the small fruits of ilex although often referred to as berries are technically drupes they range in color from red to brown to black and rarely green or yellow the "bones" contain up to ten seeds each some species produce fruits parthenogenetically such as the cultivar nellie r stevens the fruits ripen in winter and thus provide winter colour contrast between the bright red of the fruits and the glossy green evergreen leaves hence the cut branches especially of i aquifolium are widely used in christmas decoration the fruits are generally slightly toxic to humans and can cause vomiting and diarrhea when ingested however they are an important food source for birds and other animals which help disperse the seeds unfortunately this can have negative impacts as well along the west coast of north america from california to british columbia english holly ilex aquifolium which is grown commercially is quickly spreading into native forest habitat where it thrives in shade and crowds out native species it has been placed on the washington state noxious weed control boards monitor list and is a class c invasive plant in portland