Walking in the woods this time of year, my friend Bill and I always play a game of tree identification. We don’t even bother with white birches or shagbark hickories. They’re too easy.

I might be able to stump Bill if we happened upon a European birch, another white-barked birch distinguished from our native paper birch by the dark, diamond shaped fissures on its bark. (Of course, we’re unlikely to find that birch in the woods.) I’m often snagged by cherry birch, whose bark isn’t white at all, but whose young bark resembles young cherry bark, then morphs with age into longitudinally elongated plates. The giveaway for cherry birch comes with breaking a small twig and smelling wintergreen.

Trees like red oak, sugar maple, ironwood, juneberry, hop hornbeam, and ash are easy to identify once you know their bark. I’m usually the first to identify hackberry because it’s one of my favorite barks, pure gray and punctuated by corky ridges. On a wintry day when the sun hangs low in the sky, the shadows create a pattern that recalls those crisp, achromatic photographs of lunar landscapes.

If tree bark offers no leads about a tree, a few dead leaves on the ground or clinging to stems often help out. Beech leaves make identification especially easy because beech is among the few trees that clings to almost all its dead leaves all winter. The lower leaves of some oaks also are reluctant to drop.

Bark, leaves, and aroma aren’t the only things that scream out a tree’s name. Everyone knows the distinctive weeping form and light-colored young bark of weeping willows. Less universally known is the very distinctive form of pin oaks: lower limbs sweep downward, mid-height limbs grow out horizontally, and upper limbs point skyward.

On most trees, stems are alternate, that is, they don’t grow directly opposite each other. So if a tree -- one that grows wild in the northeast, at least -- has opposite stems, I can limit the choices to just a few trees: dogwoods, maples, ashes, or catalpa.

This tree game is more than fun; it’s also useful for identifying firewood. A couple of years ago, I bought some firewood that was billed as swamp oak. Swamp oak turned out to be another name for pin oak, which this wood definitely was not. Bill and I looked at the wood and the bark with its distinctive, long, flat-topped ridges again and again, wondering. Finally, about a month ago, Bill pronounced the wood to be American linden (basswood). I think he may be right. It’s not very good for firewood.

------------------------------------------

One last thing done before the snow flies: The blueberries have been fertilized and mulched. Next year, I’ll again expect bushes to put on a couple of feet of new stem growth and yield another 160 quarts of delicious berries, all from a planting only 25 by 30 feet in size.

Nothing fancy about my fertilizing. I use soybean meal, available from feed stores, because it’s good for plants that need acidic soil (as well as plants that don’t need acidic soil), it only needs to be put down once a year, and it releases its goodness, mostly nitrogen, slowly and in synch with plant growth. I whirled out 12 pounds from my Whirlybird fertilizer spreader for a rate of about a pound and a half per hundred square feet.

Mulching was slower. Two truckloads of wood chips (from the town recycling center), at 45 cubic feet per truckload, laid down a blanket and inch and a half deep under the whole planting. This organic blanket keeps the blueberry planting essentially weed-free and nourishes the soil, then the blueberry bushes, as it decomposes. The plants like the fluffy, spongy ground that has resulted from 25 years of mulching, especially during dry summers like last summer.

The mulch also reduces the number of disease spores on the ground, such as from dropped mummy berry fruits, that would waft back up into the plants to infect them in spring. Insect and diseases have never been problems on my blueberries.

-----------------------------------------

Moving indoors, to the fruits of my labor. Or, rather, the nuts of my labor.

I finally figured out the best way to roast chestnuts, which, as usual, bore abundantly this year. I start out by giving each nut a shallow slit perpendicular to its axis, easily done with a light chop from a heavy, sharp knife. A shallow layer of nuts goes into a covered pan set in a hot oven or on top of the wood stove for 45 minutes, during which time the nuts steam from their own moisture. Then off comes the lid for another 15 minutes of cooking to let the nuts roast and the shells and pellicles (the skin around each nut) turn crisp.

Massaging each nut without breaking up the nutmeat cracks the shell and the pellicle so that both come off easily -- usually. With last summer’s drought, the nuts are small, but they are pretty much insect and rot free. They have the mealy texture of a baked potato and a wonderfully sweet flavor.

I’ve said it before and Yogi Berra said it before me, “It ain’t over till it’s over.” A recent night’s temperature plummeting to 15°F. was still not enough to put the brakes on the vegetable garden. Arugula, mâche, kale, and spinach are looking as perky as ever and, most important, taste better than ever. Lettuce is surviving, not exactly perky though.

It’s a wonder that these tender, succulent leaves tolerate such temperatures. You’d think the liquid in their cells would freeze and burst the contents to smithereens. That would have been the case if the 15° night temperature had come on suddenly, without any precedents.

Plants aren’t passive players in the garden. Increasingly cold weather and shortening days acclimated these plants to cold. They move water in and out of their cells, as needed, to avoid freezing injury. And increasing concentrations of dissolved minerals and sugars in the cells make the water freeze at lower temperatures. Perhaps that’s one reason why these vegetables taste so good.

***************************************

One whole bed in the garden is very lush green, even growing a little. That bed is home to endive that’s covered with a floating row cover fabric and then clear plastic, both held above the plants by low, metal hoops.

Interestingly, temperatures I’ve measured within the endive tunnels are not that different -- actually, not different at all -- from temperatures I’ve measured outdoors. But something’s different. The increased humidity under the tunnels is probably at least partially responsible for the fresh taste and appearance of the endive. The tunnels also slow down swings in temperature, giving plants time to move water in and out of their cells and whatever else they do preparing for and recovering from cold.

