Whether feral or planted intentionally, nasturtium, Trapaeolum majus (which is actually a hybrid with two other species) is a delightful flower that just about everyone appreciates. Its eagerness to self sow and possibly naturalize in riparian situations attest to how easy it is to grow. Seed for many varieties is readily available. Feral plants provide feral seed.
Bloom of domestic nasturtium can be various shades, tints and hues of yellow, orange or red. Flowers can be striped or blotched with colors of the same range. Some are double. The palest yellow is almost creamy white. The darkest red is almost brown. Feral plants, after a few generations, generally revert to blooming with simple bright orange or yellow.
Plants are more or less annual, but can replace themselves almost as readily as they die out. Those that perform through spring and summer succumb to cooling autumn weather, as their (feral) seedlings begin to replace them for autumn and winter. Those that perform through winter may succumb to frost where winters get cool, but also self sow feral seed for next spring.
Although rarely planted intentionally in home gardens, perennial pea, Lathyrus latifolius, is somewhat common near rural roadside ditches and in riparian situations. It naturalizes to a minor degree, generally where the soil retains a bit of moisture after the rain finishes. It can eventually become somewhat overwhelming in unrefined but irrigated landscapes.
Bloom is typically rich purplish pink during late spring or early summer. A few specimens might bloom white or pale pink. Seed for varieties that bloom in any of these three colors, as well as red, is available online. Flowers resemble those of annual sweet pea, but are more abundant, and lack fragrance. Their delicate foliage might be slightly bluish green.
Vines might be lean through their first season from seed, but can get six feet long. By the middle of summer, they begin to die back to their plump perennial roots. They last longer with watering. Without watering, they may finish before July. Vines that grow from mature roots as winter ends after the first season should be bigger, fuller and perhaps voracious.
As the name implies, each individual flower of daylily, Hemerocallis, lasts only about a day. They open just after dawn, and wither by dusk. However, bloom last from a week to a month because there are several flowers on several stalks. These flowers take turns blooming, so that a flower that blooms today will likely be replaced by a new flower tomorrow, until bloom finishes. Some daylilies bloom early in spring. Others wait until summer. A few bloom again, as late as early autumn.
Flowers can be almost any color except for blue or white, and typically have a a different color in the throat. The most popular varieties are bright yellow, pastel yellow, orange, pink or rusty red. Purple flowers are not quite as flashy as the color implies. Each flower has six petals, (which are actually three petals and three sepals). Bare stems hold the flowers about two feet high, well above the clumping grassy foliage. Some stay only a foot tall. A few get considerably taller. Plants should be groomed of finished flower stems, and may sometimes want to be groomed of deteriorating foliage. Daylilies known as ‘deciduous’ daylilies shed all foliage by autumn.
Stylish modern cultivars have been restoring the popularity of formerly common weigela, Weigela florida. Traditional sorts can reach first floor eaves, with delightfully open branch structure and rosy pink spring bloom. The foliage of most is variegated with white. Newer cultivars are more compact, with more variety of form, as well as of foliar and floral color.
Bloom can be pink, red, rosy red, white, white with yellow centers, or the the familiar rosy pink. Foliage can be green, bronze, deep purply bronze, or variegated with white or pale yellow. As it develops in spring, variegated foliage might be blushed with pink. Shrubbier modern cultivars may get no taller than five feet. Some are lower and densely mounding.
Although deciduous, weigela are popular as short informal hedges. Formal or excessive shearing compromises both bloom and form. After primary spring bloom, several modern cultivars bloom sporadically later in summer. Weigela enjoys a bit of winter chill, so may not appreciate the mildest coastal climates. Partial shade is tolerable, but inhibits bloom.
Wispy billows of pinkish or tan blooms through June and July are what the smoke tree, Cotinus coggygria, is named for. It probably should have gotten more recognition for brilliant foliar color in autumn. It reliably turns bright yellow and orange, and if the weather is right, it can turn rich red and even purplish. Until then, the popular modern varieties have either dark purplish or light yellowish foliage. Some of the older plants have slightly bluish green foliage. The nearly circular leaves are about two or three inches long. Yellowish varieties tend to be shortest. Those with purplish or bronze foliage get larger. Old fashioned green plants are the largest, and can get twelve feet tall and broad. Smoke tree can be large shrubbery, or pruned up as small trees. Aggressive pruning in winter promotes better foliar color through spring and summer, but inhibits smoky bloom. Slightly distressed plants have better color in autumn. Plants that are watered too much are likely to succumb to disease within only a few years.
