Friday, November 30, 2012

What size garden do you need to grow all of your own food?

Harvest of green beans and cherry tomatoes, May 2012
Threats of economic downturn, shaky international relations, water shortages, unsustainable farming practices, climate change, genetic molesting of crops, and a dwindling supply of cheap oil have changed the way a lot of Americans look at their breakfast, lunch, and dinner. Many seemingly average citizens have begun to narrow their eyes at the Peruvian labels on their asparagus and then look up to gaze out of the window at the few hundred or more square feet of useless green stuff that they’ve been needing to mow. It dawned on a few that where there’s grass, there’s dirt, and one of the first things an aspiring food gardener wants to know is how much food can I really grow in my little yard, and could I really grow all of my own food and never have to step foot in another grocery store?

First of all, let’s ask the right question. A "garden" grows things like tomatoes, peppers, broccoli, lettuce, etc. The typical suburbanite is not growing wheat and raising cattle. There could be a few fruit trees and a chicken coop out back, but I think the question we can feasibly address is “how big of a garden do I need in order to grow all of my family’s vegetables.” Unless you are a strict vegan you will not be eating solely out of your backyard (even vegans need a source of nuts and oils if they aren’t growing these in addition to vegetables). I’m happy to purchase meat and eggs from local farmers. I also buy oils, nuts, and some fruits from the local food co-op or grocery store (I will get into homegrown fruits in a future post). What I really want to know is how much land would it take to eliminate imports from my household’s vegetable intake.

I’ve spent a lot of time rummaging through articles on the internet trying to figure out what size garden I might need if I wanted to (gasp!) grow all of my family’s vegetables. An unofficial survey of authors and internet gurus gave me widely varying estimates from a few hundred square feet to an acre or more for the average person. There is obviously little consensus, but more importantly, no one was really answering my specific question. A lot of people are talking about how much land is required to provide ALL of the food for a person or family. Being such a commonly pondered question I think it deserves some mathematical/scientific analysis, not another wild guess.

Let’s answer it once and for all.

There are a few things to consider to make these equations work for your own situation. First, how many people do you plan to feed (# people in your household)? That should be an easy answer. Second, how much vegetable matter does your household consume in a year? This is a pretty overwhelming question, so we will need to break it down.

The American Cancer Society says we should be consuming about 5 servings of fruits and vegetables per day, but disregard recommendations for this. Think about your average day. Do you have any vegetables at breakfast (spinach in your frittata)? What about for lunch (leafy salad with tomatoes)? How many servings of vegetables do you usually serve for dinner? Don’t be too critical here. Just try to average it for the day. It’s likely that not everyone in your family is consuming the same amount, so figure out the number of servings consumed by each person individually. Maybe you have 5 servings per day, your spouse has 3 servings, and maybe each of your kids have 2 servings. Add these together so that you have the total number of vegetable servings consumed in your household per day.

I tried to keep it simple for my own estimation. There are two of us in the Suburbindigenous household, and I would like to provide us with 5 servings of vegetables per day each, which is 10 servings per day for the household. The next step is to convert “servings” to a unit of weight, which will help us compare to the yields in the garden. The USDA says that an average serving of vegetables is 4 ounces. I’m sure there is some variation, but this is an estimation, not a space shuttle trajectory. So, simply take your household consumption of vegetables in servings per day and multiply by 4. Now you have the total number of ounces of vegetables consumed in your household per day. Multiply by 365 to get the number of ounces of vegetables consumed by your household in one year. To simplify, divide by 16 to convert this to pounds (there are 16 ounces in a pound). Your math should look something like this:

daily household servings x 4 oz x 365 days
                    16 oz

= pounds of vegetables per year

My number is 912.5 pounds per year. The next thing to do is to list all of the vegetables that your family would like to eat that will grow well in your region. Here’s my list...

