To some eyes, the Chinese or Hawaiian hibiscus have never quite fit into the Southern California garden. Their large, lush leaves and big, brilliant flowers seem a tad too tropical for this arid climate, and most of them grow larger than many a garden can accommodate.
But in early summer, when hibiscus appear at nurseries, doubts and caution vanish and hibiscus sell like hot cakes. They're simply irresistible.
Few flowers are so alluring. They are huge--up to eight inches across--and although a flower lasts but a day, each is quickly replaced by others, so there is no shortage of bloom during the summer and early fall. The flowers' colors are deep and warm, and their foliage is a deep jungle green.
Though Hibiscus rosa-sinensis apparently originated in tropical Asia, they have been grown in all tropical climates and have become, perhaps more than any other plant, a symbol of the tropics. Can you imagine Hawaii without them?
Hibiscus are truly tropical plants, and that limits how they can be grown in Southern California, since ours is actually a subtropical climate. To make a hibiscus happy, you must supply heat and protection from below-freezing temperatures, although most hibiscus sold in this area will take a few degrees of frost. If you live on the side of a hill--even well inland--where cold air drains to lower elevations, the plants will probably be safe. Sometimes, projecting eaves will provide protection. In most of the Los Angeles Basin, Orange County and the San Diego area, hibiscus will do well if they're in full, hot sun.
If you aren't certain whether the temperatures at your location will suffice, you can easily supply extra heat. A south-facing wall is the perfect home for hibiscus. Even near the beach--but out of the ocean breezes--they will bloom beautifully against a south wall. Hibiscus can survive without much heat, but they will bloom poorly and their foliage will tend to look cold and unhappy. Heat will keep the leaves a dark, glossy green.
Fertilizer is important--first, to keep the leaves from yellowing (although yellow between the veins is chlorosis--cured with iron chelate) and to keep the plant growing. Flowers are produced on new growth, so continual growth is important--which brings us back to the matter of size.
In the tropics, hibiscus are tree-sized, but in Southern California, few grow that tall. Although several hibiscus supposedly grow to only four to six feet, it's best to figure on at least six feet for the following varieties: Bride, California Gold, Crown of Bohemia, Diamond Head, Ecstasy, Golden Dust, Santana and Vulcan. Allow for six to eight feet for Accra, Butterfly, Cherie, Fiesta, Fullmoon, Hula Girl, President, Powder Puff, Red Dragon, Ross Estey (which is the only hibiscus with flowers that last for more than a day) and Sundown. Expect the following to zoom with ease past 10 feet: Agnes Galt, Amour, Brilliant, Empire, Fire Wagon, Itsy Bitsy Pink or White (refers to flower size), Kona Improved, Red Double Dip and White Wings. These figures reflect the height of the plants, but most hibiscus are almost as wide as they are tall.
How fast a hibiscus grows has to do with its eventual size. The big guys grow fast; the shorter varieties are slower. Make sure that you allow enough room. Don't plant them under a low window or too close to a door or path. The trouble with planting a hibiscus in too small an area is that it will need to be pruned regularly. And pruning a hibiscus in a hedge-like fashion to keep it within bounds means that you'll have to sacrifice flowering. Too much pruning eventually will produce a plant that is woody and bare of foliage. This area is full of poorly pruned hibiscus.
Pruning should be limited to cutting out older woody growth to encourage new growth that will flower. Don't prune between mid-summer and the following spring; the resulting growth is most susceptible to frost.
What should you do if frost nips back growth in wintertime? Wait for new growth in the spring, and then prune off any damaged wood above the new growth. Don't prune too quickly after a frost. Make sure that the warm weather is here to stay.
When can you plant? Right now. Hibiscus like heat and will quickly take hold at this time of year. Be sure, however, to keep the root ball moist. Every few days, at first, let the hose trickle at the base of the plant until the ground and root ball are saturated. While they're growing, water them often, but don't let the soil get soggy.
Hibiscus do best in soil that drains quickly. Add lots of organic matter such as peat moss or ground bark before planting. Yellow foliage is often a sign of poor drainage. After the plant has been in the ground for a month, begin monthly fertilizing. Stop in September; growth after that point is susceptible to frost, even though flowering continues well into fall.