Deciduous Evergreens

P91201Well, that is certainly a contradiction of terms. One might say it is an oxymoron. Decades ago, it really was how we classified what we now know more simply as ‘deciduous conifers’. There are not many of them. Ginkgo is a gymnosperm like conifers are, but is not really a conifer. Otherwise, there are only five other types of deciduous conifers, which defoliate through winter.

Laryx is a genus of about a dozen species that are known collectively as larch. Taxodium includes two species known as bald cypress, as well as a third evergreen species. Pseudolaryx amabilis, known as golden larch, Glyptostrobus pensilis, known as Chinese swamp cypress, and Metasequoia glyptostroboides, known as dawn redwood, are all three monospecific genera.

Some species of larch are common within their respective natural ranges. So are the bald cypresses. The others are quite rare. However, dawn redwood became a fad decades ago, so is not so rare in landscape situations. To those of us who expect all conifers to be evergreen, deciduous conifers seem to die suddenly in autumn. To some, it is not exactly a desirable characteristic.

The dawn redwood above lives in our landscapes. The tall evergreen trees behind it are native coastal redwood. Obscured by the yellowing birch to the right, a small giant redwood (another oxymoron) represents the third and only other species of redwood. The fall color of this dawn redwood appeals to some, but to others, it looks like one of the native redwoods abruptly died.

Our bald cypress below does not look so much like a dead redwood. The foliar texture and branch structure are quite distinct. The cinnamon brown fall color is actually rather appealing.

Of course, these pictures are nearly two weeks old. By now, both trees are likely bare because of the rain.P91201+

Buckeye

P91109KCalifornia flora is remarkable. It all does what it must to live comfortably in every ecosystem, climate and geographical region here.

California horsechestnut or California buckeye, Aesculus californica, is one of the more unusual native species. It is so in tune with the climate that it makes other deciduous trees seem to be inexperienced. Of course, to those who are unfamiliar with it, it just looks dead right now.

In chaparral climates of California, some deciduous trees start to defoliate early, before the weather starts to get cool in autumn. California sycamores, for example, can start to defoliate late in summer if the weather gets too warm and dry for them to want to hold their foliage any later. Such defoliation is more the result of minimal humidity than the result of chill.

California horsechestnut takes this technique one step further, by shedding spring foliage even earlier in summer, then refoliating once the rain starts in autumn, and then defoliating again as the late autumn foliage succumbs to frost through winter. It is ‘twice-deciduous’. It is a weird process that should not work, but obviously does.

It seems like a tree that is defoliated most of the time would exhaust its resources and wear itself out. However, California horsechestnut somehow stores enough resources to produce weirdly big seeds. These in the picture above are the same that were featured in ‘Six on Saturday‘ last week, while they were still in their husks.

Squirrels might chew on a few of these seeds, but do not bother storing them. They are mostly ignored by wildlife, perhaps because of their objectionable flavor. So, without squirrels to bury them, they fall to the forest floor near the trees that produce them, where they are too bulky to sift through the detritus to reach the soil below.

It makes one wonder why they put so much of their limited resources into seeds that are too big to reach the soil, but unappealing to wildlife that might otherwise disperse and bury them.

They know what they are doing.

Once the rain starts, and the seed sense that the weather is damp, they germinate on the surface of the detritus on the forest floor, and extend their tap roots through the detritus to the soil below. The seeds are too bulky to reach the soil directly, but contain all that their primary tap roots need to survive without desiccation until they reach the damp soil.

 

Leaves Are Starting To Fall

81003thumbAutumn is slow in getting here. Yes, as of last Sunday, it is now autumn. The date is determined by the equinox, so is the same for everyone in the Northern Hemisphere, and is the same for the arrival of spring in the Southern Hemisphere. It just takes a bit longer for autumn weather to develop in the mild climate here. Nights are cooler. Shorter days are not as warm as they had been.

Even without the pretty foliar color that cooling weather prompts in other regions, deciduous foliage is already beginning to fall. Poplars, willows and some other trees that a naturally endemic to riparian environments are the first to start. Some are actually developing a slight bit of color, mostly soft yellow. More colorful foliage needs cooler weather, so will develop as weather gets cooler.

