Mulch was not invented by humans. Most plants make some sort of mulch naturally. Even desert plants that live on bare ground shed foliage that decomposes to be recycled back into the soil, and provide nutrients for the roots below. Redwood, most pines and most eucalyptus are extreme mulchers that generate thick layers of foliar debris that benefit their own roots, but inhibit the growth of competing trees. Knotweed, Hottentot fig (freeway iceplant), ivy (both Algerian and English) and other dense groundcovers are their own mulch, and also work well for substantial plants that grow amongst them.
There are a few advantages to mulch. Although ground cover mulches consume some degree of moisture, mulches benefit plants by retaining moisture at the surface of the soil. Mulches also insulate the soil, so that it is more comfortable for roots that want to be near the surface. Most weed seeds that get covered by thick mulch can not germinate and emerge through it. Those that try to germinate on top probably can not get their roots through to the soil below. Besides, mulch simply looks better than bare soil.
Mulch is generally spread in early spring, before weed seeds are completely germinated, and while the soil is still damp. However, moisture retention is still a concern through the warm and dry weather of summer. A thin layer of finely textured mulch added over thinning groundcovers (without completely burying the foliage) can rejuvenate tired old stems by giving them something more to root into. This works well for knotweed, English ivy and even trailing gazanias.
Mulches should generally be well composted so that they do not take too many nutrients out of the soil for their own decomposition. However, uncomposted coarse wood chips, like those often recycled from tree services, are even more effective at controlling weeds while fresh, and they tend to decompose before they become a bother to larger plants.
Small volumes of mulch can be purchased in bales at nurseries and garden centers. Composted redwood soil conditioner is a popular soil amendment that can alternatively be a nice finely textured mulch to spread thinly over small areas or in planters. Larger volumes of more coarsely textured and less expensive mulching materials can be obtained by the yard from garden supply stores.
Urban sprawl replaced the formerly vast orchards of the Santa Clara Valley a long time ago. Nowadays, it is difficult to imagine that they were ever here. Apricots, prunes, cherries, almonds, walnuts and all that the region was once famous for are all now rare commodities.
Coppiced trees and shrubs are just like pollarded trees, but without the trunk and main limbs. Instead of getting cut back to the same distended knuckles at the ends of disproportionately stout limbs, they get cut back to the same stump just above grade over winter. Some get coppiced annually. Others get coppiced only when they get too big. The coppiced California sycamore in this picture may never get coppiced again.
Mutants are the source of many of our favorite cultivars of otherwise simpler specie. Many cultivars of plants with compact, pendulous or fastigiate (strictly vertical) growth, or variegated, bronzed, golden or otherwise abnormally colored foliage, were derived from ‘sports’, which are mutant stems that appear on otherwise normal plants. Thornless blackberries were sports of thorny cultivars. Fruitless mulberry is a sport of white mulberry. There is no shortage of mutants.
