How to Speed Crop Growth: Farm Aids and Building Options with their Effects

As players know, there are a number of different ways to speed the growth of your Crops. These are: various Farm Aids like Organic Fertiliser, Super Fertiliser, and Weather (Rain, Thunderstorm, Rainbow), the Greenhouse, Sprinklers and finally Neighbour actions of fertilising your Crops. The Greenhouse costs 15000 Coins and has to be built either on your Farm or on the Building Plot area. It takes a lot of space and cannot be placed on top of Crops until it is completed... so it has to stand on empty land until built. 

Note that materials that you can request from Neighbours often can be found in your Coin Mystery Shop.  Any materials for any item that must be purchased with RC may or may not appear randomly in the Green Mystron Shop.  I need to pay more attention to that!

The Water Well and Sprinklers
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The Water Well is a building that is linked to Sprinklers.  The Water Well remains stationary while you place the Sprinklers one individual plots.  Sprinklers can be placed on any plot that is outside a Greenhouse, whether or not a Crop has been planted previously.  As soon as it is placed, it will be active and if a Crop is growing there, will reduce the growth time by 15%.  In the initial stages, when you only have a few Sprinklers, it is best always to use them for the slow-growing Crops.

The Water Well now is to be found on a Building Plot. 

Sprinklers only reduce crop growth by 15 percent, but this can be useful where slow-growing Crops are involved.  The initial Water Well limit when you unlock the Building plot on which it is found is 15 Sprinklers.

1st Well Expansion
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The 1st Expansion can be completed without using any RC.  It requires the following:
15 Stones (request from neighbours or pay 1 RC for each)
15 Wood Beams (request from Neighbours or pay 1 RC for each)

This allows you to use a total of 40 Sprinklers.

2nd Well Expansion
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The 2nd Well Expansion allows you to have a total of 70 Sprinklers but you must pay a minimum of 15 RC to complete it.  It requires the following, I believe:

18 Stones (request from Neighbours or pay 1 RC for each)
18 Wood Beams (request from Neighbours or pay 1RC for each)
1 Drill Gear (cost is 15 RC)

3rd Well Expansion
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For the 3rd expansion that allows 120 Sprinklers, you must collect 18 Stones, 18 Wood Beams and pay 15 RC for 1 Drill Gear... so even if you obtain all possible materials from neighbours, the minimum cost is 15 RC. I believe that the expansion that allows a total of 70 sprinklers is the same in terms of materials and cost. The advantage of sprinklers over Greenhouse is that you can place them individually on plots anywhere on your farm.

Increasing Sprinklers to 550
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Unfortunately, Harvest Moon did not log all the prices along the way, but here are the materials required to increase sprinklers from 450 to 550:

30 Stones (Request from Neighbours or pay 1RC for each)
30 Wood Beams (Request from Neighbours or pay 1 RC for each)
1 Water Pump (pay 10 RC)

Greenhouse
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The Greenhouse costs 15000 Coins and must be built after you place the unfinished structure either on a Building Plot or on your farm.  Once complete, it cannot be expanded, and takes a total of 20 plots. You can build more than one Greenhouse, however, unlike many of the Buildings in FFS.

The materials required to complete your Greenhouse are:

15 Glass Panes (Request from Neighbours or pay 1RC for each)
15 Pipe Stacks (Request from neighbours or pay 1 RC for each)
4 Ventilation Windows (pay 5 RC for each)

The minimum cost of a Greenhouse thus is 20 RC. 

Tree Greenhouse
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Cost is 12000 Coins but then must be built using the following:

15 Tree Greenhouse Glass
  Request from Neighbours or pay 1 RC for each
15 Tree Greenhouse Pipes
  Request from Neighbours or pay 1 RC for each
3 Ventilation Windows
  Pay 5 RC for each

Total Cost: 45 RC to build instantly

Farm Aids
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Misspelled in the Menu as Farm Aides which would apply only to live helpers, you can buy the following to speed the growth of your Crops:

Organic Fertiliser: speeds growth of Crops by 25%
Super Fertiliser:  speeds growth of Crops by 100%
Rain: speeds growth of all Crops and Trees by 25%
Thunderstorm: speeds growth of all Crops and Trees by 50%
Rainbow Rain: speeds growth of all Crops and Trees by 100%

The various Weather aids have visual effects.  They can be expensive, however.   The glorious Rainbow Rain that actually produces a real Rainbow over your farm costs 30 RC and works only once.

Finally, there are Neighbour actions.  A Neighbour who visits can, inter alia, fertilise up to 5 of your Crops.  This works like Organic Fertiliser, reducing the growth time by 25%.  An empty plot cannot be fertilised, which is a reason why you always should have a Crop on every plot, even if it is mature, as your Neighbour can harvest a mature Crop but cannot interact at all with an empty plot.

Obtaining Farm Aids
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You always can purchase Farm Aids in the 'Farm Aides' section of the Market, but they can be costly.  Fortunately, there are a number of alternatives.

Farm Aids often are found in the various treasure Chests or Gift Bags/Boxes that you can earn daily by completing your Daily Quests path or logging into the game again and again for the Dedicated Farmer Bonus.  Furthermore, you will find them randomly in the Coin Mystery Shop.  I always purchase every Farm Aid I find in my Coin Mystery Shop.  The more valuable Weather Aids usually are given as Calendar Log in Rewards or offered in special Sale packages.