Autumn Leaves

Weather: Morning temperatures generally just above freezing, last rain 10/12/12; 11:04 hours of daylight today.

What’s blooming in the area: Hybrid perpetual roses.

Beyond the walls and fences: Leatherleaf globemallow, goat’s head, chamisa, áñil del muerto, golden hairy asters.

In my yard: California poppies, larkspur, chrysanthemums.

What’s blooming inside: Zonal geraniums, aptenia, petunias.

Animal sightings: Goldfinches and other small brown birds, geckos, bumble bees, other bees, hornets, harvester and small black ants.

Weekly update: As autumns go, this one has been orderly. When sun angles changed and with them temperatures, annuals and perennials went to send. Then, two weeks ago morning temperatures fell below freezing, killing off all but the most protected annuals and destroying leaves on the imported trees.

Since, the natives and colonized trees and shrubs have been preparing for winter. They slowed their production of chlorophyll. The green drained from the leaves, leaving the hidden pigments. From a distance, the colors are solid.

But sometimes, when the light is right, you can see what has happened, can see the leaves are not as solid as they were.

It isn’t just the red pigments. It’s the more common yellows as well. From a distance, like the far cottonwoods, they look the same. Then, when the light is right, you can see the yellow is really more chartreuse where the green hasn’t quite disappeared.

It isn’t just the trees and shrubs. The pink primroses have been turning red

and the Maximilian sunflowers have been turning yellow.

The animals are responding as well. There don’t seem to many fruit eating birds in this area; it took weeks for the sour cherries to disappear, and the sandcherries and Virginia creeper simply desiccated.

This week, the seed eating goldfinches returned to the Maxes. I can only see them through the window or from a distance. As soon as I’m detected, they rise, maybe a dozen, from within the toppled remains.

The leaves eventually will drop and blow away, or dry, shrivel and be worn away by winter winds. The finches will remain somewhere, showing up in the chocolate flowers after they’ve finished harvesting the sunflowers with some kind of territorial agreement with the resident chickadees.

Photographs: All taken 16 October 2012.
1. Cottonwoods through the leaves of the lilacs.

2. Virginia creeper berries.

3. Sandcherry leaves.

4. Sandcherry leaves in the sun.

5. Lilac leaves.

6. Pink evening primrose leaves.

7. Maximilian sunflower leaves.

8. Goldfinch on a Maximilian sunflower seed head.

9. Catalpa leaves.

10. Tansy flowers turning brown around the edges.

Tree Leaves

What’s happening: The snow brought moisture, and the crust responded; moss in places last Sunday; looks like snow also loosened some rocks which came down into the arroyo; new basal growth on snapdragons Thursday.

What’s still green: Moss, juniper and other evergreens, Apache plume, yuccas, Japanese honeysuckle, pyracantha, grape hyacinth, large-leaved soapwort, sea pink, hollyhock, cheese, oriental poppy, blue flax, yellow and pink evening primroses, vinca, sweet pea, gypsum phacelia, tumble mustard, snakeweed, dandelion, anthemis, coreopsis, chrysanthemum, heath and strap leaf aster leaves; pampas and cheat grasses; rose stems and young chamisa branches.

What’s grey, blue-grey or grey-green: Piñon, four-winged salt bush, buddleia, pinks, snow-in-summer, loco weed, yellow alyssum, stick leaf, western stickseed, winterfat, golden hairy aster leaves.

What’s red/turning red: Cholla, prickly pear, small-leaved soapwort, beards tongues, coral bells leaves.

What’s yellow/turning yellow: Arborvitae; globe and weeping willow branches.

What’s blooming inside: Christmas cactus, aptenia, asparagus fern; chaste tree leaves dead.

Animal sightings: Robin in cottonwood Thursday; rabbit about.

Weather: Ground wet when I got up Wednesday morning, rain Thursday night turned to frost the next morning; 9:45 hours of daylight today.

Weekly update: A week ago Friday, one of the men I work with drove in from Pecos with a great, gaping hole in his windshield where a cottonwood branch had come down during the night. Snow and small branches still rode on the roof.

Cottonwoods have relatively soft, weak wood that doesn’t tolerate bending or compression. Ron Smith, of the North Dakota state extension service, calls them "free kindling," because they drop their branches so easily. There currently is a scatter of small, maybe half-inch thick, grey-white branches on the shoulder under a male cottonwood down the road.

One of the things that’s always puzzled me is why some local trees retain their leaves into winter and why those leaves don’t cause more problems for branches when they get wet or collect snow. I remember in Michigan the ice storms of January and February were always accompanied by broken limbs and downed power lines.

