Re: Olive understory

Ben,
 
In Spain, olive orchards are usually kept free of weeds or any other kind of vegetation. This is most often achieved by tilling the soil. This intends to reduce weed competition and to facilitate harvesting. The bad side of it is, of course, soil erosion.
 
When an olive orchard is abandonned, it is first invaded by annuals and biennials, many of them in the mustard family and grasses. Bulbs like Muscari botryoides and M. comosum may be present too. After some time shrubs appear, like Retama sphaerocarpa and Cistus ladanifer. The vegetation in the olive orchard will end up being something similar to whatever surrounds it, most likely Quercus ilex subsp. ballota and its typical understory. It is important to note that olives here in Spain are planted at distances of 5x7 or 7x7 meters, to avoid trees shading each other, so there is a lot of sunlight that reaches the ground. Also, canopies are pruned to be quite open and trees stay relatively small in height compared to how they are in other parts of the Mediterranean. On the other hand, as it happens also with neglected Vitis vinifera cultivars, Olea europaea cultivars tend to lose vitality when abandonned, because they need regular prunning to promote growth and keep diseases and pests under control. If not mantained, they become leggy, and the leaf/wood ratio gets so low that the tree will eventually die. Summarizing, olive cultivars, which I assume is what you have, not Olea europaea var. sylvestris, have no understory in Spain.
 
So, what to plant under olive trees in California? If yo want to keep your trees dense, I would go with whatever grows there naturally under live oaks. Or, if you want to keep your olives looking healthy and mantain your current underplantings, pruning to thin the canopy will be required to allow more sunlight in. Salvia x jamensis and all its cultivars could be a good choice too. Arum italicum and Hyacinthoides hispanica do very well too under this conditions, but I don't know about their invasiveness status in California. Liriope muscari 'Evergreen Giant' and Viburnum tinus do great under olive trees in my yard.
 
Fran
Miraflores de la Sierra
Madrid, Spain.
(This winter, so far, about 50 days with lows below freezing, 5 of which stayed all day below freezing)
 
 
----- Original Message -----
From: b*@pacbell.net
To: m*@ucdavis.edu
Sent: Tuesday, February 17, 2009 7:56 PM
Subject: Olive understory

Hi All,
This question is directed mostly to members living near the Mediterranean Sea.
About a year ago I asked what did well under Olive trees, and had some helpful responses, but I'm still in a quandary.

I have a side yard planted with six olive trees and an adjacent small live oak and a few melaleucas.  Initially the understory was a successful combination of Cistus ladanifer and Lavandula stoechas 'Otto Quast', but as the olives' shade increased, the shrubs declined.  I've been experimenting, with fragaria, iris, nerine, arctostaphylos, carpenteria, ceanothus, but none of the subjects have really taken with enthusiasm.  Most are living, but none are luxuriating.  The trees are at that adolescent stage, not quite shade-giving canopies, but more than large shrubs.  This year's experiments include Salvia 'Mrs. Beard' and Salvia spathacea.

It's been years and years since I visited the Mediterranean, so here is my question to you: what NATURALLY grows in an olive woods?  Is the ground bare? Is there a dense under-story of shrubs? Or is it low herbaceous ground-covers?  Knowing what occurs in nature would better help me choose plants in my garden.

Thanks for your help.
-Ben Artmentrout-Wiswall
Simi Valley, inland Ventura County
Southern California
(Probably more like Tripoli than Nice)
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