What’s new in natural yards? May 2018

A recently-published study (authored in part by That Blogger’s former thesis advisor) examines how Wisconsinites think about their urban trees.

A 16-page survey sent to homeowners in and around Milwaukee, Madison, Green Bay, and Wausau asked people a variety of questions about trees. One set of questions regarded benefits and problems related to trees. Under the header of benefits, survey respondents most strongly valued trees for their ability to make a place look nice, provide shade and cooling, improve air quality, and generally enhance the livability of a neighborhood.

But about half of the homeowners said they were “strongly concerned” about the risk of trees or branches falling and damaging things. People within city limits (as opposed to those living in the suburbs) and people with smaller lots tended to be more worried about this risk, possibly because a falling tree or branch on their property was more likely to hit something. People who saw trees as dangerous, the study found, valued trees less overall.

The survey also asked who homeowners trusted for help and advice related to trees. The results showed that respondents trusted tree professionals more than any other source of information. Averaged across the four cities, 62% of people said they would trust a landscaping company or tree service, while only 14% said they would trust the staff of a non-profit organization. This is surprising and worrying, as such professionals have a financial incentive to suggest whatever service is most profitable for them, rather than the service that is best for the tree and its neighbors (human and otherwise).

The survey’s demographic questions turned up some interesting findings. Women rated trees more highly than men did, and millennials valued trees more than baby boomers, though these younger folks tended to have fewer trees on their own properties, likely because their lots were smaller than those of their more senior neighbors. Older homeowners, in contrast, expressed more concern about trees “growing too big, making a mess, or blocking scenic views”.

Finally, most people who answered the survey thought that their neighbors valued trees and took good care of trees. But, as with many domains of life, people rated themselves even more highly on questions about recognizing the importance of trees and properly caring for trees.

The relatively-brief, highly-readable report can be found here.

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What’s new in natural yards? May 2018

Why do some trees keep their leaves later into the fall?

The intuitive answer is that a healthy, vigorous tree will keep on photosynthesizing late into the fall, while a weak, sick tree will give up and go dormant earlier in the season. In fact, it’s exactly the opposite.

When it comes to the problem of how long leaves should be held onto, a tree faces a dilemma. On the one hand, a tree can only produce food and store energy while it still has its leaves. But on the other hand, as winter creeps closer, having lots of green leaves is a big risk – the leaves could be killed suddenly by a frost, or they could catch flakes in an early snowfall, causing weight to pile up on the tree and increasing the likelihood that branches will break.

In the normal course of things, a tree wants to store all the energy that its leaves have produced, reabsorb the chlorophyll and other useful chemicals from its leaves so they can be used again the following year, and then jettison the leaves and ride out the winter in a dormant state. Ideally, all of this will happen just before frost arrives, thus maximizing photosynthesis and minimizing the risk of frost damage.

Of course, the tree doesn’t know exactly when the first frost will arrive, and so it has to take a bit of a gamble with its timing.

A healthy tree that has stored up plenty of energy for the winter will play it safe, losing its leaves well before cold weather sets in, and relying on its reserves to last until spring. Conversely, a tree that is struggling will run the risk of being injured by a night of freezing temperatures in order to squeeze in a few more days of photosynthesis, in the hopes of storing enough food to make it through to the next growing season.

Thus, trees that settle in for winter early are doing well, and trees that cling to their leaves are desperately trying to survive.

Why do some trees keep their leaves later into the fall?

Why do trees lose their leaves and branches?

The common understanding is that a tree’s leaves die at the end of the summer, and then fall off. This isn’t quite accurate. It’s more correct to say that the tree kills its leaves.

What’s really happening is that the tree builds a layer of cells inside the leaf’s stem to create a seal that blocks the flow of nutrients to the leaf. Imagine putting a tourniquet around your arm and leaving it there: eventually your arm would die and fall off, and that’s exactly what happens to the leaf.

A similar thing happens with branches. Humans, like most other animals, start their lives with a fixed number of limbs, and don’t get any more. For this reason, we’re very interested in keeping our arms and legs intact. But a tree can grow a new limb pretty much whenever and wherever it wants. When a branch isn’t pulling its weight, the tree will kill it – by creating an internal seal and starving it to death – and then grow a new branch that contributes more to the tree as a whole.

When a leaf or branch that has been killed in this way falls off, it doesn’t do the tree any harm. The tree wasn’t using that body part anymore, and the internal seal prevents any infection from entering the living parts of the tree. In contrast, when a leaf or branch is broken off suddenly – perhaps due to a hungry herbivore, pruning, or a powerful windstorm – the tree loses a healthy, productive body part, and acquires a wound through which insects or fungal infections can easily enter. Because trees don’t do anything very quickly, it can take them years to seal even a relatively small wound – more than enough time for a serious infection to set in.

