The Curse of Asparagus Fern

asparagus fern (Asparagus sprengeri)

Two weeks ago, I suggested drought tolerant asparagus fern (Asparagus sprengeri) as a possible ground cover for somewhat shady slopes.  I cautioned that it is “an extremely aggressive plant” and that it “is virtually impossible to get rid of once it gets a foothold.” Yet, asparagus fern remains highly popular and widely available in the nursery trade.   It turns out, however, based on the following email from Jim Winterroth, who gardens in Torrance, that my warnings regarding this plant were, in his opinion, woefully inadequate.

“There should be a special place in hell reserved for anybody who would recommend planting Aspargus sprengeri,” Winterroth fulminated.  “In several states it is listed as an invasive species; unfortunately, not in California.  I, and several of my neighbors, have been attempting to eliminate this from our yards for the past fifteen years – the result of a previous neighbor having planted it.  It spread into the surrounding yards.  I keep finding shoots of it coming up in the middle of my lawn.  It should also be noted that the leaves secrete a sap that is toxic to cats should they brush up against it.  It’s also harmful to dogs but, since they don’t groom themselves the way cats do, it’s less of an issue unless they actually chew on it.”
Regarding this last point, I decided to check the ASPCA web site regarding toxic plants and found that, where cats and dogs are concerned, not only is skin irritation a problem when it comes to asparagus fern, but consumption of asparagus fern berries, which leads to abdominal distress, is also an issue.
When designing a garden, if you wish to check on toxicity of potential plant selections, visit www.aspca.org/pet-care and then, on the right side of the page, click on “animal poison control.”  More than 1000 pet-toxic plants are listed.  If you think your pet may have been poisoned by a plant and you can’t get immediate assistance from a vet, the ASPCA has a poison hotline at 888-426-4435 that can be reached 24 hours a day.
As far as control of asparagus fern is concerned, a number of solutions, which would probably pertain to a variety of overly aggressive ground covers and weeds, too, for that matter, are offered at homeguides.sfgate.com.  One strategy is to persistently eliminate all foliage with a string trimmer (weedeater).  With no leaves to photosynthesize and produce food, root systems will eventually deteriorate.  If the plant in question is seemingly out of control, however, you might want to embark on chemical control.   You can either spray the plants in their entirety with a product whose active ingredient is glyphosate (1% concentration), or cut back to stem bases and then spray or paint cut surfaces with triclopyr (8% concentration).   There are many products containing these chemicals that you can find on-line or in your local nursery.  Always follow application instructions precisely.
If you wish to avoid chemical application, solarization is another option, which should be done during a period of very hot weather. After mowing or weed-eating plants down to the ground, water the area and then cover with a clear plastic tarp, holding it down along the edges with large stones or bricks.  After 4-6 weeks of this hot steam treatment, plants will be dead, roots and all, and soil will be free of pathogenic soil bacteria, too.
Three weeks ago, I wrote about the ponytail palm (Beaucarnea recurvata) and received an email from Jill Pettigrew, whose experience with the tree is a testament to its toughness.  “My ponytail palm is 62 years old,” Pettigrew wrote, “and nearly thirteen feet tall.  It was given to me eleven years ago when I lived in Long Beach.  Prior to transplant, this tree, with roots exposed, was left on the curb for seven days.  Nevertheless, after being planted, and with twice monthly soakings, it settled in well within twelve months.  I recently moved to Valley Center in north San Diego County and took the tree with us as well.   She has been exposed to heavy rains, harsh winds, and high temperatures both in Long Beach and here in Valley Center.  Ponytail palms are not difficult trees to care for.  They are just very slow growing and can tolerate drought conditions.”
Tip of the Week:  I recently encountered a Winslow spur flower (Plectranthus barbatus) and highly recommend it as an evergreen shrub.  Reaching eight feet in height, it flowers from fall to spring with long panicles of violet blue flowers.  Although damaged by frost, it will survive a cold snap down to 25 degrees Fahrenheit and grow back vigorously the following spring.

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