Gardening costs: 400 square feet and a spade

fresh garden produce

homegrown salad produce from an avant gardener

Background:

It is about that time of the year again.  What has been a relentless winter for most of the U.S. is slowly giving way to green sprouts and flowering buds.  Spring is in the air, and gardening season is upon us.

Don’t be fooled by my introductory rhetoric, however.  I am not a gardener.  Last year was our first attempt, and even in the temperate, lush Portland climate, there wasn’t a green thumb between the two of us.

Our poor results last year were a big motivator for this post.  I was hoping to find out that gardening isn’t worth it, but sadly, it appears that it (barely) is, or at least can be if you plan well.  Last year we planted beets, pole beans, cherry tomatoes, and squash in a small raised bed.  The only crop we harvested reliably was the squash.

The beets never came up, the beans were eaten by insects, and the tomatoes got a nasty case of blossom end rot from irregular watering and/or low calcium levels.  The clear message was that gardening is not easy, at least not for us.  But we still might try it again this year because, well, practice makes perfect, and my wife loves summer gardens and the idea of being more self-sufficient.

The numbers:

For this example, I assumed a 400 square-foot garden plot.  As Eliot fairly points out below, this is a big-ass garden.  The reason I went with 400 is that most of the studies I used as sources were above 500 square feet.

To be fairer to urban dwellers such as myself, I also ran the numbers for a 100 square foot garden, which are at the bottom of this post.

  • 10-Year NPV: $1,633
  • 10-Year ROI: 37%
  • 10-Year Payback: 0.9 years
roi - garden

click for link to live spreadsheet

chart - garden

So a 400-square-foot garden saves you $1,600 over 10 years.  This is only $160 per year on an average annual basis, which isn’t that exciting, especially considering that the ROI is a measly 37% and the garden is pretty big!  A low ROI means that you have to invest a lot of money just to earn a little bit of additional revenue.  It ties up your free cash more so than something with a higher ROI.  But the point of the whole thing is that it DOES save you money to grow your own fruits and vegetables.  Gardening costs are high, but retail prices are higher.

As a reminder, my analysis includes labor/time costs.  So I’m estimating about 1/10 of an hour for every square foot, or 40 hours of work for the year in this example.  I valued my gardening time at $6.00 per hour versus my normal estimate of $10.00 per hour because gardening isn’t ALL work.  I like being outside, watering my plants, watching them grow, etc., but there are still a lot of other things I would rather be doing.

Time accounts for roughly 55% of total cost.  For the person that doesn’t find gardening to be a chore at all (time costs = $0 per hour), the value of this example would increase 230% to almost $3,700 over 10 years (see “Hard Value W/Growth” line above).

Considerations:

Gardening costs are a complex topic, so take all of this with a grain of salt (not the gospel, more of a directional guide).  There are as many ways to build a garden as there are fruits and vegetables to grow in it.  Some gardens will be more expensive than others because of climates, crop needs, pest control etc.  And the final “retail” value of your crops will vary significantly depending on what crops you decide to grow.

My main source of information for this example was a blog post by an Oregon State University Master Gardener, Gail Langellotto.  The blog post references six different gardening cost studies.  The value per square foot of these studies are wildly different, with the lowest value at $0.28 and the highest at $1.53, almost six times as valuable as the lowest.  That is a 600% variance!

That being said, there were some common winners in the studies that Gail referenced, meaning that these crops are the most likely to succeed and will save you the most money:

    • salad greens
    • tomatoes
    • beets
    • broccoli
    • potatoes
    • strawberries

Personally, I sort of want to throw in the towel on our garden.  I’m okay with paying a little extra for variety and the flexibility to buy my produce as needed (or maybe join a CSA).  There are also probably a lot of other things I could do with my time that have an ROI greater than 37%.  Additionally, organic food is a value of ours, and growing an organic garden seems much harder.  Heck, our non-organic homegrown vegetable produce from last year probably had more chemicals per pound than the non-organic commercial produce at the grocery store.  Paying a little extra for a lot less chemicals doesn’t seem to be a bad deal either.  And finally, to top it off, the downside risks of growing your own food are a lot higher.

purple artichokes

definitely some image filters on these purple ‘chokes

As I mentioned above, last year we lost about 75% of our crops.  That is an expensive season.  I’m sure we could research more and be more disciplined this year, but the risks would still be there.  It is similar to the rent vs. own debate.  You might pay a premium to rent, but at least you can better plan your costs and avoid major downside risks such as having to replace a roof or redo the basement after major water damage.

