Knowing when are sweet potatoes ready to harvest is the key to a successful crop. Getting the timing right means you’ll get the best flavor and storage life from your homegrown tubers. This guide will walk you through all the signs, from the vines to the soil, so you can pick them at their peak.
Sweet potatoes need a long, warm growing season, typically about 90 to 120 frost-free days. Unlike regular potatoes, they are very sensitive to cold. A single light frost can damage the vines and, more importantly, the tender potatoes underground. Your goal is to harvest them after they’ve fully developed but before the soil gets cold.
When Are Sweet Potatoes Ready To Harvest
You can’t just look at the calendar to know when to harvest. You need to check a combination of visual clues from the plant itself. The most reliable signs are the ones nature gives you.
Check the Days to Maturity
First, check your seed slip variety or your plant tag. It should list the “days to maturity.” This is your starting point. Mark that date on your calendar when you plant. For most varieties, this is around 100 days. This date gives you a general window to begin looking for other signs.
Observe the Vine Growth
The vines are a great indicator. In mid to late summer, they will be growing vigorously. As harvest time nears, this growth often slows down. The vines might start to look a little yellow or even die back slightly. This is the plant telling you its focusing energy on the tubers now.
The Leaf Color Change
Pay close attention to the leaves. A slight yellowing of some of the older leaves is normal as the season ends. If the main vines are still mostly green, you’re likely still in the bulking phase. Widespread yellowing is a stronger signal.
The Most Important Sign: Tuber Size
The best way to know for sure is to gently investigate. Carefully dig around the base of a plant with your hands, not a fork. You’re looking for one or two tubers near the center crown.
- Feel for the size. A good harvestable tuber will feel substantial, often at least 1.5 to 2 inches in diameter at its widest point.
- Check the skin. Gently rub the skin of the tuber you find. If the skin is thin and rubs off easily, the potatoes need more time. Mature sweet potatoes have a set, thicker skin that resists scratching.
Just remember to cover the hole back up gently if they need more time! This little check won’t harm the plant.
It’s All About the Weather
Weather overrules all other signs. Sweet potatoes are tropical plants. Your harvest must happen before the first fall frost.
- If a frost is forecasted, you must harvest immediately, even if the tubers seem small. Frost will damage them and cause them to rot in storage.
- Cool soil temperatures (below 50°F / 10°C) can also chill the potatoes and hurt their quality. It’s better to harvest a bit early in warm conditions than too late in cold ones.
How to Harvest Sweet Potatoes Correctly
Harvesting carefully is crucial to avoid bruising or cutting the delicate tubers. Damaged potatoes won’t store well. Follow these steps for the best results.
- Choose a Dry Day: Never harvest when the soil is soggy wet. Try to pick a period of dry weather. This makes the process cleaner and helps prevent rot.
- Cut the Vines First: Use garden shears to cut the long vines away from the crown. This clears your workspace and makes digging much easier. You can compost these vines.
- Loosen the Soil: Start digging at least a foot away from the main plant crown. Use a digging or spading fork, not a shovel. Gently loosen the soil in a wide circle around the plant. You want to lift the soil, not stab through it.
- Lift by Hand: After loosening, use your hands to carefully lift the cluster of sweet potatoes out of the ground. They often grow in a nest-like cluster. Pulling on a single potato can break it.
- Brush Off Soil Gently: Shake or brush off the loose, damp soil with your hands. Do not wash them with water at this stage. Washing introduces moisture and can cause spoilage during curing.
The Critical Step: Curing Your Harvest
This is the step many new gardeners miss, but it’s essential. Freshly dug sweet potatoes are not very sweet and their skin is fragile. Curing heals minor wounds and converts starches to sugars, giving them that classic sweet flavor.
How to Cure Sweet Potatoes
- Find a Warm, Humid Spot: Ideal conditions are 80-85°F (27-29°C) with high humidity (around 85-90%). A greenhouse, sunny porch, or a small room with a space heater and humidifier works.
- Let Them Breathe: Lay the potatoes in a single layer on a table or rack. Don’t pile them on top of eachother. They need good air circulation.
- Leave Them Be: Cure them for 10 to 14 days. You’ll notice the skin becomes tougher and more leathery. This is what you want.
Storing for Long-Term Enjoyment
After curing, sweet potatoes need different conditions for long-term storage. They like it cool, dry, and dark.
- Temperature: Aim for 55-60°F (13-16°C). A basement, root cellar, or cool closet is perfect. Do not refrigerate them, as temperatures below 50°F can cause a hard core and off-flavors.
- Container: Store them in a well-ventilated box or basket. Some people use paper bags or wrap them in newspaper. Avoid airtight plastic bags.
- Check Regularly: Every few weeks, check your stored potatoes. Remove any that show signs of soft spots or decay so they don’t spoil the others.
Frequently Asked Questions
Can you leave sweet potatoes in the ground too long?
Yes, you can. Leaving them in ground that has become cold and wet greatly increases the risk of rot and chilling injury. It’s always safer to harvest before consistent cold weather sets in.
What happens if you harvest sweet potatoes too early?
If harvested only a few weeks early, the tubers will be smaller and less sweet. They can still be cured and eaten, but their yeild and flavor won’t be optimal. The skins may also be more delicate.
Do sweet potatoes flower when they are ready?
Flowering is not a reliable indicator of maturity. Some varieties flower profusely, others rarely flower at all. It depends more on the specific type of sweet potato you’re growing.
How big should sweet potatoes be when harvesting?
A good size is the diameter of a can of soda or larger, but this varies. The “gentle dig” test is the best method. Size, combined with skin set, tells you more than size alone.
Can you eat sweet potatoes right after harvest?
You can, but they won’t be as sweet. For the best texture and flavor, always cure them first. This process makes a dramatic difference in the final taste of your crop.
By watching for the vines to slow, checking tuber size and skin set, and beating the frost, you’ll master the harvest timing. With careful digging, proper curing, and good storage, you’ll enjoy your homegrown sweet potatoes for months to come. There’s nothing quite like the taste of a perfectly timed sweet potato from your own garden.