Cal. Sts. & High. Code § 35253.1

If the petition is not signed by the requisite number of qualified signers, the clerk shall certify to the legislative body that said petition is insufficient. If the petition is insufficient, supplemental petitions may be filed within three months from the date of the certificate of insufficiency, or such additional period as the legislative body may allow, not to exceed six months from the date of the first certificate of insufficiency.