I'm not a pro at balancing games and stuff, but after reading what everyone has had to say so far on Wormwood, here's kind of what I would like to see from this new(-ish?) character:
Wormwood can plant Seeds directly in the ground without using Farms.
When above 20 Wetness, Wormwood regains Health at a slow rate.
In Spring, Wormwood blossoms, gaining increased movement speed, increased Health regeneration when wet and attracting Bees.
Wormwood loses Hunger at a much faster rate during night time.
Certain passive and neutral mobs will follow Wormwood around. Eye Plants are friendly to Wormwood.
Wormwood has a Green Thumb crafting tab:
Living Logs can be created at the cost of 20 Health.
Bramble Husk provides 75% Armor and shoots out thorns when hit, dealing 33 damage in a small radius. The wearer is also protected from thorns. Slowly repairs over time when Wet.
Bramble Trap shoots out Thorns when triggered, dealing 50 damage in a small radius.
Bramble Wall is a new kind of wall that has up to 300 health. Upon being damaged, the wall shoots out thorns, dealing 33 damage in a small radius. During Spring, the wall regenerates health at a slow rate.
Bramble Bomb: Similar to the Hearthsfire Crystals, can be thrown to deal 60 damage in a similar radius.
Compost Wrap restores 30 health to Wormwood. Can also be used as a very potent fertilizer.
Wormwood can use Manure, Guano, or Bucket-o-Poop to fertilize himself, restoring 8, 16, or 8 health, respectively.
Health-restoring food does not affect Wormwood's health.
Rot restores 5 health and 2 Hunger when eaten by Wormwood.
Wormwood takes 25% more damage from fire, and burns for slightly longer.
Wormwood loses sanity when plants are destroyed near him (e.g. picking flowers, completely chopping or burning down trees, digging up stumps, grass, saplings, or bushes, etc.) This excludes plants that are diseased or already burnt.
Sanity effects from planting or destroying plants is reduced the further it happens from Wormwood.
Wormwood gains sanity when plants are planted near him (e.g. seeds, flowers, trees, grass, saplings, or bushes, etc.)
Plants within (insert however large Ice Flingo range is) of Wormwood grow 25% faster (does not stack with Spring boost).
A lot of the changed I suggest revolve around the idea of plants Photosynthesizing and Respirating throughout the day, with water facilitating that process and Night hindering that. For health regeneration, I was thinking that when at 20 Wetness, 1 HP is regained per minute to a maximum of 10 when at 100 Wetness. During Spring, this would likely increase to 2 HP/min when at 20 and 15 HP/min when at 100.
The passive/neutral mob following Wormwood was thought of with a Disney Princess in mind. Birds, Beefalo, Rabbits, etc. will land near and follow Wormwood because he looks like food but won't try to take a bite of him. Bees will follow in order to pollinate and possibly increase Wormwood's health a bit if he stands still while the bee lands on him. These mobs will lose interest after a certain amount of time and/or distance.
I added two items to the Green Thumb tab, being the Bramble Walls and Bomb. The latter was mostly to incorporate the cool idea of Brambles from Hamlet, which restricted access to parts of the map but here they act as a great defensive barrier, though risky due to Fire Hounds and friends. The Bomb was inspired by the Hearthsfire Crystals, which were such a cool concept in The Forge that I really would love to see them again.
Added health gain from fertilizing itself is nice, since it has very few other sources and I feel like it would make sense. I also really dislike the no-health from food debuff, but considering how many other sources for Health I gave him, I think it should be okay. Especially Rot!
I didn't change Seed planting because I'm honestly not sure how you could change something like that. My only suggestion would be to have a chance for the plant to wither and/or produce rot or grass, with an increasing chance the more plants are nearby.
This is bad practice in general, but tagging @JoeW in hopes of him seeing this and taking some of the changes into account. Other suggestions are welcome, too!