Aziraphale understood the custom of presenting flowers to the object of one's affection. Of course he did. Humans had been practicing the gesture for ages.
And Crowley... Well, Aziraphale couldn't be absolutely sure, but it was entirely possible Crowley had started the whole thing when he'd plucked a small white flower and tucked it behind Aziraphale's ear after the flood waters finally receeded. Shem had watched Crowley with ernest curiosity and done the same for his wife.
What followed throughout history was that Crowley continued to present Aziraphale with gifts, little trinkets or carefully selected and arranged bouquets, always accompanied by a frown, a flippant wave of his hand, and a stammered excuse. "S'not lovely, Angel. I-I m'a demon. Temptation's all. Part of mah plan."
"Of course, dear." Aziraphale would accept the offering and graciously never mention it again (though every memento and memory found a home in the bookshop, and at least one blossom from each bouquet found itself pressed and delicately preserved in a large dusty tome only Aziraphale even remembered existed).
After the world hadn't ended, and after they'd put both Heaven and Hell to shame, Crowley seemed to have found a reserve of bold persistence he'd never felt before. And he focused every ounce of it on Aziraphale. More specifically, on making sure Aziraphale never went a single day without fresh flowers on his desk.
"Gotta make sure you don't forget how dull it is upstairs. Much, much ah... better down here." (He never said with me, but they both knew it was implied.) "Prettier." He almost always scrunched up his face and choked on the word as he would fall dramatically back onto Aziraphale's old couch and prop his feet on the coffee table. "Temptation's all."
"Of course, dear." Aziraphale gave the same answer every day since the Apocalypse. The same answer given to the same excuses for millennia.
Until the day Crowley kicked up his feet and nearly toppled the sorry little fern with a very specific tartan bow tied around its pot off the coffee table.
"Hello," he shoved his sunglasses up onto his head and leaned down to inspect the struggling plant. "Angel? What's this then? Don't tell me you finally decided to take my advice and class the place up a bit?" Crowley picked up the pot, tested the soil for moisture, and turned it slowly in his hands. "Ferns are easy enough, I suspect, but you could've picked one a little less... almost dead."
"Oh... Dear. It's not... Well," Aziraphale stood from his desk chair, took two steps toward Crowley, then one step back, and wrung his hands in front of him. "I didn't intend to keep it, you see... I, I..." He glanced up to see Crowley watching him intently, lovely golden eyes wide, and a smirk on his lips. "Bother," Aziraphale huffed and took that one step forward again.
"Well, Angel? If you aren't gonna keep it, let me at least put it out of its misery." Crowley snarled at the fern and Aziraphale could have sworn he saw it straighten and tremble.
"I went to the florist. There were so many lovely options, and I would have got them all, but that seemed excessive, at least the kind young man working there thought so, and I couldn't decide. Then I saw the potted plants, and this poor little one needed help, and I thought to myself, who better? Your plants are so lovely. And I know you hate when I say so, but you're always so lovely. And thoughtful. And kind, I'm sorry, but it's true! And... And I just..."
"Angel." Crowley stood facing Aziraphale, still holding the little fern. "Angel... wot?"
Aziraphale sighed and dropped his hands to his sides. "For six thousand years you've given me flowers, and I never returned the gesture."
"Angel, you- ya have to know those were gifts, yeah? You don't hafta repay gifts." Crowley shrugged.
"I thought they were temptations," Aziraphale sniffed and quirked smile. A tiny, kind of bastardly one.
"Ugh. Aziraphale, Angel, please. Don't make me say it," Crowley implored.
Smiling in ernest, Aziraphale reached out to take the pot from Crowley. "I'll get you something better, dear. This sad little fellow just will not do. Maybe I can keep it and care for..."
"No!" Crowley hugged the fern to his chest.
"Crowley, you said it yourself, it's pathetic." Aziraphale reached for the plant again, and Crowley ducked quickly away.
"Ngk! No! It's mine. You got it for me, and you can't take it back." He brought the fern up to eye level, glared at it once more, put his sunglasses back on properly and turned back to Aziraphale. "Besides, you'll just lose it with all this... stuff." He gestured broadly around him, paused just a moment to look at a shelf crammed full with familiar (and in some cases, absurd) little odds and ends, and rolled his eyes with a feigned sense of being put upon. "You barely remember to open your shop. Always lost in a book. You'll never remember to water Ferdinand, or..."
"Ferdinand?" Aziraphale chuckled. "Ferdinand the fern?"
"...or feed him." Crowley talked right over him. "Do you even know plants need food? Of course you don't. Or when to re-pot him. No," he shook his head. "No it's best for everyone involved if I keep him. It. This," he held up the trembling plant.
"Ferdinand," Aziraphale offered.
"Right. Yes." Crowley gave a jerky nod.
"Good. I'm glad you like it. Him."
"I do. Like him. Ferdinand. S'good, Angel." Crowley ducked his head to hide the heat creeping to his cheeks. "Ya know... I mean... Th-"
"You're welcome, dear boy." Aziraphale urged Crowley toward the couch with a particularly lovely bottle that had only moments before still been in the case.
"If you'd like, you could keep Ferdinand here."
"Uh..." Crowley stumbled over his own feet, and with unearthly grace twisted and plopped down next to Aziraphale on the couch.
"I only mean," Aziraphale cleared his throat. "That is... Yes. What I mean to say is, you're here every day now anyway. You can care for him here as easily as anywhere. And... and maybe you could teach me? We could raise him, ah, together?"
"Together?" Crowley mouthed the word. He peered at Aziraphale over the top of his sunglasses, then down at the fern, then back up again. "Really? You'd wanna? And I could..."
"If you're amenable." Aziraphale smiled sweetly.
"Ah- amena... Uhm, yeah. 'Course. 'Course, Angel. Plant raising is simple really. Long as you put the right amount of fear in 'em. You were entirely too soft on the Dowling's rose bushes, Angel. Travesty that was. An embarrassment." Crowley huffed in disdain and shook his head.
"Wonderful." Aziraphale eased the pot from Crowley's hands and replaced it quickly with the bottle. "I look forward to our first lesson."
Without pause, Crowley continued his grievances against Aziraphale's gardening techniques as he poured out two glasses.
Ferdinand leaned into Aziraphale's gentleness and shuddered in relief.