Either way, knowing how to grow my own food does seem like one of those essential life skills that I should have, and I do like the idea of at least getting good at gardening before I decide to quit.  Not to mention it will make my wife happy.  I’m not committing one way or the other, but at least I have the quantitative perspective now to help decide 🙂

The bottom line for me is that a garden can be marginally profitable, but there are a ton of other ways to spend my time and money that would provide more value.  I might still garden, but financial factors probably won’t be the main reason.

Assumptions:
  1. New garden plot costs of $0.10 per square foot ($40 here) once every 10 years (ex: wood frame for raised bed) (average of various studies sourced below)
  2. Annual garden plot costs of $0.50 per square foot ($200 here) (ex: fertilizer, mulch)(average of various studies sourced below)
  3. Time costs of 0.10 hours per square foot ($240 per year) (yahoo, personal experience, JD Roth)
  4. Retail value of garden produce = $1.25 per square foot ($500 here) (average of various studies sourced below).
  5. If you don’t garden, you have to spend an extra 4 minutes per week on your grocery store trips at $10 per hour for the entire year (estimate).  (Looking back at this assumption, it is a little generous to the pro-garden argument.)
Sources and methodology:

The most comprehensive source is the OSU Master Gardener post I mentioned above.  Gail cites 6 different gardening studies.  Of those studies, I liked JD Roth and Roger Dorian’s posts the best.  I also explored one additional blog post from Sharon Rawlette to help with estimates.

Basically what I did with all these sources is that I inflated all the older studies’ costs and revenues up to today’s dollars.  Then I averaged the per square foot costs and revenues to come up with my numbers.  Each of these studies was done a little differently, which means there is some inevitable noise in the data.  I isolated a few of the studies to figure out one-time setup costs, and I got my time estimates from J.D. Roth, my own personal experience, and yahoo questions.

I tended to round up for most of theses variables, so the average annual running costs per square foot might have been $0.45 per square foot and the fixed costs might have been $0.06, but I rounded those to $0.50 and $0.10 because they are cleaner numbers.  Plus there was already a ton of variance between each study, and on top of that, a newbie gardener is probably going to be pretty cost-inefficient for the first few years.  My net yield numbers (revenue minus costs) are pretty much right in line with Gail’s calculated average of $0.74 (I’m at $0.75).

So there you have it.  Happy planting.

Update:

So, as I mentioned above, 400 square feet is a lot of space.  I would imagine there are some economies of scale with larger gardens, but there are also drawbacks that I didn’t quantify.

First, you may not have that much space.  Second, you might end up with way too much food and have to spend extra time preserving, pickling, canning, freezing, and/or fermenting your extra produce just so that none of your hard work goes to waste.  This could add a lot of time to your gardening endeavors on a per square foot basis, acting sort of as a reverse economy of scale.

So how about a smaller, 10×10 (100 sq. ft.) garden?  This seems like it could be closer to the right amount of food without having to preserve extras, and more realistic for first time gardeners.

Here are the numbers for a 100-square-foot garden:

roi - small garden

So the ROI doesn’t change; it is still a measly 37%, and now the dollar savings (including time costs) are even smaller.  For me this further strengthens the argument that, similar to brewing beer, you should garden because you like it, not because it will save you money.

For someone that doesn’t care about the time costs and simply likes gardening or wants to learn (or might even pay to learn), it saves closer to $100 per year on average.

I did tweak a few assumptions here besides the area of the garden.  I assumed that your time costs would increase 10% on a per square foot basis because of economies of scale (ex: still need a spade regardless of how big your area is), so 0.11 hours per square foot, or 11 hours for the year.  I also assumed that the alternative scenario of grocery store shopping time drops by about 50% because the equivalent amount of groceries needed to replace your garden produce is smaller.

Feel free to download the spreadsheet and mess with the numbers on your own because this is sort of a tricky one, but most of the signs point to a mediocre return on investment on a percentage and total dollar basis.

Should you change your own oil?
Less is more: spending less vs. earning more
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Comments

  1. eliot rosewater says:

    First: I think a 400 square foot garden would take up my entire backyard! 🙂

    Second: While I’m disappointed that gardening doesn’t have a higher ROI, I suspect that 6 hours of gardening still has a higher ROI than 6 hours of watching premier league soccer, alone, next to a space heater, in a damp basement.

    Thanks for the post. If this Winter ever ends, I’m thinking I’ll give the gardening a try. I’ll just try to think of it not as work, but as a combination of science project/sun-bathing.

    • Eliot, man you are right! I actually got out the tape measure just to try to wrap my head around the actual space required for a 400 square foot garden, and it is a lot! I reworked the post a bit based on your feedback, so thanks. 🙂

      I feel you on the gardening vs. doing something that doesn’t add a lot of value. I just have these bad memories of trying to find people to water our plants when we were gone and getting my work shoes all dewy and grassy in the mornings because I was running late but had to water the plants before I left. Plus sometimes you NEED premier league. That recharge time is important, at least that is what I tell myself after a lazy Sunday…

      Hang in there till spring, and if you do start gardening, I would love to hear how it goes!