The silly common name actually suits its plump rosettes of pale bluish succulent leaves. Mexican snowball, Echeveria elegans, forms small colonies that might resemble stashes of snowballs. Individual rosettes are circular, and a bit wider than tall. The widest are four inches or so across. The evergreen leaves are as neatly radial as scales of a pine cone.
Some may know Mexican snowball, and various other species of Echeveria and related Sempervivum, as hen and chicks. Big rosettes can produce so many small pups around their edges that they are reminiscent of mother hens surrounded by their huddled chicks. These pups are quite easy to separate for plugging into pots or elsewhere in the garden.
Mexican snowball is happiest in sunny situations with rather regular watering, but should tolerate a bit of shade and lapses of watering. For small trees in big pots, it can cover the surface of the potting media nicely. Pups plugged into crevices of stone walls might grow into clinging colonies. Tiny pink flowers with yellow tips bloom on wiry stems about now.
As long as freeways have been getting landscaped, oleanders have been contributing their profuse white, pink and red bloom. Heat, exposure and lack of moisture do not seem to bother them. They have become less common recently only because of new diseases that had never before been problematic. The diseases do not necessarily kill all oleanders everywhere, but are serious problems where the nurseries that grow most oleander are located.
The largest oleanders can get more than fifteen feet tall, and can be pruned up as small trees with multiple trunks. Oleander trees with single trunks almost never stand up straight, and do not want to give up their stakes. Because flower clusters develop at the ends of new growth, frequent exterior pruning or shearing inhibits bloom. Dwarf cultivars that are naturally proportionate to their space will bloom better than larger types that need to be pruned for confinement.
Oleander flowers are about an inch or two wide, with five petals, although some have ruffly ‘double’ flowers. Unfortunately, double flowers tend to hang on as they deteriorate after bloom. Some oleanders are slightly fragrant. The name ‘oleander’ is derived from the similarity of their leaves to those of olive trees (‘Olea‘), although oleander leaves can get three times as long.
Chaparral climates are not easy without irrigation. The long summers are warm and arid. California buckeye, Aesculus californica, knows what to do if it can not stay hydrated out in the wild. It simply defoliates. Yes, it goes bare right in the middle of summer. If it does it early enough, it refoliates after rain resumes in autumn, only to defoliate again for winter.
This ‘twice deciduous’ characteristic is likely why California buckeye is not more popular for unirrigated landscapes of other natives. Shade is an asset through warm summers. In coastal, riparian or irrigated landscapes, the original spring foliage lasts through summer to defoliate in autumn, like that of most other deciduous plants. It may get shabby though.
Nonetheless, California buckeye is a delightful small tree, typically with a broad and low canopy suspended by a sculptural branch structure. Not many get more than twenty feet tall, although some get twice as tall. Bark is strikingly pallid gray. The elegant leaves are palmately compound. Six inch long trusses of tiny white flowers are sweetly fragrant in spring.
Almost all photinia in local landscapes is Fraser’s photinia, Photinia X fraseri, which is a thornless and fruitless hybrid of two species that are now rare. Some of the old fashioned photinia are thorny. Some produce copious berries that can get messy, or feed birds who can get messy. More modern cultivars of Fraser’s photinia are becoming more available.
Fraser’s photinia is popular as a shorn evergreen hedge. New foliage that develops after shearing is richly reddish bronze, and fades to dark green. Bronze color is best in spring, after late winter shearing. Summer shearing stimulates a repeat performance, although it may not last as long before the foliage fades to green. Shearing enhances foliar density.
Unshorn photinia can develop into small trees as tall as fifteen feet, with new growth that is a bit less richly colored than that of shorn photinia. It also blooms, often profusely, with big and rounded trusses of tiny creamy white flowers. Bloom is not impressively colorful. Floral fragrance is objectionable to some. All photinia types are susceptible to fire blight.
Where it had been left to develop naturally in old freeway landscapes, shiny xylosma, Xylosma congestum, grew as small trees. The largest are significantly taller than twenty feet. They can be pruned up to expose their nicely flaking bark on sculptural trunks and stems. The evergreen foliage is shiny and rather yellowish green, somewhat like that of camphor tree. The slightly serrate leaves are about two inches long or a bit longer. The tiny and potentially fragrant flowers are rarely seen, and not worth looking for. In refined landscapes, shiny xylosma is popular as a shorn hedge. Xylosma congestum ‘Compacta’ has denser growth, and can be kept only a few feet high if necessary. Vigorous shoots can have nasty thorns hidden in their deceptively gentle foliage. Once established, shiny xylosma does not need much water. It prefers full sun exposure, but will tolerate a bit of shade.