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Monday, March 28, 2016

Fruit of the gods-coming soon!

My silk tree has gone to its reward, leaving a space for a new tree. This week I received a little common or Eastern persimmon, Diospyros virginiana. The Latin genus name means “food of the gods”!

Ready to plant

This native persimmon produces fruits around the size of golf balls. My goal in planting it is to provide wildlife with food and habitat. Maybe there will be a few persimmons for human residents of the yard too.

'Yates' persimmons from a tree like mine. Grown by Hank and Nghi Frehtling in Willianston, MI in 2013

     So yesterday I went out with my shovel to plant the little tree. Over the last few years I’ve collected quite a list of does and don’ts for planting shrubs and trees. First there was the hole. When I started out, I used to think that a deep hole was good, because loose soil under the young plant would make room for its roots. Lots more is known now about tree roots. They spread mostly sideways, not down. Persimmons reportedly send down a tap root to lower depths, but still, most of the feeder root action will be near the surface where the oxygen is. You can set your tree back considerably by planting it too deep. Today’s planting holes are supposed to be wide but no deeper than the root ball. 
     As usual when I dig in my yard, my hole quickly revealed sizable roots. 

This root crossing the hole had to be left alone

Surrounding trees and shrubs were clearly spreading their roots far and wide. I hoped that my relatively small hole, two feet in diameter, would not do enough root damage to harm the new tree’s neighbors.

     The next step was a bold one. I’ve always been hesitant to mess with the root balls of container- grown plants. But recently I read about an experiment demonstrating that transplanted trees actually did better if the roots were cut back. Cringing a bit, I teased out the potting soil around my little tree’s roots and trimmed away some of the longest roots. I made sure to set the now-floppy mass of roots on a pyramid of soil to keep the stem above ground level. 

After the radical treatment
Before-fresh from the container



I restrained myself from “improving” the backfill with fertilizer or compost. That too turns out to be misguided. It’s best for your transplant to be surrounded with the same soil you dug out of the planting hole. I watered generously and surrounded the young tree with some handy wood chips.
     Last I had to decide about the stake that came with the plant.  It was tightly attached to the stem with five plastic ties. I knew that staking trees is over-rated, and young trees actually grow faster and stronger if they’re allowed to sway with the breeze. I decided to keep the stake until the new tree put out some leaves, just to prevent me from trampling it by mistake. I cut off all but the top two plastic ties. 

These ties seem especially tight

I’ll need to be sure to remove the last two soon, because as the stem expands, the unyielding plastic could girdle the trunk, cutting off the flow of nutrients under the bark.
     I read that a persimmon could produce fruit in as little as three years. I can’t wait!

Sunday, March 20, 2016

Plant power

We usually notice the power of nature in big, dramatic phenomena—waterfalls, ocean tides, shifting tectonic plates. But very small plants do things that I think are just as awe-inspiring.

    At this time of year, I’m surrounded by evidence of the amazing strength of growing plant tissue. For example, there’s the sight of growing tips of new spring sprouts, so soft and tender to our touch, pushing their way through rigid barriers like the oak leaves lying on my garden soil.

These daffodil tips grew through tough oak leaves

    How can this be? The dried oak leaves are quite resistant to tearing or punching through. But we know that growing plants are powerful enough to split rocks.

This fern widens fissures in the rock

    On Wayne’s Word, an online natural history textbook created by botanist Wayne P. Armstrong, I read:

"One of the main factors that initiates the rock-splitting scenario is imbibition--the remarkable process by which water molecules move into a porous, colloidal material and cause it to swell." Wayne explains that electrical charges carried by the oxygen and hydrogen atoms in water are attracted to charged components of large molecules inside plant cells, such as cellulose, starch and lignin (the polymer that strengthens and hardens plant cell walls): “Like tiny magnets, the water molecules permeate these polymers, adhering to the charged surfaces as well as cohering to the positive and negative ends of adjacent water molecules. This influx of water molecules and chemical bonding . . . causes the cell wall and its contents to swell several times its original size.”

    Wayne goes on to explain that water swelling a seed before germination can exert hundreds of pounds of pressure per square inch in order to split the seed coat of a hard nut like a walnut. So pushing through an oak leaf that’s frozen in place may be little challenge for a growing crocus or daffodil tip.

    It’s interesting to think about the power that small and unassuming plants can exert.  An acorn germinating in a crevice in a rock can ultimately split the rock.  Roots not only buckle sidewalks, they push their way into the joints in pipes—as I was reminded again last spring when sewer water backed up into our basement drains.

Norway maple roots defeating granite curb on my block

    In case we gardeners get the idea that we run the show, the slow power of those little shoots and roots reminds us that bigger forces are at work, gradually and inexorably. You don’t have to go to the seashore or the mountains to be awed by nature’s power.

Sunday, March 13, 2016

Mushroom superheroes

This week I went to Amherst, Massachusetts to attend the annual conference of the Ecological Landscape Alliance, this year titled, “Sustaining the Living Landscape.” One of the speakers pushing the boundaries of conventional horticulture was Tradd Cotter, who gave the keynote address, “Mycoremediation: Healing Compromised Eco-systems with Fungi.”

