Tuesday, December 11, 2012

All Purple Sweet Potato

Along with all the other contributions that have been made to the gardening world by Southern Exposure Seed Exchange (SESE), the All Purple Sweet Potato has been a wonderful addition to gardens around the United States that would not have been made possible without the desire of those at SESE to trial and distribute the most hardy, adaptable vegetable seeds and starts. SESE selected the All Purple Sweet Potato from other purple varieties because of its ease to sprout and to produce hardy slips; these are two very important factors that made it impossible for me to produce slips from the purple-fleshed Okinawan sweet potato.

Purple Sweet Potato Slips

All Purple Sweet Potato Leaves

The moderate vining habit and beauty of the All Purple Sweet Potato lends it to planting as a groundcover below taller vegetables. The tight overlap of leaves is thick enough to keep soil moisture relatively high, even in my desert garden. The beautiful white and purple flowers attract plenty of bees and would be a fine complement for any flower bed. The main problem I encountered with the vines is that, once slips are established, there is little to be done until it is time to harvest. My experience with sweet potatoes in the hot desert is that they are extremely low-maintenance crop.

Bees enjoy the flowers of the All-Purple

One of the few roots growing near the surface of the ground
The roots of the All Purple tend to grow long before they grow stalky. I would take caution to plant this variety in their deepest beds as their length lends them to be slightly brittle and set deeper than many orange varieties. I had difficulty finding some of the longer roots near the bottom of my 24 inch deep beds. As with other sweet potatoes, this variety did not require much input, other than deep organic soil and consistent watering. In mid summer I watered my garden roughly 3 times per week on a soaker hose for 3 hours at a time. Planting of slips began in late April and vines were removed for harvesting on November 12th, shortly after a very light frost burned the tips of some of the leaves.
A slight frost and a free day allowed time to clear the vines for harvest

I was humbled and blessed with a very decent harvest. Over the course of several weeks I harvested over 70 pounds of purple potatoes. Although the harvest, per slip, was not as vigorous as my orange variety, it was very much worth the wait. Because I use my sweet potatoes more as a ground cover than a main crop – which led to the vines getting less than adequate sunlight - I was glad to see that the slips had done well.

I just love the cross-section of this picture!

A bucket while harvesting Purple Sweet Potatoes

Large All-Purple Sweet Potato

This root was too heavy to weigh with the others

Most of the All Purple Sweet Potato Crop

When cutting into the All Purple Sweet Potato the first thing I noticed was that many of the roots are not purple all the way through. Minor streaks of white do make their way through many of the tubers – though I am not sure if this is something that can be selected for. The reason why this I’m a little unsure about selecting for the “complete purple” trait is that many of the potatoes will have a lighter interior on one side of the root and a darker interior on the other side. When I cook the potatoes with the skin washed (not peeled) most of the white tends to disappear and I am left with dark purple steamed potatoes.

Minor streaks of white

A typical cut Purple Sweet Potato

Purple Sweet Potato Slices

Steamed Purple Sweet Potato

So what, do you ask, do the All Purple potatoes taste like? The flavor is reminiscent of the blue “tanginess” you encounter when biting into a blueberry – but not as sweet. As noted on SESE’s description of the All Purple, the roots are “starchy, dry, slightly sweet (and) good for storage…” They tend to be “good in savory dishes and mixed mashes”. I used some of the more perishable roots to bake some one pie for a potluck at TOG (Tucson Organic Gardeners) and to bake a couple more pies for dessert at Thanksgiving.

Cooked Purple Sweet Potato

One of my Purple Sweet Potato Pies - Yum!

Above all other reasons I believe gardeners should flood SESE with orders for their All Purple Sweet Potato slips is the fact that these roots are plain cool. They are purple, and apparently the anthocyanin - the chemical that makes them purple - is really healthy for you. While researching anthocyanin I came across a comment that noted that the anthocyanin chemical acts a bit like a crude pH meter. The color of the purple juice extracted by purple crops will turn from purple to red in the presence of lemon juice and from purple to green in the presence of baking soda. So of course I had to try it and guess what? It works.

Anthocyanin 1 minute after adding baking soda and lemon juice

Anthocyanin 15 minutes after adding baking soda and lemon juice

To summarize, Purple Sweet Potatoes – especially the All Purple – are cool and easy to grow. Though they neither paid me nor bribed me to say so, Southern Exposure Seed Exchange is a fantastic company. Including this sweet potato variety, they are often on the cutting edge of reliable and productive non-patented open-pollinated vegetable cultivars. The staff at SESE know their customers and provide them with great products. If you already have your garden favorites I would encourage you to try something a little different. Perhaps you’ll decide to add a bit of flamboyance to your life this summer by adding some more purple to your garden.

Proliferators of Purple Potatoes: Here are two other companies that sell Purple Sweet Potato Slips:

Duck Creek Farms and Sand Hill Preservation Center each sell 3 purple skin/fleshed varieties.

Additionally, Kerr Center did some trials with several of these Sweet Potatoes.


