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Periwinkle

70503Like so many of the easiest to grow plants, periwinkle, Vinca major, is too easy to grow. It has become an invasive exotic (nonnative) weed in many moist riparian environments. It can get rather weedy in home gardens as well. This can be an advantage if it happens to fill in for bald spots in areas of other ground cover. It is a disadvantage if it overwhelms or competes with other plants.

It is hard to believe that such a seemingly innocent plant with sporadic but delightful light blue flowers amongst rich green foliage has such unpleasant potential. The radial flowers are about an inch or maybe two wide, and bloom almost all year except for winter. The simple evergreen leaves are likewise an inch or two long. The wiry stems stand a foot or two high before flopping over.

Once stems lay down, they develop roots where they touch the ground, and form new plants that repeat the process of producing upright stems that flop over. Without confinement, there is no limit to the trouble they can get into. Fortunately, it is not a fast process. Cultivars with white or purple flowers, or variegated foliage are more complaisant. Periwinkle is neater if mown as winter ends.

Posted on by tonytomeo · 13 Comments

Get The Lowdown On Groundcover

1Lawns composed of turf grasses are the most functional, but also the most demanding forms of groundcover. That is old news. There are so many other less demanding low growing plants that that can cover the ground in areas that are not used like lawns are. Sometimes they work nicely just to control weeds. Sometimes they help to control erosion on otherwise unlandscaped hillsides.

Like all other plants in the garden, groundcover plants must be appealing. There is no point in growing plants that look no better than the bare soil they are intended to obscure, or the weeds they are intended to control. Some provide good foliage. Some bloom nicely. Many do both. Although not as resilient to wear as turf grasses, some groundcover plants tolerate some degree of traffic.

There are of course all sorts of groundcover. Only a few want as much water as lawns need. Some need no watering at all once established. Some are low growing shrubbery like sprawling forms of ceanothus, coyote brush, cotoneaster, coprosma and juniper. Others are vines like honeysuckle and ivy. Some of the best are creeping low perennials like iceplant, gazania and African daisy.

Low growing shrubberies may not be practical for confined spaces. When they run out of room to grow laterally, they tend to pile up on themselves, and some types can eventually get quite deep. Some types look silly if pruned around the edges for containment. Vines however need to be pruned around the edges, as well as out of trees and shrubbery. Some vines eventually get deep too.

Sprawling perennial groundcovers are the lowest and tidiest of groundcovers. They might not be as practical as shrubbery or vines for large areas, but are more often the better options for tight spaces. They do not mind getting pruned around the edges, and generally do not need any other pruning, although some look better if mown annually. Periwinkle and Saint John’s wort can get deep enough to get sloppy. Many other perennial groundcovers stay low enough to barely get disheveled by light trampling.2

Posted on by tonytomeo · 12 Comments

Candytuft

80321It looks like sweet alyssum, but is not even close. The tiny white flowers and finely textured foliage work almost as well for similar uses in the landscape. In fact, the plants are most often grown as short term warm season annuals. However, candytuft, Iberis sempervirens, is really a perennial that can be cut back in autumn, regenerate through winter, and bloom for spring and early summer.

One must really examine candytuft closely to see that it is related to cole crop vegetables like broccoli, cauliflower, cabbage and Brussels sprouts. That is why is has an odd aroma when cut back. Mature plants have the potential to get nearly a foot deep, but typically stay lower. They can spread a bit wider than a foot. Candytuft can tolerate a slight bit of shade, but prefers sunny exposure.

If planted closely together, candytuft can form a nice small scale ground cover. It mixes nicely with stones, and cascades slightly over the edges of low stone retaining walls. It is more substantial than sweet alyssum, and works better for permanent planting in borders and along walkways. The barely perceptible floral fragrance of individual plants can be quite appealing in larger volumes.

Posted on by tonytomeo · 9 Comments

Rain Is Necessary But Messy

10914Water is no more scarce in California than it has been in recorded history. The problem with it is that it is a limited resource that must be shared amongst too many people. Likewise, rainstorms are no more torrential than they have ever been. Floods, erosion and wind are only more destructive now because there is so much more infrastructure that can be damaged than ever before.

Rain and wind are perfectly natural. Furthermore, it is natural for the weather to knock down limbs or entire trees. It only seems unnatural when these limbs or trees fall on houses, cars or anything else that gets in their way. Plants actually enjoy rainy weather much more than we do. Some like to be rinsed of dust and debris left from former infestations of mites, aphid, scale or sooty mold.

What plants do not like about rain is erosion. It is bad enough that so many plants in refined gardens are deprived of their own litter to insulate the surface of the soil. It is even worse if the bare soil gets eroded away from fine feeder roots at the surface of the soil. This is something that the rest of us would agree on. We do not want gullies carved into slopes, or drains clogged with mud.

Trees, shrubs and some stout perennials with aggressive roots are useful where the potential for major erosion is a concern, but might not do much for annoying surface erosion. Sprawling and spreading plants that form dense networks of low branches and surface roots are more effective. They soften the splatter of rain, slow the flow of drainage, and catch much of any dislodged silt.

Groundcover plants like ivy, gazania and iceplant are probably the best option for controlling surface erosion. Dense and low shrubbery that spreads over the ground and holds its own debris probably work just as well. These include low junipers, trailing rosemary and dwarf coyote brush. Larger shrubbery can help if it can drag its lowest limbs on the ground, and no one rakes below it.

Mulching limits erosion while new plants grow. Although new mulch needs to be added annually as old mulch decomposes, less will be necessary as plants grow and cover more area. Mulch is also effective where no plants are desired. For large areas, especially where plants are not expected to fill in, landscape cloth below ornamental bark inhibits weeds. However, coarse bark slowly shifts downhill, so replaces one kind of erosion with another, and will eventually need to be raked back uphill.

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‘Silver Falls’ Dichondra

80124No one seems to know what ever happened to old fashioned dichondra lawns. Everyone seemed to like them, especially those of us who dislike turf grasses. Somehow, they became passe and very rare. The formerly common dichondra that such lawns were made of is now merely a resilient weed in turf lawns. But wait! We have not heard the last of this resilient and appealing perennial.

Silver Falls dichondra, Dichondra argentea ‘Silver Falls’, has the same tiny rounded leaves, dense growth and fine texture as old fashioned dichondra lawns, but instead of rich deep green, it is strikingly silvery gray. It does not tolerate traffic well enough to work as lawn, but is a distinctive small scale groundcover, and cascades exquisitely from urns of mixed perennials or hanging pots.

The trailing growth spreads indefinitely over the surface of the soil, but is not very fast about it. As ground cover, individual plants should therefore be planted only two or three feet apart. They get two to four inches deep. Hanging growth (that can not root into the soil) can cascade more than three feet downward. Silver Falls dichondra prefers regular watering and full sun or a bit of shade.