You read our first article on potatoes, you have your potatoes planted in your container and a few weeks have passed (You’ve been watering often right?) you should be seeing potato sprouts. Let these sprouts grow until most of them are about 12 inches tall. Now it is time for a process called “earthing up.”

Earthing up is the prime reason I grow my potatoes in tall containers. It makes this process especially easy. Just take your compost mix and add one trowel full at a time - being careful not to damage the leaves. Keep doing this until you have added four inches of compost.

Now is a good time to fertilize. If you can find it, add 10-20-20 fertilizer as the instructions reccomend. I could not find it so I found a slow release tomato fertilizer that is 3-4-6, that should be fine for this application and great for my tomatoes. A fertilizer like this is great for potatoes because it does not focus on Nitrogen (The first of the three numbers.) Nitrogen is what you add when you want the plant to really focus on putting on new leaves. Leaves are not your focus with potatoes.

Water well.

Repeat the earthing up process every time your plants reach 12 inches from the surface of the soil. Stop when you have four to six inches remaining in the container.

Now that you are an expert, let me tell you how not to plant your potato box.

I made a mistake. There, I admitted it. My first real mistake of the year. I mean, aside from not netting my strawberries soon enough, planting radishes too close to the soaker hose, planting old spinach seeds that only germinated 50% of the time, forgetting to start seeds indoors this year, not clearing the maple tree seeds before they sprouted, failing to get my lemon cucumbers to germinate, not having my tomato cages ready yet, losing a piece from my EarthBox and underfilling both of my self watering planters. Other than those things, this is my first real mistake of the year.

When I bought my seed potatoes this year I was tempted by variety. I bought four varieties of potatoes. Three varieties went in one box and the remaining variety went in to the other box.  With most crops you can plant this way with no reprocussions, but since potatoes require the addition of more soil over time, this is a bad idea.

What happened to me is that some varieties shot up to 12 inches tall in no time while others were just sprouting. That meant that for one plant it was time to add 4 inches of soil and for another it would be a week or more before it’s turn.

Everything turned out fine as I earthed up, I was just not able to add soil as consistantly as I had hoped to. That means I may not get quite as many clutches of potatoes.

In the box with one variety I am seeing even growth and it very easy to keep things growing. (Pay no attention to the blue container, my 2 year old garden helper likes to throw things in the potato bins.)

Side note: Potatoes can take a beating from 2 year olds. Look at him looming ominously gazing in the background of the picture below. What is he going to throw in next? Tennis ball? Toy shovel? A bucket? His bubble mower? Could be anything.

Now that you have read part one in our series and you have collected all the materials that you need, you are ready to assemble your Square Foot Garden. First let me say that anyone can do this. Seriously. I am more awkward in a lumber yard than Michael Vick at Humane Society convention.

That joke work for you? No? Too dated? It’s okay, I have more.

I am more awkward in a lumber yard than Sandra Huxtable when she told her parents Clair and Cliff that she was going to skip graduate school and open a wilderness store.

Wow, a Cosby Show reference. That was really dated.

I am more awkward in a lumber yard than Willy Wonka at an Oompa Loompa union meeting when they realize that they are being paid in cheap chocolate and demand a living wage with full dental.

Too obscure? Okay, I give up, but you get the point. I am totally awkward in a lumber yard.

1: Cut the Boards
First you need your boards to be the right length. You will need two 8′ boards (You can buy them at that length) and two 4′ boards (My incredible math skills tell me you can buy one 8′ board cut it in half.)

Notice: My instructions will technically give you a box with an interior space that is 4′ x 7′ 9″. If you really need it to be exactly 4′ x 8′ then you probably should not be getting your construction instructions from me.

2: Drill the Holes
Next you need to drill some holes where you are going to insert screws. That means three holes at each end of the 8′ boards about 1/2″ from the end.

3: Screw the Boards Together
Now that you have the holes all pre-drilled it is time to line everything up and screw the box together. I suggest laying the boards out on a flat surface to make sure everything will line up well enough. The box does not have to be perfect, but if any of your boards are too warped you will have trouble getting the corners to align.

Dufus alert: Make sure you are using the appropriate bits for the screws you bought. The appropriate bit is almost for sure a #2 Philips head. Also you may want to not skimp on the screws like I did. I got the silver colored inexpensive deck screws. Some people have advised me that you should get the darker more expensive screws. This will hopefully let you avoid stripping one screw after another. Did that last sentence sound dirty to anyone else?