  1. tomatoes
  2. peppers
  3. summer squash
  4. winter squash
  5. pumpkin
  6. lettuce
  7. kale
  8. chard
  9. broccoli
  10. kohlrabi
  11. cauliflower
  12. carrots
  13. beans
  14. peas
  15. celery
  16. beets
  17. okra
  18. sweet potato

Notice I left off any herbs or onion family crops. I use them more for flavoring and accents than actual servings of vegetables, but if you eat a lot of onions maybe you should put them on your list.

I have 18 crops on my list, so the first thing I did was take the total number of pounds of vegetables needed for my household and divided by 18:

912.5 pounds per year  = 50.7 pounds of each crop 
       18 plants

I'll round down to 50 for simplification.

This means I could grow 50 pounds of each of these crops and be able to feed my family with vegetables for a year. But how much space do I need to grow 50 pounds of okra or 50 pounds of peas? I thought you would ask that.

For the next step, we need to determine the approximate yield per plant for each individual crop. I just did a Google search for each one and found most of my answers in gardening forums and Q&A sites. Remember, this is just an initial estimation. I will tell you how to fine tune it at the end. Here are the results of my yield-per-plant research:

  1. tomatoes: 10 lbs/plant
  2. peppers: 2 lbs/plant
  3. summer squash: 5 lbs/plant
  4. winter squash: 10 lbs/plant
  5. pumpkin: 10 lbs/plant
  6. lettuce: 1 lb/plant
  7. kale: 1 lb/plant
  8. chard: 1 lb/plant
  9. broccoli: 1 lb/plant
  10. kohlrabi: 1 lb/plant
  11. cauliflower: 1 lb/plant
  12. carrots: 1/4lb/plant
  13. beans: 2 lbs/plant
  14. peas: 2 lbs/plant
  15. celery: 1 lb/plant
  16. beets: 1/4lb/plant
  17. okra: 3 lbs/plant
  18. sweet potato: 2.5 lbs/plant

You might have already figured out the next step. Figure out how many plants of each crop you will need in order to achieve the desired yield. Simply take the number of pounds desired divided by the pounds-per-plant yield. For example:

50 pounds of tomatoes desired   = 5 plants needed
10 pounds of tomatoes per plant

I am aiming for 50 pounds of each crop, but your number is probably different than mine, so make sure you do the calculation for yourself. Here are my numbers:

  1. tomatoes: 10 lbs/plant...5 plants
  2. peppers: 2 lbs/plant...25 plants
  3. summer squash: 5 lbs/plant...10 plants
  4. winter squash: 10 lbs/plant...5 plants
  5. pumpkin: 10 lbs/plant...5 plants
  6. lettuce: 1 lb/plant...50 plants
  7. kale: 1 lb/plant...50 plants
  8. chard: 1 lb/plant...50 plants
  9. broccoli: 1 lb/plant...50 plants
  10. kohlrabi: 1 lb/plant...50 plants
  11. cauliflower: 1 lb/plant...50 plants
  12. carrots: 1/4lb/plant...200 plants
  13. beans: 2 lbs/plant...25 plants
  14. peas: 2 lbs/plant...25 plants
  15. celery: 1 lb/plant...50 plants
  16. beets: 1/4lb/plant...200 plants
  17. okra: 3 lbs/plant...17 plants
  18. sweet potato: 2.5 lbs/plant...20 plants

That is some great data right there. We are getting so close! Now that we know how many plants we need we can use plant spacing data to determine the number of square feet needed to grow this many plants. You can consult any seed packet for row spacing requirements, but I prefer Mel Bartholomew’s square foot method spacing. It will make this step a lot easier, too. If you don’t want to buy his book there are plenty of forums and websites that will tell you the square foot spacing for each crop. If you are using any of the crops on my list I’ve done the work for you:

