Do Potatoes Grow Underground? A Complete Guide to Growing and Harvesting

Do potatoes grow underground? Yes, potato tubers develop beneath the soil surface.

They grow from underground stems called stolons, which expand into the tubers you harvest. This underground growth keeps the potatoes safe, moist, and shaded.

Potatoes start as small shoots that push down and form tubers on these stolons. The soil around the tubers provides insulation from temperature changes. This helps the potatoes develop properly and avoid damage from sunlight.

Planting depth matters. Potatoes usually go in about 6 inches deep in loose soil. Cover the tubers well with soil or mulch to protect them while they grow below ground.

Potatoes need full sun and steady moisture to thrive underground. Make sure your soil drains well and holds enough water. That balance helps potatoes swell instead of drying out or rotting.

Do Potatoes Grow Underground or Above Ground?

Potatoes grow underground as tubers formed on specialized stems called stolons. The green leafy plant above ground supports growth but does not produce potatoes. What you harvest comes from thickened underground stems, not roots.

The potato is a stem tuber, not a root. Unlike thin fibrous roots that absorb water and minerals, tubers store energy as starch.

The growth points, called eyes, are nodes on swollen stems. They sprout new shoots for the next plant.

The underground system includes roots that anchor the plant and stolons that run horizontally. Potatoes grow at the ends of stolons as they swell into tubers.

This growth happens near the soil surface. It usually occurs in the top 4 to 6 inches.

Above ground, you see green stems and leaves that collect sunlight and make sugars. The sugars travel down to the tubers, which enlarge as they store those energy reserves. Without this underground tuber growth, potato harvest would not be possible.

How Potato Tubers Develop Underground from Stolons

Potato tubers form underground through a natural process starting with stolons. Stolons are stem-like shoots that grow out from the seed potato beneath the soil. These stolons then swell and turn into tubers as the potato plant matures.

Stolon Growth and Extension Timing

Stolons begin growing soon after the potato plant sprouts. They extend sideways and downward from the primary stem under the soil.

This growth happens during the first 3 to 5 weeks after planting. The plant develops its root system and shoots in this time.

The length and number of stolons depend on the variety and growing conditions. Moisture should be between 60 and 80 percent of field capacity. This keeps stolons hydrated.

Well-hydrated stolons can grow longer. Soils that are too dry or waterlogged stunt stolon growth.

Initiation of Tuber Swelling Underground

Tuber formation begins when stolons stop growing longer. They start swelling 4 to 6 weeks after planting.

Cooler soil temperatures between 15 and 20°C trigger this tuber initiation. Soil warmer than 20°C for a long time delays or reduces tuber set.

During this stage, stolon tips develop buds that thicken into small knobs. These knobs gradually swell into tubers, storing starches from the plant’s photosynthesis. Hilling soil around the plant helps give stolons space and promotes tuber swelling.

Tuber Maturation Phases and Enlargement

After tubers begin swelling, they enlarge over several weeks as starch accumulates. This growth phase lasts roughly 6 to 10 weeks, depending on variety and soil conditions. Tubers can reach full size as the plant’s vines grow and photosynthesize actively.

Consistent moisture levels and well-drained soil matter most during maturation. Dry soils cause smaller tubers, and overly wet soils invite rot. Tubers mature and toughen once vine leaves yellow and die back.

Here’s a step-by-step timeline to track stolon and tuber development:

1. Plant seed potatoes in well-prepared soil with moderate moisture.
2. Allow shoots to sprout and grow above ground, starting root and stolon growth underground.
3. Between weeks 3 to 5, stolons extend horizontally under the soil.
4. Monitor soil temperature; keep it near 15 to 20°C to encourage tuber initiation.
5. At 4 to 6 weeks, watch for swelling at stolon tips as tuber cells develop.
6. Hill soil gradually to create space for tuber expansion and improve oxygen flow.
7. Provide consistent moisture to support starch accumulation and tuber enlargement.
8. Check for vine dieback signaling tuber maturity around 90 to 120 days.

Keep soil evenly moist but not waterlogged. Too much water can harm tuber growth and cause rot.

