The healthiest hibiscus plant I have ever seen is never watered. It flowers heavily nearly all the time and its leaves are always a lush deep green. I know you’re wondering how this can be, so I won’t keep you in suspense.
This hibiscus is growing on the edge of an asphalt driveway. Rainwater is no doubt trapped beneath the asphalt and the hibiscus’ roots luxuriate in the constantly moist soil throughout the year. Even during a drought, the plant barely shows any signs of discontent. It will sometimes defoliate, especially after a cold snap, but always returns to its previous glory in due time.
This same phenomenon is at work with city street trees. Once the trees are established, they never need watering since the surrounding sidewalk traps every drop of rain that soaks into the soil underneath where it remains available to any roots in the vicinity.
One of the places to appreciate the full range of hibiscus beauty is the San Diego Zoo. Flowers, shoots, and leaves from the hibiscus plants growing on-site are a source of nourishment for many of the animals that are kept there. Turtles are especially fond of its flowers while primates of every kind devour its leafy branches. Two unusual hibiscus types you will encounter at the zoo are the tropical Hotbiscus hybrids with multi-colored flowers that appear to have come out of a studio specializing in psychedelic art and fringed hibiscus (Hibiscus schizopetalus), whose petals are divided into pieces that resemble the fingers on the hands of Dr. Seuss characters. And then there is Hibiscus Cooperi with red flowers and white and green foliage that is occasionally tinged with pink.
Hibiscus flowers are non-toxic and may be eaten raw but are more typically made into tea. The most edible species is roselle (Hibiscus sabdariffa). Its leaves are eaten as a vegetable in tropical countries and its flower calyx clusters (that have the appearance of red Hershey’s kisses at one stage of their development) are not only highly ornamental but are made into a sweet yet tangy drink. Roselle has a reputation for being medicinal among those who cultivate it as a staple in their diet. In one clinical trial reported in the Journal of Hypertension, regular consumption of roselle lowered blood pressure by 7.5 points. Order it directly from Annie’s Annuals at anniesannuals.com.
The word hibiscus comes from iviscus (ee-vis-koos), the Greek word for marshmallow – that is, a plant belonging to the mallow family (whose members include hibiscus, abutilon, hollyhock, rose of Sharon, okra, cotton, and the cacao tree from which chocolate is made) that lives in a marsh. The marshmallow plant (Althaea officinalis) looks a lot like hollyhock (Althaea/Alcea rosea), its close relative only marshmallow flowers are consistently white whereas hollyhocks — the abandoned parking lot volunteer plants — come in white, red, maroon, and pink. And yes, marshmallow is the plant from which a confection that bears its name was first produced. In ancient Egypt 4000 years ago, marshmallow sap was initially identified for its unique sweetness. Up until the late 1800s, marshmallow sap was still being used, combined with other sweeteners, in marshmallow candy until it was finally replaced by gelatin.
Blue hibiscus (Alyogyne huegelii) is one of the most stunningly charming of all woody perennials. Its lesser-known name of lilac hibiscus is more appropriate as it is a truer reflection of its flower color. Anyone who has seen this plant in full bloom at its mature height of 6-10 feet will want to have it. Unfortunately, it is seldom seen in the nursery trade but you can order it too from Annie’s Annuals (Annie calls it “one of the loveliest plants I’ve ever grown”) or from a retail nursery supplied by San Marcos Growers (smgrowers.com). Blue hibiscus is an Australian native whose habitat is coastal sand dunes so do not water it once it is established. The slightest amount of excess water in the root zone will kill it almost immediately.
I have a gardenia whose lack of a need for water is further proof of a thesis I have been developing over the years through both research and personal experience: if soil is properly amended prior to planting and mulch is applied after planting, watering may become an afterthought. This line of thinking began when I read about orchards and vineyards in the Los Angeles area a hundred years ago prior to the arrival of sprinkler irrigation. These orchards were dry-farmed meaning the only water they received was winter rain. And many vegetable crops were also dry-farmed as well as watermelons.
Soil preparation involved heavy incorporation of aged manure. Planting was done early, in late February, and mulch was applied. I have found that tomatoes, for example, can easily go for two months if not more without water under such circumstances. And nearly all herbaceous perennials (rhizomatous and bulbous plants) and woody ornamental shrubs will do fine with once a month watering or less as long as a two-inch layer of mulch circles the plants.
Getting back to my gardenia, it was planted 16 years ago. It’s a representative of the Mystery cultivar and is known for the size of its flowers although it does not bloom as heavily or as uninterruptedly as the more widely planted Gardenia veitchii. My gardenia receives half-day sun and suddenly last week it burst into bloom although it had not been watered except for rainfall – admittedly, there were late rains this year — during all of 2020, a stretch of six months.
Successful gardening, I think, has much to do with awareness. Each year is different and the gardener needs to take into account the amount and timing of the rain, for example, in order to make informed decisions when it comes to watering. Fertilization, too, may be more of a safety measure than a necessity for lots of perennial plants, keeping in mind that over-fertilization leads to rapid, but not necessarily robust vegetative growth that is a magnet for insect pests.
Tip of the Week: Roger Allen who gardens in Santa Monica sent the following email: “I have a 45-year-old avocado tree and sections of the tree are dying and the trunk and lower branches are cracking and oozing white fuzzy stuff. The tree is about a mile from the coast. Please share if there are any remedies for these conditions.”
It appears that you have Dothiorella canker. The fungus that causes this disease is attracted to wounds and pruning cuts. Once the disease is observed, it is vital that any dead wood and leaves be pruned out and any fallen fruit be taken away since such wood, foliage and fruit could harbor the offending fungus. Also, pruning and harvesting of your tree should be done when wood and soil are dry, and never following a rain, since wet conditions will encourage the disease to spread. That being said, your tree could persist for a number of years and you should be congratulated since keeping any fruit tree productive in an urban setting for 45 years is a major accomplishment. Mulching avocado trees with their own leaves is a recommended practice. Finally, being only a mile from climate moderating coastal waters, you should barely have to water your large, long-established tree since at its age and suffering from a fungus condition, the least bit of excess water would be detrimental to its health.
Please send questions, comments, and photos to Joshua@perfectplants.com.