  1. tomatoes: 1 plant per square foot
  2. peppers: 1 plant per square foot
  3. summer squash: 1 plant per square foot
  4. winter squash: 1/4 plant per square foot (i.e. one plant needs 4 square feet)
  5. pumpkin: 1/4 plant per square foot
  6. lettuce: 1 plant per square foot
  7. kale: 1 plant per square foot
  8. chard: 1 plant per square foot
  9. broccoli: 1 plant per square foot
  10. kohlrabi: 1 plant per square foot
  11. cauliflower: 1 plant per square foot
  12. carrots: 16 plants per square foot
  13. beans: 9 plants per square foot
  14. peas: 16 plants per square foot
  15. celery: 1 plant per square foot
  16. beets: 9 plants per square foot
  17. okra: 1 plant per square foot
  18. sweet potato: 1 plant per square foot

Next, simply divide the number of plants you need by the number of plants per square foot to get the number of square feet of space required for each crop. For example:

     5 tomato plants       = 5 square feet
1 plant per square foot

  5 winter squash plants       = 20 square feet
.25 plants per square foot

Here’s my list:

  1. tomatoes: 5 square feet
  2. peppers: 25 square feet
  3. summer squash: 10 square feet
  4. winter squash: 20 square feet
  5. pumpkin: 20 square feet
  6. lettuce: 50 square feet
  7. kale: 50 square feet
  8. chard: 50 square feet
  9. broccoli: 50 square feet
  10. kohlrabi: 50 square feet
  11. cauliflower: 50 square feet
  12. carrots: 12.5 square feet
  13. beans: 3 square feet
  14. peas: 3 square feet
  15. celery: 50 square feet
  16. beets: 22 square feet
  17. okra: 17 square feet
  18. sweet potato: 20 square feet

We can finally add these numbers together to get a total number of square feet required to feed your family vegetables. My number is...drumroll please...507.5 square feet! That's actual growing space (not including pathways).

While you may find this number useful, don’t stop here! Go back and review your calculations and consider adjusting your initial assumption that your family would really want an equal amount of all of the crops on your list. I will be doing this for myself. I know, for example, that my family would want a lot more tomatoes and probably a lot less chard. Just make sure that your total number of servings equals the number your family consumes for the year and re-run the numbers. Maybe space-saving is important to you, and you now realize that you can get a lot more peas for a lot less space than, say, cauliflower. In that case you might adjust your numbers to grow crops that have a higher yield in less space.

Another thing to consider is how many possible growing seasons you have in your region. Remember my number? 507.5 square feet. If I lived in Maine, I would probably need a garden that had at least 507.5 square feet of growing beds. Luckily, I am in the subtropics, so I can really have 3 growing seasons. I can grow a crop from about September to December, another from December to March, and another from March to June. July and August is not a good time to be in the garden around here...that goes for people and for plants. Now watch what I can do...take 507.5 and divide by 3. That means I really only need about 170 square feet of growing space!

Remember I said I’d tell you how to fine tune your math a little more? I think the most variable part of our estimation is the “yield per plant”. Not only did it come from a non-scientific source, but it also can vary greatly based on your region’s climate, your gardening methods, and your skill level. The data we gathered was a quick way to get us close, but to have a better grasp on how much space you need will take time and record-keeping. Keep a garden journal (or, better yet, start a blog!) and track how many plants you grew and how much produce you harvested. After a season or two you will have a much more accurate “yield per plant” figure for each crop and can modify your calculations and your garden plans accordingly.

You do have a few choices now.

You could go out and dig up a space in your yard to accommodate the exact number of plants calculated. If you think gardening is that precise, you will probably be disappointed. Pests, disease, windstorms, and family emergencies happen. If you want to ensure you are able to grow all of your family's vegetables you will need to plant a little extra of everything. I'd say grow at least 10% more than the number you calculated. You should also consider making room to grow some herbs and onions for flavoring your food. These are some of the easiest things to grow.

You could choose to dig up less than your calculated number. Maybe your goal is to grow 50% of your family’s vegetables. Maybe you only have room for 10%. At least now you have an idea what 10% of your family’s veggie needs are.

Maybe you actually want to produce more vegetables than your family can consume in a year so that you can preserve food for the future or give some away to family, friends, and charities. Whatever you decide to do with your number it’s a place to start, and starting is half the battle!

I know this was a long post, but I really thought others would benefit from this analysis. Hopefully, you found it helpful!