  2. It’s more worth it the more space you devote to it, and the longer you do it. With decent native soil, if you start your own compost heap/vermiculture bins, you’ll never really need fertilizer aside from very occasional applications of remineralizer (azomite,greensand). The soil will get richer over time with application of compost, crop rotation, etc. Most vegetables can easily be grown from seed which is much, much, much cheaper than transplants. Salvaging assorted materials to use as containers or trellissing, etc. will save a ton. So, aside from a spade, hoe, organic pest control, and seed packets and a few transplants of the species that are difficult for amateur gardeners to germinate, what costs really are there aside from time?
    Some things like fruit trees take years to come to FRUITion, but after that they’re no real work at all, just harvesting.
    I’d like to add to that list of most worthwhile crops to grow, for the chefs out there, growing your own herbs, even if you have to get transplants is worth it, too. Many recipes just call for a teaspoon or so of an herb- but you have to buy the whole bunch at the store for $2-$3, and most of it will go to waste within a few days if you don’t use the rest of it in another recipe. The only problem with this is that most herbs will either die or at least all of their leaves in winter (aside from Rosemary in most US climates,) but there are now indoor lighted set ups that can grow enough of any herb you’ll need (they’ll keep growing back even if you pluck a few leaves,) and if you cook enough, you’ll probably make back the cost in savings within two years.

    • Yes, pretty much summarizes some of my thoughts, specially the longer you do it.
      It’s funny how most people I see start gardening with tomatoes, and If I ever wrote a book, my first advice for beginners would be, stay away from tomatoes, in the beginning! Tomatoes are difficult if you don’t have the experience yet (in my opinion, I know people will disagree), compared to, for example, arugula and chard. Arugula grows like a weed, produces the whole year (minus snow of course), and swiss chard is pretty resistant.

      My first year I’ve started a lot of tomatoes from seed and “killed” them. Pretty frustrating. Then I’ve planted some arugula and, oh boy, they just grow. They don’t mind if you water too much or forget to water, very easy.

      We’re plant based, so eat lots of greens and vegetables, so for us it’s a bigger savings/returns than most people; we don’t buy any meat or cheeses, but we buy greens on a regular basis, pretty expensive to buy it organic. And, you buy in bunches, have to wash it all, it goes bad if you forget to eat; now our garden has so much greens, chard, arugula, collards, green onions, leeks, that we save $10 to $15 bucks a week.

      We’re expanding and this year will add cabbage, beets and herbs. Herbs does cost at least $2 every time you buy and you have to buy a whole bunch, like mentioned above.

      Another great point, gardening doesn’t feel like work!

      Cheers everyone, and KEEP GARDENING! Grow your own food!

  3. Tim Mulherin says:

    I have a few things. We save our washed egg-shells over the winter and grind them up the day we transplant the tomatoes. We heard a rumor (after losing all our fruit to blossom end rot our first year) that the shells slow-release calcium, and that watering the tomatoes leaches calcium into the soil rather than washing it out. We experimented our second year, and after 13 years of experimenting, we had zero occurrences of this disease.

    Second, should you have a successful green bean harvest, you will never be satisfied with the quality of those you buy from the grocer. Most of the time the green beans I see at the store would have ended up in my compost heap. The flavor and texture of most of the vegetables that you eat right out of the garden simply cannot be compared to the produce found at the grocery store.

    Finally, you might also add health benefits to your calculations. From Michigan State University:
    “According to the Centers for Disease Control and Prevention (CDC), moderate-intensity level activity for 2.5 hours each week can reduce the risk for obesity, high blood pressure, type 2 diabetes, osteoporosis, heart disease, stroke, depression, colon cancer and premature death.”What are the physical and mental benefits of gardening?

    I’m not sure how to go about quantifying taste, texture, and health benefits, however they should add to the weight of your intangibles.

    • Well said! First year gardening, you pretty much “kill” a bunch of plants. There’s a learning curve, and, it will be worth it after 2 or 3 years.

  4. I grow in 200 sq feet of raised beds, in central florida. I work a full time job and I grow vegetables all year around(except July and aug, too hot!). I have plenty of delicious veggies to eat, can some and give away to friends. Although it may seem like the cash value isn’t there, the benefits to your health cannot be gauged by any dollar amount. It is a trial and error at first, but with lots of reading, watching videos and perseverance success will come. The magic is all in the dirt.

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