Question: How safe is it to use horticultural vinegar on graveled drives? Is it safe to use it close to a well? Answer: Jonathan Foster, Home Horticulture Outreach Professional “Safe” is always a relative term when using chemical interventions in the garden–horticultural vinegar is a 20% solution of acetic acid (4x stronger than household vinegar), read more Is it safe to use horticultural vinegar on graveled drives?