Saturday, November 24, 2012

State of the Garden #3

As much as I enjoy sharing my journey with you, I must say I would rather be outside pulling weeds right now. Days like today are the reason why snowbirds and tourists flock to Florida in numbers so great that the state government is able to cut us some slack and not collect state income tax. Gotta love 72 degrees and mostly sunny in late November! I am making this monumental indoor sacrifice for you because if I wait until this evening I won’t remember everything I just spent an hour looking at and taking pictures of. So, here we go! 

I don’t think I’ve mentioned the strawberries in previous posts, but here they are. These are a "June-bearing" variety called ‘Sweet Charlie’ that I bought mail-order as crowns and planted in early October. This is my first time growing strawberries, so I’m not quite sure what to expect. Right now I just have 5 plants in containers, but if they do well I will increase production.

'Sweet Charlie' strawberries

Ground cherry update! I have little “lanterns” coming in! What a fascinating little plant. I can feel the little fruits growing inside the husks with a light squeeze, but I am not supposed to pick them. I read that they are only ripe when they fall off the plant (hence the name). Because they are on my front porch I am able to see them every day and watch for the fruit to fall. If you wonder why gardeners are so patient, a lot of times it is forced.

'Cossack Pineapple' ground cherries
Speaking of ground cherries, I need to clear something up. In my last garden update I said that I had four ground cherry plants in containers. Well, I lied, but not on purpose. I have been wondering why three of the plants were starting to form the little lanterns while the fourth wasn’t getting passed the flower stage. The other day as I was walking up to the porch I stopped and stared for a second at the stubborn fourth plant and realized…it’s not a ground cherry! I guess I had mistakenly planted a tomatillo in one of the pots. When the plants are small they are kind of hard to tell apart, but at this stage it is obvious. Can you tell which one of the three in the picture is a tomatillo and not a ground cherry?

Two ground cherries, a tomatillo, and a Golden Retriever :)

Sad update on the little fig that you’ve been hearing about since the first garden update…it did not make it. For the second time now, the fig tree is being attacked by some kind of rust/fungus. I sprayed it with an organic copper fungicide last week, but it still looks pretty sad. You can see all the spots on the leaf in the picture. I’m hoping it will spring back like it did when this happened a few months ago.

Rusty, fruitless 'Brown Turkey' fig

This little confession goes to show you that this blog is about reality, not idealism. I think spending too much time looking at shiny garden catalogs where blemishes and pathogens are “Photoshopped” out is sometimes as dangerous to your self-esteem as looking at fashion magazines flaunting emaciated supermodels with unnaturally flawless skin. Don’t fall for the lie that to have a “green thumb” means that no plant in your care will ever die or get sick. Gardening is a lifelong learning process. If you want to have a greener thumb...learn from your mistakes, celebrate every single success, and be annoyingly persistent. That’s my sage garden advice for the day J

Speaking of not-quite-successes, I thought I would give an update on my “two sisters”/bean-banana project. The beans are growing pretty well (considering it is late November), but they are having a hard time using the banana plant for support. Pole beans like something skinny to climb on like a thin trellis or string. I think I will tie somewhere high on the banana plant and then anchor the string to the ground to give the beans something to grow on. Without it they are going to be flopping all over the place. The picture below is the largest of the bean plants and you can see it already falling over having given up on the banana “trellis” that I provided. Live and learn.
'Kentucky Wonder' pole bean and 'Ice Cream' banana plants

On to the vegetable garden…lots going on here! Here’s an overview shot of all three beds (looking to the north).

The veggie beds, looking north

The other day I thinned out the carrots to about 1” apart. Next to the carrots are the leeks, scallions, and ‘Granex’ bulbing onions. They all seem to be doing well.

Carrots (left 3 rows), leeks, scallions, onions (right)

The romaine lettuce is filling in nicely. I tasted a leaf yesterday, and it’s very good! The cool weather keeps the leaves from turning bitter. I could probably harvest the lower leaves now, but I think I will let the plants grow a little bit more.

