Hillside planting has to be one of the most challenging types of landscaping for so many reasons including erosion, keeping water directed to the root system of plants without runoff, and providing decent soil for the roots to take hold in during initial planting.
Just describing issues around hillside planting finds me exhausted! With that being said, let’s take it one step at a time for easier management.
Steep slopes are the biggest challenge for planting. Oft times, when designing around those near-vertical cliffs, it was easier to consider either planting at the top and allowing the plants to cascade down, or find self-climbers that would cling to rocks or crevices. Irrigating from the top or bottom of a slope can easily be done by using a drip system which is always the method of irrigation to use on or around hillsides. Erosion is eliminated as the structure of the hillside is not compromised with added weight, or disturbed soil.
One plant that is easy to find that fills the need of steep hillside planting is Virginia creeper (Parthenocissus quinquefolia). It tendrils cling to any surface they come in contact with and the end result of filling in bare hillsides is a site to behold – especially in the autumn when it turns brilliant red before dropping its leaves. A word of caution: keep it away from any structures unless the desire to cover the structure is also a goal.
Moderate and gentle rolling slopes and hillsides have their own unique challenges. Preparing the soil can be done by digging a hole twice as wide as the plant rootball, back filling with 75% site soil and 25% soil amendment. Create a compact berm around the face of the plant before installing a drip system for irrigation. Use mulch that will cling to itself to retain moisture in the ground. Wood chips are a good source for staying on a sloped area without washing away.
Native plant types are wise choices for hillside planting. They do not need much water once established, Their roots typically run deep into the soil and, if they are native plants indigenous to the area where they are planted, they will do well without a lot of care.
One of my favorite natives is Toyon (Heteromeles arbutifolia) that can be found in the Sierra foothills or coastal regions. It produces beautiful white flowers in the spring that turn into red berries in the late fall. Butterflies and birds are drawn to this plant for their sustenance throughout the year.
Another native plant that grows much shorter than the 6-10 foot tall Toyon, is what is commonly known as the “Fried egg plant” or Matilija Poppy (Romneya coulteri). The remarkably huge poppy flowers resemble that of a fried egg in it coloration and blooms during the summer months when most plants are spent. They are more temperate found growing in zones 8-10.
I would be remiss if I didn’t include two of my favorite spring time bloomers. California Lilac (Ceanothus ssp.) and Western Redbud (Cercis occidentalis) The combination of colors of the intense blues of Ceanothus and magenta blooming shrub of Redbud is enough to stop traffic!
The best advice for hillside planting is to be patient, take care by avoiding soil disturbances, and choose low water using plants. The time you put into that initial first year will be the ultimate reward once the plants become established.
Take care and have a great weekend.