The Sapling

 was one of the saplings generated by the Planting.

Creation
After the Planting seeded itself in a desert planet and replaced all indigenous life with a forest of itself, it created the Sapling with the intention of sending the Sapling to a different to do just the same. However, the Scream captured the Sapling in a Memory Engine Machine during its formation. The Scream planned to feed the Sapling with the memories of several long-lived individuals and then use the large amounts of memory energies to merge himself with the Sapling and become part of the sentient ecosystem of an entire planet.

The Scream's plan was fairly successful up until the end. (COMIC: The Scream) He managed to feed the Sapling the full memories of a Nebulon and a Rockra, (COMIC: Remembrance) and some of the memories of the Eleventh Doctor and Alice Obiefune. While the Sapling was absorbing the memories of the Doctor and Alice, the Scream came inside the Memory Machine to merge with it. The process was disrupted when Alice caused the Doctor's TARDIS to materialise around the machine. The TARDIS saw that the Scream was dangerous and deposited him outside, leaving the Sapling to grow into a sentient child-like being inside the Memory Machine. (COMIC: The Scream)

Adventures with the Doctor and Alice
After the Doctor and Alice escaped the Scream and briefly reunited with John Jones and the Entity, they returned to the TARDIS and met the Sapling for the first time. Having many of their memories, the Sapling was already intimately familiar with their lives. Due to his nature as a biological weapon capable of genocide, the Sapling asked the Doctor to destroy him, but the Doctor refused. The Doctor and Alice instead took on the Sapling as a companion. (COMIC: The Scream)

The Doctor took Alice and the Sapling to Plex's planet, where they found its inhabitants to be at war with each other. In the ruins of Plex's laboratory, the Sapling extended the length of his arms to grab Plex's biodata nodule for the Doctor. The Doctor used the nodule to restore Plex's memory to one of the clones of Plex, elevating the clone to be a god among his people who would lead them into a new period of peace. (COMIC: The Promise)

The TARDIS trio went on a "shopping trip" to a European village in 1189 which involved them meeting an "old friend" of the Doctor who tried to kill the trio with a legion of archers. During this adventure, the Sapling accidentally became a well-known figure in the village's history, inspiring them to create a statue of him in the village green.

Shortly afterwards, they revisited the village circa Alice's home era and spent an afternoon at the Village Green Festival. Festival-goers assumed that the Sapling was wearing a costume to imitate the statue. However, even this trip was not without a malign alien influence: a Krovian tried to steal some of the Sapling's memories with a Memory Trap, but instead transferred all the memories it had already stolen into the Sapling's mind. This initially went unnoticed, but the Sapling came to realise that he could remember elements of the lives of other people at the festival which they themselves had forgotten. The Doctor tracked down the Krovian and destroyed the Memory Trap, removing the memories from the Sapling's mind and returning them to their rightful owners. (COMIC: Fooled)