Sentient Plant's ages can vary widely depending on the type of plant or tree from which the creature evolved. Most plant based species reach adulthood by age 10 and live about 50 years. The tree based species reach adulthood around age 20 and can live between a few centuries to a couple millenia, though this is rare.

You are a small tree, a bush, a fern, a collection of plants, etc. Your height can vary from just over 4 feet, to just over 7 feet tall. If you are the plant based variety, you weigh between 80-120 lbs. If you are the tree based variety, you weigh between 200-400 lbs, depending on the density of your type of wood. Regardless of your height and weight, your size is Medium.

You can speak read and write Common and Sylvan.

Accustomed to life in a canopy covered forest, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.

While motionless and silent, this creature is indistinguishable from other plant life.

You have Advantage on Stealth checks to hide while motionless, silent, and among other plant life and others have Disadvantage to perceive you when hiding in this way.

You have a thick hide, either made from bark, if you are tree based, or leaves and other plant material, if you are plant based. Your AC= 13+ your Constitution or Strength modifier, whichever is higher, as long as you are not wearing any armor. A Shield's bonus still applies normally. 

Starting at 1st level, you are able to draw health from the light of the sun. As long as you are in an area of bright sunlight, you are able to photosynthesize as an action and heal 1d6 + your Constitution modifier HP. This healing increases by 1d6 every 5th level; 2d6 at 5th, 3d6 at 10th, 4d6 at 15th, and 5d6 at 20th. You can use this feature a number of times equal to 5 - your Constitution modifier, minimum of 1. You regain all uses of this feature after a Long Rest.

Additionally, at 11th level, you gain the ability to spend 4 hours using this feature to regrow a lost limb or appendage, once per Long Rest. You also gain HP as described above during this process.

Your bark or leafy hide is naturally resistant to all non-magical bludgeoning and piercing damage. All non-magical bludgeoning and piercing damage is halved for this creature.

Your race is vulnerable to cold, fire, and slashing damage due to their plant based lineage. All cold, fire, and slashing damage is doubled for this creature.

You have lived in harmony amongst nature since your awakening. You are proficient in your choice of the following Sentient Plant skills; Animal Handling, Nature, Stealth, or Survival.

Being born of a plant, you have a natural ability to move your roots through the ground. You have a burrowing speed of 15ft. As an action, you can enter loose earth and move up to your burrowing speed. You can stay there indefinitely, as long as you leave one sprout of your body above ground to absorb sunlight. While burrowing, you can use your movement to move up to half your walking speed through loose earth. You may exit the ground as a bonus action.

As you are able to photosynthesize your sustenance from the light all around you, you do not need to eat, though you may choose to. You do need water, as any other creature would, however.