Agata Bloom Tricks
As Agata's Guardian Sapling is underground, it cannot be directly accessed and bloomed, despite its proximity to both entrances into Agata from Shinshu. There are a few ways to circumvent this and reach the sapling faster than intended.
In NG+ when using the upper Shinshu entrance, one can perform an immediate Brush Adventure to push the camera behind the loading zone and out-of-bounds until the sapling comes into view. It can than be Bloomed. This is the fastest method currently known. A similar Brush Adventure cannot be performed at the lower entrance, as there is collision behind that entrance which blocks the camera from quickly getting OoB.
Out of Bounds
It is possible to get Ammy out-of-bounds above the lower entrance, then fall near the sapling to Bloom it. This can be done via 3 KTs (https://youtu.be/6zAyWckl-58?t=694) or a single KT (https://youtu.be/6tqrposDwAE), which was the previous optimal method before the above Brush Adventure was found.
It can also be done in NG via an unreliably precise jump from a rock on the East side of the entrance, followed by an air-tackle bounce onto the top of the entrance. From there, one can use Seam Grip to scale the collision and jump over the loading trigger below to fall OoB. See https://www.twitch.tv/videos/88445436. If done perfectly, this would save about 3 seconds in NG versus Blooming the sapling normally, but isn't done due to the inconsistency of the trick.
With very precise positioning and movement of the camera, it can sometimes be forced to clip through the geometry directly West of the lower entrance. The camera can then be forced through the wall, enabling Bloom to recognize the sapling OoB. See https://twitter.com/kkbase515/status/1156251869691252736. This saves about 5 seconds in NG, but similar to the above OoB method, isn't done in runs.