If you’re a gardener in Indiana, knowing when to plant sweet potatoes is the key to a successful harvest. This guide will walk you through the optimal planting season and everything you need to get it right.
Sweet potatoes are a warm-season crop that love heat and hate the cold. Planting them at the correct time ensures they have a long enough growing season to produce those tasty tubers you’re after. Getting the timing wrong can lead to disappointing results, so let’s make sure your garden is set up for success.
When to Plant Sweet Potatoes in Indiana
The single most important factor for planting sweet potatoes is soil temperature. These plants are very sensitive to chill.
You should aim to plant your sweet potato slips outdoors when the soil has warmed to at least 60°F, but 65°F is even better. In Indiana, this typically happens from mid-May to early June.
A good rule of thumb is to plant 2-4 weeks after your last average spring frost date. Since Indiana’s frost dates vary, here’s a general breakdown by region:
- Northern Indiana: Plant from late May to early June.
- Central Indiana: Plant from mid-May to early June.
- Southern Indiana: You can often plant as early as early to mid-May.
Always check your local weather forcast. A late cold snap can ruin young slips.
Why Timing Is So Critical
Planting too early in cold soil stunts growth and can cause roots to rot. The plants just sit there, unhappy. Planting to late shortens the growing season, which is a problem because sweet potatoes need 90 to 120 frost-free days to mature properly.
Their growth really takes off in the heat of summer. You want them to be established and ready to vine out when that summer heat arrives.
How to Check Your Soil Temperature
Don’t guess—use a soil thermometer. You can find one at any garden center.
- Insert the thermometer about 4 inches deep into the soil, in the area you plan to plant.
- Do this in the morning for several days in a row to get a consistent reading.
- Make sure the temperature holds steady at that 60°F minimum before you plant.
Preparing to Plant: Slips vs. Store-Bought
You don’t plant sweet potatoes from seeds. You grow them from “slips,” which are small rooted sprouts.
Starting Your Own Slips
This is a fun and cost-effective method. Start the process about 6-8 weeks before your planned outdoor planting date.
- Choose a healthy, organic sweet potato from the store or from last year’s harvest.
- Suspend it in a jar of water using toothpicks, with the bottom half submerged.
- Place it in a warm, sunny spot. Change the water weekly.
- In a few weeks, sprouts (slips) will grow from the top. When they are 6-10 inches long with roots, gently twist them off.
- Place these slips in their own shallow water to develop stronger roots before planting.
Buying Slips
Many garden centers and online nurseries sell sweet potato slips in the spring. This is a great option if you’re short on time. Order them in advance so they arrive at your optimal planting time.
When they arrive, if they look wilted, place them in water for a few hours to rehydrate before putting them in the ground.
Choosing and Preparing the Perfect Garden Site
Sunlight and Space
Sweet potatoes need full sun—at least 6 to 8 hours of direct sunlight daily. They are vigorous vines that can spread over 10 feet, so give them plenty of room.
Soil Requirements
This is non-negotiable for good tuber development. Sweet potatoes prefer loose, well-draining, slightly sandy soil. Heavy clay soil will result in misshapen, small potatoes.
- Loosen the Soil: Dig down at least 10-12 inches.
- Improve Drainage: Mix in several inches of compost or aged manure. For very heavy clay, consider building raised rows or beds.
- Go Easy on Fertilizer: Too much nitrogen, especially from synthetic fertilizers, gives you huge vines but tiny tubers. Use a balanced organic fertilizer or one slightly higher in potassium and phosphorus.
The Step-by-Step Planting Process
- Plant on a Cloudy Day: This reduces transplant shock on the young slips.
- Space Them Out: Plant slips 12-18 inches apart within a row, with rows 3-4 feet apart.
- Plant Deeply: Bury the slip so that all the roots and about half the stem are under the soil. The stem will grow additional roots along it.
- Water Thoroughly: Give them a good drink after planting to settle the soil.
Using Black Plastic Mulch
This is a fantastic trick for Indiana gardeners. Laying black plastic over your planting rows 1-2 weeks before planting warms the soil much faster. It also suppresses weeds and retains moisture.
Simply cut an X in the plastic and plant your slip through the hole. This method can allow you to plant a week or so earlier.
Caring for Your Growing Sweet Potatoes
Watering Wisely
Water consistently after planting until the slips are established. Once they’re vining, sweet potatoes are somewhat drought-tolerant, but consistent moisture is best for even growth.
Reduce watering significantly during the last 3-4 weeks before harvest. This helps the potatoes cure and develop their sweetness.
Weeding and Vine Management
Weed carefully early on. Once the vines spread, they’ll shade out most weeds. Avoid disturbing the vines too much, as roots can form at every leaf node. There’s no need to prune the vines unless they are escaping your garden space.
Harvesting and Curing Your Indiana Sweet Potatoes
Your sweet potatoes are ready to harvest in late September through October, but always before the first hard frost. Frost will damage the tubers.
Signs of readiness include yellowing leaves. Use a garden fork to carefully lift the tubers from the soil to avoid bruising them.
The Essential Curing Step
Don’t skip curing! This process heals minor cuts and converts starches to sugars, enhancing flavor and storage life.
- Gently brush off excess soil—do not wash them.
- Place them in a warm (80-85°F), humid place for 10-14 days. A shaded table in a warm garage often works well.
- After curing, store your sweet potatoes in a cool (55-60°F), dark, and well-ventilated place. Properly cured, they can last for months.
Common Problems and Solutions for Indiana Gardeners
- Wireworms or Grubs: These can bore into tubers. Rotating your crops each year is the best prevention.
- Deer and Voles: Deer may eat the vines; fencing is the only real solution. Voles can tunnel and eat tubers; raised beds can help deter them.
- Scorched Leaves: If leaves look bleached or scorched, it’s often just sunscald during extreme heat. The plants usually recover.
FAQ: Sweet Potato Planting in Indiana
Can I plant sweet potatoes from the grocery store?
You can start slips from an organic store-bought potato, but it’s not guaranteed. They are sometimes treated to prevent sprouting. For reliability, buy certified disease-free slips.
What are the best varieties for Indiana’s climate?
Look for varieties with a shorter days-to-maturity. ‘Beauregard’ (100 days) and ‘Georgia Jet’ (90 days) are excellent, reliable choices for our state.
Is it to late to plant in July?
Yes, planting in July is generally to late. The tubers won’t have enough time to size up before fall frosts arrive.
Can I grow sweet potatoes in containers?
Absolutely! Use a large container (at least 20 gallons) with excellent drainage. Choose a compact or “bush” variety for best results in pots.
Why did my plants have huge vines but no potatoes?
This is usually caused by soil that is too rich in nitrogen, planting too early in cold soil, or a variety not suited to our climate length. Stick to the timing and soil tips in this guide.
By following this guide for when to plant sweet potatoes in Indiana, you give your garden the best possible start. Paying close attention to soil warmth, preparing your site properly, and choosing the right slips will lead you to a bountiful autumn harvest of homegrown sweet potatoes. The patience required for this heat-loving crop is always rewarded with delicious results.