Sooner or later, falling leaves will need to be raked from lawns and groundcover. Trees that drop their leaves for a long time through autumn and into winter necessitate more frequent raking, even if their leaves do not accumulate enough to do much damage. Trees that drop their leaves within a shorter season can quickly drop enough to shade out turf or groundcover, or cause them to rot.

Because fallen leaves can stain hardscape surfaces, they should be raked efficiently from pavement and decking as well. Those of us who do not mind the staining, or even appreciate its rustic patina, might leave some of the fallen foliage out for a while, but should not leave it out long enough to promote rot in decking. Some leaves cause staining quite quickly, especially if wet from rain.

If leaves need to be raked from the garden and pavement, they probably need to be cleaned from roof gutters and anywhere else they accumulate on roofs. Just like raking, the clearing of fallen leaves from gutters and roofs is scheduled around the timing of the falling leaves, although it is not nearly as frequent. It may even be unnecessary if trees are too far from roofs for their leaves to fall or be blown onto them. Leaves that stay in gutters too long eventually decompose and clog downspouts.

How Shade Is Made

70816thumbMany of our trees live at our homes longer than we do. Some of our trees were there before we got there. Some of the trees we plant will be there for whomever comes along after we are gone. Trees very often evolve into something very different from what they were intended to be. Nonetheless, since they are the most significant features of our gardens, trees must be selected carefully.

The recommendation that shade trees near the home should be deciduous is cliché but accurate. It makes sense that the trees that provide cooling shade in summer will also allow warmth and light through while bare in the winter. Evergreen trees are better for obscuring undesirable views around the perimeter of the garden, where they will not shade the home too much through winter.

The problem is that many modern gardens are too small for such diversity. Modern homes are so close to each other that evergreen trees are more important for obscuring views. Consequently, evergreen trees that provide privacy between homes and gardens might also function as shade trees. Limited space also means that trees affect neighboring homes and gardens significantly.

This is why so many of the small trees (that are known almost disdainfully by some arborists as ‘microtrees’) are so popular. Japanese maple, flowering cherry and smoke tree that were once popular for atriums and small enclosed gardens are now popular shade trees. Realistically though, some modern backyards are not much bigger than what was once considered to be an atrium.

Small evergreen trees or large shrubbery, like Australian willow, mayten, photinia and the larger pittosporums, work nicely by providing both privacy and shade for small areas. Contrary to popular belief though, evergreens are generally messier than deciduous trees. They drop small amounts of foliage throughout the year instead of dropping most or all of their foliage within a limited season. Flowers or fruit add another dimension of mess, even for deciduous trees like crape myrtle, flowering crabapple and saucer magnolia.

Summer Deciduous

P80623K+++That is a term that we do not hear much. There are not many plants that it applies to. Cyclamen is one of the more familiar plants that is summer deciduous. It is from a climate with reasonably mild winters and unpleasantly dry and warm summers. Just like most deciduous plants are dormant through winter to avoid the unpleasantries of the weather, cyclamen defoliates as the weather gets warm in early summer to avoid the expected heat and aridity. It somehow knows how to stay dormant until the weather starts to get cooler in autumn, and is ready to regenerate new foliage and bloom as the rain starts. The active growing season is through autumn, winter and into spring. It is all a matter of taking advantage of the weather while it can, and avoiding the discomforts of severe weather when necessary.

Rhody, like most dogs, has been shedding his fluffier inner winter coat through spring. He still seems to be too fluffy for the weather, but he must know what he is doing. The remaining wiry outer coat provides a bit of shade, and helps to dissipate a bit of warmth when necessary.

Unlike Rhody, I do not have a fluffier undercoat to shed. All that I could do is shed some of the sparse and wiry outer coat. It might have provided shade, but also interfered with cooling air circulation. It does not seem to be designed to dissipate heat like Rhody’s is. Regardless, it was shed just before the Summer Solstice, and will not regenerate until autumn. A barber sheared back the upper evergreen growth first. I then pollarded most of the lower growth, leaving only a pair of formally shorn hedges flanking the upper margin. They too may be removed soon. Antithetically of https://tonytomeo.wordpress.com/2018/01/17/winter-coat/P80623KP80623K+P80623K++