August 11 is the date when the dog days of summer, extending each year from July 3 until today, officially come to an end.  These days are characterized by extreme heat along with the lassitude and indolence we experience when temperatures soar.  They are called dog days since Sirius, the outstanding star in the Canis (dog)  Major constellation (as well as the brightest star in the night sky), rises together with the sun during this period.

Certain plants really come into their own during summer’s dog days and several of the them, ironically enough, are members of the dogbane family (Apocynaceae), recognizable by their five-petaled, pinwheel flowers.

Vinca, a popular bedding plant, is the most widely planted dogbane, flowering in white, pink, purple, apricot, and red.  Vinca is notoriously prone to fungus diseases that quickly spell its demise.  You can minimize fungus issues by watering with drip irrigation since overhead watering splashes fungal spores from the soil onto vinca leaves.

Plants in the dogbane family are toxic to dogs.  Dogs generally know instinctively which plants to avoid but, to err on the side of caution, it is advisable not to plant vinca or other dogbanes where dogs are present.  Many popular ornamentals, including oleander, plumeria, natal plum (Carissa), star jasmine (Trachelospermum), and milkweed (Asclepias) are members of the dogbane family.

While vinca is generally planted as an annual, I have seen it persist for several years where it is minimally watered and given half day sun.  It can grow into a 2-3 foot tall specimen when conditions for growth are just right.

Then there is that fiery waterfall known as coral fountain or firecracker plant  (Russelia equisetiformis), native to Mexico.  The plant is named for Alexander Russell, an 18th century Scottish physician and botanist.  In those days, doctors were often botanists, if not pharmacists, too, since medications were invariably herbal and a knowledge of plants and how to extract their healing components was vital to a successful medical practice.

Coral fountain, once established, is drought tolerant and even when not in bloom is noteworthy due to a plethora of thin, arching stems covered with miniscule, bright green leaves.  Plant it in full to half-day sun.

Euphorbia ‘Diamond Frost’, like coral fountain, blooms most of the time, including now, but in white.  It forms a billowy mound in full to partial sun exposures.

Ornamental peppers start to appear this time of year at the nursery.  They come in a number of different forms and may be orange, red, pink, yellow, purple, or black.  Use them as house plants or plant them in the garden.  You can eat the peppers but they are extremely hot and do not have a true pepper taste, having been bred for looks, not flavor.  When the peppers have lost their luster, this means the seeds inside have matured to the point where you can extract them, store them in a paper bag in a cool, dry place, and plant them out next spring.

“During the blistering heat, my avocado really got hit!  Leaves are fried and the avocados burnt, turned black, and fell off.  I am assuming this is from the heat.  Will the tree recuperate and how should I be treating it?”

Patti Faucher, Northridge

Yes, your avocado tree definitely suffered a heat stroke.  Water it as you normally would and it should recover.  Resist the temptation to over water and do not apply fertilizer until next srping when strong new growth is visible.

Tip of the Week:  Karen Mansky, who gardens in Oak Park, wonders why her mandarin orange tree has suddenly sprouted thorns.   Fruit trees consist of the scion variety that you eat (a mandarin in this case) grafted onto a rootstock species, which is meant to impart vigor to the scion.  If the graft is imperfect, the scion is damaged in some way, or the tree’s productive years are over, rootstock growth may engulf the tree.

The growth Mansky sees is that of a flying dragon (Poncirus trifoliata) rootstock, a species upon which mandarin oranges are often grafted.  You can allow your flying dragon to remain as an ornamental.  Its spring flowers and autumn fruit are fragrant.  It is a rare citrus species since it loses its leaves in the winter.  On the plus side, it is extremely hardy and would grow in the Antelope Valley.  Fruit is edible but best turned into marmalade since it is highly acidic when fresh.  Flying dragon makes an outstanding living fence with its impenetrable thorns.