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This crop starts with a jar of water and toothpicks

Get sweet potato plants growing on your windowsill

Sweet potato sprouting in glass jar
This Garnet sweet potato has plenty of leafy sprouts and
pink roots. (Photos: Debbie Arrington)

Get going on your summer garden without getting your hands dirty. All these sprouts need is water, not soil.

It’s easy to grow your own sweet potatoes. In fact, you can start this favorite vegetable on your windowsill right now – without any seed.

Home gardeners can grow new sweet potato plants by sprouting a sweet potato tuber in water. All you need is a jar (with a mouth large enough to accommodate a sweet potato), toothpicks and a mature sweet potato.

The method is super simple: Stick the sweet potato in the jar. Position the sweet potato so that half of it will be below the jar’s rim (but not touching the jar’s bottom) and the other half above. Use three or four toothpicks stuck into the sweet potato to suspend it in that position. Fill the jar with water and place it in a sunny warm spot (such as a kitchen window). Then, wait. The sweet potato will start sprouting roots and leaves within two weeks.

It’s those leafy sprouts on top – called “slips” – that will become new plants. Let them grow out until they are at least 4 to 6 inches long. Each sweet potato will produce at least a half dozen slips.

When the slips are long enough, gently remove them from their mother sweet potato and root their stems in water, letting their leaves hang over the rim of a jar or dish. In mid-spring, those rooted slips will be transplanted into the garden or large pots outdoors.

In addition to giving you a head start on your summer garden, pretty sweet potato plants brighten your winter windowsill – and fascinate kids (and gardeners) of all ages.

In general, supermarket-bought sweet potatoes will work. The most popular varieties (all high yield) are Beauregard, Jewel and Garnet; they’re mild in flavor with yellow or orange flesh. Purple-fleshed Japanese sweet potatoes as well as white-fleshed sweet potatoes such as Hannah also can be started with this method.

First, remember sweet potatoes aren’t really potatoes; they’re members of the morning glory family. They even have trumpet-shaped flowers that look like lavender morning glories.

They’re also not “red yams.” That name was a century-old marketing gimmick to differentiate orange-fleshed varieties from the more common (at that time) white sweet potatoes.

Besides edible tubers, some sweet potato varieties such as Garnet also have edible leaves. (When cooked, sweet potato leaves taste similar to spinach.)

Sweet potato harvest
Since sweet potatoes like warm, loose soil, one way to grow
them is in a straw bale. These were harvested after growing at
the Fair Oaks Horticulture Center in 2018. (Photo: Kathy

Sweet potato foliage comes in several different shapes, from simple hearts to deeply lobed five-point leaves. Like squash, varieties may be vining or bush.

A native of Central America, Ipomoea batatas likes it warm (75 degrees and up is ideal), but can’t stand frost. So, young plants are transplanted outdoors after all danger of frost and when air and soil temperatures have warmed sufficiently. In Sacramento, that will be some time in May.

Depending on variety, sweet potatoes take 60 to 90 days (or longer) to form tubers. They prefer rich, loose soil and consistent moisture (not too wet, but never totally dry).

But that crop all starts with a sweet potato in a jar of water.


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Dig In: Garden checklist for week of Sept. 25

This week's warm break will revive summer crops such as peppers and tomatoes that may still be trying to produce fruit. Pumpkins and winter squash will add weight rapidly.

Be on the lookout for powdery mildew and other fungal diseases that may be enjoying this combination of warm air and moist soil.

* Late September is ideal for sowing a new lawn or re-seeding bare spots.

* Compost annuals and vegetable crops that have finished producing.

* Cultivate and add compost to the soil to replenish its nutrients for fall and winter vegetables and flowers.

* Plant for fall now. The warm soil will get cool-season veggies and flowers off to a fast start.

* Plant onions, lettuce, peas, radishes, turnips, beets, carrots, bok choy, spinach and potatoes directly into the vegetable beds.

* Transplant lettuce, cabbage, broccoli, kale, Brussels sprouts and cauliflower.

* Sow seeds of California poppies, clarkia and African daisies.

* Transplant cool-weather annuals such as pansies, violas, fairy primroses, calendulas, stocks and snapdragons.

* Divide and replant bulbs, rhizomes and perennials.

* Dig up and divide daylilies as they complete their bloom cycle.

* Divide and transplant peonies that have become overcrowded. Replant with "eyes" about an inch below the soil surface.

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