Knotweed

Knotweed by any other name. . .

There are no fancy varieties, but many different fancy names for knotweed. It used to be known as Polygonum capitatum, but is now easier to research as Persicaria capitata. The many common names include pink knotweed, pink clover, pink fleece flower, pinkhead, pink bubbleweed and smartweed. Obviously, the tiny and spherical blooms are pink, about the color of bubble gum. Each small leaf has a distinctive brown chevron, which makes the collective foliage rather bronzy. The wiry stems can not stand much more than three inches high, but creep indefinitely, rooting as they go. Knotweed is an excellent but potentially invasive groundcover, and is also a nice component to mixed plantings in large urns or behind retaining walls, where it can cascade several inches over the edges. A bit of partial shade is no problem. Bloom continues through the end of summer, and resumes at the end of winter.

English Ivy

Rampant English ivy can overwhelm trees.

Compared to Algerian ivy, English ivy, Hedera helix, may seem to be more complaisant. As ground cover, it mostly stays a bit lower, with smaller leaves, and a more refined foliar texture. It is generally easier to maintain and to mow if it does not get too deep. However, where it naturalizes, English ivy is more aggressive and more invasive than Algerian ivy. 

If contained, English ivy is a splendidly dense and evergreen ground cover that excludes most weeds. Containment is very important! English ivy must not climb into shrubbery or trees. It otherwise overwhelms its support and disperses seed. Although reasonably safe on bare concrete walls, it ruins wooden, painted and stucco surfaces. Growth is very fast! 

‘Hahn’s’ is likely the most popular cultivar of English ivy. It branches well, to fill out fast as ground cover. Cultivars that are variegated with white or yellow grow significantly slower, but provide elegant foliage for big pots or planters of mixed annuals or perennials. Foliar lobes are variable. For example, lobes of ‘Needlepoint’ are distinctly narrow and pointed.

Cockscomb

Plumose cockscomb blooms with pinata colors.

The flowers of the two different specie known as cockscomb do not seem to be as closely related as they are. Celosia cristata exhibits two or three inch wide, weirdly stunted and crested blooms that resemble the combs of roosters, although the most popular varieties are so densely furrowed that they look more like fuzzy little brains. Celosia plumosa, as the name implies, has plumose flowers that look more like three or four inch long pampas grass flowers than like anything associated with chickens. What they have in common is their very bright red, orange, yellow, pink or white blooms. Foliage can be bright green to rich bronze.

As short lived annuals, cockscombs blooms only for about two months from the middle of summer to autumn. As cut flowers, they can last a week or two. However, because those popularly grown as summer annuals are mostly less than a foot tall, the flower stems are rather short.

Petunia

Petunias are quintessential warm season annuals.

There are too many varieties of petunia to be familiar with nowadays. The species name is Petunia X hybrida because almost all are hybrids of two primary species, as well as a few others to complicate the situation. The color range of the bloom of these hybrids now lacks only a few colors. (GMO orange petunias are only beginning to become available.) 

Besides an impressively extensive color range, bloom can be spotted, speckled, striped, blotched, haloed or variegated by too many means to list. Flowers can be rather small or as wide as four inches. Some are surprisingly fragrant. Some have frilled double flowers. Stems of cascading types may sprawl wider than three feet while only a few inches high. 

Petunias are warm season annuals that perform from spring until frost. They can survive as perennials for a few years if cut low for winter. Cool season annuals can obscure and shelter them until they resume grown in spring. They prefer rich soil, systematic watering and sunny exposure. Although mostly sterile, some appreciate occasional deadheading. Trimming during summer may promote fluffier growth for lanky stems.

Coleus

No flowers needed with this foliage!

Out in the garden, coleus, Plectranthus scutellarioides, prefers partial shade where the foliage is less likely to get roasted during arid and warm summer weather. It is grown as a warm season annual instead of as a perennial, because it gets so tired through winter, and can be killed by even a very mild frost. Its sensitivity to exposure in the garden is probably why it is more familiar as a houseplant.

