Our native plants are not weeds. Weeds are aggressive invaders, often brought to this country in animal feed. Many plants that you might consider native, especially grasses, endemic in natural areas are actually weeds that came with the stagecoaches. The most troublesome weeds in our gardens are foxtail grass, oxalis species, and milk thistle. Persistant removal by hand, especially before flowering, is the most effective way to get rid of weeds. Oxalis may require chemical destruction. Bear in mind that it is difficult to control Roundup spray which often will kill a cherished plant growing beside the weedy target. A small paintbrush is a good alternative method of applying Roundup.
There are other kinds of weeds too. Lamb’s quarters is a common weed that is also edible. It is difficult to eliminate if it goes to seed, but if you eat it when it is young it won’t get a chance to seed! Chickweed is another common edible weed that is fodder for birds as well as having tremendous nutritional properties for humans. I tried some recently and it is a delicious addition to a salad. Chickweed water is said to be a cure for obesity! Chickweed spreads rapidly if unchecked.
Drought tolerant plants are gaining popularity which is a good thing. However, drought tolerant plants tend to be more invasive than those that are tender or thirsty. Eschiumcandicans, Pride of Madeira is striking, a favorite for bees, but drops forests of seedlings that grow readily without irrigation. Fortunately it is easy to uproot. In any case we are going to have to be careful about adding non-native drought tolerant plants into our gardens. Some, such as Grevillea long john are hybridized and seem to be infertile. This is a complicated subject with little useful information out there for the novice or even expert gardener.
Invasive ornamental plants such as common honeysuckle, Algerian ivy, Pennisetum, Arundo, and Pampas grasses, Periwinkle or Vinca major, and Spanish broom should never be planted because we know how easily they spread into wild lands, their seeds carried by visiting birds. These plants were once encouraged in California because they are extremely drought tolerant and are great for soil rentention. However, once rooted they will spread vigorously. The flora of the Big Sur coastline is being decimated as pampas grass becomes the monoculture on those dramatic cliffs. It is a pity that nurseries still sell many of these nuisance plants. A comprehensive list of invasive plants may be found on the California Invasive Plant Council website. As you can see here, it is impossible for any other plant to survive the strangulation from these fast growing vines.
Many plants will set seed in the bountiful waterwise garden. Lavender dentata often sets seedlings around the garden and salvia chameadryoides spreads by underground runners and seeds. These plants can be transplanted to appropriate areas or potted up for friends, or a plant swap. Succulents also pup readily and are very useful for colonizing bare ground while other plants become established. The succulents can be removed later, rather easily as most of them are shallow rooted. However, some agaves, such as the giant Americana, put out offsets very close to the mother plant making them difficult to remove and therefore invasive. Aloes make much better colonizing plants as the thorns are blunter and they flower at least once a year.