Living with Redwoods
One of the questions I often get asked by my clients is, "Are my redwood trees hazardous?" This is a complicated question. If you ask 3 arborists you'll probably get 4 different answers.
Redwoods can shed whole tops, drop branches, break off of rotting stumps or in saturated soils even tip over. This is true of ALL trees but, Redwood trees by their nature of being very tall are often viewed as being higher risk trees in the urban environment.
This does not mean that all redwood trees are hazardous and it certainly does not mean that removal is the best course of action. What it means, is that redwoods in close proximity to targets ie. houses, parked cars, play grounds, power lines, etc. need to be managed to reduce risk. What makes managing trees in the urban environment so challenging and interesting, is that there is no one way to correctly prune a tree. There are however, some wrong ways to prune trees.
This is by no means a complete list of poor pruning practices, but these are the most common mistakes I see as a climber and operator of a tree service:
What not to do
1. Tree topping Redwood trees grow really tall. So, naturally, cutting the top off will keep it short, right? Wrong! Redwood trees have evolved to send out new sprouts from the fresh cut or wound. These new shoots grow vigorously in full sun to the original height of the tree, but now the new top is growing on the edge of a wound, which can cause the top to peel out and fall. Wounds from large topping cuts can become a point of decay, which can cause hollows, sometimes deep into the trunk of the tree. Topped trees can often send out multiple new leaders, creating a "candelabra" or "codominant crown structure". Multiple leaders may compete for space, pushing against one another to cause future "crown failure". Almost any time a tree is topped, the tree will need continued pruning and management to correctly direct it's new growth. It's also been my observation that topped redwood trees can have their horizontal branches start to turn upwards to create new tops. In wildland environments I would say that the redwood is increasing in crown complexity and taking on old growth characteristics. In the urban environment I would say that this is a good example of the law of unintended consequences and a darn good reason why Certified Arborists take an oath to NOT TOP TREES!
2. Stripping Redwoods If you've driven around West Sonoma County you may have noticed redwoods that have all of their branches shaved off of one side, all the way to the top.
This has been done to protect a utility under one side of the redwood trees. Again, the law of unintended consequences is at play. It has been my observation that redwoods that have been severely pruned in this way begin to take on a sweep or bend in the trunk to find a new balance point. Time will tell how damaging this pruning practice will be to the huge redwoods over our roads. I would strongly dissuade home owners from doing this to the redwoods in their own yards.
3. "Raising the Skirt" Old Growth Redwood trees are known for their huge, cinnamon colored trunks extending for 200' or more before the first branch. What many people don't understand is that it takes hundreds of years for a redwood tree to grow to this "fine forest form". It may take thousands of years for the forest to reach a climax structure that supports this form and there may have been dozens of "disturbances" to the forest that led to this form. For example, fire burning off lower branches, strong winds breaking off branches, neighboring trees falling and breaking off lower branches, tops breaking out and stripping off lower branches etc.The process of a growing redwood tree stretching to the sky and shedding it's lower branches takes time. As the branches down low are lost, the function of photosynthesis is taken up elsewhere in the tree and the redwood builds new wood to balance itself with it's changing form.
Pruning off too many lower branches in one session can cause a redwood to become top heavy and unbalanced. Then there is the impact to the targets below the tree. Limbs shed from high in the redwood canopy can spear through roofs. The longer the branch travels uninterrupted through open air, the more it tends to turn butt end down and puncture whatever is underneath. Leaving even a few branches down low over the house can brake the fall of branches falling from higher in the tree. A redwood branch landing flat on a roof is less damaging than a branch that falls vertically through a roof.
"So if these are all things to avoid, what should I do to manage my redwoods?"
1. If you must prune your redwoods to open up light to your property, leave some live branches down low on the trunk to provide some measure of protection to houses or decks under the tree and to contribute to the tree's diameter growth.
2. Consider shortening especially long branches rather than pruning them back to the trunk. Redwoods can send out new sprouts at the ends of stubbed branches. Given a few years, redwoods that have had their branches cropped back can look indistinguishable from unpruned redwoods unless you look very carefully.
3. Hire a competent climber to only remove deadwood from the crown if there are no obvious problems with the tree.
4. Have forked tops thinned to one sturdy top. If both forks are unstable, cut back to strong wood and budget to have the new sprouts thinned in a couple years.
5. Hire a consulting arborist to look at your trees. Consulting arborists are trained to look at the root zone of the trees, take note of prevailing winds, soil compaction and many other considerations that a logger or climbing arborist might not think of.
6. For any tree to be hazardous there needs to be a "target" around to be damaged. By definition, if a tree is located away from structures, wires and people it cannot be hazardous.
Redwood trees are endemic to Northern California. They are the very reason some people live in our beautiful county. I find it heart-breaking to see large healthy redwoods, the ones that have the potential to be millennium trees, cut down due to fear or ignorance or greed. Redwoods are part of this county's identity and can be passed down through the generations with good stewardship. Let's work together to be sure that these rare forest giants are healthy and here for future generations.