Keystone plants and trees like the Coast Live Oak and California lilac are key players in the health of your garden.

You’ll need a big yard to plant most oaks, of course, and there are a lot to choose from. Out of the more than 50 native to the U.S., keystone species by region include: white and black oaks for ...

A keystone in an arch's crown secures the other stones in place. Keystone species play the same role in many ecological communities by maintaining the structure and integrity of the community.