It’s therefore inaccurate to say that cutting off a tree’s limb doesn’t hurt the tree. Of course, it doesn’t hurt the tree the same way that it would hurt a human, because the tree can regenerate. But the loss of a productively photosynthesizing branch, coupled with the energy demands of sealing a wound and growing a replacement branch, can put serious stress on a tree. While pruning may be desired for other reasons, the idea that pruning is good for a tree’s health just doesn’t cut the mustard.

Why do trees lose their leaves and branches?

What is regenerativity?

We all know what sustainability is – living in such a way that we could continue to live that way indefinitely. Sustainability, though, is a zero-sum game, equivalent to spending exactly as much money as you earn. Sure, you could live on that budget indefinitely. But by doing so, you don’t put anything into savings to protect yourself against an emergency or to pass on to your children.

Some experts are now saying that we need regenerativity – a way of living that takes less than all of the sustainably-available resources, in order to build up our ecosystem savings account. For example, we need to plant enough trees not just to replace what we cut down, but to increase the size of forests. We need to take few enough fish from the ocean that those who are left can reproduce and increase their total population. That’s living regeneratively.

There are two main ways to live more regeneratively. Just like with our finances, we can decrease our expenses or we can increase our income. In ecosystem terms, we can use fewer resources – by reducing our energy consumption, eating lower on the food chain, and eliminating single-use disposable items from our daily lives – or we can mindfully help the Earth be more productive, by using compost to build soil, gardening with native plants that support pollinators, and taking care of trees to maximize their ability to clean air and water.

Last year, Earth Overshoot Day – the day on which we have used as many resources since January 1st as the Earth will produce in an entire year – was August 8th. This year, it fell on August 2nd.

If we were living sustainably, Earth Overshoot Day would be on December 31st every year. If we lived regeneratively, it would fall sometime in the next year. Our world’s resources would continually increase, allowing our children to live the same way we do and enjoy thriving ecosystems on a healthy planet.

What is regenerativity?

What is a tree spade?

A tree spade is a piece of heavy equipment designed to dig up and move large trees.

Small trees can be dug up and moved by hand, but what is a property owner to do when a mature tree is growing into power lines, standing in the way of a construction project, or casting shade on an area the property owner would prefer to be sunny? Many would respond by pruning the tree, or by destroying it entirely. Often, a better solution is to move it.

Tree spades were invented in the 1800s, and early versions could move trees more than 30 feet tall. Modern-day tree spade operators say they have moved trees well over 100 feet tall, as well as trees with trunks more than 5 feet across.

Tree spade operators don’t really recommend moving trees that large, though, since survival of the transplanted tree depends on whether enough of its root system can be picked up and moved with it. A tree’s root system can be larger than the aboveground part of the tree, but even the biggest tree spades can only dig up a chunk of soil about 7 feet across and 4 feet deep.

Medium-sized trees, though, can be successfully moved, and it is not even very expensive to do so – especially when compared against the cost of destroying the tree, including the loss of the services that a relocated tree could have gone on providing for many years.

By creatively rearranging our yards, we can have room for everything we want, while respecting the needs of many species.

What is a tree spade?

What’s new in natural yards? May 2017

Two weeks ago, the City of Madison made a change to how it will handle emerald ash borer (EAB).

Previously, the City had decided that it would not give any ash trees that were already unhealthy a treatment to protect them from EAB. What the City did not make clear to residents was that any tree located under a power line would be considered unhealthy, regardless of what condition it was actually in.

In thinking about the impact that this decision would have, the City realized that older neighborhoods in Madison, which have overhead power lines, stood to lose a lot of trees, while newer neighborhoods, in which the lines are underground, would be able to keep their trees. Recognizing the immense value of trees to nearby residents – due to trees’ ability to clean the air, reduce flooding, moderate temperatures, increase property values, and so on – the City concluded that it would not be fair for some neighborhoods to lose a lot of trees while others are able to keep their trees.

Based on this conclusion, Madison’s Common Council voted that ash trees under power lines should be treated to protect them from EAB, provided that they meet the City’s other requirements for treatment.

The full text of the resolution can be read here.

What’s new in natural yards? May 2017

What is this week?

Recognizing the importance of trees in our neighborhoods, the city of Madison has declared the coming week to be Arbor Week. The following resolution was adopted last month:

 

WHEREAS, the City of Madison has been a Tree City USA for 28 years; and

WHEREAS, children and youth living in greener neighborhoods are healthier; and

WHEREAS, trees give us oxygen, clean the air, and filter air pollutants; and

WHEREAS, trees in our neighborhoods increase property values; and

WHEREAS, the continued planting and care of trees in our city shall provide the same benefits for the present and future residents of Madison.

NOW, THEREFORE, BE IT RESOLVED that the Mayor of the City of Madison, Wisconsin, does hereby proclaim the week of April 30 through May 6, 2017 as ARBOR WEEK in the City of Madison, and urges everyone able to observe this week to plant trees and to participate in programs that the sponsors of Arbor Week may provide.

What is this week?