I had some ideas for the Gardener tree, as well as for another plant type. I like the idea of the Gardener being a sort of "Hippy Doctor" For a ship, not able to heal like the real doctor can, but can certainly provide some long-term healing and buffs in a pinch.

Gardener tree:
Holistic Medicine: Perk grants the Botanist the ability to craft a new item, Incense Sticks, which allow the Gardener to spread the effects of a plant in a gaseous form without them needing to be present. Anyone near the inscense gains the effects of the plant product placed inside (Pomgrenade Extract would slowly heal, Mudraptor Bane would melt Mudraptors entering the room, that sort of thing.) The stick lasts for 30 seconds.

Essential Oils: Pomgrenade Extract and other extracts made by the Botanist are 20% better, Extract heals faster, Mudraptor Bane kills faster, that sort of thing.

New Plant: Calcium Skeletosum.
Commonly referred to as Boneboo, Calcium Skeletosum can be harvested for Calcium compounds. Calcium Skeletosum has a symbiotic relationship with the Husk parasite, the parasite survives on the calcium deposits in the plant, while the Husk Parasite infects small coral-eating fish, taking control of the creatures before they can consume the plant entirely.

As a result, any botanist looking to have the plant aboard their vessel should keep it far away, as the spores it gives off can become a Husk Infection if left for too long.
Harvested Boneboo can be deconstructed for seeds and Calcium (which, along with Husk eggs, can be used to make Calyx Extract.)