How many different types of garden weeds are there?

The number of different types of garden weeds only can be answered most accurately on a case-by-case basis. The number depends upon the definition being used, with the description ranging from a plant whose value is irrelevant, lost, misunderstood or unknown to any plant that is where the gardener does not want it to be or that jeopardizes environmental and human well-being. It therefore may range from only those that harm people, pets, structures and wildlife to thousands of native and non-native plants that seem not to hesitate about taking over space without any sign of sharing, as mentioned by Richard Dickinson and France Royer in their Weeds of North America from 2014.