4: Seal the bottom
Now that you have a totally awesome box you need to seal off the bottom so you can keep your soil mix separate from the native soil.

For this step I am assuming your box will end up on the ground where some grass currently is. There are other methods for special situations. For example, people that have trouble bending down - the elderly for example - can use boxes that have a solid wood bottom so they can be lifted to table height.

Roll out your landscape fabric and make sure you have enough to cover the entire bottom of the container. Now staple the fabric to the box every 12″ or so all the way around.

Bonus Infestation Tip: Have that gopher from Caddyshack always popping up and gyrating all over your yard to classic Kenny Loggins songs? You may want to add a couple of layers of chicken wire along with the landscaping fabric. This will create a physical barrier that will keep burrowing animals from getting in to your raised bed.

5: Add the Growing Mix
Now that you have your raised bed fully assembled you need to put it in place. After we add the soil-free mix it will be more challenging to move it than a… nevermind. No more “jokes”. Just put the box where you want it.

The mix is very simple. It is:

• 1/3 Vermiculite
• 1/3 Peat Moss
• 1/3 Compost

Pour the ingredients in to make three even piles and then mix thoroughly.

When you are done your mix should look something like this and it should be almost to the top of the box.

6: Build a Grid
Now you have something that looks like a garden! Time to setup the grid. The grid is the part that makes this technique go from raised bed gardening to Square Foot Gardening. You can make this grid any way you like. Some people seem to prefer hard materials for the dividers. They will use things like thin strips of wood, cheap window blinds, etc. But I prefer something I can easily remove and replace whenever I want.

What I use as a divider is Mason’s string. People installing concrete use it to mark the lines where they will be doing their work. It’s a lot like me. It practically glows in the sunlight, it’s durable, it does not move much once you get it installed and it’s cheap.

Measure at the center of the boards on the top of the box and mark every 12″. These locations are where you are going to install screws to mount the Mason’s string on. Now predrill each mark as close to the center of the board as possible and insert a screw in to each drilled hole. Make sure you leave a centimeter or so of the screw above the surface so you can tie the string to it.

Click here to view a video of how I installed the grid. After I was done I tightened the end screws to make sure the knots hold.

In the next post in this series I will tell you how to plant in each square. To hold you over until then check out my article on Planning your Square Foot Garden planting in Excel.

I’ve been sold on raised bed gardening for a while now.  I’ve seen great results year after year. What I have never gotten around to trying is Square Foot Gardening - even though I own the book:

What is Square Foot Gardening?
Square foot gardening is an intensive raised bed gardening technique where you build a box about 6″ deep and fill it with a specific soil mix. Then you greate a grid on top to form 1 foot squares, pick a crop for each square then put a new crop in whenever you harvest. Think of it as gardening for control freaks.

There was one reason for me not trying out this type of gardening. It’s a dastardly ingredient that is required for this technique. A material so elusive that no home improvement store, garden supply store, giant box store, warehouse, farmhouse, henhouse, outhouse, doghouse (Movie Reference) or mom and pop nursery carries. Vermiculite.

Nerd Tip:
Vermiculite is a mined rock that is then put through a heating process that makes it pop like popcorn. After the heating process you are left with a very lightweight material with a ton of surface area.

Well this year I was determined to build that first Square Foot Garden so I did some research. Vermiculate is commonly used in the construction of swimming pools. So I called a pool and spa shop that is on my work commute and they told me they would have it in a day.  $27 per 4 cubic foot bag.  I bought two.

Everything else is easy to find, here is the supply list for a 4′ x 8′  6″ deep box and enough of the mix to have some to spare for other containers:

Supplies:

Lumber: I bought A2 treated lumber. It contains no arsenic. To be really safe you can use untreated if you like. 2 2"x6"x8', 2 2"x6"x4'.

Vermiculite: 8ft³ If you can't find it in your garden center, call a pool supply shop. You need it in bulk to be cost effective.

Peat Moss: 8ft³ This isn't a renewable resource like you would think, but you only need it the first year.

Compost: 8ft³ and as many different kinds as you can find. Most of mine was bought in bulk from a landscaping company. This is the ingredient you will have to replenish yearly. Remember, variety, variety, variety.

Here are the small supplies you will need to build your box like I did:

• Cordless drill with philips screwdriver head and a drill bit appropriate for the screws you are using.
• 12 3″ - 4″ Deck screws.
• Landscape fabric.
• Staplegun & staples.

That is it for supplies. When you have your supplies gathered continue reading our post: Four Steps to a Square Foot Garden - Step Two: Construction