Clemson University Extension service offers over 500 horticulture guides to landscaping, ground covers, trees, garden vegetables, houseplants, and pests & diseases. Available in HTML or PDF format.

A school of agriculture and horticulture located in Queensland, Australia. Provides research, short courses and community services, groups and centers and news and events.

Presents information on horticultural services. Includes quarterly newsletter, media releases, gallery of shop products.

RHS plant finder database lists suppliers of over 70000 plants grown in the UK. Membership allows free access to RHS gardens in the UK and France. Gardener's references and calendar.