Why Autumn Is Also Fall

50923thumbNow that leaves are falling, they need to be raked. Large leaves, like those of sycamore and fruitless mulberry, can shade out lawn, shallow ground cover or dense shrubbery. If shade is not a problem right away, mildew can be after only a bit of rain. If abundant enough, finely textured silk tree or jacaranda foliage that typically sifts harmlessly through shrubbery and most ground cover, can accumulate and damage lawn, dichondra and the densest of ground cover. Walnut foliage has an herbicidal effect on sensitive annuals and some perennials.

Foliage is only beginning to fall. Cooling weather causes deciduous trees to shed more. Rain and wind bring the foliage down even faster. Even evergreen trees that naturally shed throughout the year will likely shed more through the upcoming wintry weather. Some trees start to defoliate early in autumn. Some hold their foliage until frost. Some trees that seem to be evergreen hold their foliage through winter, and then only drop their older foliage as it gets replaced by new foliage as winter ends.

Pavement and decks should be raked of leaves, not only to avoid staining, but also because rotting leaves can become dangerously slippery. Curbside gutters are too visible to get neglected for too long. However, heavy rain can quickly deliver to the cleanest of gutters a mess of fallen leaves as well as any other debris and litter that happens to be up the road. Strong wind can be filtered through hedges, leaving drifts of blowing leaves.

Leaves should also be cleared from roof gutters and downspouts, and may need to be cleared away again later in the season. More debris may need to be removed from awkward spots where it might accumulate, such as behind chimneys. Flat roofs may need to be raked.

There are a few exceptions to the need to rake fallen leaves. Where they get absorbed into coarse ground cover like Algerian ivy, falling leaves are generally not a problem. Pine needles and cypress foliage can be left if it happens to be useful for the natural suppression of weeds. Mature coast live oaks and valley oaks that are accustomed to a layer of their own fallen leaves over the surface of the soil actually want it to stay. For them, the foliar debris is a mulch that adds organic matter, insulates the soil, and retains moisture.

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Snails, Weeds And Falling Leaves

P90713KThe coloring of foliage is a bit slow this autumn. The cooling nights after such warm weather is bringing some of the deciduous foliage down while it is barely yellowing. Honeylocust and black oak have already gotten notably sparse without much notable color. Hopefully, the more colorful sweetgum, flowering pear, pistache and gingko trees will retain their foliage later into cooler weather, so that they can put on a worthy show before filling compost piles.

It is probably slightly too early to clean gutters and downspouts. Unless the rainy season somehow starts first, this should probably wait until most of the foliage that is expected to fall has already fallen. Lawns, certain ground covers, decks and pavement should be raked as needed though. Decks and pavement can get stained from the tannins that leach from decomposing foliage. Lawn and ground cover do not like the shade under the debris.

However, slugs and snails really dig the mess. Fallen foliage keeps the ground cool, damp and shaded. Raking leaves does not eliminate slugs and snails, but inhibits their proliferation. There are always plenty of other hiding places. As the weather eventually gets cooler and damp, snails that stay out in the early morning should be collected and disposed of. Of course this technique is not convenient for everyone, since most snails hide before the sun comes up. Small slugs hide earlier in the morning and are even more unpleasant to handle.

Once found, neither slugs nor snails are too elusive . . . or fast. Yet, plucking and collecting them is not a fun job. Once collected, no one knows what to do with them. They can be put into plastic bags and disposed of; and will eventually succumb. Some people prefer to simply toss them onto a dry and sunny driveway or roof where they succumb more quickly and get taken by birds. Snails may need to be squashed to limit mobility.

Even though it is too late to prevent most types of weeds from dispersing their seed, a few types continue to disperse seed as they deteriorate through autumn and winter. Weeds in areas that get watered last longer and disperse their seed later than those without watering. Perennial weeds that are still green in dry areas areas will be easier to pull after the first rain.

Falling Leaves Get Into Everything

51028thumbEven if they had been clean since they were emptied out last winter, gutters (eaves-troughs) near deciduous trees will eventually need to be cleaned again as they collect falling leaves through autumn. Leaves may continue to fall for several weeks, and will fall more abundantly as they get dislodged by rain.

Too many fallen leaves clog gutters and downspouts. If too much debris is left in downspouts for too long, it rots and settles so that it can be very difficult to dislodge. If rainwater can not adequately drain through gutters and downspouts, it can only flow over the edges of gutters. The falling water can erode the ground below, and splatter mud onto nearby walls.

This may not seem like much of a problem, but the reason that gutters and downspouts drain rainwater to the ground gently is to keep the walls dry and clean. Damp walls are likely to rot, especially if water splatters into basement vents. This is why early American homes that lacked expensive gutters were often outfitted with dense ‘foundation’ shrubbery or perennials to soften the splatter.

