How to Grow Sweet Potato Slips (Easy Windowsill Method)

Start with a firm sweet potato that has clean, unblemished skin. Gary buys his from the local organic grocery so they have not been treated with a sprout inhibitor, which is the stuff that keeps store potatoes from waking up. An untreated tuber sprouts willingly.

You do not cut it or prep it in any way. One whole potato can throw off a dozen or more slips, so a single tuber is usually all you need for a home row.

Fill a shallow tray or a clear plastic shoebox with seed-starting mix. Lay the whole potato on its side and bury it about halfway, leaving the top ridge exposed. That partly buried tuber is the whole setup, no rooting hormone, no cutting.

This soil method is the one Gary recommends over the classic glass of water. In his side-by-side test the buried potatoes sprouted far more slips, and they got going weeks sooner than the ones balanced on toothpicks.

Set the tray on a sunny windowsill and keep the mix damp, never soggy. Sweet potatoes are tropical, so warmth is the real driver here. A spot that stays warm through the day wakes the buds up fastest.

No grow lights are needed for this. Give it bright natural light, mist or water the mix when the top starts to dry, and let the potato sit while it does its thing underground.

Over roughly six to eight weeks, green slips push up out of the buried tuber. Each little sprout with its own set of leaves is one slip. On the soil tray you get a flush of them, which is exactly why this method beats the water glass.

Let them run until they stand about six inches tall. At that height each slip has enough stem to clip and root on its own, and the potato keeps pumping out more behind them.

Once a slip reaches about six inches, clip it off right where it meets the potato with a clean pair of scissors. Then strip the leaves off the lower half of the stem so you have a bare length to sit in water.

Take as many slips as are ready. Cutting does not hurt the tuber, so it keeps sending up fresh shoots and you can harvest several rounds from one potato.

Drop each clipped slip into a glass or jar of water and set it back on the sunny windowsill. Keep the bare stem submerged and the leaves above the rim. Top the water up as it evaporates.

In about three weeks each slip grows a strong white root system. Rooting them in water first gives you a plant that takes hold quickly once it hits the garden, which beats planting a rootless cutting straight into the ground.

Once your slips have a good root system and the soil outside holds above 50 degrees with warm days settled in, they are ready to go. In most gardens that lands around the middle of May. Set each rooted slip into loose garden soil and water it in.

Sweet potatoes love heat, so let them run all season. They keep growing right up to the first frost, then you dig the tubers in fall, usually late September into October.