The revised instant grow guide

What’s so great about Instant Grow? Well, it functions pretty much just like how it sounds: it can instantly grow your crops so you can harvest them immediately, and/or it can make your trees (and orchards) instantly harvestable. Now you can Master those crops really fast, or hopefully get a Mystery Seed from an Orchard or two quickly.
I Want Instant Grow!
You can’t just buy bags of Instant Grow. The first thing you need to do is buy a plane; specifically, the Biplane or Chrome monoplane (only purchasable on mobile devices) in the Market (in the “Vehicles” tab). The cost for either is 30,000 coins, and you’ll need to be level 15 in order to make the purchase. Once you have it purchased, place it on your farm:

With the plane you essentially spray your farm with Instant Grow, making all of your crops and/or trees suddenly harvestable. Use of Instant Grow doesn’t alter how many Coins you’ll get from harvesting, nor does alter Crop or Tree Mastery. If you use it on trees, it’ll cover both the individual trees on your farm and all of the trees in your Orchards. Note that you cannot put the plane in the garage like other vehicles.
The plane! The plane!
Let’s take a gander at this situation. I have a bunch of Cotton crops and a full Orchard, both of which are at least a day away from being harvestable:

And I just bought a Biplane in the Market and placed it on my farm. The very first time you get a Biplane, you get one free Instant Grow use. Click on the Biplane and select “Apply Instant Grow”:

You’ll then be asked to use it on your crops and trees. Click on “Grow My Crops!” and you’ll see the plane take off and fly around your farm, then land. Your crops and trees are now fully harvestable:

It’s that easy!
Keeping Your Plane in the Air
After you use your free Instant Grow you must pay Farm Cash for every usage afterward. When you click on “Apply Instant Grow” you’ll get a window like this:

Exactly how much Farm Cash you need to pay depends on how much you have to grow—the higher the number of crops or trees/orchards, the more you have to pay in Farm Cash. However, you can choose which you want to apply Instant Grow to (crops or trees) by clicking on the check box under the category you don’t want to grow:

So now you’ll only apply Instant Grow to the trees/orchards on your farm. Click on “Grow Now!” to start.

This article I got from the official site.
Not written by me. But sharing the information with you.