Up to a Maximum of 50% total variety bonus
Plants that need to be watered or have started wilting will still contribute to the variety bonus as normal, but as soon as the wilting plants die, they will no longer contribute to variety. There are no limits to the combination of plants that can constitute 50% variety so anything from 3 different flowers to 10 different trees can net 50%.
If picked, wildflowers are subject to the variety bonus; however, they do not contribute to the total when other plants within range are harvested.
The best way to approximately describe the distribution of a variety bonus a plant can apply is 4 hexes wide and 3 hexes tall. The actual distribution includes an additional flower and can vary slightly depending on location.
Distribution of the variety bonus one plant can apply to another is based on the coordinates of each individual plant. Due to the precise numbers required for accurate coordinates, there are rare(?) instances of rounding issues on certain grids that will exclude a plant that would normally contribute to the variety bonus. Plants within three spaces will always contribute normally to variety bonus.
These are just a small selection of various templates for efficient and pretty patterns that give either full 50% variety coverage or close to it.
Click on any of the images for a full size image as well as a more thorough analysis of each pattern for its utility for variety purposes.