Growing Sweet Potatoes in My Northern Garden

A Deliberate Agrarian Special Report
Dateline: 20 October 2011

I grew this amazing 3-lb Beauregard sweet potato in my garden this year. It was one of the easiest things I've ever grown.

Sweet potatoes are rarely grown by gardeners in the northern latitudes. Fact is, I’ve been gardening for nigh unto forty years and it was only three years ago that the idea of growing sweet potatoes here in Central New York State seriously entered my mind. It was then that a friend of mine showed me some sweet potatoes he had grown. They were huge, beautiful specimens of the Ipomoea batatas and I was duly impressed. That was when I determined that I should grow (or, at least, try to grow) sweet potatoes too.

As is so often the case when I get it into my head to do something new, a couple years (or more) may elapse before I finally get around to actually doing it. Some further incentive along the way helps. The incentive for me to finally grow some sweet potatoes came earlier this year when I read This Article in Mother Earth News magazine. 


The author, Ken Allan, of Ontario, Canada is an authority when it comes to successfully growing sweet potatoes in the north. Mr. Allan wrote a whole book on the subject. Sweet Potatoes For The Home Garden : With Special Techniques For Northern Growers is a book that every gardener who loves sweet potatoes and desires to grow them should have in their personal library.

The Book
 

Ken Allan's 200-page sweet potato how-to manual was self-published in 1998. It is not available from Amazon.com and I’m sorry to say that it is not available from any U.S. garden catalogs that I am aware of. But it is available directly from the author (details at This Web Site), and that is where I got  my copy. If you get a copy of the sweet potato book, please let Mr. Allan know that you learned about the book from me.

Now that we have those introductory comments out of the way, I’d like to provide you with a select few quotes from Ken Allan’s book and tell you about my first sweet potato harvest.

The first thing we northern gardeners need to understand when it comes to growing sweet potatoes
(I assume you southern gardeners already know this) is that they are not grown, cured, or stored anything like the more common solanum potatoes (a.k.a., “Irish” potatoes or, as the old farm almanac editors called them, “murphies”). Here’s a quote from the book:
“When an experienced gardener uses knowledge of similar crops as a guide to growing sweet potatoes, the reward is a small crop of small tubers which have little flavour and which spoil sometime before Christmas. The potential, when you do everything right, is to have a large crop of the best sweet potatoes you ever tasted, with the additional bonus that, in conditions that are easy for the average gardener to supply, they keep better than any other crop.

Indeed, quite aside from eating quality and nutritional value, longevity in storage is one of the best arguments for making sweet potatoes a staple in the home garden. If this is counter to what you have read or observed about sweet potatoes, it is because the storage requirements of sweet potatoes are not generally known.”

I ordered sweet potato “slips” from Burpee. I chose the Beauregard variety because I liked the name and the description said that Beauregard is a large, very orange sweet potato. Slips are nothing more than short lengths of leafy stems that sprout and grow out of sweet potato tubers placed in water. They are totally unremarkable little pieces of vegetation, and it was hard to imagine that they would ever amount to anything much.

Nevertheless, I followed the directions for planting as given in the Mother Earth News article (and in the book). In time, the little slips grew to a dense tangle of vines.

 
I hoed up close to the fledgling row of vines with my Planet Whizbang wheel hoe as they spread out and did nothing else with them all summer. I didn’t even water them when we had a lengthy dry spell. The vines grew lustily; they dominated and suppressed virtually all weed growth. Which is to say that sweet potatoes are very easy to maintain and grow in the garden. I added no fertilizer to my soil and there were no problems with insects.

Come the first light frost this month (October) some of the vines suffered frost damage and I went looking for “the book” to see what I needed to do next. There I read...

"Sweet potatoes should never be allowed to cool below 50°F (10°C) and preferably not below 55°F, either in the garden or later in storage. This fact may dictate harvest time. Soil temperature usually drops to 50°F at the time of the first frost. Sweet potatoes don’t mature, they just keep on getting larger until the weather gets cool. Since expansion of the fleshy roots is most rapid in late summer and early fall, harvest should be delayed as long as the weather holds. They won’t do any growing at 60°F or below, however, so for those of us in the north there is little to be gained in leaving them in the ground past the second or third week of September (unless they are protected by a cold frame or some form of rowcover)."

