sweet gum (Liquidambar styraciflua) photo by Rob Young

This month, Valley dwellers have been privileged with the sight of brightly colored foliage on crape myrtle, liquidambar, Modesto ash, ginkgo and Bradford pear trees. This is the result of a cold snap during the last week in November, when one night’s temperature was the lowest recorded on that date in more than 60 years.
New England’s annual fall foliage display is more brilliant than ours because of the colder temperatures in that part of the country. Although our deciduous trees generally manifest some color change during December, this year’s vivid display in orange, gold and burgundy may be attributed to colder than normal weather.
Contrary to what many people think, leaves do not change color in the fall by producing something that was missing in spring and summer. The process of foliar color change is brought on by the breakdown of chlorophyll – the pigment that makes leaves green – to reveal other pigments that had been present all along but whose colors were masked by the chlorophyll. These revealed pigments are known as xanthophylls (yellows), carotenes (oranges) and anthocyanins (deep reds).
Q. All of the ground covers I plant either die after a year or two or become so invasive, like ivy, that I can never get rid of them. What are your favorite ground covers?
A. The following ground cover selections, as long as soil, water and sun exposure requirements are met, should last from a decade to a century in the garden, blooming on and off throughout the year. None should ever require water more than once or twice a week as long as water is delivered through drip irrigation tubing or you are willing to allow a slowly leaking hose to soak the area where your ground cover is planted.
Daylily. Although not generally classified as a ground cover, daylilies will take over your garden bed, if that is your desire, thanks to an indestructible tuberous root system. The beauty of this plant, in terms of its care, is that it may be cut down to the ground when it begins to look shabby and, within days, fresh green shoots sprout up again.
Daylilies thrive in the Valley, whether on slopes, in open areas or in patio containers, as long as they receive no more, but no less, than half-day sun and their soil does not go bone dry.
Daylilies eventually form a rather dense carpet of foliage from which chalice-shaped blooms in yellow, orange, salmon, violet or burgundy will appear. Soil that contains a measure of clay in it, which would be a problem for many other plants, is not a problem for daylilies.
Gazania. For a long-lasting stand of gazania, plant seeds or purchase mixed gazanias in 4-inch or quart-sized containers, which are also grown from seed, at the nursery. Dirt flats of cloned gazania varieties are not particularly long lived and generally do not self-sow, unlike those grown from seed, which are self-sowing.
All gazania types require fast-draining soil and should never be watered more than once a week. When frequently watered, gazanias are attacked by soil and leaf fungi that lead to their untimely demise. In very hot weather, their leaves may curl up as a defense against desiccation but you should resist the temptation to overwater in the summer since this is when soil fungus is active.
Gazania does best when it benefits from most, if not all, of the day’s sun.
Trailing rosemary. Whatever is true of gazania, in terms of water management, is even truer for trailing rosemary. Trailing rosemary (Rosmarinus officinalis ‘Prostratus’) is extremely sensitive to excess soil moisture. I have seen it die after heavy spring rain and a sudden heat wave, the combination of excess soil water and high temperature activating the lethal Phytophthora fungus, which is found in most soils. Phytophthora (from Greek phyton = plant + phthora = destruction) persists in durable, double-walled fungal spores that may lie dormant in the soil for years, waiting for the right conditions to come to life.
Established plants should not be watered more than once a week. Unlike gazania, trailing rosemary will flourish in either full-day or half-day sun exposure.
Not only does it trail on slopes, but it will spill over block walls and grow vertically downward for several feet or more.
Flower carpet rose. This is not exactly a ground cover but more like a thicket that can easily grow 3 feet tall. Cut it back drastically from time to time and it will quickly return to its former stature.
Available in red, pink, apple blossom, white, yellow or amber, flower carpet roses bloom nearly all the time as long as they are given full sun exposure but are backed up by a block wall or fence, or mixed together with other perennials that shade their roots. I have planted carpet roses in full sun on slopes and as stand-alone subjects in sidewalk planters with unhappy results. They absolutely must have their roots kept cool in summer, which may be achieved by spreading a thick mulch around them, or they will dash your expectations for nonstop color.
Because of their constant bloom capacity, they do best when regularly fertilized, yet they are sterile and produce meager rose hips so that deadheading of spent flowers is not required.
There are excellent examples of flourishing red carpet roses in the entrance planters at the shopping center at Riverside Drive and Fulton Avenue in Sherman Oaks.
Campanula. Campanula poscharskyana, also known as Serbian bellflower, is the first choice for semi-shady or semi-sunny beds. It is a reasonably drought tolerant selection that you can use as a filler around impatiens, begonias and ferns. Campanula grows rampantly at times but its roots are superficial, making it easy to control. Star-shaped flowers are typically lavender blue, but you may also see them in white.
– Patricia Hagopian, Arleta
Tip of the week
For a bright addition to the shade garden, plant variegated Hawaiian elf (Schefflera arboricola ‘Variegata’). The gold splotches in the foliage illuminate dark corners. To add texture to your shady retreat, plant Philodendron ‘Xanadu.’ Its scalloped leaf margins provide a touch of whimsy that is a pleasant departure from the funereal formality often associated with shade-loving species. Keep in mind that shade plants require at least three hours of good ambient light to grow. Sometimes, a planter is so shady that nothing will grow in it and you are better off filling the space with ornamental stones or a small fountain.