You spend the casting time tracing magical pathways within a precious gemstone, and then touch the target. The target must be either a Beast or Plant creature with an Intelligence of 3 or less or a natural plant that isn’t a creature. The target gains an Intelligence of 10 and the ability to speak one language you know. If the target is a natural plant, it becomes a Plant creature and gains the ability to move its limbs, roots, vines, creepers, and so forth, and it gains senses similar to a human’s. The DM chooses statistics appropriate for the awakened Plant, such as the statistics for the Awakened Shrub or Awakened Tree in the Monster Manual.
The awakened target has the Charmed condition for 30 days or until you or your allies deal damage to it. When that condition ends, the awakened creature chooses its attitude toward you.
* - (an agate worth 1,000+ GP, which the spell consumes)
If you use Nystul's Magical Aura to make this spell think a zombie is a beast, does it remain INT 10 after Nystul's wears off in 24 hours?
I don't know but it's a very good question
I can't think of much in the official rules about creatures changing their creature type, but I would personally rule a creature is no longer affected by an effect that doesn't work on its new creature type.
Awaken being an Instantaneous effect means that probably doesn't apply, though
An awakened animal isn't under the effect of Awaken, otherwise the duration would be Until Dispelled
I don't think they considered that particular combination of spells carefully enough...
what would happen if a beast with 4 or more INT was under an effect that reduced its INT to 3 or under, than you casted awaken, and then the INT-reducing effect wore off
I'd be inclined to say that since this spell has an instantaneous duration and its Intelligence-enhancing effect is intended to be permanent, the other effect ending doesn't change anything. That is, the target would keep its new Intelligence score of 10.
It would be different, maybe, if this were an ongoing spell that ended after a certain number of hours or something?
How does casting this spell actually work?
Do I have to select the target before I start casting, or can I do so when I finish?
Do I have to touch the target immediately after I finish casting or can there be a delay?
The general spell-casting rules (surprisingly) don't actually say that you have to select a target before starting casting a spell. For most spells that wouldn't be relevant, but it would be for long-casting-time touch spells. Most of _those_ don't actually describe how or when you touch the target. The main exceptions I can find are this, and Simulacrum.
Simulacrum (2024 version) specifically states that you have to remain within 10ft of the target and the simulacrum for the duration of casting, and have to touch them to complete the spell. Awaken _doesn't_ make such a restriction, so one could plausibly interprete it to mean you can spend your 8 hours casting the spell, and then at any time after that touch any creature to awaken it. Which could allow all sorts of fun shenanigans, but feels like it's not intended rules-as-intended.
I am a novice player, but it seems reasonable to interpret "and then" as a sort of Ready action or delayed trigger to defer your target selection, although Ready does specifically state that it is only applicable to spells with a casting time of an action.
"You spend [8 hours] tracing magical pathways within a precious gemstone, and then [for an instantaneous duration] touch the target."
I'm curious as to the utility of this spell? At 5th level a CR 0 (shrub) or CR 2 (tree) don't seem particularly significant, but I'm probably missing something. Also, I'm trying to imagine when the 8-hour casting time would allow for this spell to feasible, since you can't cast this while also doing a long rest, and not sure how often the rest of the party is going to be willing to wait for you to cast a spell like this that doesn't seem to be of any major benefit to the party (again, I'm probably missing something here).
The spell is pretty niche. There are a bunch of higher-level spells that seem like they're intended more as plot points than as spells you throw around all the time.
That said, it sounds like you may be missing the fact that you don't have to use it on a plant; you can also use it on any creature with the Beast or Plant creature type as long as its Intelligence is 3 or less.