Animal Crossing: New Leaf - The Stalk Market Strategy Guide

On Sunday mornings, Joan, a brown boar, visits your town from 6am to 12pm to sell white turnips. Turnips serve primarily as a way to invest your money in the game's Stalk Market.

Easy money, right? There's a catch though! You have until close of business Saturday night of the same week to sell all your turnips at Re-Tail or all of your turnips rot at exactly 6am the next Sunday morning, reducing your valuable turnips into mere profit-less ant-traps.

Buying Turnips

To buy turnips, look for Joan walking around your town Sunday between 6am to 12pm. She will be selling her turnips for between for anywhere from 90 to 110 bells each, in units of 100 turnips. 

So if you buy a single unit from Joan at 90 bells per turnip, you will be buying 100 turnips total costing 9000 bells. 

Ten units stack to fill a single slot in your inventory, which is comprised of 16 slots. In New Leaf, turnips cannot be placed in envelopes. 

To fill a completely empty inventory with turnips selling at 90 bells each, you would need 160 units of turnips, or 1600 turnips, costing 144,000 bells.

Storing Turnips

If you've been doing the math, a single full inventory of turnips, even at the maximum price of 110 bells each, would cost between 144k and 176k bells. 

If you're new (like me), here's a bird's eye of costs in game:  a second floor upgrade is 298k, and the most expensive upgrade to expand other rooms to 8x8 is 598k each. If you invest your money wisely, get lucky, and/or figure out some money-spots, you can accidentally/easily make a million by day 10.

So what?

1 million bells / 176k bells = ~5.68 full inventories of turnips.
~5.68 x 16 slots = 91 full item slots.

"Sure, I can manage to make that space," you say. "I have a gigantic locker, din'cha see? I'll stick em next to my clothing, my hats... oh here're several spaces next to my partial sets of furniture."

See where this is going? I have several million bells now... that's... a lot of turnips. Let's talk storage.

Storing Turnips, the TL;DR

ACNL UPDATE: Locker and storage space has been greatly increased in a more recent ACNL update. Feel free to disregard this section if the extra storage space has been made available to you in game already.

In your locker.

Pros:

• Portable and ready to sell; don't need to gather up all the turnips before traveling. 
• Less chance of overlooking turnips, come time to sell.

Cons:

• May have to boot out furniture/clothing/ore etc to make space.

On the ground.

You can drop stacks of turnips on the ground anywhere, like fruit, and they won't rot until Sunday 6am. 

Pros:

• The edges of the map is the limit. Ground is free, ground is everywhere.
• Easy access, any time.

Cons: 

• Your villagers will see them as eyesores and complain about litter.
• If you have internet strangers visiting for trades, etc, you risk losing investment if you are unfortunate enough to encounter wandering people with sticky fingers.
• If you leave them in the Plaza, and a traveling visitor sets up camp on top of your turnips, you might as well have eaten your turnips.
• If you leave them in a clearing, and someone moves in on top of your turnips, you might as well have eaten your turnips.

In your house.

Pros:

• Safe.
• Easily accessible.

Cons:

• Extremely limited space.
• Personal eyesore.

Second character.

Use your other character slot's house and inventory to store items/turnips.

Pros:

• "Natural" storage integration.
• Out of sight, safe-ish storage.

Cons:

• Reasons vary from person to person (siblings, time consuming to switch, etc)

Second New Leaf game:

Pros:

• Have all the perks of a second game (separate turnip prices, premiums, fruit, trade etc).

Cons: 

• Additional monetary investment: another game, access to another 3DS.
• Additional time to move/access items at a whim.

Selling Turnips

Trends

1) the "constantly-decreasing" pattern,
2) the "large-spike" pattern,
3) the "small-spike" pattern, and
4) the "random-price" pattern.
The constantly-decreasing turnip price pattern starts Monday morning with a
price less than 100. Each successive price is a few bells less.
Here are some examples:
M T W Th F Sa
99 95 91 86 82 78 73 70 65 60 55 51
93 87 82 79 74 71 67 63 58 55 50 46
92 88 85 80 76 72 68 64 59 55 52 47
83 78 74 70 66 61 57 54 50 45 42 38
81 77 74 70 66 63 59 55 51 48 45 42
The large-spike turnip price pattern is a constantly-decreasing pattern that is
interrupted with five prices: a two-price run-up to a spike followed by a two-
price run-down. Usually, a constantly-decreasing pattern resumes after the
interruption. Here are some examples:
M T W Th F Sa
96 93 124 215 577 163 150 51 45 85 97 90
94 89 86 82 77 72 67 144 180 626 160 137
84 81 77 131 139 478 159 90 65 79 85 71
81 76 73 92 180 295 132 111 79 44 40 42
80 76 73 70 65 62 89 134 465 154 122 52
77 74 71 108 157 216 159 106 48 59 80 ??
The small-spike turnip price pattern also involves an interrupted constantly-
decreasing pattern. The maximum price is the fourth price after the
interruption (as opposed to the third price with the large-spike pattern).
Here are some examples:
M T W Th F Sa
126 142 150 152 149 68 64 61 56 52 48 43
93 90 86 82 101 133 188 211 205 89 85 81
79 75 72 106 122 153 160 154 66 62 58 52
65 62 57 89 103 128 132 129 46 42 38 34
53 50 46 43 40 36 32 113 89 145 180 168
38 34 30 128 119 163 168 152 77 73 69 66
Notice above that the "interruption" can start at the beginning of the week.
The random-price "pattern" really has no pattern; the prices jump up and down.
Here are some examples:
M T W Th F Sa
139 77 66 101 99 123 131 69 64 55 127 148
136 100 128 115 117 63 54 44 98 67 62 101
90 118 95 69 63 93 119 103 61 55 48 95
85 124 100 90 95 125 70 64 98 60 51 42
71 66 89 65 62 57 92 90 94 113 93 113

Riding the Market

I've found that a good place to find places to buy and sell turnips is on www.reddit.com/r/acturnips, where you can interact with other people playing Animal Crossing: New Leaf. While most people are civil and fair, there will/may be scammers/thieves. Participate at your own risk!

Note: it is general courtesy to leave a gift or tip for their time and efforts.

Determining Your Trend

The only way to tell what trend you have this week is to check in on prices every now and then. Turnips are sold at Re-Tail. Prices change twice a day: once at opening (9am; 6am with the Early Bird ordinance), and then again at noon.

Every time the price changes when you check, add the new price to the text line, separated by a comma. Obviously, the more data points you have, the more accurate and meaningful your results will be!

Kurt Boyer created a prediction tool to help you determine which trend you have.