Ideal Soil and Environmental Conditions for Underground Potato Growth

Potatoes grow best in loose, well-drained soil with a slightly acidic pH. Ideal pH levels range from 5.0 to 6.0, helping nutrient absorption and reducing scab risk. Soils that are too acidic or alkaline can stunt growth or increase disease chances.

Consistent soil moisture near field capacity is key for tuber growth. This means keeping soil moisture between 60% and 80% without waterlogging. Overly wet soil causes rot, while dry soil slows tuber development and reduces yield.

• Use organic mulch to retain moisture and regulate temperature
• Water deeply but infrequently to promote strong roots
• Check soil moisture with your finger about 2 inches deep
• Avoid wetting foliage to reduce fungal issues
• Add organic matter for better drainage and water retention

Potatoes prefer cooler temperatures, roughly 45°F to 60°F during growth. Tuber formation peaks between 59°F and 68°F (15°C to 20°C). Hotter temperatures reduce tuber set and can stress the plants.

While tubers grow underground, potato plants still need 6 to 8 hours of sunlight daily. Leaves convert sunlight into energy for tuber development below. In shady spots, expect reduced yields and smaller tubers.

Best Planting Depths, Spacing, and Methods for Underground Potatoes

Plant seed potatoes 4 to 6 inches deep and space them 12 to 18 inches apart. The exact depth depends on soil type and planting method. Good spacing prevents competition and helps stolons develop well underground.

Traditional In-Ground Planting Depth and Spacing

Plant seed potatoes at 4 to 6 inches deep in loose, well-drained soil. Space pieces about 12 to 15 inches apart. Keep rows 12 to 15 inches apart.

This gives plants room to grow well. For main-crop potatoes, increase spacing to 18 inches for room to grow.

Spacing keeps sprouts from blocking light and forces stolons to expand, not compete. Planting too deep delays shoot emergence and stunts growth. Shallow planting risks tubers drying out.

Container and Grow Bag Planting Considerations

Containers need at least 12 to 15 inches of depth to support tuber growth. Use well-draining, nutrient-rich potting soil to avoid waterlogging. Space seed pieces roughly 12 inches apart.

Grow bags let you add soil or mulch as plants grow. This helps tubers form higher in the container.

You can keep building up the soil over time. Make sure the container is large enough for mature tubers and supports good airflow.

No-Dig and Mulch-Based Planting Methods

No-dig methods use a thick layer of mulch or compost without digging holes. Spread 2 inches of organic matter on the ground first. Then place seed potatoes just under the surface.

This helps tubers develop in loose soil. Cover with more mulch as shoots grow.

This method provides protection from pests and keeps soil moisture consistent. It also makes it easier to harvest tubers later. But tubers may grow closer to the surface and need gentle care.

Cutting and Preparing Seed Potatoes

Slice large seed potatoes into pieces about the size of a golf ball. Each piece needs one or two healthy eyes. Let cut pieces dry 1 to 2 days before planting to seal wounds.

Using certified seed potatoes reduces disease risk. Avoid grocery store potatoes since they often carry diseases and have sprout inhibitors. Proper cutting and drying help prevent rot and promote healthy growth.

Follow these steps to prepare and plant seed potatoes:

1. Select certified seed potatoes, free from disease and damage.
2. Cut large tubers into golf ball, size pieces, ensuring eyes are present.
3. Let cut pieces dry for 1 to 2 days in a cool, shaded area.
4. Prepare soil or container by loosening and adding compost or organic matter.
5. Plant pieces 4 to 6 inches deep in loose soil or just under mulch.
6. Space seed pieces 12 to 15 inches apart for early types. 18 inches for main crop.
7. Cover with soil or mulch, leaving room for shoots to emerge.
8. Water moderately to keep soil moist but not soggy.

How Long Do Potatoes Take to Grow Underground?

Potatoes start growing tubers just a few weeks after the plants emerge. Typically, potatoes take between 70 and 130 days to mature underground. The exact time varies by variety and growing conditions like soil temperature and moisture.

Early potato varieties mature faster, often ready in about 70 to 90 days. These are great if you want new potatoes for fresh eating. Mid-season potatoes take roughly 90 to 110 days.

Late or main crop potatoes need 100 to 130 days to grow. They are planted later in summer. Harvest happens in fall.

