The incredible shedding live oak
Trees are constant shedding organisms. As they grow and put on new “cones of wood” throughout their structure, the branches, trunks and roots are expanded, new twigs and leaves are created, and old branches, bark, twigs and leaves are shed from the plant. Additionally, weakly attached limbs break off due to storms or weight related breakage from new growth.
Trees are perennial organisms, meaning that they survive year after year, getting larger and larger season after season. Under ideal climate conditions, some tree species never go dormant. Tropical trees, for example, do not even have growth rings because they don’t have seasons and rapid weather/temperature swings to affect their yearly growth on a seasonal basis.
Live oaks, for example are considered to be semi-deciduous trees. They are interesting trees in this area, because they keep their leaves year-round. Live oaks do, however, shed their leaves slowly to some extent all year long. This constant shedding is of course exacerbated by insect or fungal outbreaks, most often caused by extreme rainfall and humidity, causing damage to the leaves and therefor premature leaf drop. In extreme cases, some leaves are often re-grown during these periods of extreme leaf drop in certain parts of the canopy.
In most cases, during these extended periods of heavy rainfall, lack of air circulation and extreme shade in the lower parts of the live oak canopies will slow down the evaporation process. This will keep the moisture in the soil and in the understory, causing more extreme fungal issues and insect problems. This is especially true not only during long extended wet summers when the air is warm AND wet for many months at a time, (with no or very little dry out periods), but especially when these shaded trees or motts of live oaks are located in extremely shaded back yards.
These extremely shady (mostly back yards) are often north facing yards which get significantly less overall sunlight, are many times sandwiched in between houses and tall fences, or may just be in yards with extremely dense shade due to overplanting of shade trees or extremely dense canopies due to a lack of standard maintenance pruning. Consequently, pruning to remove dead wood and general thinning can often reduce the premature shedding during these wetter summers by increasing evaporation of trapped moisture due to increased sunlight penetration, and allowing for better air flow throughout the canopies.
Sometimes in the case of overplanting, as the trees crowd each other out it is often necessary to thin out the back yard by selectively removing the unnecessary or poorly placed understory trees, especially the suppressed ones that are being out-competed by the larger ones. It is often shocking to me how often many large shade trees (live oaks, cedar elms, bradford pears, red oaks etc.) are planted in such small back yards. When shade trees are newly planted they often appear to be properly spaced, but as the canopies expand they quickly outgrow the yard creating total darkness, and miss-shape each other forcing all of the lower branches to shed due to lack of penetrating sunlight, and also forcing all of the leaves to the upper canopy.
In the spring each year, each live oak will shed all of the last year’s growth and re-grow the entire canopy. Although this timing varies, in the Austin area this process typically takes place in the last week of March through the first 2-3 weeks of April. This year (2016), however, the process was kick started 2-3 weeks earlier due to the lack of frost days and the unseasonably mild winter weather. This process causes tremendous leaf shedding, as all of last year’s growth invariably ends up blown into your hallway or garage, gets down into the cushions of your patio furniture and covers your lawn. Depending on the size and amount of oak trees on your lot, you may end up with 50-100 lawn bags of live oak leaves to rake up and drag to the street.
To make matters worse, these crazy leaf shedding trees then form their male flowers, or catkins, which spew forth a seemingly endless amount of pollen, which coats everything in that thick yellow-green powder, which is responsible for allergies many people (including myself) are plagued with. The high spring winds then blow it everywhere. Once this is over, the male flowers then die, turn dark brown, and fall out of the tree all over the yard, creating the third springtime shed. As they are very light, they blow into everything and then break into a million pieces, coating everything especially furniture, and can be a major challenge to clean up in patio areas.
Central Texas residents often have a love-hate relationship with live oaks. We love the shade during our long hot summers, but have a hard time dealing with the yearly maintenance. Because they do have a long growing season, we often feel like we are endlessly raking leaves and removing dead wood, clearing the roof, thinning the canopies and removing crossing branches. That said, they are the most valuable of the native trees due to their size at maturity and their amazing longevity. They can also add up to 20 percent to your home’s value, and are one of the most heavily protected urban trees.