How to sprout and propagate sweet potatoes?

Originally tropical, the sweet potato (Ipomoea batatas) is a perennial with long creeping stems, grown as an annual in our climate for its tasty tubercules. Multiplying sweet potato by propagation by cuttings makes it easy to obtain several young plants from a single tubercule. Before that, it is essential to germinate the sweet potato to obtain the young shoots, also called « slips », which are then used for cuttings. Follow our tutorial: we detail steps to germinate then propagate sweet potatoes.

Step 1: germinate sweet potatoes

Why and when to germinate sweet potatoes?

Germinating a sweet potato produces shoots ready to be propagated by cuttings and later planted outdoors after frosts. This method is particularly useful when you want to grow sweet potato yourself and cannot find ready-to-plant young plants.

A few days are enough for shoots to appear. However, wait about one month before taking the stems for cuttings, which should measure around 10 cm. Start germinating sweet potatoes:

• from mid-January for planting around April in warmest regions or for growing sweet potatoes in a greenhouse.
• in February or March to produce young plants for planting in May in rest of country.

Materials required

• 1 healthy sweet potato, preferably organic. They can come from surplus of previous year’s harvests or be bought in our online shop: sweet potato plants.
• 1 glass, jar or flowerpot depending on method
• Toothpicks (for water method)
• Light, well-draining potting compost (for pot method)
• A bright, temperate spot

Method 1: germinate sweet potatoes in water

You can germinate several sweet potatoes, depending on how many young plants you want to put in ground, bearing in mind a single sweet potato can easily provide several young plants.

• Take a sweet potato and wash it gently if it shows traces of soil or if it has been treated.
• If your sweet potatoes are too long, you can cut them into sections and use the ends.

• Place the sweet potato in chosen container, pointy or cut end down, supporting it with 3 or 4 toothpicks gently inserted.
• Fill container with water so the sweet potato is submerged about halfway up.

• Place jar in warm spot between 20°C and 25°C and in light, ideally by a window.
• Change water every 2 to 3 days to avoid stagnation and mould

Method 2: germinate a sweet potato in soil

1. Choose one (or several) small healthy tubercule, firm and free of rot. It can be organic or untreated, as some anti-sprouting treatments slow shoot development.
2. Fill a pot with light, well-draining potting compost, preferably a seed mix or universal compost lightened with sand or perlite.
3. Plant sweet potato flat or slightly tilted, burying about two-thirds. Top of tubercule should remain visible above substrate surface.
4. Water lightly to moisten compost without waterlogging, then place pot in warm, bright location around 20 to 25 °C. Conservatory, greenhouse or sunny windowsill are ideal.
5. Maintain steady humidity by watering moderately as surface begins to dry. Warm, stable atmosphere encourages first shoots.
6. Watch for development of leafy stems after 2 to 4 weeks. Once about 15 cm, they are ready for cuttings.

Step 2: propagate sweet potatoes by cuttings

Why propagate a sweet potato?

Propagation by cuttings allows you to quickly obtain several young plants from a single tubercule. This method is ideal for gardeners who want to produce in quantity without buying multiple young plants. Cuttings root easily and produce vigorous plants that can be installed in vegetable patch, raised beds or large planters.

There are two ways to proceed: in water or in compost

Materials required

To take cuttings from sweet potato you will need:

• shoots obtained from germination (see previous step).
• a clean pruning shear or sharp scissors
• small containers filled with water or buckets with light potting compost
• a bright place at constant temperature
• optionally plant hormone, although not essential

How to take and prepare cuttings

As soon as shoots measure about 15 to 20 cm, cut them at their base, just above the tubercule, using a clean tool. Remove lower leaves to keep only terminal part. Stem should be healthy, flexible and well developed.

Method 1: rooting cuttings in water

1. Place young shoots taken into glasses or small clear containers, immersing only base of stem without submerging leaves.
2. Put glasses in bright, warm spot, sheltered from draughts, with stable temperature around 20 to 25 °C.
3. Change water regularly, every two to three days, to avoid stagnation and encourage good rooting.
4. Watch for root emergence after a few days. When roots reach about 5 cm, cuttings are ready to be potted on.

Method 2: rooting cuttings in compost

1. Plant stems directly into buckets filled with light potting compost, burying only base a few centimetres deep.
2. Place buckets in warm, bright spot but out of direct sun, to avoid substrate drying out.
3. Water moderately, just enough to keep compost moist without excess. Stable humidity is essential for rooting.
4. Let cuttings establish. After two to three weeks they begin to develop a root system. They can then be potted on or pinched out as needed.

Tip: Don’t hesitate to plant your germinated sweet potato in the vegetable plot too!

To find out more…

To learn how to plant and when to harvest a sweet potato, also consult our full sheet Sweet potato: planting, cultivation and harvest in the vegetable garden.