Grow Sweet Potato Slips from a Grocery Store Spud

I spent actual money on certified sweet potato slips my first year. Real dollars, at a nursery, for little rooted cuttings in a plastic tray. They were fine. Also completely unnecessary, which I did not figure out until my neighbor showed me a mason jar on her windowsill with a sweet potato hanging in it like some kind of botanical science fair project. That was the last time I bought slips.

Growing sweet potato slips at home from a grocery store sweet potato is genuinely one of the cheapest things you can do in vegetable gardening. One sweet potato, a couple of toothpicks, a jar of water. That’s the whole budget.

Pick Your Potato

Grab a sweet potato from the store. Organic is better here, not for any wellness reason, but because conventional ones are sometimes sprayed with a sprout inhibitor. Which, if you think about it, is exactly the opposite of what you need right now. One medium sweet potato is plenty. You’ll get more slips than you expect.

Worth knowing: the eyes and buds come primarily from the stem end of the tuber, where the cambium layer is most active. The narrow end. Worth orienting that end upward.

Two Ways to Get It Started

The classic move is the toothpick method. Stab four toothpicks into the middle of the potato at even angles, suspend it in a jar so the bottom half sits in water and the top half doesn’t. Keep the water topped up. That’s it.

The other option, which I actually prefer, is burying the bottom half in a small pot of moist potting mix. Less mess than a jar, less water to remember to change. Either way works. The potato doesn’t care about your aesthetic preferences.

Keep It Warm

This is the part most people skip and then wonder why nothing is happening. Sweet potatoes want 75 to 85 degrees to wake up. Your kitchen counter in a grey Pacific Northwest May probably isn’t getting there. On top of the fridge works surprisingly well if your fridge vents heat from the back. A seedling heat mat under the jar is even better and will basically pay for itself after one season of not buying slips.

The science-y bit: auxin and cytokinin ratios in the tissue start shifting once the tuber gets consistent warmth, which is what triggers bud break. The potato’s internal alarm clock doesn’t go off until it’s warm enough. So if nothing’s sprouting after two weeks, check your temps before you give up.

Plan for 4 to 6 weeks. I know. It feels like forever. Stick it somewhere warm, ignore it mostly, and let it do its thing.

Twisting Off the Slips

When a sprout hits about 6 inches with a couple of real leaves on it, it’s ready. Grab it near the base and twist gently. It’ll pop off clean. Don’t cut them, twist. The slight wound actually helps with what comes next.

Here’s where a tiny bit of plant biology earns its keep: when you twist off a slip, the cut end will start to suberize within a day or so. That’s the plant forming a protective layer over the wound. Rooting in water actually works better after that little callus forms, which is a great excuse to leave the slips on the counter for a day before you dunk them. I skipped this step the first time I tried it. The roots still showed up, just slower. So. Now I wait.

Then drop the slips in a glass of water, just the bottom inch or two, and put them somewhere bright. Roots show up in about a week. You’re looking for roots at least half an inch long before these go in the ground.

One potato can throw 8 to 12 slips over the course of the season if you keep it warm and keep pulling them. That’s a lot of free plants from a vegetable that cost less than a dollar.

Getting Them in the Ground

In Redmond, late May to early June is about right. Sweet potato roots don’t really get going until soil temps hit 65 degrees consistently, ideally closer to 70. Planting into cold soil just makes the plant sit there looking sad, which I can relate to but prefer not to enable.

Raised beds warm up faster. Black plastic mulch warms them up faster still and I have used this trick shamelessly for years. Plant the rooted slips a few inches deep, water them in, and then mostly leave them alone. Sweet potatoes are not needy once they’re established. They’re the opposite of needy. They’ll take over if you let them.

Anyway. One grocery store sweet potato, a jar, some toothpicks, and a warm spot. That’s the whole system. I yam not kidding when I say it’s the cheapest sweet potato planting on earth.

(Couldn’t help myself. Sorry.)

Photo by Bekky Bekks on Unsplash