When to Harvest Sweet Potatoes

Sweet potatoes are a nutrient-dense, delicious, and versatile root vegetable that gardeners love to grow. One of the most rewarding moments in the gardening process is knowing when to harvest sweet potatoes to ensure the highest yield and flavor. Timing the harvest correctly can make a significant difference in taste, texture, and longevity of storage. This guide will walk you through every aspect of determining the right time to harvest sweet potatoes, as well as offering insights on the proper techniques to use.

Understanding the Growth Cycle of Sweet Potatoes

Sweet potatoes, scientifically known as Ipomoea batatas, are warm-season crops that thrive in tropical and subtropical climates. To properly time the harvest, it’s important to first understand the life cycle of the plant. Sweet potatoes typically require between 90 to 170 days to mature, depending on the variety and growing conditions. The growing season begins with planting slips (young plants) in the spring or early summer after the threat of frost has passed.

Once the slips are planted, the sweet potatoes go through several stages of development:

• Root Development Stage: This occurs in the first 30-40 days after planting. The plants focus on growing roots and vines.
• Tuber Bulking Stage: From around 40-90 days after planting, the tubers (which are the edible parts of sweet potatoes) begin to develop. During this phase, they will bulk up and grow in size.
• Maturation Stage: After 90 days, the tubers continue to mature, and depending on the variety, they are ready to harvest within the next few weeks to months.

Factors That Influence When to Harvest Sweet Potatoes

Several factors affect the timing of when sweet potatoes should be harvested:

a) Variety of Sweet Potato

Different varieties of sweet potatoes have different maturity rates. Some varieties are ready to harvest in 90-120 days, while others may take up to 170 days. Popular early-maturing varieties, such as ‘Beauregard’ or ‘Covington,’ can be ready in as little as 90 days. If you’re growing a late-maturing variety, such as ‘Jewel’ or ‘Henry,’ you may need to wait longer.

b) Growing Conditions

Sweet potatoes thrive in well-drained soil with full sun exposure. Ideal temperatures for sweet potatoes are between 75-85°F (24-29°C). If your area experiences cooler temperatures, it may take longer for sweet potatoes to reach full maturity. On the other hand, warmer climates can encourage faster growth. Poor soil conditions, lack of sunlight, or irregular watering can delay the maturation process, causing the harvest to take longer.

c) Frost Threats

Sweet potatoes are very sensitive to frost. Even a light frost can damage the tubers, so it’s important to harvest them before the first frost in your area. Watch the weather forecast closely and plan to harvest at least a week or two before frost is expected.

Signs That Sweet Potatoes Are Ready to Harvest

To ensure the highest quality of sweet potatoes, there are several key indicators to look for that signal it’s time to harvest:

a) Yellowing of the Vines

One of the most obvious signs that sweet potatoes are ready to harvest is the yellowing and dying back of the vines. As the plant reaches maturity, the leaves begin to turn yellow and wilt. While this doesn’t mean the tubers are immediately ready, it’s a strong indication that they are nearing maturity. Once the vines start to die back, it’s time to consider harvesting within the next week or two.

b) Length of Time in the Ground

As mentioned earlier, sweet potatoes typically take between 90-170 days to mature, depending on the variety and conditions. If you know the variety you planted and when you planted it, you can calculate the approximate harvest window. For early varieties, check around the 90-day mark, and for late varieties, plan for a longer growing season.

c) Size of Tubers

Before digging up the entire crop, you can check the size of a few tubers by gently loosening the soil around the base of the plants. Carefully expose the tuber without damaging it and check its size. If the sweet potatoes have reached a desirable size, they are ready for harvest. If they still appear too small, allow them to remain in the ground for a little longer, as they will continue to bulk up.

Harvesting Techniques for Sweet Potatoes

Proper harvesting techniques are essential to avoid damaging the sweet potatoes, as any cuts, bruises, or breaks in the skin can lead to spoilage during storage.

a) Tools You Will Need

• Shovel or Garden Fork: A shovel or fork with rounded prongs is ideal for loosening the soil around the plants without puncturing the tubers.
• Gloves: Wearing gloves can help protect your hands while working with the soil and roots.
• Bucket or Basket: Use a container to collect the sweet potatoes once they are dug up.

b) How to Harvest

1. Loosen the Soil: Begin by loosening the soil around the base of each plant. Start about 12-18 inches away from the center of the plant to avoid damaging the tubers, as they tend to grow outward from the root.
2. Lift the Tubers: Gently lift the sweet potato plant from the ground, working your way in from the edges. Use the shovel or fork to lift the tubers and free them from the soil.
3. Handle Carefully: Sweet potatoes have delicate skins when freshly harvested. Handle each tuber carefully to avoid any damage. Place them gently into your basket or container.
4. Inspect the Tubers: Once harvested, inspect each sweet potato for signs of damage or disease. Tubers that are damaged should be eaten first, as they will not store well.

Curing and Storing Sweet Potatoes

After harvesting sweet potatoes, curing is a crucial step that enhances their flavor and prolongs storage life.

a) Curing Process

To cure sweet potatoes, place them in a warm, humid environment for 7-10 days. The ideal conditions for curing are temperatures between 80-85°F (26-29°C) and a humidity level of around 85-90%. This process allows the skins to toughen, and the starches to convert into sugars, resulting in sweeter-tasting tubers.

• How to Cure: You can cure sweet potatoes in a warm shed, greenhouse, or even a sunny room in your home. Make sure to spread the tubers out so they don’t touch each other, allowing good air circulation.
• Monitoring Conditions: Keep an eye on the temperature and humidity levels during curing. If the environment is too cool or dry, the curing process won’t be effective.

b) Storage Tips

After curing, store sweet potatoes in a cool, dark, and well-ventilated area, ideally between 55-60°F (13-16°C). Avoid storing them in a refrigerator, as the cold can cause the tubers to develop an off-flavor and affect their texture.

Properly cured and stored sweet potatoes can last for several months, providing a steady supply of this nutritious vegetable throughout the winter.

Common Mistakes to Avoid When Harvesting Sweet Potatoes

While growing and harvesting sweet potatoes is generally straightforward, there are a few common mistakes that can negatively affect your yield:

• Harvesting Too Early: Harvesting sweet potatoes too soon can result in small, underdeveloped tubers with poor flavor. It’s better to leave them in the ground longer if you’re unsure of their readiness.
• Leaving Tubers in the Ground Too Long: While it’s tempting to leave sweet potatoes in the ground to continue growing, doing so for too long can lead to cracking or rotting, especially if there is excess moisture in the soil.
• Not Curing Properly: Skipping or rushing the curing process can result in sweet potatoes that don’t store well and lack sweetness.

Conclusion

Harvesting sweet potatoes at the right time is essential to maximize both yield and flavor. By understanding the growth cycle, paying attention to environmental factors, and following proper harvesting and curing techniques, you can enjoy a bountiful harvest of sweet potatoes that will last for months. Whether you’re a seasoned gardener or a beginner, the key to success is patience and close observation of your plants. Happy harvesting!