Too many people, even gardeners(!), consider endive as nothing more than a bitter, green leaf best used as garnish. Reconsider. Given close spacing so that inner leaves of each head blanche from low light along with cool and cold temperatures, and endive takes on a wonderful, rich flavor. Only the slightest hint of bitterness remains, enough to make the taste more lively -- delicious in salads, soups, and sandwiches.

*****************************************

Man can’t live on greens alone. But I still have no need to go to a store to round out my vegetable fare. Much of what grew in last season’s garden is in storage, on tap for when I need it. Besides the usual frozen green beans, corn, okra, and edamame, steamed, cooled with a fan, then packed into freezer bags, and the usual canned tomatoes, a lot of vegetables are in cool storage.

That cool storage could have been my refrigerator, except that no refrigerator is spacious enough for a winter’s worth of turnips, winter radishes, beets, and leeks, and a few heads of cabbage. A couple of years ago I built a walk-in cooler. Saving money and energy, I cool this cooler with CoolBot (www.storeitcold.com), a nifty device that tricks a window type air conditioner in believing it has not reached its pre-set minimum temperature of 60°F. I set the indicator on my CoolBot to 40°F., and there it stays. I also have some boxes of apples and pears in there, as well as, up to a couple of weeks ago, pawpaws.

As temperatures continue to drop outdoors, the CoolBot will no longer be needed. Then I’ll move all the boxes to my unheated mudroom. As temperatures drop even more, the boxes will go down into my basement, the temperature of which should by then have dropped into the 40s.

It’s amazing, if you sleuth around your house with a thermometer, especially a house built more than 50 years ago, how many different temperature zones you find. Below 40°F but above freezing is ideal for most fruits and vegetables, except for tropical fruits, sweet potatoes, and winter squashes, which like slightly warmer temperatures.

I’m looking up at my green roof, and it’s not green enough. Literally. I had expected that by now, 8 years after being planted, the roof would be solid green. It’s not.

The green color of this roof is from plants. Conditions up on the roof are pretty rigorous so the plants I chose for it were tough ones, hens-and-chicks (Sempervivum spp.). Hens-and-chicks look like little cabbage heads of stubby, succulent leaves. Baby plants push out from around the mother plants, grow, and make more babies, and so on, ad infinitum. Or so I hoped.

The roof only has a couple of inches of “soil” on it and covers a porch, so has no he

ated space or insulation beneath it. If winter temperatures plummet to 10 degrees below zero, not uncommon here, temperatures within that thin layer of soil also plummet to 10 degrees below zero. If summer temperatures hit 95° in the shade, the soil, which is shaded at one end, also hits 95°, and more in the sunny end. The roof never gets watered, except by natural rainfall.

The hens-and-chicks have established and survived and spread. But not enough. By now, I expected the roof be packed solid with hens-and-chicks to the point of excess plants spilling over the front edge. But too much soil still shows. Part of the green problem is that hens-and-chicks are not all that green; the leaves are more pale blue-gray.

*********************************

I’m taking two steps to green up the roof.

The first step is to introduce another plant. A plant, which I believe is ‘Angelina’ rocky stonecrop (Sedum rupestre), has been magically appearing here and there in and around my rock walls. Well, not magically. As with other succulents, ‘Angelina’ easily grows into whole new plants wherever any piece of stem or leaf merely drops onto the soil. Over the past few years, I have dropped pieces of ‘Angelina’ onto the green roof; they’ve rooted and spread and parade there as forest-green patches.

Now I’m getting more serious with ‘Angelina’. Today I filled some cell-type seedling flats with a “soil” of equal parts moist peat and perlite, and poked inch-long pieces of leafy ‘Angelina’ stems into the mix. After a winter in the greenhouse or a sunny window, those cuttings will be rooted enough to plug into holes I’ll dibble into the soil on the roof among the hens-and-chicks. The roof is a little more than 100 square feet. Each plant should fill up a square foot in a couple of seasons, so I need 100 plants cuttings which take up only a couple of square feet.

Step two to rooftop greenery will be beefing up the “soil.” The soil is actually a mix of equal parts peat and calcined montmorillonite clay (a.k.a. kitty litter, unused). The mix is heavy enough not to blow away, and has enough mineral matter and recalcitrant organic matter so that little of it decomposes into thin air. Some shovelfuls of this mix tossed up on the roof will replace what’s washed away or settled. The mix is lean in nutrients so, come spring, I’ll also beef up the rooftop with some fertilizer.

********************************

I don’t get it. Green roofs are so “in” these days, for their green appearance and for their environmental green-ness. Sure, green roofs insulate rooms below from heat and cold. And green roofs capture and evaporate some rainwater rather than let it run down gutter pipes and into sewers or streams. The air above green roofs stays cooler than that above conventional roofs, so heat islands aren’t created.

Are these good enough reasons to put plants on a roof? After all, good insulation also insulates, a lot better than soil and with a lot less weight. And how much water could a roof of succulent plants -- plants known for their low water usage -- evaporate?

Much as I love plants, I’d rather see solar panels on roofs. My green roof is for looks (and not sunny enough for solar panels).

*******************************

My green roof is a testimonial to the tenacity of plants. Despite a “soil” that started out free of weed seeds, weeds have colonized the roof. And they survive, despite the rigorous growing conditions up there.

The weeds that came in weren’t succulents, but grasses and perennials such as foxtail grass and goldenrod. Every time I look up at the roof, I am awed that these and other plants not only arrived and grow there, but survive year after year. Weeding up there would seem such a travesty -- and be very difficult.