Ask MerriAuthor
Just as a standard Mod Announcement: MerriAuthor will be attending Bronycon!
Not as an exhibitor or seller, mind you; just a guest.  I’ll be hanging out with TechnoMod, Rusty Mod, and Shai Mod at the least.  If you happen to spot me, come say hello!

Just as a standard Mod Announcement: MerriAuthor will be attending Bronycon!

Not as an exhibitor or seller, mind you; just a guest.  I’ll be hanging out with TechnoMod, Rusty Mod, and Shai Mod at the least.  If you happen to spot me, come say hello!

tweaking anon's idea: Merri reacts to suddenly gaining superspeed for a day. As she pushes herself to move and think faster, she accelerates rapidly, to the point the rest of the world seems to be standing still, but can hit the brakes and slow down to being able to hold normal conversation.

So she’s basically Filli-Second then?  She’d just go about with her normal day, aside from perhaps skipping off briefly for a quick trip across the country to pick up some fresh coffee beans from her favored coastal region.  You can always rely on Merri to be absolutely mundane with her powers.

Merri reacts: Discord has decided to 'help' Merri attain the fastest service award again... By making her unable to move at any speed lower than supersonic levels for a day or so. This applies to every move she makes, but not her thoughts... A simple wave creates a sonic boom, every step breaks the sound barrier, and she can't think fast enough to make the most of it, and NOT crash into stuff... Discord might've bitten off more than he can chew, as far as Merri-rage goes.
Anonymous

Well, seeing as how the very first move she would make would likely send her hurtling face-first into a wall at supersonic speeds, Merri would be pretty dead and not capable of further action.

MLP in general is rather idealistic. The only types of magic that seem to cost something are 'dark magics' like the alicorn amulet, which was beginning to cost Trixie her sanity, or the green spell that overtook Rarity, which, well, kinda did the same thing, or that stuff Sombra was using, which when Twilight used it... I'm starting to see a trend here.

Dark magic doesn’t so much seem to have a cost as it does unfortunate side-effects.  Trixie and Rarity both suffered a gradual shift toward insanity, but were totally fine as soon as the source of the magic left them.  It acted more like a toxin in their system.

As for Sombra’s dark magic: ie, magic fueled by hatred and fear?  That’s actually a questionable point as we do not know how Sombra behaved prior to being evil and Twilight didn’t actually seem to be negatively affected by using dark magic herself.  Celestia demonstrated that there would be consequences if dark magic was allowed to spread, but the actual impact its frequent use would have on the user is unclear.

We’ve got the IDW comics to refer to for a Good King Sombra being corrupted by dark magic he absorbs before going all smoke-eyes, but that entire arc and especially its conclusion were downright confusing and muddied on the details.  We have no indication that Sombra Prime was ever exposed to something evil that corrupted him or if he just abused his own fear-centric dark magic until it totally consumed him.  Twilight and Celestia were able to use that same magic without needing to be exposed to evil first, after all.  In the comics, despite apparently “turning evil”, Good King Sombra still had his feelings for Celestia and was still working to protect his Equestria from the darkness, so… was he actually evil or not?  That entire last chapter was packed full of plot holes.

Good to know those MLP First Readers are well made. I've seen numerous that are just retelling of show plots so I'm really happy that not only are these unique stories, but are actually fairly well done.

Yep, they’re all pretty enjoyable… with the notable exception of the Rainbow Dash book.  That one was just awful.  Also, I noticed I didn’t tag my posts properly: I’ve now gone back and edited all my book review posts so they have “book review” and “g.m. berrow” tags.  Should make it easier if anyone wants to follow up my earlier reviews.

If earth pony magic is akin to these age spells, then yes, it will do nothing to the soil - because it's directly changing physical form (the question of where does it take energy and materials to do so is entirely another issue...), but if it just accelerates growth to compress a year into a minute, then it will probably deplete the soil. Unless it only gives appearance of fast growth, while the underlying principe is same shapechange as in the former case.

That’s all still going on the foundation that Earth Ponies can induce spontaneous growth in plants.  Which they have not been shown to be able to do in canon.

Sort of?  In the “Journal of the Two Sisters” book, Starswirl’s first perfected time travel spell also has an “age traveling” effect, as they call it.  It causes him to lose years when he travels back in time, becoming younger relative to how many years he jumps.  When he returned to his original present time to tell Celestia and Luna of his success, he had de-aged considerably from an old man into a young adult.  It was not made clear if he ages when he jumps forward in time.

Sort of?  In the “Journal of the Two Sisters” book, Starswirl’s first perfected time travel spell also has an “age traveling” effect, as they call it.  It causes him to lose years when he travels back in time, becoming younger relative to how many years he jumps.  When he returned to his original present time to tell Celestia and Luna of his success, he had de-aged considerably from an old man into a young adult.  It was not made clear if he ages when he jumps forward in time.