When the snow fell last week, my black locusts still had half their leaves, while the catalpa had some on its lowest branch and the cottonwood had scattered leaves near the bottom. Some cottonwoods growing near arroyos kept most of their leaves, while those near the river were bare.

This year the coming of winter in the Española valley has been marked by discrete, widely spaced events. We had our first hard freeze, when temperatures dropped into the high 20's, on October 26. Before that, the leaves on all three species were turning yellow in an orderly manner, but neither the locust nor the catalpa were prepared. The leaves on the one exotic turned dead green, the others brown. The native cottonwoods continued to yellow.

Night temperatures got decidedly colder, 20 on my front porch, on November 10. The cottonwood leaves turned brown.

The first snow moved through on November 16. When I woke the temperature was hovering around 32 and water was condensed on many leaves. I don’t know if we actually got snow, or only very cold moisture. The cottonwoods and catalpas dropped many of their leaves, but the locusts remained the same.

Another storm moved through on November 28, leaving snow in the mountains. High winds stripped my locusts of many of their leaves, especially toward the top. Three days later the morning temperature fell to 10 on my front porch. The remaining locust leaves turned brown.

Last week, the snow started falling just before dark on Thursday and stopped by the time blizzard conditions moved through the open lands between Santa Fé and Albuquerque that night. Pecos was already buried. The temperature was only 32 when I got home Friday night and little had changed except the roads were dry.

Saturday the sun never really broke through the clouds, but the temperature rose into the 40's. Snow either sank into the ground or evaporated into the air. Sunday morning was foggy from the heavy moisture load in the air. By mid afternoon, it was 50 on my front porch and most of the snow was gone.

Ice and leaves behaved the way I expected. On Saturday, evaporating water condensed on my metal roof and fell towards the roses’ drip line where it cooled as it dropped. When it landed on a vertical stem, it simply slid to the ground. When water landed on a leaf on a horizontal branch, it first encased the leaf in ice, then formed icicles which coalesced into elaborate, clear structures. Many rose leaves are now turning brown.

The immediate effect of cold damp wasn’t something I’d ever noticed before. Leaves on many non-woody plants turned black, especially the baptisia, which was never covered, and the purple coneflowers, which were buried. When I walked out towards the arroyo Sunday, I had a sense things were darker, but couldn’t identify any particular plant: it could have been the general wetness or it could have been leaves and stems darkening on some, but not all, individuals of plants like golden hairy asters.

The impact of the snow was less obvious. It tended to collect on lower, horizontal branches facing the storm. Leaves happened to be present on some of those branches that collected snow in my yard, but it was probably because both the leaves and the snow responded to similar wind patterns. The trunks of the trees must deflect the winds which keep leaves in place and allow snow to accumulate.

The weight of the snow did break the final connection between the leaves and the black locusts. By Saturday afternoon, there was a great mess of leaflets lying atop the snow. On the prairie, it looks like one cottonwood branch snapped, one that still retained its leaves. All the other downed wood looked old, long ago bleached and stripped of any signs of life.

The reason the leaves survived so long seems to be related to location as much as species. Botanists tell us plants respond to water stress and lower fall temperatures by slowing photosynthesis and producing abscisic acid, a hormone that seals the joints between leaves and stems so dead leaves can fall. If those biochemical messages are absent or contradictory, the plant is less likely to adapt to the changing season.

The cottonwoods growing on the relatively dry land back from the river near the city had no leaves this week, and the ground below was littered with long dead branches no one had cleared. Nothing looked like a new fall.

The cottonwood that lost its branch was growing in a gully cut by water leaving the end of an irrigation ditch for the arroyo. The tree that still has its leaves near the village sprouted in the run off of another irrigation ditch which has since dug a trench around the tree, exposing its roots. The arroyos kept running after the natural environment began to dry last fall, apparently countermanding any stress messages.

In my yard, the cottonwood is protected by a wooden fence on two sides, north and east. The surviving leaves are below the top of the fence towards the center of the tree. The locusts are close enough to the house, that the building may slow the wind near the ground where leaves still exist, while the leafy end of catalpa branch is less than 2' above the warmer ground.

The effect of piles of snow seems less important to trees than either damp or ice, which combines the weight of snow with the cold moisture. However, species seems more important than location. The locust shrugs off loosened leaves, while the cottonwood breaks from too much pressure.

Notes:
Smith, Ron. "Questions on Cottonwood," North Dakota State University extension website.

Taylor, Jennifer L. "Populus deltoides," 2001, in United States Forest Service, on-line Fire Effects Information System.

