...the narrator thought they were hot pink. Okay, lesson learned and then immediately forgotten.
"That's cool," Sunny remarks, which sounds weird coming from him. Not because it's too casual, but rather...oh, you know the meaning. "Did you see them around often?"
Somehow, he manages to jolt his head toward the café entrance while keeping his words completely level. Bro, don't do that, or one of your neck hinges might snap. 

"I'm glad they grow in places where the frost isn't heavy enough to get to the roots," says Sunny. He doesn't check to see if Caster's legs are long enough to reach him under the table.

(Hey so just so you know, I think Sunny implied an answer for Caster's question a few posts ago here, let me know if you want to make any changes before I respond or not)

(Cursed thought of Caster kicking Sunny in the knee and Sunny just buckling xD)

Sunny blinks, seemingly puzzled. "Between the alstroemeria and fireweed, or something else?" 

(Gotta love my ultra lazy method of "just have the character ask rather than try to understand themselves", but hey, this is good communication! Right! ...Right?)

(I am so worried for all the other Servants rn)

Funnily enough, it's easier for Sunny to choose one for two--as indicated by him tilting his head this way and that at the question, while simultaneously making some kind of effort to not make the head tilting apparent. 
"Snapdragons are nice," he says at the end. 
By the way, the blandness of the answer means he couldn't actually choose one. 

(We [Sunny and I] feel judged xD)

Sunny takes the book as naturally as one would breathe or eat. He even scoots out on his chair slightly, places it on his lap, and flips through the pages that way. Looks like he's more comfortable doing it this way.
"Snapdragons are funny as well. Well, not necessarily funny, but it's amusing, the family they belong to. Figwort." Flipping the pages, he makes a point of looking up at Caster as he says that. "It's like if you had a last name and it was that. Snapdragon Figwort. Isn't that sort of funny?"
Bro, your name is Sunshine Meep. 

The narrator sees communication classes being in their foreseeable future.
"It sounds kind of like a Whomping Willow," Sunny says. 
He definitely doesn't know what he's saying anymore. 

Sunny doesn't notice his own sister coming in. His situational awareness probably needs some work. Mostly, he's just focused on brainstorming more names related to plants, because apparently that is where the conversation is going. 
"Mhm. And Magnolia. And Holly. Yvonne too. And Rosa." 

(For some reason when I read Caster being on the table I imagine him Expanding like some sort of humanoid goo)

Sunny nearly kicks the table base, but other than that, and the fact he forgets to keep the naming conversation going, and the way he's staring at Sollux like a startled cat...where was this sentence going?
Sollux must be seeing quite a pretty sight. Her brother has a book on his lap like an absolute nerd, and Caster is partially sprawled out onto the table. Plus there is no food on the table yet. 
"...Juniper," the young man finally mutters.