To change a plants Harvesting settings go to the plants blueprint so for example the BP_TomatoPlant and select the BP_PlantComponent in the Components panel, then in the Details panel and inside the Plant Settings Category find the Harvesting category like the image below.
Here you can change this plant’s Harvesting settings, you can hover your mouse over each settings name to get a tooltip with more info about each setting.
If Destroy on Harvest is true when the player harvests the plant it will destroy.
If Regrow Harvested Vegetables is true and Destroy on Harvest is false then when harvested the plants vegetables will start regrowing.
If Can Harvest when Dead is true then even if the plant is dead the player will still be harvest able.
If Should Respawn After Harvesting is true the if Destroy on Harvest is true the plant will destroy and then respawn after the respawn time has past. The respawn time setting is in the Respawn category.
If Restart Plant Growth when Harvested is true the plant will reset to 0 growth and will beginning regrowing.
If Use Destruction Mesh on Harvest is true then the plant will attempt to spawn its destruction mesh when it is harvested, there is more info about the destruction mesh in the guide linked below.
Harvest Destruction Mesh Hide Time controls how long the destruction mesh will be visible before being removed.
If Use Min Harvest Growth Amount is true then the plant wont be harvestable until the plants growth value is => the Min Harvest Growth Amount.
If Use Growth Effects Harvest Amount is true then the current growth value of the plant when harvested will effect the number of resources the player receives when harvesting the plant. So if the plant is not fully grown the player will receive less resource then if the plant was fully grown.