San Diego Hillside
Gardening Question From Janet:
I live in San Diego, in the mission bay area. I have a huge hill/ slope in my back yard. I have planted Rosemary and ceonothus. Some survived but the side of the hill that didn’t survive there was a pine tree at the top of the hill. We have since removed the tree. Will it be ok the plant the same plants, or will then soil still hold the acids from the pine tree. How long should I wait to plant? I had the weeds pulled thisweek and there are very large bare areas. Do you think honeysuckle will work well in my area.
Answer From Pat:
In general fall planting is better than spring planting especially for native plants such as ceanothus. That said, now in March is not too late and since there are large bare areas I think you should go ahead and plant. However, depending how deep or shallow were the roots of the pine tree, you will need to plant between them if any of them were shallow or surface roots. Do not dig out the roots since that might cause collapse of that part of the hill. Leave the roots in the ground since they will hold the bank until something else takes over. If the plants you put in show any signs of nitrogen deficiency such as slow growth or yellow leaves then fertilize with nitrogen more frequently, but in the case of ceanothus it thrives in poor soil so nitrogen fertilizer is not advised. The worst problem with ceanothus is root rot from too much run-off of water from higher on the hill. A neighbor of mine, who is an avid gardener recently lost a whole bank of large ceanothus due to root rot, but she watered the plants in her garden above the bank so the ground was too wet. She has recently replanted with a variety of large succulents, including aeoniums, Agave attenuate, and crassulas. They look fine and held the bank through the recent torrential rains.
Now about what to plant: I would avoid honeysuckle since it is not an efficient bank cover, does not hold soil well and also is invasive. Birds love the seeds and spread them widely. You would be fighting it all over your garden.
If rosemary and ceanothus have already performed well for you in this location, then I would continue with the same theme. I don’t think pine needles or remaining roots will negatively impact these plants. I often walk past a steep bank near my home with pine trees at the top and many large ceanothus that have been flourishing for ten or twenty years on the hill below. Sometimes tall varieties such as Concha, for example, do better on banks and hold the ground more effectively than shorter, ground cover types.
If despite everything your ceanothus does not survive, then I would replace it with something like coast bush sunflower (Encelia californica) or a non-native such as lantana.
Photo by Hectate1
Photo by Brian Smithson (Old Geordie)