  1. A lot of what we enjoy eating is affected by color and our preconceived notions of what color something should be. So I just have to ask. What was the response at TOG? Did you bring any of that pie home?

    1. Dear Southernruralroute,
      I was told be members of TOG that they enjoyed it a lot. My wife loved the two purple pies we had for Thanksgiving and couldn't stop talking about them. I really work hard to grow things my family enjoys so it was really nice to have my family enjoy the pies so much. (=

  2. I will check them out...love my purple potatoes and love sweets so this is perfect!!

    1. Thanks for the response, Donna. I hope you do check them out - these potatoes are delicious.

  3. We have a sweet potato variety almost the same in morphology as that, although it might not be the same variety. I guess yours is a hybrid. We have many varieties, but i always look for that one because of its taste, texture and absence of latex when cooked. I just fork-prick it and microwave with turning, and eat as is. I love it with coffee. I guess i also prefer the anthocyanins than the beta-carotenes, haha! But i envy you because i cannot plant it in our garden as ours is mostly shaded.

    1. Dear Kalantikan,
      Thank you so much for your response. I have never heard of sweet potatoes producing latex. That is something completely new to me.

      The purple variety that I grow is not a hybrid. It is definitely open-pollinated. I'm sorry to hear that your garden has so much shade. I'm sure there are many other things that you can grow.

      Do you have many fruit trees?

  4. Oh your pies look very yummy-licious. There are a few purple sweet potato variety here I think some can be a bit starchy compared to the common oranges one.

    1. Thank you so much for the comment. They were great. Hopefully I can get some people to buy my potatoes! (=

  5. My daughters saw the purple sweet potatoes and were thrilled. Thanks for the great info on growing them. We'll be buying some slips to try this year. We grew sweet potatoes for the first time last year to great success. My husband is looking forward to a purple pie.

    1. Thank you so much for the compliment, Mia,
      I hope you do enjoy growing some purple sweet potatoes! The variety I tried did quite well and I hope you have fun growing the purple sweet potatoes. It is so fun to try different colors and different tastes. Everyone who has tried my purple sweet potato pies wants more. For me, these were a blast!

      Best wishes with your gardening this next year!

  6. What scale is that above? I'm in the market. Beautiful taters.

    1. Thank you for the question and compliment, Somnium. I happened to get it for $20 on clearance at Big 5 Sporting Goods. I had been looking for a while and happened to find this one. The power required is minimal and I have never had to change out the two AA batteries. As I have never had a single problem with it, I would definitely recommend purchasing a Sharper Image brand digital scale.

  7. I've been growing SP's in Tucson for awhile but I actually grow them for the foliage, which is a vigorous and highly nutritive crop. Eat the leaves! There is so much more you can get out of this plant than just tubers! Another great one in this respect that does fine in our climate is the chayote squash. They are viviparous seeds so must sprout within the fruit before planting. All parts are edible.

    1. Dear Ming,
      Thanks for the response!

      I have tasted the leaves. They are alright though they are a bit more like beet greens than spinach. I have not tried growing Chayote yet, though I have heard it is good for eating. How long can Chayote store in the winter time? How many years does it take for the roots to become well enough established to come back in the spring? Have you ever grown Chilacayote?

  8. hi i am in winnipeg canada. i have a purple sweet potato that i grow in my garden and i have been trying to figure out what variety it is. i noticed you have grown several purple varietys and was hoping you may recognize it. i posted several pics of this variety a couple days ago on my facebook if you would have the time to have a look---https://www.facebook.com/billy.pchajek/posts/10153883871712845?pnref=story

    1. Thanks for the link and the pictures, Billy. Those are some fun pictures. If you haven't already noticed - the sap will stain all clothing!

      Sweet potatoes can be beautiful, delicious and fun. However, productivity is often better realized at lower latitudes. Because of a number of factors, including latitude, my small garden produced over 175 pounds of mostly purple sweet potatoes last fall. Now that I am living in California, I only have a pot with 2 struggling plants left. Hopefully they will rebound in the spring!

  9. Hi Jay, Such an interesting read! I'm trying to keep my recently harvested (first time!) sweet purple potatoes until Jan/Feb to use them to make slips but they are already growing slips in November! I keep them indoors in semi lighted area of a room at about 70 degrees F. I’m fraid the tubers will die if they grow slips now which I can’t yet plant in the soil. Any help appreciated.
    Kind regards,

    1. Dear Anne,

      That is a really good question. Where do you live? In the northern hemisphere you can keep slips alive like you would house plants for a while with a lot of light, but the best way to keep potatoes over the winter is to have a healthy tuber or potato in storage. If the tuber is long and narrow it will not last long, but if it is thick and round it should last a while packed with newspaper in a small box. Indoor slips/plants tend to get thin and spindly if left inside too long, but you can always try.

  10. We recently tried purple sweet potatoes and my husband enjoyed them so much we are going to attempt to grow them. Thank you for the info on them.


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