Information on the biology and appearance of Vash the Stampede in Trigun Stampede (2023).
Physical Characteristics: Basic Physiology | Drain Gate | Hair | Plant Markings | Plant Wing and Flight | Portal Gate | Roots and Flowers | Scars, Amputation, and Healing | Strength and Agility
Wardrobe and Accessories: Clothing | Duffel Bag | Earring | Energy Bullets | Energy Cube | Glasses | Prosthetic Angel Arm | Prosthetic Arm
Other: Bounty | Gun and Marksmanship | Music | Personality | Plant Communication and Healing | Relationships | Toma Equestrianism
Vash is able to hear the distress cries of dependent plants. When he communes with them, he is able to communicate with them in some fashion. We hear him speak to the plants but they do not speak back. Communication is likely telepathic in nature, as is the case in the Trigun manga.
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Healing Powers/Energy Transfer
We see Vash interact with several dependent plants with different results. The SEEDS03 electricity plant was suffering from some incompatibility with the planet’s environment. It is not specified exactly how he helps the plant. He may provide energy from his own reserves or from the Core. He may somehow help the plant adapt to the planet’s environment.
After he discovers this ability, Vash spends the next five years traveling around No Man’s Land with Brad, helping plants with what is likely the same basic method. He may be able to help plants in a variety of ways that are not specified.
After the loss of his arm, Vash continues to travel No Man’s Land, helping and healing dependent plants. He made at least one prior visit to Jeneora Rock to heal their water plant. However, his healing ability has limits, and once a plant reaches a critical level of poor health, he can no longer heal it, and it will die.
Vash also appears to also have some ability to negatively affect dependent plants, as seen with the Sand Steamer plant. This plant provided the power for the Sand Steamer. In order to stop the steamer, Vash somehow harmed or took power from the plant, causing its fingertips to turn black.