California Code, Probate Code - PROB § 16225

(a) The trustee has the power to deposit trust funds at reasonable interest in any of the following accounts:

(b) A trustee may deposit trust funds pursuant to subdivision (a) in a financial institution operated by, or that is an affiliate of, the trustee. For the purpose of this subdivision, “affiliate” means a corporation that directly or indirectly through one or more intermediaries controls, is controlled by, or is under common control with another domestic or foreign corporation.

(c) This section does not limit the power of a trustee in a proper case to deposit trust funds in an account described in subdivision (a) that is subject to notice or other conditions respecting withdrawal prescribed by law or governmental regulation.

(d) The court may authorize the deposit of trust funds in an account described in subdivision (a) in an amount greater than the maximum insured or collateralized amount.

(e) Nothing in this section prevents the trustee from holding an amount of trust property reasonably necessary for the orderly administration of the trust in the form of cash or in a checking account without interest.