May a wife give charity from her husband's property without his permission?

A wife may give a little charity from food or household items for which permission is customarily given, but may not spend her husband's property in large amounts without his permission.
The Prophet ﷺ said that when a wife spends from her household's food without wasting it, she has the reward for her spending and her husband has the reward for his earning (Sahih al-Bukhari 1425; Sahih Muslim, Kitab az-Zakah). Scholars understand this as customary permission ('urf) for small matters; if the husband clearly forbids it, or the amount is large, permission is needed.
The wife's own property — salary, mahr, inheritance — is hers, and she is free to give charity from it. If the husband is so miserly that basic needs are not met, the wife may take what she and the children need in a reasonable manner, as in the case of Hind bint 'Utbah (Sahih al-Bukhari 5364), but that is for maintenance, not charity. See Rights of Husband & Wife and Maintenance.