My book and web site

Check out my book, The Sustainable-Enough Garden, available on Amazon, and the book's web site at See more plant photos on Instagram.

Sunday, November 27, 2016

Fungus among us

Thank goodness some rain fell this fall, although we’re still in a drought. Apparently mushrooms were biding their time, waiting for a bit of moisture before making their move. Once it rained, they popped up around the yard.

    These mushrooms are the fruiting structures of a group of fungi called basidiomycetes. The mushrooms are small parts of these organisms, which include extensive underground networks of hyphae, slender filaments that take up water and carbohydrates. A single individual fungus can send up fruiting bodies over an area as big as a baseball diamond.

    Invisible to me, even after welcome rain, are two huge groups, the saprophytic and mycorrhizal fungi. Saprophytic fungi are decomposers, breaking down dead organic material, including wood, into nutrients plants can use. 

Mycorrhizal fungi join in a symbiotic relationship with plant roots. Thinner and more extensive than root hairs, their hyphae seek out water and nutrients from far and wide. They share these with plants in return for simple sugars.

Fungal hyphae

    Some mycorrhizal fungi excrete a sticky polysaccharide called glomalin that glues soil particles together in small clumps called macroaggregates. These clumps improve growing conditions for roots by creating pore spaces in the soil for water and air. As if that weren’t enough, fungi in the soil also sequester carbon, attack plant pathogens, and cultivate helpful bacteria.

    Luckily the best way to foster these useful partners is to stay out of their way. If I tilled my soil with a rototiller, I’d be breaking up their networks. If I sprinkled chemical fertilizer, I’d turn off their nutrient-collecting efforts. Fortunately there’s no call to do either in my garden. If I need to plant something, I get along fine by digging an appropriately-sized hole. Compost and mulch are providing enough nutrition for my plants.

Offering a home for soil fungi

    It turns out that by mulching with fall leaves and wood chips, I was unknowingly creating a happy environment for soil fungi. I learned about this when I researched the reasons for balancing types of ingredients in the compost pile. Before this I’d thought compost recipes were unnecessarily fussy.

    Compost professionals can titrate ingredients and conditions in their compost piles to determine the proportion of bacteria and fungi in the finished product. By managing the balance of “brown” high-carbon and “green” high-nitrogen compost ingredients, they can cause bacteria or fungi to predominate. Bacteria thrive on simple sugars from green plant material, and fungi prefer high-carbon woody material. 

    Compost high in fungi is best for use around trees, shrubs and perennials, whereas annuals and vegetables prefer more bacteria in the mix. This is because of what soil organisms do with nitrogen from the air. Fungi convert atmospheric nitrogen to ammonium that long-lived plants prefer, whereas bacteria make nitrate that fast-growing short-lived plants particularly need.

    Making compost by recipe probably isn’t in my future, but it’s nice to know that my high-carbon mulches are friendly to soil fungi.

Sunday, November 20, 2016

Skip the fall clean-up

It used to be good gardening practice to clean up your flower beds in fall. We cut perennials to the ground with the theory that leaving their stems standing would provide shelter for insects. How gardeners’ perspectives have changed!

    Now much of what I do in my garden is aimed at providing that very shelter, as well as food, for native insects. That means I shouldn’t cut down my perennials in the fall. I’m unlearning the habit, although my pruner hand still tends to twitch when I see those “messy” stalks.

Ox eye sunflower seeds and stalks will provide winter food and shelter for insects

    There’s a conflict between some of my favorite garden authorities regarding this fall clean-up issue. At the popular blog Garden Rant, Elizabeth Licata writes that tree leaves shouldn’t lie in yards through the winter because they “smother plants and soil.” All I can say is that I haven’t found this to be a problem.

    Elizabeth doesn’t want to get involved in shredding leaves, which I can understand. It’s work, but for me it’s well worthwhile. I like converting leaves into shreds that make pretty, useful mulch. 

Shredded leaves make useful mulch

Because of what I’ve learned this year, though, I’m shredding less this fall and leaving more leaves whole.

    I just discovered that another trusted authority, Jessica Walliser, is contributing to a site and newsletter at Savvy Gardening. I’d already learned from Jessica’s book Attracting Beneficial Bugs to Your Garden that winter stalks, leaves, and berries provide needed shelter for over-wintering insects. Her post “Six reasons NOT to clean up the garden this fall” provides useful detail. 

    Did you know that some butterflies pass the winter here as adults, some in chrysalises, and some as caterpillars? 

Black swallowtail chrysalis. Photo by S. Detwiler

All of these forms could be depending on us to leave them some leaf litter or hollow stems for winter quarters. Jessica advocates letting whole leaves lie to avoid cutting up insects sheltering among them.

    Then there’s the matter of winter food for birds. I’ve spent a fortune on birdseed that’s mostly snapped up by nonnative English sparrows. Both Jessica and George Adams, author of Gardening for the Birds, point out that birds can find more varied food in our yards if we’ll garden with them in mind. I’ve been working on providing a bird menu of berries and seeds on native shrubs and perennials. 

Native winterberry provides food for birds

It’s interesting to hear that hibernating insects are also food for birds such as chickadees that forage for them through the winter. 

    There’s a seeming conflict between trying to help insects survive and offering them as food for birds. But in fact these are part of the same goal. The idea is to grow plants as food and shelter for a large and varied population of insects, so many that birds can eat their fill and still leave enough for other ecological roles, such as pollination and predation.