You can harvest new potatoes within a week for fresh eating. Pick them when the tubers reach 2 to 3 inches in diameter. At this size, the skin remains thin and vitamin C levels stay high.

Waiting longer makes the skin thicker. Potatoes then store better. They also get less tender.

Mature tubers usually signal readiness by the plant’s vines dying back. When the foliage gets yellow or brown, it’s time to dig. Avoid digging too early or late because this affects tuber size and storage life.

Using too much fertilizer late in the season causes big leaves. Plants grow leafy but produce small potatoes underground.

Common Problems Affecting Underground Potato Growth and How to Fix Them

Common Problems Affecting Underground Potato Growth and How to Fix Them

Potatoes turn green when exposed to sunlight. This happens because they produce solanine, a bitter and toxic compound. To avoid green potatoes, cover tubers with soil or mulch to block light completely.

Poor tuber development often results from unbalanced soil nutrients. Potatoes need nitrogen, phosphorus, and potassium in the right amounts for healthy growth. Adding a balanced fertilizer during planting and mid-season can improve tuber size and yield.

Several pests attack potatoes underground, including wireworms, potato cyst nematodes, and root-knot nematodes. These pests damage tubers and roots, reducing the crop’s quality. Crop rotation, good soil preparation, and certified seed potatoes help reduce pest problems.

Diseases like potato scab, blackleg, and common scab harm tubers beneath the soil. These diseases thrive in dry, poorly managed soils. Keeping soil moist without waterlogging, avoiding infected seed potatoes, and practicing crop rotation minimize disease risks.

• Keep soil moist and cover tubers fully to prevent greening and bitterness
• Use balanced fertilizers to support strong tuber development
• Plant certified disease-free seed potatoes to avoid soil-borne infections
• Rotate crops yearly to reduce pest buildup in soil
• Inspect plants regularly for signs of wireworms and nematodes
• Apply organic mulch to maintain even soil moisture
• Avoid planting potatoes in overly shady spots to prevent weak growth

Make sure soil is not too dry or too wet. This helps stolons and tubers grow well. It also improves their taste.

Dry soil can expose tubers to light, causing green spots and bitterness. Mulching and steady watering keep tubers protected and healthy underground.

When and How to Harvest Potatoes Grown Underground

Harvest potatoes once their leaves start to yellow and die back. For mid-season potatoes, this usually happens 80 to 100 days after planting.

Early digging is possible for new potatoes. But mature potatoes need more time underground to bulk up.

Identifying the Signs for Harvest Timing

Check the plant foliage for signs of maturity. When the leaves turn yellow and begin to wilt, tubers have stopped growing. Waiting too long after this stage risks frost damage and nutrient loss in the potatoes.

New potatoes can be harvested about 60 days after planting, once the plants flower. Mature potatoes need full leaf dieback. Avoid digging after a hard frost, which can bruise and spoils tubers.

Tools and Techniques for Safe Digging

Use a garden fork or spade, ideally with narrow, sharp tines to loosen soil. Dig about 12 to 18 inches from the plant’s base to avoid stabbing potatoes. Lift soil gently and shake off loose dirt.

Start by loosening soil around the plant’s edge before digging deeper. Soil should be soft before planting.

Water it a day earlier. Move slowly to prevent cuts or bruises, which reduce storage life.

Harvest Handling to Protect Tuber Quality

Lay harvested potatoes on the ground briefly to dry off excess soil. Avoid washing them before curing, since moisture promotes rot. Sort out damaged or green tubers for immediate use.

Let potatoes cure in a dark place. Keep the air flowing well. The temperature should be 50 to 60°F for 1 to 2 weeks.

This thickens their skins and heals small cuts. Store cured potatoes in a cool, dark spot around 40°F with moderate humidity to extend freshness.

Follow these steps to harvest potatoes safely and at the right time:

1. Watch for yellowing leaves and dying vines as maturity signs.
2. Test a few tubers by gently digging near plants.
3. Use a garden fork to loosen soil about 12 inches from stems.
4. Lift soil slowly to avoid piercing potatoes with the fork.
5. Gather tubers carefully, placing them on the ground without dropping.
6. Leave potatoes to dry for a few hours before moving.
7. Sort and remove any green or soft potatoes from the batch.
8. Cure tubers in a dark, cool, ventilated space for up to two weeks.

