Wednesday, May 25, 2016

Live Oak Pruning Problems

Q. When is the proper time of year to trim a Coast Live Oak tree? And,is a permit required? My neighbor is having his tree trimmed today, May 14 and I'm concerned about the tree. Lisa

A. Sorry I wasn't able to get back to you before the tree was trimmed. What is the situation? Exactly where is the oak in question? As far as trimming, generally you should only trim live oaks if it is absolutely necessary, otherwise you’re just damaging their chances of surviving. What town do you live in? Could you send me a picture of the tree as it was and as it is now?

Q. Hi Frank, Thanks for getting back to me.  Sorry, I don't have pictures to forward, but I can tell you that the tree in question is a huge, old tree which has been here for all the 43 years we've lived in our E. Pasadena home.  The tree can be seen from the corner, where it is located in the backyard of that house.  It has been severely trimmed, in my estimation and according to the trimmers, they had a permit.  I'm just hoping it will survive.  Thanks for your input.  Lisa

A. You might want to mention to the owners that:

1.       The main thing keeping any tree up is its own weight acting through the force of friction. The heavier the tree the more likely it is to stand up to storms and winds.
2.       The fine structure of oaks and other trees helps dissipate the winds force on them, leading to greater stability and less chance of failure.
3.       Trimming a tree degrades the above two factors and causes a tree to be MORE likely to fail.
4.       Tree canopy density is proportional to the amount of nutrients a tree receives via photosynthesis (it has no other way to make energy), so when you trim your trees you starve them as well.
5.       The new growth that trees put on after trimming relies mostly on their stored food reserves –it further robs the trees of nutrition and puts them in danger of disease, insect infestations and ultimately, failure.

Q. Hi Frank, Thanks so much for the info...wish more people knew that!  I'm sharing w/ folks I know.  One Q. about Coast Live Oak trimming remains: Is there a correct season for trimming them?  Regards, Lisa
A. Yes, live oak trees, like Quercus agrifolia the California live oak, are best pruned when dormant in the late summer and early fall.

  1. Living Among the Oaks: This University of California Agriculture and Natural Resources booklet describes the special needs of California native oaks. A must read if you have an oak tree. Many people are killing their oak trees with kindness and the landscaping they have surrounding the trees -this pamphlet tells you if you are doing just that. 
  2. Pruning California Live Oaks: Published by the Ventura County Agricultural Extension. Goes over the how when where and why of pruning oak trees (no surprise; states that the best pruning is often no pruning at all). 

Saturday, May 7, 2016

140 Year Old Rose Variety Picked as Best Smelling Rose in the Arboretum Rose Garden

Diana Liu-McDonough posing with a Compte de Chambord rose bloom, the winner of our 'Best Smelling Rose at the Arboretum contest.

This week the participants in my plant information class held a contest to determine the finest smelling rose in the Arboretum Rose Garden. Although the rain has decimated many of the roses (black spot is a big problem when we have unseasonable rains). After sniffing at least over a dozen roses a concensus was reached: Compte de Chambord. Compte de Chambord is a fairly old rose -it was bred by a Gentleman named Moreau-Robert in France around 1862, a cross between an older hybrid between the Chinese tea rose and Rosa gallica (Called a 'Portland Rose' ) and a newer rose (1842) called 'Baronne Prevost'. Being the scion of two 'ever-bearing' (remember an 'everbearing' rose in France was one that bloomed spring through fall) roses it two had a long blooming period as well as being a lower and fuller bush than its two parents.

Thursday, May 5, 2016

Plant Advice for a London Flat

My London block of flats includes a small car park with small south facing 'sliver' garden.
Underground root development is not envisaged, due to semi-surface utility services, etc.
Is a mini-rock garden feasible at our low altitude ? (SW15 6BB.) What plants - self propagating subject to climate/survival possibilities would enhance such a small area ?
Any free advice you may offer would be appreciated. Sorry if you do not offer U.K. advice.
 I am Scottish retired from architecture, wife Japanese.

Thank You for any advice you may offer, Brian

Hi Brian,

You should be able to do amazing things where you are with Sempervivums.

Check out these links:

 As far as air pollution goes, most of these things work here and we have plenty of polluted air.

Cheers,   Frank

Wednesday, May 4, 2016

Arboretum Rose Garden Map

Here is a map to the varieties of roses included in our rose garden. Although most of these roses are still here, the map was last updated in 2008 so their may be a few missing. Just click on the dot closest to the rose you are looking at for a tentative ID.