Cruel Plant & Slope Planting

cruel plant (Araujia sericifera)

cruel plant (Araujia sericifera)

Bougainvillea spectabilis 'Torch Glow'

Bougainvillea spectabilis ‘Torch Glow’

Myoporum parvifolium

Myoporum parvifolium

Adjacent to the Veteran Affairs complex in West Los Angeles, there is a parrot sanctuary, and opposite this parrot sanctuary there is a vine, and upon this vine there are flowers, and these flowers are white and seductively perfumed.  And, as an added bonus, this is a vine attractive to monarch butterflies, too.

After the flowers fade, seed pods are produced.  You may be tempted to pluck off one of them and sow the seeds.  But you would want to think twice before doing so because this vine (Araujia sericifera) can easily grow out of control and eventually strangle every plant in your garden.
The common name of this vine is cruel plant.  A strange name, I’ll grant you, yet a name that has nothing to do with its strangling capacity.  In addition to the cruel plant appellation, this vine is also known as mothkiller.  Its pollen is so sticky that the proboscises of night flying moths get stuck in it. When dawn arrives, most of the moths manage to free themselves and fly away.  But occasionally, a moth gets permanently stuck and dies a cruel death.
But this plant is not without redeeming virtues.  Biochemists have analyzed its sap and found it to be rich in lipase, which is a fat-dissolving enzyme.  Who knows?  Perhaps there will some day by a fat-burning pill manufactured from cruel plant sap, making it not so cruel after all.  Cruel plant has also been identified as a source of nourishment for monarch butterflies.  When milkweed plants are unavailable, monarchs will visit cruel plants instead.  
The drawbacks of cruel plant may be overlooked as long as measures are taken to prevent its spread. Seed pods must be removed before they open and hard pruning of the plant itself must be done annually.  Horticulture, after all, is manipulation of plants for human benefit and cruel plant, too, has its value provided you are aware of its crueler tendencies.
The fact that monarch butterflies visit cruel plant tells us a lot about its toxicity.  Plants in the milkweed family (Asclepius species) are the monarch’s clear dietary choice due to their sap and foliage, which are more toxic to animals than to people.  Milkweed leaves make the monarchs that consume them toxic, too, at least where insectivorous birds are concerned, so that monarchs are left alone to reproduce and lay eggs.  Cruel plant is a member of the dogbane family, whose species include highly toxic plants such as oleander (Nerium oleander) and lucky nut (Thevetia peruviana).  So it would appear that monarch butterflies, in consuming cruel plants, are rendered toxic to birds just as they are rendered toxic through milkweed consumption.
Can you tell me if red apple is considered a water thrifty plant?  We want to replace the ivy on our front hill and were wondering what the best drought resistant alternative might be.
Carol Stern, Granada Hills
It would be easy for me to say that red apple (Aptenia cordifolia) — a succulent ground cover with small, heart-shaped leaves — grows well on slopes and then send you on your way.  However, I have seen this plant thrive and I have seen it flounder and, even under the best cirucumstances, its longevity is questionable.
A proper answer to your question must take into account of the size of your slope.  If the slope is only one or two hundred square feet in size, you can plant almost anything and not be concerned that, if it should fail, you will have squandered a large investment.  If the slope is larger and there is a larger investment involved, you will want to be circumspect, and proceed with reasonable certainty that what you plant will thrive for years to come.
The fact that ivy has been growing on this slope is a significant plus and a significant minus.  On the plus side, ivy has deep roots so that wherever it grows, the soil beneath is broken up and perfectly aerated, leaving the soil soft and well-drained so that virtually anything will grow in it.  The minus is that ivy will re-grow, no matter how diligently you dig up its roots.  And so you must regularly check your replacement landscape for any ivy re-growth, which should be immediately removed.
Red apple could conceivably grow quite well on your slope since it is sensitive to full sun in the Valley and your slope sounds like it is probably a half day sun location; otherwise, ivy would not have succeeded there.  Myoporum parvifolium is another tough ground cover that can withstand Valley heat without any problem and does quite well in half day sun.  A favorite, colorful slope-planting scheme for more than half-day sun includes discrete patches of purple, yellow, and orange lantana, which nicely complement each other.  For full to partial sun exposures, trailing rosemary (Rosmarinus officinalis ‘Prostratus’) is another excellent drought tolerant ground cover for slopes.
A ground cover favorite of mine is Acacia redolens ‘Low Boy.’  It is a spreading, evergreen, woody, highly drought tolerant ground cover with gray green leaves and tiny yellow flower puffs in the spring. It does not eclipse 2 feet in height, yet individual plants will spread out 10 feet or more in every direction.  Perhaps you want a slope covered with a moderately sized bougainvillea cultivar such as ‘Raspberry Ice, ’‘Rosenka,’ or ‘Torch Glow.’  You can trim the bougainvillea occasionally or just let it grow.  Once established, bougainvillea seldom, if ever, needs watering.
Tip of the Week:  I recently saw a slope planted with citrus trees.  The trees were irrigated with a drip system and the slope was covered between the trees with jute netting/matting.  If you don’t know what to plant on your slope, you can always simply cover it with jute matting which, on its own, will help prevent erosion.  However, jute netting will break down after twelve months so, at least several months before that time has elapsed, you will want to plant in it.  Simply pull apart the netting where you want to insert your plants, dig your holes, and plant away.
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