Wednesday, January 25, 2012

Browse Our Magnolia Collection -Beta Testers Wanted

I've published a Google map of our Magnolia collection. Each one of the blue icons is a Magnolia in our collection, just click on it and you'll get a short description and history of each plant. It's cool, but the coolest thing is that you can load this map up on your Google Maps app on you iPhone or your Android phone and use your GPS to find out what Magnolia you're looking at in the field. Try it out if you have one of the above and let me know how it works for you.

View Flowering Magnolias at the L. A. Arboretum in a larger map

Saturday, January 21, 2012

Wild and Wooly

When I started this job 14 years ago I'd get lots of stuff in the mail. Sometimes the packages would be dripping strange fluids, emitting strange odors and containing strange life forms. These days with email and digital photography I'm mostly spared these surprises but there are still things that require a sample. The pest below is a good example of this. What you see is a citrus whitefly. Now 'citrus whitefly' is a term for any of three different species of whitefly that currently infest citrus trees.

Sample of citrus leaves with wooly whitefly infestation. 

The sample you see on the left is a lemon tree that has been infested with citrus whitefly. Notice the fuzzy white patches. These patches are the reason I needed to see this sample. When this had been originally described to me it was described as a 'fungus'.

Now of the three whiteflies that infest citrus here this one appears to be the 'wooly whitefly'.

Now if you look closer (the lower two images were taken with a magnifier) you'll notice that the 'fungus' looks more like cotton and that there are what look like scale insects surrounding the fuzzy stuff. These 'scales' are actually the immature (nymphal) stages of the whitefly. These 'nymphs' will eventually cover themselves in a cottony tuft of wax fibers (the 'wool' in the pests common name)  that the exude from their bodies. This wax serves to protect them from predators and it also repels water (that's why most contact insecticides will not control them very well).

Some methods of control that do work are:
1. Pruning the tree to increase air circulation.
2. Spraying horticultural oil solution on the tree. This has to be done during the cool time of year or else the oil spray will damage or kill the citrus tree's foliage.
3. Decreasing the amount of nitrogen that the tree receives. Instead of feeding three times a year feed just once.  If you feed citrus too frequently their sap's concentration of nitrogen goes up. Since nitrogen is the limiting factor in the growth of the pests (they've got all  the sugar they need for energy -what they need is nitrogen to form the proteins of their body tissues) if you over fertilize you're practically sending out an invitation to white flies and pests like them to infest your trees. Use organic fertilizers because their availability coincides with the availability of the natural predators that keep the white fly under control -in other words when its warm outside there are lots of predators to control the whiteflies so that is the ideal time you want fertilizer to be available to your citrus trees.  Do not use fertilizers that are immediately available to the plant like ammonium nitrate and urea (found in commonly available water soluble  fertilizers like 'Miracle-Gro').

For more information on control of this whitefly download this PDF:

Wednesday, January 18, 2012

January 17th out in the Arboretum

Flowering stalks of the King palm (Archontophoenix cunninghamiana).

Tan, pom-pom like flowers of Acacia stenophylla blooming in the Australian section.

Acacia spectabilis, the 'Glory Wattle', earns its common name. Located in the Australian section.

Acacia merinthophora's distinct arangement of stems and phyllodes (leaf-like stems) gives it its common name: the Zig zag wattle.

Friday, January 6, 2012

Back from Flu Bout; Class Rescheduled

I'm back after a wicked bout with that seemed like the flu. For all of you who missed the class yesterday I'll be holding it next Wednesday, same time same channel (1:30 to 3:00 in my office). I'll be covering Spring bulbs, local fungus (in preparation for the rainy season which is not here just yet), and of course the best of 2012's plant information questions so far.

Here's a cool link; it's the UCR Avocado variety page. The trick is to select at least two varieties that are good for your climate zone and are A and B type Avocados respectively. Having both of these flowering types can help insure a steady and abundant supply of Avocados.