Ask Mr. Smarty Plants

Actually, our first suggestion would be to get in your Time Machine and go back to the time when you planted that tree, and then don't do it! Here is a previous Mr. Smarty Plants answer to the same question.

The simple fact is that the willow is aggressive, invasive and non-native. That means it very nicely discourages or destroys any plant seeking to compete for space and resources. The Lady Bird Johnson Wildflower Center is dedicated to the growth, propagation and protection of plants native not only to North America but to the area in which the plant is being grown. The weeping willow originated in China.

But, if your Time Machine is not working, we know a spot where you can get all kinds of information and/or plants that fit your need. You need to decide ahead of time how much shade the plants will have to tolerate, under that tree.

You (or we) are in real luck because the Las Pilitas Nursery has a website on some of the California native plants that can be used as less than a foot high ground covers. We believe that the Escondido store would be the nearest to you in Orange County. They have contact information and directions on the webpage.

We have one other suggestion for that under-tree space. A good quality shredded bark mulch will cover the roots, help to protect the roots from heat or cold, prevent evaporation of moisture, is attractive and smells good. As it decomposes, it will go into the dirt under the tree, improving drainage and making nutrients in the soil more accessible to the roots. About every 6 months it will probably need to be replenished, but it will never need mowing.