Tree Goes Boom. Film at 11

   The variable spring weather we have been dealing with isn't just vexing gardeners. The cycles of rain-wind-cold-warm throughout the last few months are playing havoc with trees all over Northern California. As a result pictures like this are popping up on the evening news:

 Boom! A limb falls, even on a nice day. In this instance, the limb of this tree fell through the roof of the home.

And, of course, the TV reporters on the scene ask penetrating, insightful questions such as:

"Have you had trouble with the tree in the past?"

No, it wasn't any trouble before! This is the first time that a third of the entire tree fell into the roof. It was so quiet, and kept mostly to itself. 

(It's always the quiet ones you have to watch out for.)

As part of the televised aftermath, there are always homeowners who panic and call an arborist or a non-certified tree company and want their large statured trees removed or topped, even though that may not be needed (especially topping). That is collateral damage. It is tragic.

Why does this happen on a nice spring day? 

We queried local arborists and got these thoughts:

A tree can fail anytime if it is in poor shape to begin with, especially combined with the weight of new spring leaves. A tree's first leaf set of the season is often the heaviest, especially in the kind of rough, on again/off again moisture and temperature fluctuations we've had this spring.

Subsequent leaf sets in late spring are generally smaller and more adapted to summer wind and higher temperatures than the first leaf set.

This was completely preventable with some routine maintenance performed on a regular schedule by a knowledgeable professional. A regular pruning schedule runs from 3 - 10 years on a mature tree.

This tree has 3 co-dominant stems and the heavy side over the roof split out. Here are the reasons why:

1. Co-dominant stems with included bark are weak places in tree structure - a lot of weight is extending out in different directions from a single point of origin on the trunk.

2. These limbs were very heavily end weighted.

This failure was not a function of high wind or summer limb drop - this was a function of an unmanaged co-dominant stem reaching critical mass and failing.

If the tree had been managed by a certified arborist (a knowledgeable professional) they would have reduced the end weight of those co-dominant limbs. They may have installed a cabling system. Cabling systems do reduce the risk of failure, although they do not prevent all failures. 

The intent of a cabling system is two fold: 1. Reduce risk of failure. 2. Control the direction and fall of a cabled limb away from targets like structures and back into the tree. Instead of finding the limb in their roof and living room they most likely would have found the failed limb pulled back into the tree.

 Arborists routinely try to educate people about levels of risk, but at the end of the day it is up to the homeowner to decide what level of risk they're willing to assume. It does happen where an arborist advises removal and the

homeowner insists on retaining the tree. In those circumstances, an arborist will make the tree as safe as they are reasonably able. 

 So what to do now? Remove the failed tree.

For information about trees and certified arborists, visit this site: treesaregood.org . This is the consumer education arm of the International Society of Arboriculture, which is the professional association that governs arborist

certifications.

Bottom line: trees require regular maintenance, done by people who know what they are doing. And that probably isn't you or me.

Winter Citrus Problems Showing Up in Spring

     One of the problems of answering gardening questions on the radio: a lack of time to fully explore all possibilities. For example there was this exchange on a recent show.

Cross Section of Rootstock Citrus

Bill asks:

"My young citrus trees (Santa Teresa lemon and Valencia orange) had their first crop this year and the fruit was near worthless. The rinds were very thick and the flesh contained very little juice. In addition the oranges were nearly tasteless. I fertilized them with organic fertilizer according to package directions. I live in Elverta (Sacramento County) and have a sandy clay soil. What might I have done wrong?"

Fred responds:

"It sounds like rootstock fruit. If the fruiting wood goes in decline and the suckers take over from beneath the graft, one of the byproducts is fruit that fits your description: thick rinds, little juice and fairly tasteless. One way to make lemonade out of these lemons, so to speak, is to use the thick rind as a zest.

In his excellent book, "Citrus", citrus grower Lance Walheim explains the importance of growing citrus varieties on different rootstocks. The advantages of citrus rootstocks include keeping the overall height of the tree smaller, offering disease resistance, imparting more cold hardiness as well as better soil adaptation. 

But if that rootstock takes over, possibly if the top part of the tree is killed in a freeze, watch out. Besides inedible fruit, citrus trees that grow from rootstocks such as Flying Dragon and Trifoliate orange have thicker leaves and many more thorns along the stems. 

When you see those sprouts beginning below the bud union, cut them out.

Bill responds:

"No, no this is not root stock. I carefully removed the sprouts of rootstock which was some sort of trifolate orange and I had the trees protected from frost."

Fred responds (while looking anxiously at the clock):

"If it is not rootstock growth, then you may want to take a sample branch or a sample of the next fruit harvest to a good nursery for a positive I.D. Or, take those samples (or pictures of the tree) to Harvest Day at the Fair Oaks Horticulture Center on Saturday, August 7. There will be representatives of  there who can help identify it."

 I would never claim to know all the answers. One big advantage of my job: access to people who do have the answers. I forwarded this question to Mary Helen Seeger, one of the principals of wholesale citrus tree growers, Four Winds Growers.

Mary Helen provides another possible culprit to Bill's dilemma:

"This year, a lot of citrus fruit was damaged during the freeze," she explains. "It is especially noticeable on young trees as there is not much canopy to provide some frost protection.  During a hard freeze, the vesicles burst and then, over time, they lose their juiciness, leaving the fiber of the vesicles. Lemons are more thin-skinned when they first turn yellow and are usable.  During the winter, the fruit grows larger and the rind gets thicker. Oranges do that as well, but not to the extend that lemons do (in my experience.)

Anyway, don't give up on the trees yet.  It has been a challenging year for plants with the wild temperature swings. Keep amending your soil with compost and organic matter to balance the clay.  Keep amendments  away from the trunk. Check out fourwindsgrowers.com for more tips."

And Mary Helen adds:

"Fred, remember to tell people to make sure large citrus trees in the ground are deeply watered and fertilized this time of year, to prevent "June drop". That's when temperatures rise suddenly, often accompanied by winds."

Consider it done, Mary Helen.