It was October 10th when I read that and I hastened to put my soil thermometer to use. I was concerned that my soil temperature would be less than 55°, but it was 60°.   I commenced to dig....


Digging potatoes by hand with a garden fork is always hard work but it’s always downright satisfying when you uncover a lot of good potatoes and, boy howdy—did I find potatoes!




This is what the sweet potatoes look like with some of the earth around them removed.



I harvested four bread trays of sweet potatoes like shown here.

I had read something about properly curing sweet potatoes and found the full story on this critically important (but little understood) process in Chapter 10 of Ken Allen’s book:

"Curing sweet potatoes involves holding newly dug tubers at a fairly high temperature and humidity long enough for important physiological changes to take place: the skin becomes impermeable to moisture; cuts and scrapes scab over; starch is converted to sugar. The higher the curing temperature, the shorter the curing period. Optimum conditions are 85° to 90°F and 80% to 90% humidity for five to seven days. If the temperature is reduced to 80° to 85°F then the curing time can be doubled."

So proper curing is essential to long storage and  Mr. Allan explains what exactly makes this so...

"What happens during curing is that a layer of suberin forms in the skin of the fleshy root, enclosing each tuber in its own little organic plastic baggy. In suberization, starch is converted to unsaturated fatty acids which combine with oxygen to make suberin, a remarkable mixture of waxy substances which allows the tuber to breathe but which holds in almost all of the tuber’s moisture. Suberin, in combination with wound priderm (which forms a corky layer over wounds), seals in  moisture and seals out rot-producing organisms, thereby protecting against infection. Cured sweet potatoes do lose moisture but the loss is very slow. A properly cured sweet potato can sit at room temperature in the open air for several months and lose scarcely any weight."

Proper curing is also absolutely necessary if you want a truly sweet tasting potato— a natural malt-sugar sweetened potato.

Allan stresses that curing should begin immediately upon digging and he offers several ideas for how and where to get your just-dug sweet potatoes properly cured. He states....


"Gardeners who don’t have a climate controlled room will have to use some ingenuity to provide the warmth necessary for curing, and there are almost as many solutions to this problem as there are gardeners."

A climate controlled room could be nothing more than a spare bathroom or big closet in your house with a heating source and thermostat. But I have a small house with no room to spare. So my solution to the problem was a small chicken coop that I undertook to make several years ago and never finished. It was out behind my workshop, along with several junk lawnmowers, bicycles and other such items. I cleaned the chicken house out, put a small electric “milkhouse heater” inside and powered it with an extension cord out the window of my shop.
 

A milkhouse heater just inside the sliding door of this small chicken house took care of the heat source for my makeshift sweet potato curing kiln.


One end of my new “curing kiln” was completely open and I covered it with several layers of painter’s drop cloths, held in place with spring clamps. I placed my potatoes in plastic bread trays, stacked them in the kiln, and monitored the temperature with a digital thermometer (it's a handy tool to have on the homestead).
 

I closed in the end of the "kiln" with dropcloths.

A view behind the drop cloths, into the "kiln."
 

My kiln worked very well. The temperature fluctuated between 85° and 105°. After seven days I brought the warm potatoes into our house.

 

Kiln-cured sweet potatoes about to go into storage. Each of those egg baskets is holding 45 pounds of tubers.
 

That old wainscot cabinet is in our living room, just off the kitchen, and not far from the woodstove, which is our only source of heat. The temperature can really fluctuate inside our home on winter days. Hopefully that cabinet will do the job.

I packed 110 pounds of sweet potato tubers into the bottom of the cabinet.
 

My 110-pound sweet potato harvest stored away.
 

We have not yet tasted the potatoes. I’m giving them another month to cure in the cabinet. After we cook some up I’ll report back here with the taste-test results.

If those sweet potatoes do taste good and keep good you can bet I will grow them again in next year’s garden. If I decide to grow the Beauregard variety again I won’t have to buy my slips. I’ll simply grow my own. It’s easy to do and full details are in “the book.”


Thank you Ken Allan!

14 comments:

Matt B said...

Wow those look great. Bake one of those up and server with butter, sugar and cinnamon. Nothing better!

vdeal said...

