooms I’m admiring are just the tip of an underground iceberg, the fruiting bodies of vast networks of thread-like fungal hyphae in the soil below. Compost couldn’t happen without the work of soil fungi. Bacteria, fungi, nematodes, insects and protozoa all work together to break down the organic material we throw on the compost pile into nice black compost.

Microscopic view of fungal cells

    I was amazed to learn a few years ago that experts can customize the balance of fungal and bacterial content in compost by choosing the right mix of ingredients. This is when they make compost on the scale of tons, moving giant mounds of material around with backhoes. 

At large-scale composting operations, piles are turned by machines

High-carbon, tough woody materials are what soil fungi like, so our yard’s endless supply of oak leaves predisposes the compost I make to have high fungal activity. I once had my compost tested for its biological content. The report came back showing excellent fungal presence.

    That’s just as well, because shrubs, trees and perennials—what my garden is mostly made up of—particularly like soil and compost with lots of fungi. By mulching with fall leaves and wood chips, I give the fungi even more to chew on.

Shredded leaf mulch

    Not only are these organisms hard at work in the soil. They actually create an underground architecture in the rhizosphere, the top few inches of soil where there’s the most oxygen and the most biological activity takes place. Roots and soil fungi have evolved to work together, exchanging nutrients. 

A stump in my yard is hosting this impressive mushroom bouquet

     This justifies the lazy woman’s approach to soil amendment: layering compost and good stuff such as composted manure on top of the soil and letting the soil organisms do the work of mixing them in. Tilling the soil, or even turning it with a spade, breaks up those underground networks that fungi have labored to create. That makes it harder, not easier, for plants’ roots to obtain the nutrients they need.

Let soil organisms do the digging

    As the beans and tomatoes in the vegetable garden finish producing and start to wind down, it’s almost time for me to play my part, spreading some compost on top of the bed. By spring, those fungi will have made the soil ready for another season’s planting. I appreciate their beautiful above-ground creations, and I’m even more grateful for the work they’re doing underground.

A contender

Since reading Bringing Nature Home in 2011, I’ve wanted to grow a black cherry tree (Prunus serotina). Doug Tallamy highlights this native tree in his book because it’s a champion at providing food for wildlife.

Black cherry in spring-photo Krzysztof Ziarnek, Kenrais

 The genus Prunus, which includes cherries, peaches, and almonds, is in the top three for supporting Lepidoptera (butterflies and moths). Black cherry also provides food for bees and other pollinators, and birds and many mammals eat its fruits.

A red-spotted purple on black cherry

    As it turned out, I didn’t have to go out and buy or even dig up a black cherry seedling. One arrived right on schedule in the clearing created when we removed two big hemlocks along the fence line. Black cherry travels when birds eat the berries (technically, drupes) and excrete the seeds wherever they go. An animal’s digestive system scarifies the seeds, breaking through their hard outer coating and preparing them to germinate.

The fruits turn from red to black

    Black cherry seems to have adapted particularly well to living around humans. It used to grow mostly in forests and can reach a height of 100 feet, which makes it the tallest cherry tree. But now it takes advantage of growth opportunities in areas of new construction or open ground such as the space left by our late hemlocks. Black cherry grows in sun or part shade and puts up with moist or dry conditions.

    Once you know what it looks like, you’ll spot this tree in many public places. 

Distinctive leaves

To me, the tip-off is the shiny leaves, extended ovals ending in a pointed tip. In spring it covers itself with wands of tiny white flowers.

The little white cherry flowers attract pollinators-photo AnRo0002

    I learned that black cherry has found a way to enlist ants to protect it from leaf-eating insects: extra-floral nectaries. As Ohio State University Extension blogger Joe Boggs writes, “Nectar is the currency used by plants to pay insects and other animals to do their bidding.” Most flowering plants locate this sugary liquid inside flowers, but many species add less conventional nectar outlets. Cherries ooze nectar from little knobs on the petioles, or leaf stems. 

The dark bumps on this leaf stalk are extra-floral nectaries

Ants swarm the foliage to harvest the nectar. While they’re at it, they eat leaf-eaters; for example, one visiting ant species preys on Eastern tent caterpillars.

    Although black cherry’s nectar and fruits are delectable, its leaves are poisonous. They contain glycosides that hydrolyze to hydrogen cyanide in an animal's digestive system. 

     With tolerance for a range of growing conditions, irresistible fruit and nectar, and dual strategies for defending its leaves, this tree is a resourceful survivor. When it was introduced to Europe, it became invasive there. Here it fits into plant communities without taking over.

    The black cherry that emerged last year in the new clearing is now three feet tall and bushy. The question for my garden will be how big I’ll let this tree get and how many of its relatives I’ll allow to grow here. With birds spreading the seeds, there will always be new saplings ready to fill any patch where sunlight reaches the ground.

A younger black cherry volunteering in the yard

High life for hummingbirds

Last year I gave up on my hummingbird feeder. I was concerned that I might be offering moldy or infected sugar water, because I couldn’t get around to refilling the feeder every day in hot weather. And truth to tell, I wasn’t seeing any hummingbirds using the feeder.

    Because they beat their wings constantly, hummingbirds have to keep eating whenever they’re awake, and at night they lower their metabolic rate to use less energy. They’re welcome in the garden community because their quest for nectar makes them important pollinators. They also eat lots of insects for protein, consuming up to half their body weight daily.

