Biodynamic Gardening
Information on this method of gardening using mineral preparations and planetary rhythms, and services including workshops and garden design. Based in the UK.

Exploratorium: Science Of Gardening
Features articles and videos on several topics, including gardening with nature, carnivorous plants, soils, fruits, and vegetables, propagation, and plant reproduction.

Garden Ideas
Articles and advice on a variety of gardening topics.

Garden Terms
Gardening dictionary with brief definitions of a large number of terms, optionally arranged by category.

Hort.net
Offers a collection of garden reference materials, including a plant gallery and profiles, archives of mailing lists, gardening news, and links.

Let's Go Gardening
General gardening site, with versions geared towards US and UK gardeners. Tips and articles, informational resources, links to events, societies, and public gardens, and a forum.

LoveToKnow Garden
Short informational articles on gardening topics, vegetables, and ornamental plants, contributed and edited by users.

Mimi.hu: Gardening
Provides a directory of biological and horticultural terms, with links to online encyclopedia entries for each term.

MyGardenGuide
Offers plant database with photos and summary information, Q&A on various garden topics, and a garden blog.

Pioneer Thinking: Gardening Center
Information and tips on outdoor and indoor gardening. Many articles grouped by topic.

Yardener.com
Lawn and garden resources for homeowners whose garden is not their hobby. Includes information and care data for many plants, shrubs, and trees, and dealing with pests and problems.