My lilac bush is 2 years old, about 2 feet high. One part or branch has leaves that are turning brown and are like "crispy"? I thought it had died during the winter, but in the last 2 months it has about 5 branches, and I have it in a pot. I haven't anywhere to plant it. Do I need a bigger pot. Also, I live north of San Francisco in the wine country. It is very warm here, but we did have a deep freeze of 10 days this last winter.