A hummingbird on the job, pollinating while it sips nectar

    This year I focused on growing flowers that would attract hummingbirds. Conventional advice is to offer a succession of red, orange and pink flowers with long tubular shapes from spring through fall. Recent research clarifies, though, that the birds seek out the location of known nectar sources rather than searching by flower color.

    Until this year, I’d rarely seen a hummingbird in the yard. This year I hoped to lure some to visit the back deck so I’d have a chance of seeing them. 

    Sure enough, we’ve seen hummingbirds near the house this summer. Yesterday one visited the cobalt-blue flowers of a hummingbird sage (Salvia guaranitica) growing in a big pot on the deck. 

That blur in the center of the photo is the hummingbird--best I could do

He hovered to dip his beak in the thin tubular flowers before darting away to perch on a nearby tree branch—the first time I’ve seen a hummingbird sitting still.

    I’ve also seen a hummingbird feeding from a tall meadow rue (Thalictrum rochebrunianum) that has sprays of tiny shallow lavender flowers, not trumpet-shaped at all. I guess the birds’ choice of flower shape must be a preference rather than an invariable rule.

Surprisingly, these flowers attracted a hummingbird

    So what accounts for more hummingbirds visiting the yard and coming near the house this year? I can’t be sure, but I have some guesses. First, I now have three honeysuckle vines (Lonicera sempervirens) blooming along the back and side of the house near the deck. 

Honeysuckle has everything hummingbirds like

Their flowering has lasted longer this summer than usual, perhaps because it’s been such a wet year. There’s that hummingbird sage, which started blooming in August and is covered with flowers. I’ve also learned that the old-fashioned magenta-flowered rhododendron (Rhododendron catawbiense) facing the deck is popular with the birds. Virginia bluebells (Mertensia virginica), whose trumpet-shaped flowers also offer nectar for hummingbirds, had a good year in a shady spot around the corner from the deck.

Virginia bluebells' blooms start pink and change to blue

    The yard also provides nesting material for hummingbirds: spider webs and dandelion fluff. I can’t take any credit for those; they’re just here. 

    Another important factor could have cleared the way for hummingbirds. Because they eat so many insects, they’re highly affected by pesticides. This is my first year with no pesticide spraying at all. I wasn’t thinking of hummingbirds when I made the decision to stop the last pesticide application, for winter moth. If it’s made a better life for hummingbirds, I’m glad.

Hummingbird sage draws other visitors too

Spare those weeds

Pulling out weeds always seems like a virtue, and letting them grow a sign of slovenliness. But it turns out that a few weedy patches promote biodiversity in the yard. 

A neighbor has let these weeds take over a stretch of curb strip

When we removed large hemlocks last year to avoid spraying them for hemlock woolly adelgid, we were left with two sunny clearings. I planted native shrubs and small trees, but it’ll be a few years before they grow big enough to fill the space. Meanwhile, lots of weeds have stepped forward to fill the open space.

A stand of what I think is hawkweed taking over some newly sunny ground

    With the idea that this could be a good, I’ve been looking up our weeds in Wild Urban Plants of the Northeast, Peter Del Tredici’s guide to “spontaneous urban vegetation.” Many are listed as “disturbance-adapted colonizer of bare ground,” true to their behavior in my yard.

    One of their useful functions is to provide food and habitat for beneficial insects, the ones that prey on leaf-eaters. Although these insects are predators in at least one life stage, they often need nectar and pollen in another. That’s one way that weeds such as lamb’s quarters and chickweed can be a plus.

Lamb's quarters wilting in this week's heat

Their flowers provide extra forage and fill in during the lean times when our preferred flowers aren’t blooming. Weeds may also attract prey insects that the beneficials need to eat or parasitize. 

    Here are some of the weeds that have popped up where the hemlocks grew:

Pokeweed (Phytolacca americana): This is a North American native that, although toxic to mammals, has fruits that birds love. At least 30 bird species use pokeberries as a major food source. 

Pokeweed grows quickly into a substantial presence

Warblers and other migratory birds eat them on their flights south. The berries help mockingbirds, cardinals, cedar waxwings, and others to get through the Northeastern winter. Pokeweed is larval food for several moth and butterfly species, including the giant leopard moth. Bees feed on its pollen.

Giant leopard moth-photo NPS Phillip Brown

Yellow woodsorrel (Oxalis stricta): Also a native, this low perennial shows up all over my garden. At summer camp we called it sour grass and chewed on the leaves when we were thirsty on a hike. 

Recognize this yellow woodsorrel? It's all over the place.

The plant’s tissues are high in oxalic acid, so it’s better to sample the leaves in moderation. It too provides seeds for birds, pollen for native insects, and leaves for butterfly and moth caterpillars.

Devil’s beggarticks (Bidens frondosa): This native annual gets the prize for its many colorful names: sticktight, devil's bootjack, pitchfork weed, Spanish needles. You can see it hasn’t made a lot of friends among gardeners, but it provides pollen for bees and, interestingly, food for muskrats when it grows near water.

Devil's beggarticks has pretty flowers; its bad rep comes from the burrs that follow.

    These weeds are easy for me to pull out, especially because they’re growing where I previously put down a layer of wood chip mulch. Under the wood chips, the soil stays soft. I’ll remove some weeds that are shading my squash and melon plants (a story for another day), but now I know to leave some for their contribution to the garden’s ecology.