According to David Nellis in "Poisonous Plants and Animals of Florida and the Caribbean", Euphorbia tirucalli can infuse the soil around it with poisons in order to repel other plants. It is possible that these poisons are carcinogenic. I have removed several of my specimens and put the others into planters. The sap is very irritating to skin and eyes.
Melianthus major (honey bush) from South Africa is extremely large and not suitable for a small garden. However, if you have space to plant this peanut scented beauty in a semi-shaded area you will please a lot of garden visitors. Orioles love its plentiful nectar. Melianthus major is drought tolerant, but might require monthly water in summer, depending on its geographical location. Cut the stems off to the lowest bud after it fades in early summer. The plant will grow again into an attractive hump until it's time to bloom in spring. Then it will grow its enormous flower spikes.
This plant from South Africa loves heat and sunshine. It grows quickly (but not as fast as its unruly cousin, Tecoma stans) and should be cut back and shaped in fall and after the first spring blooming. Bees love it.
Isn't this gorgeous with its fat spring foliage? It should be planted in full sun and never irrigated. Thankfully, this plant is getting easier to find in general nurseries. All the native plant nurseries stock it.
Look how well the color matches Teucrium fruticans, a completely drought tolerant plant related to rosemary and beloved by bees. They look very good together in a silver garden. Teucrium grows quite large over the years and plenty of space should be allowed between these plants should you use them together.
The Los Angeles Department of Water and Power will pay cash rebates to its customers to encourage the removal of 250 to 2,000 square feet of wasteful lawn and replace it with drought tolerant plantings, or even mulch. Be aware that if you include the parkway in your plan, that the City of LA will require a permit which costs $500! There is a permit waiver program which requires you to plant specific plants in the parkway, not the greatest selection alas. The cities of Corona and Long Beach also offers financial incentives for lawn removal. Find out if your city or local water provider is offering this type of rebate because it is available in several counties in California. Arizona, Nevada, and Texas have similar programs in place or in development.
$$$. Water rates are going up fast and most homeowners use a lot more water in their gardens than they do inside their homes. Take a look at www.bewaterwise.com to find tips on how to save water at home and in the garden.
Weekly lawn maintenance and bedding plant replacement are costly, whereas waterwise gardens require much less frequent maintenance.
Have you looked at your water bill lately? Ouch. Our water providers are raising rates quickly to deter us from using excessive amounts of water during shortages.
It is always difficult to find plants to grow under oak trees where irrigation cannot be used. The best plan is to stick to native plants. However, following is a short list of appropriate drought tolerant plants that will look good together. Achmaeas and Bromeliads will need a sprinkle into their cups in the summer and fall from time to time, but it does not require damp soil.
Achmaeas and Bromeliads
Aloes, various
Cycads
Dudleya lanceolata (California native)
Gasteria Mahonia repens (California native)
Rosa banksiae
Salvia Spathacea (California native)
Symphoricarpos, any (California native)
Here is a California live oak with a climbing rose, Rosa banksiae lutea, weaving through its branches. It’s wonderful to behold in springtime, and in summer the rose lies dormant and does not impact the oak at all. The rose is quite old and grows with no irrigation at all, its roots shaded by the sheltering oak.
Careful plant choices prove that you can mix native and non-native plants with great success. Patience is important as drought tolerant plants such as this rose must grow slowly because the root system must plunge deep into the ground in order to survive the long dry summers.
This particular rose requires no pruning as all of the growth is up in the tree. As the rose grows slowly, without irrigation, economy of branches is built in.
Below, on the left you will see Salvia spathacea which has a nice lush look for a dry shade garden. Although slow in its first year, this salvia spreads laterally from roots and will make a pretty ground cover in time.
Symphoricarpos mollis can be found in California as well as all over the western states and its form and color varies slightly in all the different microclimates it enjoys. In Malibu it is very green and lush under oaks in winter.
At last, the city of Los Angeles is enacting new environmental rules for landscaping. One aspect of these new rules deals with run-off. Previously homeowners were required to eliminate rainwater via gutters, downspouts, and drains to the street, where it would flow into storm drains and down to the ocean. Run-off carries vast quantities of dog faeces and street pollutants to our beaches and marine habitats. The new rules require that water is retained on the property where possible and allowed to percolate through the soil and into our aquifers. Dry wells (large perforated tanks buried in the soil can be installed for this purpose. However, if the soil is sandy a low berm will be sufficient to hold the water while it sinks into the ground. You can also dig a pit in sandy soil and fill it with broken concrete, gravel, etc. Direct water from the downspouts to this area and the water will percolate down. The pit can be covered with pebbles for appearance.
