【Fertile】 , 【fecund】 ,  【fruitful】 ,  【prolific】  mean having or manifesting the power to produce fruit or offspring.

The same distinctions in implications and connotations are observable in their corresponding nouns fertility, fecundity, fruitfulness, prolificacy.  【Fertile】  (opposed to sterile, infertile ) applies particularly to something in which seeds take root and grow or may take root and grow because it contains the elements essential to their life and development.

Consequently the term often applies to something in which ideas take root and thrive.  【Fertile】 is also applicable to something which has in itself the elements essential to its growth and development or to a person or animal or pair that is able to produce normal living young.

【Fecund】  (opposed to barren ) applies especially to something which actually yields in abundance or with rapidity fruits, offspring or, by extension, projects, inventions, or works of art; thus, one speaks of the fecundity of a mother if one wishes to imply that she has a large family, but of her fertility if the intent is to indicate that she is not sterile; so, by extension, a  【fecund】  rather than a  【fertile】 inventive genius.

【Fruitful】  may be preferred to  【fecund】  when the reference is to plants and may replace  【fertile】  in reference to soil or land, but it is especially applicable to something that promotes fertility or fecundity <a  【fruitful】 rain>  In its extended sense it is applicable to whatever bears results, especially useful or profitable results.

【Prolific】  is often interchangeable with  【fecund】 , but it often suggests even greater rapidity in reproduction and is therefore more frequently used than the latter term in disparagement or derogation especially when applied to types or kinds of things or beings.