Storing and Curing Freshly Harvested Potatoes

Freshly harvested potatoes need curing to heal minor cuts and toughen their skins. This step greatly reduces rot and water loss during storage. Place potatoes in a cool, shaded spot for 10 to 14 days.

Make sure the area has good airflow to prevent moisture build-up. This helps the potatoes cure properly before storage.

The best place to cure potatoes stays between 50°F and 60°F. It should also have humidity levels from 85% to 95%. These conditions help heal skin cuts and toughen potatoes.

These conditions help the skins thicken without drying the potatoes out. Good airflow is key to avoid mold or mildew forming during this period.

After curing, move potatoes to a dark, cool storage area. Keep the temperature steady between 38°F and 40°F. This slows spoilage and keeps potatoes fresh longer.

This prevents sprouting and slows down decay caused by warmth. Avoid light, which can turn potatoes green and produce solanine, a toxin.

• Maintain soil pH between 5.8 and 6.5 to keep it slightly acidic. This environment helps lower the chance of potatoes sprouting early. Adjust soil with amendments like sulfur to manage acidity.
• Avoid storing in damp or wet spots to stop rot
• Use breathable containers like burlap sacks or wooden crates
• Check stored potatoes regularly for soft or shriveled tubers
• Don’t wash potatoes before storage; brush off dirt instead
• Separate potatoes from apples to prevent early sprouting

Common storage mistakes include skipping curing, using plastic bags, or storing in warm places. These errors cause sprouting, shriveling, or rotting. Proper curing and steady cool temperatures extend your potatoes’ shelf life for several months.

Keep potatoes in total darkness to avoid green spots and toxins.

Step-by-Step Action Plan for Growing Potatoes Underground

Follow these clear steps to grow your potatoes below the soil successfully. Each step includes a sign that shows you are on the right track.

1. Before planting: Prepare loose, well-draining soil with added compost. Soil should feel crumbly and not sticky.
2. Planting day: Place seed pieces 4 inches deep and 12 inches apart. Cover them with soil and water gently.
3. Week 2 to 3: Look for sprouts emerging above soil. This means tubers are growing underground.
4. Week 4 to 6: Hill soil around stems to protect young tubers. You’ll see soil mounded up near plants.
5. Mid-growth (8 weeks): Keep soil moist but not waterlogged. Check soil moisture by feeling it about 2 inches deep.
6. After 10 weeks: Watch for yellowing foliage. This signals tubers have matured below.
7. Harvest time: Gently dig around plants to reveal firm potatoes. Avoid cutting or bruising them.
8. Post-harvest: Cure potatoes in a dark, cool, and dry place. Check after two weeks for firm skins.

Frequently Asked Questions

Can Potatoes Grow Underground in Containers?

Yes, potatoes can grow underground in containers. Use loose, fertile soil and containers at least 16 inches deep to give tubers space.

Are All Potato Tubers Edible?

Most potato tubers are edible, but some wild varieties have toxins. Garden potatoes sold as seed or grocery types are safe for eating and growing.

Do Potatoes Growing Underground Need Sunlight?

No, potato tubers grow underground without sunlight. Stems above ground perform photosynthesis, while tubers mature in darkness to store energy.

Can You Grow More Potatoes from the Underground Stems?

Yes, growing more stems underground, called stolons, leads to more potatoes. Encourage healthy stem growth above ground for better tuber production.

How Do Potato Varieties Affect Underground Growth Time?

Potato varieties influence underground tuber growth time. Early-season potatoes mature in 60-80 days, others may take up to 120 days, depending on type.

Do Potatoes Need to Be Hilled to Grow Underground Properly?

Hilling potatoes helps by covering tubers with soil, protecting them from sunlight and pests. It encourages more stolons and larger tuber growth underground.

Key Points to Remember

Potatoes definitely grow underground as tubers develop from shoots below the soil. Start with good soil and proper planting depth for the best results. Next, plan your planting date and get your seed potatoes ready to dig in.