Yes, it does require physical stamina and mental fortitude for Unicorns to cast spells.  But that’s not quite what I was talking about.  I was referring more to the sort of cosmic balance a lot of other stories and mediums use with magic.  The sort of “to get this effect, you have to pay this cost”.  Such as your original example: “you can instantly grow a tree to full maturity, but you have to deplete the soil in order to do so”.
MLP magic doesn’t seem to have that same impact.  Twilight was exhausted by her efforts, but she bounced back pretty dang quick.  We’ve also seen her get better and better as time goes by, to the point that she can now teleport at will effortlessly, or easily shrug off performing rapid-fire casting of spells such as when she was banishing the Pinkie Pie clones.  It’s a practice-makes-perfect sort of situation.
The closest thing we have to there being any sort of sacrifice for a magical effect was with the Unicorn Tribe raising the Sun and Moon.  As the “Journal of the Two Sisters” book detailed, it took a group of Unicorns all their magic to do it and eventually the strain caused them to lose their magic entirely.  Celestia and Luna were immune to that effect because they were naturally attuned to the Sun and Moon respectively.  Once they took over, they were also able to restore the magic the other Unicorns had lost and all was good as new.  Magic is just kind of fast-and-loose in the MLP-verse, it seems.

Yes, it does require physical stamina and mental fortitude for Unicorns to cast spells.  But that’s not quite what I was talking about.  I was referring more to the sort of cosmic balance a lot of other stories and mediums use with magic.  The sort of “to get this effect, you have to pay this cost”.  Such as your original example: “you can instantly grow a tree to full maturity, but you have to deplete the soil in order to do so”.

MLP magic doesn’t seem to have that same impact.  Twilight was exhausted by her efforts, but she bounced back pretty dang quick.  We’ve also seen her get better and better as time goes by, to the point that she can now teleport at will effortlessly, or easily shrug off performing rapid-fire casting of spells such as when she was banishing the Pinkie Pie clones.  It’s a practice-makes-perfect sort of situation.

The closest thing we have to there being any sort of sacrifice for a magical effect was with the Unicorn Tribe raising the Sun and Moon.  As the “Journal of the Two Sisters” book detailed, it took a group of Unicorns all their magic to do it and eventually the strain caused them to lose their magic entirely.  Celestia and Luna were immune to that effect because they were naturally attuned to the Sun and Moon respectively.  Once they took over, they were also able to restore the magic the other Unicorns had lost and all was good as new.  Magic is just kind of fast-and-loose in the MLP-verse, it seems.

Yes, but that was an unintended side-effect.  Discord planted the seed with the intent that they would immediately sprout and try to strangle the Tree of Harmony to prevent himself from being sealed.  Which they did.  The problem was that the Tree had enough power to keep the vines at bay for 1000 years first.  The seeds had still sprouted all the same though.  They just didn’t get to spread until the Tree weakened enough for them to continue their progress.
My original point was that Plunder Vines and Zap Apple Trees are the only type of plants we’ve seen that instantly sprout into maturity, and they do so entirely without Earth Pony involvement.  Earth Ponies, meanwhile, have not been shown to have that ability on plant life.

Yes, but that was an unintended side-effect.  Discord planted the seed with the intent that they would immediately sprout and try to strangle the Tree of Harmony to prevent himself from being sealed.  Which they did.  The problem was that the Tree had enough power to keep the vines at bay for 1000 years first.  The seeds had still sprouted all the same though.  They just didn’t get to spread until the Tree weakened enough for them to continue their progress.

My original point was that Plunder Vines and Zap Apple Trees are the only type of plants we’ve seen that instantly sprout into maturity, and they do so entirely without Earth Pony involvement.  Earth Ponies, meanwhile, have not been shown to have that ability on plant life.

Because there’s such a thing as Summer Apples (McIntosh, Royal Gala, Sunrise, Summer Red, etc) that are harvested during the Summer months.  Also, Fall season apples can easily be preserved in cold storage (like, say, Applejack’s apple cellar, for example) for anywhere between 3 to 12 months and still be perfectly edible, though the overall quality of the fruit’s taste and how well it holds up depends on its water content.  Apples that the Apple Family harvests in Fall could quite nicely be stored through the winter and sold in the following Spring before the next harvests come in.  That would allow the apple trees time to blossom throughout the Spring since, as Applejack sang in “Winter Wrap Up”, the Ponies can’t grow anything during the Winter months.

Because there’s such a thing as Summer Apples (McIntosh, Royal Gala, Sunrise, Summer Red, etc) that are harvested during the Summer months.  Also, Fall season apples can easily be preserved in cold storage (like, say, Applejack’s apple cellar, for example) for anywhere between 3 to 12 months and still be perfectly edible, though the overall quality of the fruit’s taste and how well it holds up depends on its water content.  Apples that the Apple Family harvests in Fall could quite nicely be stored through the winter and sold in the following Spring before the next harvests come in.  That would allow the apple trees time to blossom throughout the Spring since, as Applejack sang in “Winter Wrap Up”, the Ponies can’t grow anything during the Winter months.