Leaves that accumulate in the valleys of the roof (where perpendicular slopes meet) should also be removed. Debris can also collect on the upslope side of a chimney. Homes with room additions have more awkward spots to collect debris than unaltered homes. Flat roofs and parapet roofs are of course very likely to collect debris under trees, and may need to be raked more than once.

Vines should not be allowed to climb onto roofs. They can tear apart roofing material, collect debris, and promote rot. Likewise, limbs of trees and large shrubbery should not be allowed to touch roofs, gutters, or even walls. Their motion in the breeze is abrasive to shingles, gutters, paint and siding. They can literally grind off shingles and break terracotta tiles.

Tree limbs should also be kept clear of chimneys. Even during rainy weather, hot exhaust from a chimney can dry and ignite limbs that get too close. Pine, cypress, cedar, and palms with beards (accumulated dead fronds) are very combustible.

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.

Gutters And Chimneys Need Attention

71101thumbThere is no time that is best to clean the gutters on the eaves. They should probably be cleaned early before the debris within them gets dampened by the first rains. However, they will only need to be cleaned out again after more foliage falls. If cleaned only after all the foliage falls, they will be grungier, and there will be potential for some of the debris to flow into and clog the downspouts.

Most of the fresh leafy debris that fell recently is relatively easy to clean out. Debris that has been accumulating through the year will be more decomposed and settled in. Evergreen trees are somehow messier than deciduous trees. They drop smaller volumes of debris in autumn, but they drop the rest throughout the year. Deciduous trees drop all their foliage within a limited season.

That certainly does not mean that deciduous trees can not make a mess. All that foliage has to go somewhere. If the weather gets cool slowly, foliage falls slowly, and for a longer time. Some deciduous trees innately defoliate slowly, and may even wait all winter to finish. Fruitless mulberry, tulip tree and poplars typically defoliate efficiently, making a big mess that gets cleaned up once.

Flat roofs that lack gutters collect debris too. So do the spaces behind chimneys and in roof valleys (where the slope changes direction). Even if this debris does not interfere with the function of gutters and downspouts, it promotes rot in roofing material. Trees and vines that touch a roof are likely to be abrasive to roofing material if they move in the breeze, or hold debris against the roof.

Trees and vines must be kept clear of chimneys, not only because they can interfere with ventilation, but also because they can be cooked by exhaust from the fireplace below, and ignite! Fan palm beards (dead foliage that accumulates on trunks), pine, cypress, spruce and cedar are particularly combustible. Clinging vines can separate brick from mortar, which is another fire hazard.

Working on the roof and gutters is of course potentially dangerous. It might be best to get a professional for these sorts of jobs, especially if trees need to be pruned. While that is being done, there is plenty of raking and other gardening for us to do (without a ladder). Raking leaves is an important job too, since fallen leaves can shade out lawn, ground-cover and flowering annuals.

Why Autumn Is Also Fall

71011thumb.jpgThe calender says that it is now autumn. The weather does not necessarily agree. Some of the trees are dropping their leaves. However, the leaves are not falling because the weather is getting significantly cooler. The leaves got cooked during that weird heat wave a few weeks ago. If the weather can be this confusing here in our very mild climate, it must be really crazy everywhere else.

It is hard to make sense of what trees are dropping leaves in response to the earlier heat. Coast live oak, which normally tolerates heat quite well, was really annoyed by the heat in some areas. Cottonwood and other poplars are expressing their discomfort too, but that is to be expected from them. Sycamores, which are normally sensitive to weather anomalies, are not overly concerned.

All this means to us, the janitors of our trees, is that some of us might be raking leaves earlier than expected. These leaves will not be the nice colorful sort that we like to see in autumn. Those will come later. It is still too early to know how the weather will affect autumn color. All we know so far is that some trees will have less foliage for coloring. Sweetgums are hinting at a colorful autumn.

Leaves should be raked as they fall. However, because no one wants to clean the eave gutters any more than necessary, they can be cleaned only a few times, or maybe only once if trees shed efficiently. They are easiest to clean before the rain starts and the wet leaves start to decay. Unfortunately, most deciduous trees continue to drop their leaves well into the rainiest part of winter.

Lawns and shallow or dense groundcovers really do not like to be shaded by fallen leaves for too long. To perform through winter like we expect them to do here in our mild climate, they want as much sunlight as they can get while the days are shorter and the sun is lower on the horizon. Besides, fungal pathogens like mildew and rot, are more likely to proliferate under damp fallen foliage.

Finely textured leaves under low shrubbery and coarsely textured groundcover that ‘eats’ fallen leaves is a nice mulch, so does not need to be raked. If it can not be seen, and is not too abundant, it is probably not a problem. The exceptions are fallen leaves of roses, grapes, cane berries, deciduous fruit trees, and any plants that are susceptible to diseases that overwinter in fallen leaves.