Photograph: Cottonwood growing in a gully carved by an irrigation ditch, with a leaf laden broken branch, 24 December 2010.

Pasture Rose

What’s blooming: Freeze dried purple aster by front gate; many trees still hold dead leaves; one family has bagged their dead debris while their neighbors were burning yesterday.
What’s still green: Juniper, arborvitae and other conifers, roses, yucca, prickly pear, honeysuckle, red hot poker, vinca, rock rose, hartweig, yellow evening primrose, blue flax, sea pink, winecup, pinks, soapworts, bouncing Bess, beardtongues, snapdragon, Jupiter’s beard, snakeweed, senecio, yarrow, Mount Atlas daisy, Mexican hat, chocolate flower, June and other grasses, alfalfa; only protected leaves survive on sweet pea, hollyhock, catmint, chrysanthemum and purple coneflower
What’s gray, blue or gray-green: Piñon, winterfat, saltbush, buddleia, loco, snow-in-summer, yellow alyssum, chamisa, Silver King artemisia.
What’s red or orange: Pasture rose, spirea, raspberry, cholla, privet, coral bells, white beardtongue, pink evening primrose.
What’s turning yellow: Cottonwood, willow, globe willow, Apache plume, iris, Saint John’s wort, golden spur columbine.
What’s blooming inside: Aptenia, rochea, bougainvillea; Christmas cactus leaves turning red.
Animal sightings: Brown bird with dark head in cherry; horses brought in to browse mown alfalfa field down the road.
Weather: Rain Monday with heavy frost on windshield subsequent mornings when temperatures fell to high 20's after dawn; 9:13 hours of daylight today.
Weekly update: A run of mornings with consistently cool temperatures this year has given the valley something rare: fall color. Not only have huge cottonwoods changed into golden domes, but tamarixes and other small-leaved plants have transmuted into orange-shaded lattices. The sand cherries turned their usual purple, but here and there some neighbors’ shrubs have been the brilliant red of maples.
In my yard, the pasture roses have been the most amazing because they not only turned red, but the leaves glowed when light filtered through them. The maroon raspberries at their feet were comparative dullards, opaque ground-hugging triangles of hairy corduroy.
The reds come from anthocyanins, flavonid chemicals formed by interactions between sugars and proteins that protect plant tissues by absorbing ultraviolet light. They become more prevalent in leaves when cool weather slows the production of chlorophyl and other protective agents are generated. With many hybrid roses, the new growth is red until photosynthesis accelerates. On some cultivars, the leaves keep a red edge long into the blooming season.
In the fall most hybrid rose leaves darken, then dry and fall from stems that tend to stay green all winter. The only other roses I have that shaded into burgundy this year have been the crenellated rugosas. The precise shade of an anthocyanin red is determined by the pH in the plant sap, which in turn is controlled by the soil: the more alkaline the soil, the bluer the color.
Japanese scientists have been curious about the distribution of the some 550 anthocyanins so far identified. Among wild and cultivated roses they found chemical patterns identified three subgroups within the Rosa genus: one the gallica, chinensis, Synstylae (including winchurana, musk and multiflora), Cherokee, Macartney and Banksia, another the species of Scotch roses, and a third which includes dog, carolina, and cinnamon roses.

Volker Wissemann and Christiane Ritz found members of the last two groups did not share the same DNA patterns as the first. Others found the carolinas, native to eastern North America, are natural scions of Rosa arkansana and Rosa virginiana, both themselves natural hybrids of other native roses. Apparently, as the plants evolved on two continents, the chemistry of the American roses diverged from the Eurasian ones originally used to create modern hybrids.

I got my carolina rose through one of those impulses that happen after one has dutifully pruned one’s wish list to fit the budget, and then said, "oh why not" when filling out the order form. In 1998 I bought seeds from Prairie Nursery, blithely ignoring the warning that the "seeds are double dormant and require treatment to break dormancy and induce germination." When nothing sprouted I shrugged.

Four years later, in 2002, I noticed what looked like rose leaves in the drip line where I had dropped some 300 seeds and wondered, but I cautioned myself with memories of other briars that had looked like roses only to become unwelcome pests. Leaves continued to appear each year, teasing me with possibilities, and then colonized last year among the raspberry canes.

Then on June 10 a single pink flower appeared, and I knew I had grown a carolina rose from seed. That doesn’t sound like much if you live where pasture roses sucker into great thickets, but here the "dry prairie" of a Wisconsin seed company is only a wet dream. Even if all I ever get are leaves, I now know at least once a decade, when the fall is both cool and dry, I’m going to have the most spectacular red leaves in the valley.

