While many plants that appear dead can be revived, a plant that is truly dead cannot be brought back to life. Many of the plants that people perceive as being dead are alive but have lost leaves to preserve their more vital components. A plant that is dead has a stem and roots that are either mushy or brittle; healthy plants have firm but flexible parts, says Gardening Know How.
Reviving a dead plant can take a month or more, and care varies from species to species. Generally, gardeners prune the plant very close to the soil to remove the "dead" parts and transplant it to new soil. Plants that are not getting the proper amount of water, sunlight and nutrients wither and turn brown, giving the impression they are dead.
The plant ceases nutrient distribution to its leaves and flowers to keep the roots and stem alive, similar to an animal that needs an amputation. Since this is the part of the plant that is visible, the plant appears dead, but the healthy roots are preserved underground. The best way to tell if a plant is truly dead is to check the roots. If they are healthy, a skilled gardener may be able to revive the plant.