Troubled Exotics

by Connie Beck

Some of the most reliable, popular, and therefore overused exotics that Southern Californians have depended on for years may be disappearing from our landscapes. This change creates a great opportunity to promote the planting of natives.

Oleander

Bad oleander between good ones

We’ve all noticed the Oleander scorch which is killing virtually all of the Oleanders. Lemonadeberry or Toyon would be effective replacements. Victorian Box (Pittosporum undulatum) is still being sold and recommended in nurseries in spite of the fact that the same glassy-winged sharpshooter that is killing the Oleanders is causing even mature Victorian Box to yellow, defoliate, and then die. This pest is the vector for a bacterial disease (Vilella fastidiosa) which can attack other exotics as well as grapes.

When the Myoporum shrubs were first hit with thrips years ago we were told they would only be affected east of La Mesa. Not so. I’ve seen them all over the county now with their crinkled ugly leaves. Toyons would be an ideal replacement, offering wildlife value as well as beauty.

Raphiolepis, 60% dead

Raphiolepis, 60% dead

It would be hard to find a grocery store or bank in the county that doesn’t have Indian Hawthorne (Rhaphiolepis) lined up in hedge rows along the parking strips. The flathead borer is killing them, both in the nurseries and in the landscape. In nurseries it’s a doubly bad scene as pesticide drenches are used to try to control the pest, to no avail. So not only is the plant going to die but the soil becomes contaminated with toxins. There are dozens of native shrubs that would be so much more appropriate than these exotics in our commercial and residential landscapes.

The list of exotics affected by exotic pests doesn’t stop with these few. A significant proportion of Deodar cedars are losing more than half of their needles due to the Deodar weevil larvae.

Hacked back Junipers

Hacked-back Junipers

Mites and weevils are also attacking one of the most ubiquitous of the juniper varieties we’ve had to look at for the past many decades. Big brown patches on the junipers would require perfectly timed spraying each spring for control. Perfectly timed pesticide application is something I have not ever seen a homeowner perform. One of my neighbors has gradually hacked his affected junipers back by 2/3 and now they are even more hideous.

Eugenia was a sentimental favorite in so many older San Diego landscapes, but the psyllid continues to ravage the plants. This creates another good opportunity to replace with Lemonadeberry or Coffeeberry, Manzanitas, Ceanothus, Toyon, which are all more attractive native plants.

Monterey Pines and Japanese Purple Leaf plums have pretty much already been replaced due to the effects of climate change. They just can’t handle the hotter, drier weather.

Roger’s Gardens, the destination nursery in Corona Del Mar, has recently stopped sales of Impatiens due to Downy Mildew. This was a real moneymaker for the wholesale growers as an Impatiens cutting could go from cutting to six pack ready for sale within 8 days.

So next time your client tells you that natives are too difficult to grow, you can tell them that exotic plants get exotic pests and perhaps they should, in these days of climate change and worldwide spread of insect pests and diseases, take another look at the natives that are so reliable and appropriate here.


Connie Beck is an organic gardening instructor and landscape designer in San Diego’s east county. 

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