The Circle of Life is Made of Leaves (and Big Logs)

“I like trees because they seem more resigned to the way they have to live than other things do.”--Willa Cather, O Pioneers (1913)

One of the unfortunate consequences of living in a drought-prone area is the occasional need to cut down dead or dying trees which should have been healthy for many years to come.  We at Myrtle’s place are in the middle of just such a project, with three exceptionally large elm trees all having died during the last couple of summers – had they only been able to hold out one more year, Summer 2014 was especially wet by comparison to the dry blast furnaces of the last couple of years.

Felled logs make excellent garden bed borders

We have undertaken this sad task at precisely the time of year when we are ordinarily thinking a lot about our trees anyway, given that we are on the verge of the autumnal leaf-drop season.  Of course, a lot of leaves drop throughout the year, simply based on the wide variety of species of trees and bushes on our lot, but the largest number of our trees conform to the stereotypical fall foliage festival, and so, we are eagerly anticipating that day (probably in October, but one never knows for sure) when our tallest oaks start looking a little pale, and then overnight turn to gold, and then quickly to red, and then quickly to bare.

The first signs of the coming of fall actually come from our grape vines, which start going all brown and crinkly in late August every year, though they manage to limp along sometimes until cooler weather finally arrives shortly before Halloween.  Every year the timid among Brazos Valley gardeners wonder if they’ve done something wrong, if their muscadine vines are dying… and every year, they come back stronger than before, often because of and not just in spite of the abuse and neglect they received the year before.

We find a lot of surprises when the grape leaves start falling.  Some of these surprises are charming and amusing, like the birds’ nests tucked away in precarious nooks and crannies that are tantalizingly oh-so-close-and-oh-so-far-away from our cat’s reach.  Some are natural and important ecologically, but still give us the willies, like giant nests of wasps going about their business mere inches above our heads on a daily basis with us none the wiser… until the leaf cover falls.

We know, though, that the falling of the grape leaves is the surest sign that we are entering an important part of the leaf cycle of our garden.  Er… life cycle.  Sorry about that.

Chickens in the foreground.  Oaks in the background.
The oaks are the tall ones who don't cluck.

Anyway, as we were saying… we frequently joke that we operate on an oak leaf economic basis.  The bedding for our chickens comes from a three-foot deep layer of oak leaves, for example, and as that stews and composts it becomes the rich hummus which we use to fill our raised planter boxes for our various veggies.  Likewise, while we use cypress mulch for our pathways, when we mulch our herbs and vegetables we use the much cheaper and much more readily available oak leaf mulch – sometimes whether we plan to do so or not, particularly in our herb beds directly beneath the canopy of our largest water oak, which exfoliates so dramatically that there is simply no way we could keep the leaves out of the rosemary even if we wanted to, which, of course, we don’t.

There is almost unanimous support in the composting world for including leaves in any mix of organic matter being broken down for soil nutrition, and there are good reasons for that.  We have mentioned before that the healthiest soils are those which best reflect the natural growing conditions for whichever ecological niche you happen to occupy.  In most of the world, the biggest contributors to the native “compost” will be trees and shrubs, and usually it will be the deciduous varieties of each.

But… apart from their obvious bounty, why?  What makes leaves so important nutritionally for the myriad plants and animals that live on them?

The primary clue comes from the fact that leaves are so important to the plants which grew them in the first place.  Photosynthesis – the conversion of light to food – is the first and foremost function of leaves.  Their green color comes from the chlorophyll which forms the building blocks of their light-conversion-engines, and the spines and veins you can see in a leaf if you hold it up to the light show that they are very much more akin to animal life forms than we typically give them credit for being.  Trees and shrubs have circulatory systems, and it wouldn’t be too far off the mark to credit them with a central nervous system, albeit one that reacts somewhat differently from what you might see in the animal kingdom.

Pretty much everything in our garden is growing in
composted oak leaves, even the stuff in baskets.

The process of leaf loss is technically referred to as abscission, and though it happens every year, it never ceases to amaze us.  In temperate, boreal, and seasonally dry climates, abscission allows the tree to allocate resources properly for the seasonal unavailability of one or more essential components of its usual life-cycle.  Basically, in cooler climates, or in regions far enough north that winter daylight is insufficient for enough photosynthesis to meet usual nutritional needs, or in areas where long monsoon rains are followed by many months of drought-like aridity, trees will shed their leaves and “shut down” – the metabolism of the entire organism slows to as close to nothing as possible, and the plant waits for conditions to become favorable again before sprouting new leaves.

Obviously, given this strategy, the tree or shrub would not want to discard leaves which still had any sort of nutritional value to the organism as a whole, and for that reason alone one might question whether fallen leaves have any organic value, but that would be an oversimplification.  There is still plenty left in the biochemical goodie bag of a fallen leaf, it’s just that it is not in a form readily accessible to the plant “as is”.

It doesn't matter where you are on our property, the
big oaks out front dominate the horizon.  Good.

In addition to creating energy, leaves are often storehouses for energy, as well.  Further, many of the defense mechanisms plants use to fend off foraging animal life – thorns made of tightly arrayed lignins, tannins, other natural poison compounds – are comprised of nutritional components which have been allocated for the purpose of defense, and which are readily broken down in the compost heap (or the natural hummus of a decomposing forest floor), but which would not be easily broken down by the tree itself when getting ready for a long winter’s nap.

It makes sense, then, that the animals which forage on green leaves would ignore fallen browns, reds and yellows, but it also makes sense that a whole new category of creatures would feast on the discard pile.  A wide variety of insects and worms (not to mention microbes), in addition to molds and other miscellany, go to town on the forgotten side of the forest salad bar.  And that’s before even considering the leaves that get hauled off to the chicken coop, where they get mixed in with… ahem! other organic materials.

Even if we didn’t use fallen leaves in our garden or our chicken coop, of course, it still goes without saying that a pile of raked up leaves is just plain fun to jump in.

Happy farming!