Notes:Joly, Simon, Julian R. Starr, Walter H. Lewis and Anne Bruneau. "Polyploid and Hybrid Evolution in Roses East of the Rocky Mountains," American Journal of Botany 93:412-425:2006.

Mikanagi, Yuki, Masato Yokoi, Norio Saito and Yoshihiro Ueda. "Flower Flavonol and Anthocyanin Distribution in Subgenus Rosa," Biochemical Systematics and Ecology 23:183-200:1995.

Prairie Nursery. Wildflowers and Native Grasses, 1996 catalog.

Wissemann, Vilker and Christiane M. Ritz. "The Genus Rosa (Rosoideae, Rosaceae) Revisited: Molecular Analysis of nrITS-1 and atpB-rbcL Intergenic Spacer (IGS) versus Conventional Taxonomy," Linnean Society Botanical Journal 147:275 - 290:2005.

Photograph: Pasture rose, 9 November 2008, with darker raspberry leaves at bottom left and native grasses in rear.

Autumn Leaves

What’s blooming in the area: Áñil del muerto, purple asters.

What’s blooming in my garden: Snapdragon, coral bell bud, petunia behind hollyhock leaves, sweet alyssum from seed, blanket flower, chrysanthemum.

Inside: Aptenia, geranium.

Animal sightings: Quail, ants.

Weather: Some very cold mornings; last rain, 29 September.

Weekly update: We’re having a genuine autumn this year, after several years with no serious frost until late November. After the cold a week ago Monday, trees that had stayed green suddenly were brown. Those that had some intimation of the coming desolation were more intensely yellow. A few had brown, yellow, and green patches.

Beneath the surface, abscisic acid is sealing the joints between branches and leaves, so that no open wounds remain when leaves finally drop. Meanwhile, the rate of photosynthesis is slowing as perennials enter winter dormancy, and the quantity of chlorophyll in leaves is decreasing. As the green fades, other leaf pigments become visible, including the yellow xanthophyll.

Xanthophyll had been known for years when Frederick Addicott’s team reported abscisic acid as a long sought growth inhibiting hormone in 1963. It begins as xanthoxin with 15 carbon, 22 hydrogen, and 3 oxygen atoms which have split from the 40 carbon, 56 hydrogen, and 4 oxygen atoms in a molecule of violaxanthin.

Xanthoxin is inherently unstably, and loses two hydrogen atoms to become abscisic acid aldehyde. When exposed to oxygen, that molecule converts into abscisic acid with a half life of about eight hours and four oxygen atoms. That in turn becomes phaseic acid with another oxygen atom, then dihydrophaseic acid with two more hydrogen atoms.

Xanthophyll sounded much simpler when Jöns Jakob Berzelius described the pigments in fall leaves in 1837. Scientists have since applied the term to any oxygen compound with 40 carbon and 56 hydrogen atoms.

The most important xanthophyll in leaves at dawn is violaxanthin. Instead of shucking off atoms and moving through the plant as abscisic acid, it stays in the leaf and loses an oxygen atom to become antheraxanthin. Later in the day, it loses another oxygen atom to become zeaxanthin, before reverting to its original state in the night.

Scientists want to know more than that zeaxanthin is created to protect the photosynthesis centers in leaves from increased solar energy levels in the day or that abscisic acid is a response to threats from low temperatures and drought. They want to know the nature of the bonds that connect those carbon atoms, the type of oxygen, the enzymes that transform each of the compounds, and the system of communication that triggers the creation of xanthoxin.

I don’t think about molecules, when I look through my windshield at the changing patterns of color formed by groupings of trees against the open fields, the sky, and each other. Still, it’s reassuring to know laboratory scientists remain who use the simple methods we were taught in high school chemistry to submit any scientific postulation, no matter how complex, to the old tests of dissolution, heating, sniffing, and spectrum analysis to reveal the beauty beneath senescent skin.
Notes:
Compounds in the abscisic acid chain
C40 H56 O4 - violaxanthin
C15 H22 O3 - xanthoxin
C15 H20 O3 - abscisic acid aldehyde
C15 H20 O4 - abscisic acid
C15 H20 O5 - phaseic acid
C15 H22 O5 - dihydrophaseic acid

Compounds in the violaxanthin chain
C40 H56 O4 - violaxanthin
C40 H56 O3 - antheraxanthin
C40 H56 O2 - zeaxanthin

Photograph: Yellow and green leaves on young cottonwood, 3 November 2007.