'Sweet Valentine' romaine lettuce
This is a close-up of the purple kohlrabi. You can see the base of the stem starting to thicken up. They should be nice and fat in a few weeks!

'Purple Vienna' kohlrabi

The broccoli is getting really big. I hoped to have a harvest for Thanksgiving Dinner, but they are still at the leaf stage. I expect to see heads forming any day now. One of the two varieties I'm growing is called Veronica Romanesco, which I learned recently is actually considered to be a cauliflower. It looks like something from another planet, but I guess it does look more cauliflower-ish (except that it's green). I grew it once before, and it was the best tasting broccoli/cauliflower I’ve ever had. The other one I’m growing is a “normal”-looking heirloom broccoli called De Cicco.

'Veronica Romanesco' and 'De Cicco'

Last in the “cool-season crops” bed is the Swiss chard and dinosaur kale. Both seem to be doing well. I might start harvesting the lower leaves of the kale this week.

'Rainbow' Swiss chard and 'Lacinto'/dinosaur kale

The tomatoes, tomatillos, and peppers are putting out a lot of fruit! Everything is still at the green stage, but I’m looking at weeks, not months, until I can start harvesting juicy, red, homegrown tomatoes and bright, crunchy peppers…AND, I have bees! I was worried about pollination because I hadn’t seen any bees around, but now that the tomatillos are in full bloom there seems to be a constant presence of bees! They are so fun to watch and really make the garden come to life. On with the pictures…

Tomatillo fruit forming

Tomatillos in full bloom

Tomatillo flower and an adorable little bee!

'Supersweet 100" cherry tomatoes

'Cherokee Purple' tomatoes

'Amish Paste' tomatoes

'Yellow Pear' cherry tomatoes

'Brandywine' tomato

'Principe Borghese' tomatoes

'Gilbertie Paste' tomatoes

'California Wonder' bell pepper

'Jimmy Nardello's Italian" sweet pepper

'Chinese 5-Color' hot peppers

'Sweet Banana' peppers in bloom
The squashes seem to be hanging on for dear life after a heavy dose of neem oil. Squashes and melons are a real pain in the neck around here. Maybe they would be healthier in the spring when it’s warmer. I think I will give them a few more weeks, and if there is still no sign of fruit I may rip them out and plant more cool season crops in their place.

Squash bugs on yellow summer squash

Summer squashes, zucchini, and cucumbers

'Seminole' pumpkin growing up the trellis

'Queen Anne's Pocket Melon' about dead
Lastly, I thought I would mention two very unique edible plants that I’m growing in containers right now near the front porch. The first is Moringa, a small tropical tree with edible leaves, seed pods, and seeds. Its leaves contain twice the protein of yogurt, 4 times the calcium of milk, the potassium of bananas, the vitamin A of carrots, and 3 times the vitamin C as oranges. It also contains antioxidants, essential amino acids, and it is anti-inflammatory. Now THAT is a superfood! People are actually starting to cultivate the tree in Africa to help fight malnutrition. My plant is pretty small, so I’m not really getting a harvest yet, but I have pinched off a few leaves here and there to munch on. I think it makes a nice homegrown multi-vitamin.

This last plant is one I bought on eBay recently. It is botanically very interesting and was actually marketed on eBay as a bonsai plant. I don’t have much interest in bonsai (they are neat to look at, but not very functional), but this particular “bonsai” plant grows fruit! It is joboticaba (Myrciaria cauliflora). For you botany types, you might have a clue of what this plant looks at by its species name, “cauliflora”. A plant that is cauliflorous grows its flowers and fruits directly on the main stems and trunk rather than on new shoots. It makes for a very peculiar-looking plant. The fruit of jaboticaba looks and supposedly tastes a lot like grapes, and it grows into a small tree in zones 9 and 10. I know it will be a long time before I see fruit on my jaboticaba, but more than fertilizer and neem oil, growing fruit requires optimism and hope for the future.


A mature jaboticaba (from Wikipedia)