Nice looking sweets there Herrick. I grew some last year and they were nice. I ordered mine from the Sand Hill Preservation Center since they have all kinds of heirloom sweet potatoes. They stress not planting them too early and that really worked out. Check them out.

Jeremy said...

Herrick, how many did you plant? Maybe the better question is how long was your row? I curious about yield.

Thanks,

Jeremy

Linda said...

Those look great! My question is the same as Jeremy's...

Robin said...

Wow, thanks for the information. I think I will give these a try next year. I wonder if the slips can be started from organic store-bought sweets. My favorite breakfast is a roasted or boiled sweet potato with butter and plain tart yogurt. Yum.
By the way, I am the woman who lives in a yurt. A few years ago I commented here about life in a yurt. Three years later it is still marvelous!

the canned quilter said...

My family always cured the sweet potatoes in the smoke house until it got cold enough to butcher.My father used to say that the sweet potatoes got his family through the depression. His absolute favorite was sweet potato pie.

Jason Barker said...

Another great post Herrick.Now I have another project to add to my gardening list for next year.

spiritedrose said...

I have grown sweet potatoes 2 years and this is the first I heard about "curing" them. I might give it a try next year on some of them. We just bring ours inside and keep them in a cool place next to the potatoes. They lasted just as long...

Thanks for the pictures and information. I grow Beauregards, and they are tasty. :)

I'm curious, how cold did your C. NY location get during the time the sweet potatoes were planted?

Has anyone tried starting sweet potatoes in a greenhouse and transplanting them when the weather warms enough?

timfromohio said...

I live in NEOhio and this year was my second growing sweet potatoes. To cure, all I did was place on an old screen door suspended between a couple of sawhorses in a detached garage - the temps probably did not get as high as recommended, but the sweet potatoes do eventually cure - I then put them in drywall buckets and store in the garage or basement - again, not as warm as the book recommended. We ate them all last year before any started going bad, so I'd definetly follow the higher cure temp. advice for max storage time.

Herrick - another benefit that I experienced this year (not last) was pretty purple flowers that developed on the vines late in the season. I planted on row, about 30 feet long and it wound up looking quite nice when the flowers developed. So, good eaten, easy to grow, and visually pleasing - what more could one want?

One final commment - my wife makes a sweet potatoes and onions dish that is outstanding!!! Roasted sweet potatoes and onions, some spices, a little olive oil drizzled over the top. If you get it just right, the onions will be slightly carmelized and the taste of the sweet potato combined with onion is delicious.

Herrick Kimball said...

Thanks everyone for all the great comments and suggestions.

I just went out and measured the row. It was 44 ft. long.

The vines never did make flowers. I think I got the slips planted a little late for that.

It did not get all that cold during the time the sweet potatoes were planted. Central New York can get quite hot during the growing season.

Robin,
Thanks for the yurt update. One of these days......

Anonymous said...

In my second attempt at sweets, I planted a 'bush' variety - Porto Rico. I couldn'y keep up with the weeding (other honeydos) and the mice tunneled in and ruined all the tubers of any size. Undiscovered until harvest. The little rats....

Paige said...

Sweet potatoes are awesome food! My sister-in-law spent some time in Paupau New Guine as a missionary and about 95% of their diet there consists of home grown pork and sweet potatoes. Sweet potatoes are the most nutritionally complete food that we can have, ranking up even higher than the rice and beans mix of South America--without all the threshing. Definitely a very nutritious food--even moreso that you grew your own! Great job!

Sylvie in Rappahannock said...

Herrick, your sweet potato curing house looks almost like miniature version of the sweet potato curing houses that used to be all over the south. They used furnace and fans then. One can still see remnants of them in some areas.

Charity said...

Hi there, I've been growing sweet potatoes for over 10 years in our garden, first in NH, now in Canada. I always started the little plants in pots in the greenhouse --and got some big potatoes (one was 7.5 lbs,but it wasn't a orange kind. BUT, they were always all twisted and funny shapes, not like Herricks! Last year, we learned from a Jamaican, they just plant the plants in the ground. And if you start them in a pot, they will always be convoluted! So, last year for the first time we did it direct in the ground, and got 3 lbs.Beuregard per foot of row, all lovely shapes. I admit, not all were huge tubers, some more carrot sized, but kept and tasted just fine!!