Saturday, July 28, 2012

Selected Questions From the Last Two Weeks

Was given an Ice-cream bean tree (Inga edulis).  Wanted to know how to grow it here.  Has it for 3 years under a huge Ficus tree in a pot.
Advised that it might not survive our winter because it would freeze over at 27F.
Also asked that if the tree successfully produces fruit to bring it over for ‘inspection’.
Her 40 years old cypress trees are dying.  She lives in Malibu.  She actually sent over some sample leaves to us by mail.
Told her the trees are dying from Cypress canker, a kind of fungi. Once your cypress get the fungus there is little you can do to prevent it from eventually killing the tree. Pruning can extend the life of the tree, but it is vitally important to disinfect your pruning equipment between each cut. One thing that really helps promote the fungus is the number of Italian cypress trees you have in your neighborhood and how close together your cypress trees are planted. Closely planted cypress spread the disease quite readily, and if your neighbors have lots of cypress planted nearby, they can serve as sources of infection for other Italian cypress in the neighborhood. Another reason you have the infection now and not 40 years ago (the fungus was first detected in the 1920’s) is that the range of this fungus has been slowly spreading over time

Cypress canker links:
Fungus from California suspected of killing cypress trees worldwide | Nature | The Earth Times
Gene sleuths trace tree-killing pathogen back to California
San Diego Master Gardeners - FAQ - Italian Cypress turn brown
Italian Cypress Video –
I work on the Master Gardner help line and have a question I do not know how to answer. I would appreciate any help you can give.

" I have a Liquid Amber question for Santa Monica. When do the trees defoliate, and for how long? I'm trying to plant a winter vegetable garden and my hope is the sun would shine between the bare branches. In the summer the sun is directly overhead avoiding the tree. "

Hi Rose,

Liquidambars here defoliate in late November early December or later (they’re seem to be the last to put on color as well) with re-foliation occurring around March through April. That could be different for Santa Monica because it is not as cold; they could re-foliate sooner.
Our 80-yr-old mission fig tree has splotchy yellow areas on its otherwise dark green leaves. The tree has lots of small green figs on now, but they seem a bit smaller, as do the leaves, from normal. I did some on-line research, and it could be fig leaf rust. How do we tell for sure? Could I send you a couple leaves to I.D.? What's the cure? We have a dog who eats figs - loves them - and will even chew on fallen leaves because they're so good! We don't want to use herbicides that will harm her or us or even the squirrels and other connoisseurs of these figs.

Here's some photos of one leaf, front & back, and of others on the tree.  I hope you can tell something by these photos -- it's more obvious in person.   We live in 90064 - in the NW quadrant of the I-10 and 405, west end of Rancho Park Golf Course.

Hi Paula,

Your fig looks like it has Fig Mosaic Virus. There is no cure; it’s best to get a resistant variety –Black Mission is the most susceptible to this virus which is transmitted by mites or by rootstock.
Spraying may work for rust, but not for viruses. However you can prevent the spread of the virus to other Fig trees by spraying for mites on a regular basis.

UC Davis page on Fig Mosaic Virus:

Thursday, July 19, 2012

Peach Tree is Dropping the Ball

Q. Can you help me resolve a problem that has developed with my two peach trees? They are now giving reasonably good quantity and good size fruit, but the problem that has developed is that the fruit drops before it is ripe. Is there anything that can be done to help the tree hold on to the fruit until maturity?

APeach trees regularly thin themselves out before ripening occurs; if this didn't happen the peach’s branches would break under the weight of the ripening fruit. In fact, when the peach starts to show signs of fruit dropping (it's starting to self thin) it isn't a bad idea to water the tree heavily and then, the next day, shake the main trunk gently but rapidly to thin out the juvenile peaches before they get too big and pose a risk of collapsing the branches that bear them.

Friday, July 13, 2012

A London Planetree in Pain?

London Planetree leaf (Platanus x acerifolia) showing symptoms of Mildew infestation.
I found this sitting on my desk with a note wondering what was wrong with the tree. No identification but the soft maple like leaves coupled with the the problem itself ruled out anything but the leaf being from a London Planetree (California sycamore leaves are similar but usually much larger). The problem is a fungus known as mildew. London Planetrees are susceptible to mildew, and the recent long period of cool weather has increased the amount of mildew I'm seeing on everything. Mildew is what is known as an obligate parasite, in other words it needs its host to survive so it will not kill it...but -it can make the tree look pretty bad, especially if its a variety that is not resistant to mildew. If the tree were in the wild this would not be a big deal, but here the life and death of trees is dependant on how we like them as ornamentals and a tree that is constantly coated with leaf curling fuzzy-white mildew could irk someone enough to consider removing it; thus curtailing its changes of surviving.

So what can be done to alleviate this blotchy leaf-deforming parasite? The best thing to do is wait -time will heal this as long as we have a summer that is somewhat close to normal. Hot temperatures and dry weather will desiccate the mildews branching, threadlike vegetative state and cause its existence to be less noticeable by us human beings who don't appreciate its leaf distorting fuzzy presence.
What about fungicides? Applying fungicides to large trees is, unfortunately, inherently expensive and dangerous. A spray service could do this for you but you'd be literally spritzing your money away.

There are varieties of London Planetree that are more resistant to mildew and another leaf disfiguring fungus called anthracnose; these include 'Bloodgood', 'Liberty' and 'Columbia' but unless the extended June gloom that we've been having that caused this problem in the first place becomes a permanent climate feature here I would just keep the tree you have and wait out the fuzzy invader. Also, remember to keep the old leaves picked up off of the ground -they could be the source of other fungal problems if you allow them to rot on bare ground. Many leaf attacking fungi are spread when infected leaves touch the bare ground and stimulate the production of fruiting bodies (the term for the mushroom like structures that grow off of the leaf that would be roughly analogous to a plants flower).
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