Defining a content garden:
A high quality site, edited by journalists and community managers, where there's a combination of paid journalist content, moderated free content, and aggregated content.
The emphasis is on curated content that's high quality, the quality is derived either from moderation of the content, or choosing contributors carefully for their knowledge of an industry or topic. If you will, the content gardeners plan the layout of the content garden, plant all the crops, water and weed the garden. Where a content farm is full of row crops, in a content garden there's variety and personality.
To encourage contributions from thought leaders in an industry, contributors are often termed columnists even though no payment is given by the site to the author. Instead, the site lends its credibility to the author, and in turn the author lends their credibility to the site.
@bethdunn Beth Dunn adds her thoughts on the definition of a content garden:
"Farmers grow crops for the market, but gardeners grow food for the table...Cultivation versus mass- production, more niche and person-focused than broad, quantity-focused."