I don't think aingw is found in Quenya.

Malma could work...

Lainca modelled after lunca?
Or then laicama/laiquama?

Since cm can become cw/qu, laic-ma could seemingly become laiqua again, interestingly. Going back to the root doesn't work: lai-ma is already a word for "plant". My initial thought would be to use cm > nc and thus lainca. The combination aist occurs somewhat regularly, so it would seem that the diphthong followed by a ("short") consonant cluster is at least permissible even if not favored. Laicama/laiquama seem fine, though perhaps less compact with the extra syllable. Malma looks good.

One could always go for other words meaning "green, fresh green, yellow-green" => GWEN, so perhaps *wemma.

Malma and wemma look good.

As we began talking about plants, may I discuss a word for potatoes? I like the variant suggested by Laisi Finwen, cembas (earth bread). Another possibility is cemorva(r). But +Łukasz Szkołuda​ says those words are too human, non-Elvish in mentality. What do you think?

+Ицхак Пензев it's not about elvishness or humane-ness(?), but the fact that potatoes are widely eaten now, by people in specific cultures but I have no memory of potato being a cheap and stomach-filling miracle kind of food in Middle Earth... 😏

+Ицхак Пензев well the two attested Gnomish words for potato (grothorf "earth apple" and podod (clearly an adaptation of potato)) show that Tolkien was not really bothered by that. Nevertheless if anyone comes up for a nice Elvish name for the veg I am all for it.

+Łukasz Szkołuda they were certainly known in the Shire...

+Tamas Ferencz how could I miss Gnomish?! Then cemorva seems quite plausible.
And yes, I'll be extremely glad if you join the Elvish channel on Discord. https://discord.gg/uw3YBJD

+Ицхак Пензев OK I'll install the app and will see

+Tamas Ferencz nm sometimes became nw. Maybe wenwa?

+James Coish also a possibility!