This green lacewing eats herbivorous insects

     Jessica’s book explains in fascinating detail how predator insects can help keep your garden’s population of leaf-eaters in balance. That’s yet another reason to leave the welcome mat out for insects in winter.

Sunday, November 13, 2016

Weathering disappointments

Back in April there was no reason to think this wouldn’t be a typical gardening season. Various weather phenomena were jockeying for position—spring rain, late snow, cool sunny days, warm spells.

Everything seemed normal in April

     Drought was in the running, but no one thought it could win. It was offensive, and it just didn’t fit with our New England (horti)culture. After all, we were well-informed, progressive gardeners. We knew our history, and we knew the climate wouldn’t deal us such a blow.

Not In Our Back Yard

    June and July were awfully dry. Against all odds, drought seemed to be pulling ahead. Other weather options tried to compete. Heat and humidity made a bid for the top slot. They seemed much more likely to win. Their kind had always won in the past. Clearly drought was going to fade. It couldn’t make a sustained run. We could all see its deficits. It wouldn’t supply the needs of our plants. It was just a matter of time until rain would take the lead, and we’d be back to a normal gardening summer.

    Pundits explained that drought was bound to fizzle out. Statistics showed that summer rain was by far the more likely pattern. Comparing this summer to previous ones, it was obvious that drought couldn’t maintain a lead in New England.  It might hold on in the Western states, but not here.

Clearly drought couldn't last

Everyone we knew was in favor of rain. It was more popular than ever. In the past eight years, rain had started us on the right path. Rain had promoted new growth that we all wanted to continue. Anyone could see that a balance of rain and sun was in everyone’s interest.

On a green path in years past

    As the summer dragged on, drought brought out the worst in us. It was tempting to water our own yards and forget about the gardeners who couldn’t. People were angry. 

Green grass wins out over community spirit

    We weren’t surprised when a scandal hit the news: drought was assaulting our most vulnerable plants. That was sure to clinch its defeat. There was a wave of outrage. State officials warned that if drought continued in the lead, crops would be destroyed and endangered animals would die. 

Drought was destructive

Gardeners would need to water less. We’d make some sacrifices for the common good. But that would turn the tide, surely.

    Despite some fall rain, a late October dirty trick put drought back on top. We hoped no one would be fooled.

    You all know the end of this story. Tuesday night we sat down to watch the returns, nervous but still certain that drought would be defeated. That’s what all the experts predicted. Rain was going to come, and we could stop worrying.

    Instead, we woke up Wednesday morning to face the reality: drought was still with us. In fact, we’d be dealing with the painful consequences for a long time to come.

    Fortunately the gardening world is made new every spring. We can still hope that winter snow and spring rain will bring lush gardens next summer. If only other disappointments faded as fast.

Gardens may be green next year, but will we lose our last chance to slow climate change?

Sunday, November 6, 2016

Conventional wisdom that's wrong

With fall garden work in my future—spreading compost, chopping leaves for mulch, and generally preparing for the cold months ahead—I’m glad to learn that some conventional gardening wisdom turns out to be false. 

Time to prepare the garden for winter

My heroine Linda Chalker-Scott, professor of urban horticulture at Washington State University, has the research to prove it. Here are three myths we can forget about:

Nitrogen-sucking mulch
It used to be an article of faith that high-carbon mulches such as the ones I use—shredded leaves and wood chips—would use up nitrogen in the soil in their decomposition process, thereby leaving plants short of this important nutrient. 

Does wood chip mulch cause nitrogen deficiency?

Chalker-Scott found that it doesn’t happen. So we can go on spreading organic mulch without adding high-nitrogen chemical fertilizer to make up for the imagined loss. 

     There may be a narrow zone of nutrient deficiency just at the mulch-soil interface. That’s actually a good thing, because it’s where young weeds would try to get started. The lack of nitrogen will help keep them from succeeding. It doesn’t hamper the growth of plants with established root systems, though, because they feed further down under the soil surface.

Acidifying soil
Another shibboleth is the proposition that adding oak leaves or pine needles to compost or using them as mulch will acidify soil. Soil is not as simple as we used to think. Adding acidic components to soil is not like putting vinegar on your salad. The soil has a buffering system that prevents swings in its pH. People who mulch with oak leaves year after year see no change in their soil’s pH, and pine needles, widely used in the Southeast, make some of the best mulch there is. 

Pine needles make great mulch

If you really want acid soil, you have to add chemicals such as ammonium sulfate, which only works temporarily. Here in Massachusetts our soil is naturally acid, so we don’t need to add chemicals to grow acid-loving plants like blueberries and rhododendrons.

Winter wraps
Some people in my town wrap their broadleaf evergreen shrubs in burlap during the winter. This is intended to prevent drying caused by sun and cold winter winds. There’s some justification for this; leaves can indeed be killed when they lose moisture to evaporation and the frozen ground offers no replacement. 

     You may also see ads for anti-dessicants sprays that purport to prevent evaporation from leaves. Chalker-Scott found that using these materials is more likely to prevent your plant from taking in carbon dioxide, photosynthesizing, and avoiding overheating. 

    To my mind, wrapping rhododendrons and boxwood shrubs in burlap cancels the benefits of growing them in the first place. One of my main reasons for planting evergreen shrubs is the chance to enjoy their green leaves in the winter landscape.

Greenery is welcome in winter

     It turns out you can protect your shrubs best by making sure they’ve had enough water before winter starts and by mulching generously to hold that moisture in the soil. That way they can lose some water without ill effects.