California, although often dry, sometimes is blessed with plentiful rainfall and before the land was paved over much of this rainfall was absorbed through the soil and into the aquifers. With paving came run-off and drains, directing the water to the sea. Now we have diminished aquifers and a huge thirst. The above drawing shows how you can help augment our water supply.
One way to deal with water that drains from roof is to build a seasonal creek using gravel and rock. It is important that the level of the seasonal creek is below the foundation of the house, see drawing. Allow the water to exit the downspout into a drain in the usual way. Dig out the location of the seasonal creek , which can meander around until it reaches the street, or preferably stop in a low point in the garden. The banks of the streambed should be stabilized by rock or broken concrete. Line the bottom with four inches of coarse gravel or pebbles so that the water can flow cleanly. Planting the edge of the streambed with grasses and other plants will enhance the natural appearance. In summertime or when the streambed is dry the it should be cleaned of leaves and debris to maintain an attractive appearance year-round.
If the stream ends at a low spot in the garden, the end point might be widened to emulate a small pond and a large boulder or two can be embedded in the gravel bottom.
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.
Hillsides can be daunting because concrete or block retaining walls are expensive and often, in time, they will fail or tip out. The land knows where it wants to be and I would retain it where it is rather than trying to impose a new shape upon it. Here is a fairly inexpensive plan that will make soil retention and access a lot easier. The materials are very simple: linseed oiled redwood planks or pressure treated landscaping lumber cut into three or four foot lengths, and 5/8” rebar, cut into lengths varying from three to five feet long.
Firstly, if the soil has a clay content you will want to be very careful to ensure that the planks are sturdy enough. Use 2 x 10 or 2 x 12 lumber. Railway ties are heavy and should not be more than two rows high.
If your hillside is gentle and your soil is sandy or loam, use 2 x 8s. Start at the bottom and work with the lay of the land, so that the planks follow the curves. Set a plank on the hillside, angled just a little bit in toward the hill and settle it into the soil by tapping it down. Place two three foot long pieces of rebar in front of the plank to hold it in place and hammer it into the ground with a small sledge hammer. Hammer down on the plank to ensure that it is solid and then tap the rebar down. Backfill the plank and then you can stand on this to work above. Offset the planks so that water cannot gain a long path through the gaps. Carefully wedge in a rock at the ends of the planks to stabilize the soil. Use a piece of rebar to hold it if it looks like it could roll out. Work your way horizontally and up the hill.
For steeper grades, use 2 x 12s and four or five foot long rebar and step on the layers as you work up the grade, to ensure that all is stable.
When the retention is complete then you may put in drip irrigation lines and plants. For steep slopes use lightweight deep rooting plants such as Salvias, (leucophylla point sal and bee's bliss are good ones), low growing Coyote bush, Lantana (not the invasive pink one), Epilobiums, prostrate rosemary, smaller Aloes, Sempiveriums, Parry’s agave, and other smaller succulents. If you can find Dalea greggii it is an excellent ground cover for hillsides. Avoid invasive or prickly plants to keep maintenance simple. When all is done, add a layer of mulch to protect the soil and slow water penetration.
Graptopetalum paraquayense is a very useful succulent for hillside planting. It is lightweight, fast spreading, easy to remove and very drought tolerant. Here it is seen tumbling down over a wall in the harshest of locations, facing south west on a dry slope. Note the mimulus on the top right. Eventually it will become large and replace the graptopetalum.
Another way of treating a hillside is to use broken concrete to construct terracing. This method of retention works well with gentle slopes and will add a semi-formal appearance. Concrete is weighty and cannot be used on steep grades.
If you look at the drawing above you will see that the concrete is sloped back into the hill. This will ensure that should there ever be displacement, earthquake, unusually heavy rain etc, the concrete terraces will fall back into the hillside and not give way. Be sure and compact the soil as you build the terraces. This form of retention will last a lifetime or more.
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.
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Water is becoming our most precious resource as the glaciers melt away and rising snow levels reduce our storage capacity. Mandatory water restrictions are in place in many parts of the country and those of us in dry climates will have to change our gardens whether we like it or not. If you plant your garden to be compatible with the local flora and climate you will reduce your water use considerably. Using less water has several environmental benefits:
1. Fewer demands on our aquifers and rivers, allowing fish populations to recover.
2. Less run-off which carries dog poop and engine oil etc. into the storm drains and down to the ocean.
3. When we reduce irrigation, we are not adding so much cloramine (a water purification chemical that has replaced clorine) to the soil. Cloramine, unlike clorine, does not break down quickly and resides in the soil as ammonia where it may harm the microorganisms that are essential to soil health. Cloramine kills fish.
4. Reduced irrigation prevents unhealthy molds and fungi such as oak root rot (which does affect other trees and shrubs) from developing in our gardens.
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