Fall

What’s blooming in the area: Lance-leaf yellow brush peaked, datura, purple aster, tahokia daisy almost gone, lamb’s quarter, áñil del muerto peaked, golden hairy aster, bigleaf globeflower, purple mat, large white rose of Sharon, roses, sweet peas, heavenly blue morning glory, silverlace vine. More Maximilian sunflowers are blooming while the natives are going to seed. Apples are starting to drop. Three fields and a yard have recently been plowed; one’s already bright green.

What’s blooming in my garden, looking north: Black-eyed Susan, gloriosa daisy, blanket flower, chocolate flower, perky Sue, fern-leaf yarrow, Mexican hat, yellow cosmos, creeping zinnia, nasturtium, lance-leaf coreopsis, chrysanthemum, miniature rose (Rise and Shine).

Looking east: California poppy, crackerjack marigold, tall zinnias, winecup, large flowered soapwort peaked, pink bachelor button, larkspur, Shirley poppy, sweet alyssum.

Looking south: Crimson rambler morning glory, sensation cosmos peaked, heath aster peaked.

Looking west: White phlox (David), frikarti aster, lead plant, catmint, purple ice plant. Russian sage is sheathed in purple, but has no flowers to attract bees.

Bedding plants: Dalhburg daisies, marigolds, sweet alyssum, snapdragons, petunias, profusion zinnia, nicotiana.

Animal sightings: Gecko, bees, grasshoppers, ants; rabbit and gopher back; horse grazing near main road, turkeys near village.

Weather: Warm noontides, but frost on my windshield in the mornings; no rain. Shorter days make it harder to see the garden and more difficult to water during the week. Leaves beginning to turn yellow on area catalpas, cottonwoods, and weeping willow, as well as my cherries, peach, roses of Sharon, Siberian pea shrubs, rugosa and tomatilla; spirea, caryopteris and white spurge turning orange.

Weekly update: Fall is here. So far there’s been no hard frost, but dawn temperatures have dropped enough to damage flowers and turn leaves yellow.

Usually, autumn is abrupt: a single night destroys tender annual plants and perennial flowers. Spring is the gradual season, when microclimatic differences in water and temperature mediate change, when a week may pass between the time a plant blooms in the village, and wheb it appears on the main road, that’s higher and farther from the river. Another week may pass before it opens on my still higher, more exposed ground.

Cold a week ago Wednesday killed my grape leaves. The following Saturday, most leaves were dead on vines just down the road, and many, but not all were brown a bit farther. Closer to the village, only the top leaves on a rail fence were brown, and vines in the village did not seem to be affected.

Yesterday, the leaves in the village were brown while the ones over the wooden fence were turning yellow. Between the two, the leaves on an iron fence near an arroyo were still green. The others that had survived last week were either brown or red.

More exposed parts, like the upper grape leaves, are the first to go. Petunias in a tall ceramic planter down the road were dead last Saturday, but the ones I’m growing between irises near my retaining wall are still bright. This past week, the erect and top horizontal stalks on my neighbor’s moss roses withered, but tangerine flowers were still open along the ground yesterday.

Variety within species may contribute to the nonuniform durability of plants. Ruby is the only grape I’ve managed to grow, and almost every year its leaves are felled by spring frosts; my neighbors may have hardier types. It was that same time a week ago my friend in a nearby settlement said her hybrid tomatoes had succumbed but not her heritage Brandywine.

Subtle genetic changes resulting from the selective histories of growers may also explain some variations in how similar plants respond to cold. Many of my small zinnias were gone by the end of last week, but not all. Some still bloom between the corpses where I sowed three brands of thumbelina and three of lilliput.

Last Saturday, the tall zinnias in the village looked unfazed from the road. Yesterday, I could see brown heads, but not as many as were in my garden. My taller zinnias, which happen to be protected by marigolds, didn’t die but had a shock. The hybrids opened July 22 and had never gone to seed. The day after the cold temperatures, a number of flowers had exchanged their brilliant raiment for the drabbery of confinement.

My morning glories had a different reaction. Like the tall zinnias, the flowers were scotched by the cold, but not the vital stems and leaves. Every few days last week, I spotted a flower. Then, yesterday, there were nearly the same number as before the cold spell, but the trumpets were smaller and they didn’t open until warmed by the late morning sun.

The stay of the executioner has let some plants harden themselves for the next month, perhaps to rebloom. Others are now busily completing their life cycles, producing seed. A week and a half later, the youthful lush garden has vanished; the infirm mingle with the young, flowers peak through dead stems and leaves. Individual differences in specialized locations prevail.