Repotting

Based on Professor Slughorn's performance just now, the plan to borrow plant seeds from Slytherin could practically be abandoned. Pomona was once again glad she had gone to the Forbidden Forest. At least Wilhelmina knew someone needed her. Perhaps, once she had seen to all those patients, she would suddenly remember that there was still a student in her own House who needed her help.

A Head of House's office was generally near the House common room, but Pomona left the task of opening the door to Hagrid. Professors were called professors not only because they taught, but because they also conducted research in their respective fields of expertise. To avoid being disturbed or having their research stolen, they set wards in their offices. A giant—even a half-giant—had stronger magical resistance than an eleven-year-old child.

"All right." After opening the door, Hagrid's hair was standing on end. "Go on in, you two little ones."

"Thank you." Pomona was the first to dart inside, brushing past Hagrid's stomach.

"Thank you." Lupin said the same as he passed Hagrid. Then he waved his wand and said, "Lumos." The scene inside the office appeared before the three of them.

Behind the completely bare desk was a bronze plaque engraved with Hufflepuff's One Hundred Rules of Conduct. The first rule was to keep a low profile, while the hundredth was: "Keep a low profile because you can always raise one."

"Lupin, we need to dig out the soil beneath the willow and replace the Whomping Willow's soil from the bottom up."

"You say I'm crazy, but you're the crazy one." Lupin stood there speechless for a long while before saying, "Do you know how much work that will take?"

"You said you'd read your mother's books on potted plants. How much do you know about the changes roots undergo as plants grow?"

Lupin fell silent, while Hagrid eagerly raised his hand at the doorway.

"Plant roots are divided into vertical roots and horizontal roots. Even great trees grow on barren cliffs. Their structural roots can drive deep into the subsoil, taking root in cracks in the rock. Horizontal root systems are the opposite; they mainly affect flowering and fruiting. When downward transport is obstructed in a young tree, or when its above-ground portions rapidly decline for any reason, the horizontal roots are the first to suffer serious damage, followed only then by the vertical roots. In an adult tree, when downward transport is obstructed, the vertical roots are threatened more quickly and severely. Clay has poor permeability. It tolerates neither drought nor flooding, and roots cannot spread easily through it. But it retains water and nutrients well, and nutrients do not leach away easily. It was precisely because the soil had fertility that Professor McGonagall and the others used growth magic to turn a sapling into a full-grown tree. Once the soil's fertility is exhausted, if the vertical roots cannot bore through the soil and continue growing, the horizontal roots will turn into vertical roots. The ones trying to knock down the wall today were horizontal roots. If we don't free the vertical roots, they'll keep trying to knock down the castle walls so they can become vertical roots. The Whomping Willow isn't a Mandrake, after all. We can't pull it out by the roots and put it into another pot already prepared with loam. So we can only replace the soil from the bottom up while doing our best not to damage its deep vertical roots."

"Then what did you originally want Wolfsbane for?" Lupin asked.

"I was wrong. I only thought about changing the soil's properties and forgot that the Whomping Willow also needs nutrients as it grows. It doesn't have enough nourishment for itself right now. If other plants compete with it for nutrients, it will grow even more enraged. Clay and sand mixed in a certain ratio make loam. The soil underground is either already sandy or compacted into hardpan. The Whomping Willow is so violent precisely because its life is being threatened."

"What do you need us to do?"

"Collect charcoal ash and stones, along with things like fruit peels and eggshells."

"There are fruit peels and eggshells in the kitchen." Hagrid finally found a chance to speak and said excitedly.

"Besides replacing the soil, we need to fertilize the Whomping Willow. That fertilizer has to ferment completely before it can be mixed into the dirt. Otherwise, the heat produced while it decomposes will burn the roots to death. Making fertilizer will stink terribly. Do you know somewhere we can make it without affecting anyone else, Hagrid?"

"The groundskeeper's hut will do."

"Too far." Pomona shook her head. "Forget it. Go prepare the things I just mentioned first."

"Okay, Professor," Hagrid said naturally. "Do you need me to call Professor McGonagall?"

"Not for now." Pomona took out How to Care for the Whomping Willow. "We need to dig a tunnel beneath the tree. It would be even better if you know of any magical creatures in the Forbidden Forest that are good at burrowing. Hurry up. That vial of potion will last only until midnight at most. I don't know when it will wake up!"

"Come on, Remus. Pomona knows what she's doing. We'll meet at the Whomping Willow later."

Remus Lupin gave her a meaningful look, but in the end, he still left with Hagrid.

Pomona kept smiling on the surface. Only after they had both gone did her smile fade.

Judging from the Centaurs' earlier reaction, digging that tunnel into the Forbidden Forest was impossible. If Lupin entered their territory, he would most likely be attacked. Their only choice now was Hogsmeade.

If a werewolf lost control in the village, who knew how much chaos it would cause?

She had to find Lupin a place where he could transform without worrying about escaping, preferably outside the village. But where exactly should it be built?

"Is anyone there? Professor, are you back?" Pomona was deep in thought when she suddenly heard Pete's voice.

"Pete!" Like she had seen a savior, she threw herself into his arms.

"Pomona, why are you here?" Pete was even more surprised than she was. "What are you doing in Professor Grubbly-Plank's office?"

For an eleven-year-old, the first day of school had been truly thrilling—perhaps too thrilling. Clinging to Pete, Pomona burst into loud sobs. She was only a step away from crying and shouting that she wanted to go home like the other first-years.

"Did someone bully you? Tell me, and I'll teach him a lesson!" Pete declared solemnly.

"I'm just afraid you can't beat him," Pomona sniffled.

"Who?" Pete looked as if he would cast Avada Kedavra the moment Pomona said the name.

"Professor Dumbledore." She paused, then added, "And Professor Slughorn from Slytherin. I ran into him in the corridor just now, and he took two points from me."

"Didn't you tell him you were lost?" Pete pointed at the Hufflepuff rules on the wall. "What's the second rule?"

Strike back against direct insults, but playing dumb when necessary was also essential.

Pomona was not stupid enough to read it aloud. Instead, she said, "I told you I was being bullied. Do you think he'd let me off if I said that to him?"

"Damn Slytherin." Pete gritted his teeth in hatred. "We'll see about that."

Pomona tugged at Pete's sleeve.

"What now?"

"I have a small favor to ask."

"What are you up to this time?"

"Nothing much. Just repotting a plant." She smiled sweetly. "Can you call all your friends over?"