When To Plant Sweet Potatoes In Kansas

For Kansas gardeners, knowing when to plant sweet potatoes is the key to a successful harvest. This warm-season crop needs a long, hot growing period, and timing your planting correctly is the most important step you can take.

Sweet potatoes are not started from seeds or regular potato pieces. Instead, they are grown from “slips,” which are small rooted sprouts. Your planting date is determined by soil temperature, not just the last frost. Let’s break down the ideal schedule and how to prepare for a great yield.

The perfect planting window for sweet potatoes in Kansas is from mid-May to early June. You must wait until the soil is thoroughly warm—at least 65°F, but 70°F is even better. Planting in cold, wet soil will stunt the plants and can cause the roots to rot.

A good rule is to plant slips about 2-4 weeks after your area’s average last spring frost date. Since Kansas has varying climates, here’s a more specific guide:

Southcentral & Southeastern Kansas (Zones 6b-7a): Target May 10th to May 25th. This region warms up the fastest.
Eastern & Central Kansas (Zone 6a): Aim for May 15th to June 1st. Watch the soil temperature closely.
Western Kansas (Zones 5b-6a): Wait until late May or early June, from May 25th to June 10th. The drier climate can mean cooler spring soils.

If you have a short growing season, consider using black plastic mulch to warm the soil faster. It can give you a valuable head start of a week or two.

Why Sweet Potatoes Need Heat

Sweet potatoes are tropical plants. They thrive in heat and sunshine. Their growth practically stops when temperatures dip below 55°F. The “days to maturity” listed on slip varieties—usually 90 to 120 days—count from the day you transplant the slip, but they only accrue during warm weather.

Planting too early offers no benifit and lots of risk. A late spring cold snap can ruin your entire crop. It’s always better to be patient and wait for genuine warmth.

Preparing Your Garden Bed

Sweet potatoes prefer loose, well-drained soil. They don’t need highly fertile ground; in fact, too much nitrogen will give you huge vines but small tubers. Follow these steps to prepare:

Choose a Sunny Spot: Select a location that gets full sun for at least 8 hours a day.
Loosen the Soil: Dig or till the bed to a depth of 10-12 inches. Break up any hard clumps.
Amend with Care: Mix in a few inches of compost. Avoid fresh manure or high-nitrogen fertilizers. A light application of a low-nitrogen, phosphorous-rich fertilizer (like a 5-10-10) is sufficient.
Consider Mounds or Rows: Forming raised rows or mounds about 8 inches high improves drainage and helps the soil warm up quicker.

Selecting the Right Varieties for Kansas

Choosing a variety suited to our climate is crucial. Look for types with a shorter days-to-maturity rating to ensure they mature before our first fall frost.

Beauregard: The classic choice. Reliable, produces well in varied soils, matures in about 90 days.
Georgia Jet: Known for its fast maturity (around 90 days) and good cold-tolerance for early growth.
Centennial: Another fast-maturing, productive orange-fleshed type.
Murasaki (Japanese White): A drier, white-fleshed sweet potato with purple skin. It stores exceptionally well.
Covington: A popular Beauregard-like variety with a uniform shape, taking about 110 days.

How to Plant Sweet Potato Slips

You can order slips online or start your own from organic sweet potatoes. When your slips arrive or are ready, they need to be hardened off before planting. Set them outside in a shaded, protected spot for a few hours each day, increasing their time outside over 5-7 days.

On planting day, follow this method:

Water the Slips: Give the slips a good drink before removing them from there container.
Dig Holes: Space holes 12-18 inches apart in rows that are 3 feet apart.
Plant Deeply: Bury each slip so that only the top leaves are above the soil. The stem will root along its length, giving you more potatoes.
Water Gently: Water them in well to settle the soil around the roots.

Caring for Your Growing Sweet Potatoes

Sweet potatoes are relatively low-maintenance once established. Your main tasks are watering and weed control, especially early on.

Watering: Provide about 1 inch of water per week. Keep the soil consistently moist for the first few weeks, then you can reduce frequency. Stop watering altogether 3-4 weeks before your planned harvest to let the tubers cure in the ground.
Weeding: Weed carefully by hand when the plants are young. Once the vines spread and cover the ground, they will smother most weeds.
Fertilizing: Usually not needed if you prepared the bed properly. If growth seems slow mid-season, you can side-dress with a potassium-rich fertilizer like wood ash.

Avoid pruning the vines. Let them run! They are producing energy for the roots underground.

When and How to Harvest

Your sweet potatoes are ready to harvest in late September through October, but definitely before the first hard frost. A light frost will damage the vines, but you should dig the tubers immediately if one is forcasted. The signs of readiness are yellowing leaves and cooler fall weather.

Choose a Dry Day: Do not harvest when the soil is soggy.
Cut the Vines: Use pruners to cut away the long vines first. This makes digging easier.
Dig Carefully: Use a digging fork and start well away from the main plant stem. Loosen the soil and gently lift the cluster of tubers. They bruise easily.
Cure for Storage: This step is non-negotiable for good storage. Brush off excess soil (don’t wash), and place the unbruised tubers in a warm (80-85°F), humid place for 10-14 days. A greenhouse or a table in a warm bathroom works.
Store Properly: After curing, store your sweet potatoes in a cool (55-60°F), dark, and well-ventilated place. Do not refrigerate. Properly cured and stored, they can last for months.

Common Problems and Solutions

Sweet potatoes have few pests in Kansas. The biggest issues are usually related to weather or animals.

Wireworms & Grubs: These soil pests can bore into tubers. Rotating your crop each year is the best prevention.
Voles: These small rodents love sweet potatoes. Planting in a raised bed or using underground mesh barriers can help deter them.
Cracking Tubers: Caused by uneven watering, especially a heavy rain after a dry period. Try to maintain consistent moisture.
Scraggly, Small Roots: Often caused by planting too early in cold soil, using too much nitrogen fertilizer, or having soil that is too compacted.

FAQ for Kansas Gardeners

Can I plant sweet potatoes from the grocery store?

You can try, but it’s not recommended. Store-bought potatoes are often treated with sprout inhibitors. For best results, buy certified disease-free slips from a garden supplier.

How long do sweet potatoes take to grow in Kansas?

From transplanting slips, most varieties need 90 to 120 warm days to reach full size. Your total timeline from planting to harvest will be about 4 months.

What if I planted my slips too early?

If a cold, wet period hits after planting, growth will be stalled. You cannot really reverse this. If the plants look severely stunted or yellowed after weeks of warm weather, you may need to start over with new slips.

Can I grow sweet potatoes in containers?

Yes! Use a large container (at least 20 gallons) with excellent drainage. Fill it with a light, sandy potting mix. This is a great option for gardeners with heavy clay soil.

When is to late to plant sweet potatoes in Kansas?

Aim to get your slips in the ground by mid-June at the absolute latest. Planting after this date risks that the tubers won’t have enough warm days to size up properly before fall frosts arrive.

By following this timing guide and giving your sweet potatoes the heat and loose soil they love, you’ll be rewarded with a generous harvest of homegrown sweetness. There’s nothing quite like digging up your own cluster of orange tubers on a crisp fall day. With a little planning, Kansas gardeners can grow fantastic sweet potatoes every year.