The flashy and sometimes deeply lobed foliage is variegated with any combination of green, chartreuse, yellow, orange, red, burgundy, pink, white, brown and almost black. Flower spikes should be snipped as they develop to keep foliage dense. The tiny purple flowers are not much to brag about anyway. Large plants can get to two feet tall and broad. Cuttings root easily in rich and regularly moist potting soil or just plain water. Seeds need sunlight to germinate, so should only be pressed onto the surface of damp potting soil without getting covered, and misted daily.

Star Jasmine

Star jasmine blooms with fragrant profusion.

This jasmine is quite a star. However, this star is technically not a jasmine. Star jasmine, Trachelospermum jasminoides, is instead related to mandevilla and oleander. For many years, it has been one of the most popular vines for home gardens as well as large scale landscapes. It works well either as a ground cover, or as a relatively docile climbing vine. 

As ground cover, star jasmine gets about two feet deep. It will be lower and more refined with shearing, but will likely bloom less. It tries to climb shrubbery and trees, so will need exclusionary pruning. However, on a chain link fence, star jasmine works splendidly as a shorn faux hedge. It grows fast to more than ten feet high, but can get significantly higher. 

The richly fragrant bloom is most profuse about now, and can continue sporadically until autumn. The inch wide and bright white flowers are shaped like stars, and hang in small clusters. After bloom, the distinctly glossy and dark green evergreen foliage is handsome alone. Individual leaves are a bit longer than two inches and a bit broader than one inch. 

‘Angelina’ Stonecrop

‘Angelina’ is a bright chartreuse stonecrop.

Until the patent expires, unauthorized vegetative propagation (cloning) of ‘Angelina’ stonecrop, Sedum rupestre ‘Angelina’, is still illegal. However, it regularly flaunts its own unlawful proliferation wherever dislodged bits of stem can find anything to take root into. It can be just as happy to root into cracked concrete as in bare soil. Yet, it is a surprisingly complaisant small scale ground cover that cascades only several inches over stones, low retaining walls or the edges of planters.

Without getting more than four inches deep, stems root as they creep indefinitely but slowly along the ground. The bright yellowish evergreen foliage and bright yellow flowers that bloom about now contrast nicely with darker green or bronze foliage. Exposed foliage can get blushed with orange in winter. Shabby plants regenerate vigorously after getting pruned back. Pruning scraps sprinkled over bare soil and lightly mulched with finely textured compost will happily but illegally grow into more of the same. ‘Angelina’ stonecrop likes somewhat regular watering, but can survive with less.

Oleander

Oleander, although pretty, is famously toxic.

Prior to the appearance of oleander scorch disease in the early 1990s, oleander, Nerium oleander, was almost too popular, and for good reason. It is remarkably resilient to harsh conditions. It had been one of the more common plants within freeway landscapes since freeways were invented. Now, new plants are rarely available. Only older plants remain.

White, pink or red bloom is most abundant through warm summer weather, with sporadic bloom continuing through most of the year. Some dwarf cultivars bloom with peachy pink double flowers. Plants with enough room to grow wild without much pruning bloom best. Frequent shearing deprives the healthiest oleander of its blooming stems prior to bloom.

The biggest oleander get as tall as fifteen feet, so can be pruned up as small trees, either on single trunks or multiple trunks. However, because their limber trunks can not support much weight, occasional pruning is necessary while trunks develop. Such pruning limits bloom, so should happen mostly at the end of winter. Straight single trunks need staking. Oleander wants warm and sunny exposure, but is quite undemanding.

Fern Pine

Narrow leaves resemble pine needles.

It is neither a fern nor a pine. Fern pine, Podocarpus gracilior, can be a tree taller than fifty feet, and half as broad, but is often a shorn shrub or hedge that can be kept less than eight feet tall. Stems are limber enough while  young to be espaliered. The finely textured evergreen foliage is somewhat yellowish out in full sun, and darker green in partial shade. Individual leaves are as long as two and a half inches, and less than a quarter inch wide, and hang almost like fat pine needles. Some but not all mature trees can drop a bit of messy fruit with hard pits that are a bit larger than those of cherries. Bark gets distinctively blotched as it ages. The deep roots can be remarkably complaisant with concrete. Outer growth can get damaged by the harshest frosts every few winters or so, or roasted by hot dry heat every few summers.

Nasturtium

Nasturtium bloom is sensitive to aridity.

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.