To change a plants death 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 Death category like the image below.

Here you can change this plant’s Death settings, you can hover your mouse over each settings name to get a tooltip with more info about each setting.

Destroy


You can set the plant actor to destroy when the plant dies by enabling or disabling the Destroy on Death setting.

Destroy Time is used only if Destroy on Death Setting is true, if > 0 this is how long after the plant dies until the plant actor is destroyed.

Death Stages


Death stages are used to set different meshes on death depending on the plants current growth. This can be enabled or disabled using the Use Death Stages setting.

Here you can set the different static or skeletal mesh the plant will use when the plant dies at a certain growth amount. To change when the meshes that will be used you can set the Growth setting for that Index in the Growth Stages setting. Here you can also change the static mesh or skeletal mesh that will be used for that growth value.

You can also set the Effects for each death stage this can be a sound and/or particle effect that will be played at the plants location when it dies if it uses that death stage.

Destruction