Okinawan purple sweet potatoes


Hi. How hard is to grow them in Toronto? If I can grow them here, can you give me a time frame from start to finish (eg, time of year to plant, time period from from water to soil). Most importantly, where can I get the slips? I can not even find the potatoes in the stores. The purple ones seen in grocery stores are varieties i don’t want. thanks!


Okinawan sweet potatoes (Ipomoea batatas) belong to the morning glory family.  The skin of this sweet potato is thin and edible, while the interior is purple, from antioxidants called anthocyanins.  Despite its name, your sweet potato is native to the Americas – a few hundred years ago it became popular in Japan and Hawaii.

The Okinawan sweet potato is grown like other sweet potatoes, from slips, or live cuttings that can be transplanted in the ground.  The slips would be planted after all danger of frost has passed (in Toronto, usually mid to late May).  Of note, the plant requires a long and hot growing season – it may take from 120-180 days from planting to harvest.  It needs full sun (at least 6 hours a day) and well-draining soil that is (ideally) slightly acidic (pH from 5.5-6.5).  The vine would be considered an annual if grown in Toronto, and it’s not clear if our summers are long or hot enough to allow the plant to grow to the point where it would yield a crop of sweet potatoes large enough to eat.

The plant is recommended for USDA Zone 6b or warmer — so growing it in Toronto is pushing the envelope, as our climate is usually considered Zone 6 (USDA Zone 5) – although there are pockets where zones may be warmer (a higher number).  See Ask a Master Gardener’s Plant Hardiness Zones. The plants have little resistance to cold weather – during cold snaps, they would require protection.

We’re not permitted to recommend sources of plants, however I can suggest that you search the internet using terms like “sweet potato slips Canada” (or Ontario).  As well, check on-line Canadian seed catalogue companies – they may sell slips.  If these companies don’t offer slips, I’d suggest that you contact them directly to see if they know of a supplier. You may even find a few US companies during your search, they may have information about Canadian suppliers.  Note that US companies won’t be permitted to ship slips across the border.

Here are some helpful links:

All the best in growing these elusive sweet potatoes!