"Grow, damn you," Crowley breathed.
Beside him Aziraphale watched intently.
"You herbaceous swine, I'll dismember you inch by inch with a rusty toe-nail clippers and leave you here as an example for others lacking appropriate..." Crowley paused to glower significantly at each plant. "...enthusiasm..."
The plant in question, a reasonable looking Fiddleleaf Fig, trembled and its waxy leaves brightened considerably.
"You call that healthy-looking? You are pathetic; you sicken me to the depths of my unholy being!" Crowley snarled. "Confound you to the Ninth Circle of Hell, you odious prig, you vile, insufferable wretch-" here he paused for breath "-you...you whoreson loggerhead, you pathetic nit!" (good ol' Will)
The plant was shaking most violently now, and if you listened carefully, you could almost hear the pitiful whimpering of the unfortunate Fiddleleaf Fig.
"But, all hope is not lost," Crowley grinned like the Cheshire Cat who had fallen into a vat of fresh, full fat, ice-cold cream. He spread his hands amiably. "There's a use for everything. And it's getting cold out. Real soon..." Crowley paced slowly away, hands behind his back. "...I'm going to have to light the fire. And to light a fire, I need...kindling. And firelighters. But...kindling..."
He returned to the Fiddleleaf Fig and placed his hands palm-down either side of the little terracotta pot shaped to look like a habitable boot. The plant looked electrified, its whole fibrous being stretched to capacity in order to look full and healthy.
Crowley languidly plucked a leaf and ripped it to absent-minded little shreds. The plant swayed and went limp.
"What a shame," he murmured, green confetti falling from his fingers. "Some are just..." Here he picked up the pot and carried it over to the bin under the sink. "...not up to the task." He kicked the door shut and rubbed his hands together. He observed his flourishing flora with deep satisfaction.
"You are a sick, sick man. Person. Demon. Thing." Aziraphale shook his head sadly.
Crowley would've blushed, but he settled for a modest shrug. "I fool around with different techniques. Sometimes I go for a more menacing...sort-of-thing, then I might try physical violence, and the Language of Hell works quite nicely for anything that flowers..."
Crowley had implemented a great deal of his own personal experiences in the devising of numerous tortures that would make anything remotely plant-ish go weak at the roots. The Spanish Inquisition was particularly inspiring.
"Don't look so disgusted. How many plants died for your bloody books?"
"That's a fair point actually," Aziraphale admitted.
Crowley gave his old friend a sly smile as he plucked a ripe red apple from a bowl in the centre of an old table pockmarked with tannin circle stains. He took a small wooden handled knife, the kind hard-core old countrywomen use to peel potatoes, and began to slice sections off the apple. Crowley made sure to stand in full view of his houseplants and sliced with a certain deliberation that could be interpreted as rather menacing.
The houseplants were suitably menaced and Crowley was content. He had the most beautiful plants in all of London, he thought lovingly.
He proffered a nice cut of apple to Aziraphale, who accepted it gratefully.
"Pink Ladies are good this time of year," the angel commented.
Crowley made a contented munching sound that was in all likelihood agreement.