This area operates like a regular harvest zone except that it remains a zone after being placed, and will check every in-game hour to see if there are any new harvestables to flag.
This is useful for things like Berry bushes, silkweed, herbalist flowers, etc. This is also useful for tree-farms - designate an auto-harvest area and plant saplings in them as soon as they are available to be queued for harvest as soon as they are placed. (Yes, not as efficient as waiting until they mature, but sometimes what you way anyway.)