    Cotter came across as an obsessed genius and kind of a wild man. He introduced himself by explaining that he had been accepted to train as an Air Force fighter pilot when he decided instead to go into mycology. At Mushroom Mountain, his mushroom farm and research facility in South Carolina, he has developed fungi that can break down toxic chemicals in soil and water.

    As I understood it, the fungal mycelium (the vegetative stage that gathers nutrients, usually out of sight, before creating the mushroom that is its fruiting body) can be “trained” to feed on a particular substrate. 

Oyster mushroom mycelium growing on coffee grounds-photo by Tobi Kellner

Cotter isolates fungal cultures on Petri dishes with substances he wants them to “eat.” When it has no other food, in a few generations the fungus modifies itself genetically to extract nutrition from that substance, which could be a chemical, a microorganism (such as coliform bacteria in sewage), a particular plant, or even an unwanted insect. It breaks down the noxious entity into building blocks that can be useful, for example for soil improvement.

    While fungi in general are opportunistic, some have more potential to develop this capacity to attack specific chemicals and organisms. Interestingly, one of the species Cotter finds most useful is the oyster mushroom, Pleurotus ostreatus, a familiar ingredient in Asian cuisines. 

Oyster mushrooms on a sugar maple-photo by David Spahr
    Cotter put out a call for people to send him problem insects they find that are infected with fungus. He showed a slide of a fire ant covered with white filament. The creepy part: a mushroom eventually grows out of the insect’s brain! When he receives these local ecotypes, or genetically distinct geographical populations, of fungi, he can grow them in his lab and reproduce them for use in the field. This offers a way to reduce use of toxic pesticides.

    I must say that the image of that mushroom growing out of the ant’s head gave me pause. I’ve never been stung by fire ants, but I understand it’s quite unpleasant, so I can understand why a killer fungus would be appealing. The red imported fire ant, Solenopsis invicta, comes from South America and is thought to have been introduced to the US accidentally. With climate change, we can expect it may continue migrating north from humid southern states.

Red imported fire ant-Photograph by David Almquist, University of Florida.

    An audience member suggested we could use a fungus to attack winter moth, Operophtera brumata, a nonnative insect damaging New England trees. 

Birch leaves chewed by winter moth caterpillars
That’s not so different from the work that’s being done releasing insect predators for winter moth. Before those are released, they’re comprehensively tested to make sure they’ll only eat the nonnative insect and won’t go on to disrupt the ecosystem. I’d want the targeted mushrooms to be just as fully screened.

Sunday, March 6, 2016

Time for wood chips

With spring almost in the air, I asked my neighbor Kevin Newman to drop off some wood chips from his arborist business. Kevin and his men came over and carefully dumped a moderate pile of chips in the driveway. 

Three years ago they brought a whole dump truck’s load, and it made a pile almost too huge for me to deal with.

    I got the idea of using wood chips as mulch from reading Linda Chalker-Scott, known to her admirers as “the Mulch Queen.” She is a professor of urban horticulture at the University of Washington at Puyallup and a myth-buster who applies scientific principles to conventional wisdom in gardening. She and colleagues blog at The Garden Professors, which is a great source of unembroidered horticultural truths.

    Chalker-Scott has reviewed the scientific literature on mulch and conducted her own experiments. She recommends arborist wood chips as the best mulch of all. 

     Before trying the wood chips, I was happy with the mulch I made from fall leaves. I never have enough for the whole yard, though, and the leaf mulch decomposes fast, mostly melting into the soil within a year. 

I was still supplementing this homemade product with bark mulch I bought at garden centers or Home Depot.

    The wood chips are superior in several ways. First, they’re free. Kevin is willing to give them to me; otherwise he’d pay to dispose of them. Second, they do impressive work building soil. I was amazed when I first dug through a layer of wood chips to plant some native Allegheny spurge (Pachysandra procumbens) in a shady area under a line of trees. The soil under the mulch was rich, black, moist, and easy to work. When I’ve dug under bark mulch, I’ve sometimes found the soil dry and hard, possibly because the wax in the bark can prevent water from penetrating the mulch layer. 

     Another good feature of the wood chips is that they’re easy to handle. A wheelbarrow full of chips is much lighter than an equivalent volume of bark mulch, which is so dense that I can barely heft a bag from my car to the wheelbarrow.

    The look of the chips is an acquired taste. I found their blonde color jarring when I first laid them down. Now I’ve gotten used to it, and I know that over a few months they’ll fade to a less conspicuous gray and later to brown.

A path of aged wood chips

    So I’m spending this weekend shuttling back and forth with my wheelbarrow, adding a new layer of wood chips to my garden paths. The next priority will be the berm at the back of the yard, where they’ve been enabling water to soak down to the roots of mature evergreens that screen us from our neighbors (The only place not to use the chips is around vegetables and annual flowers). 

     It almost feels like the gardening season has started!