How to Grow Sweet Potatoes in Water (The Jar Method That Actually Works)
Growing sweet potatoes in water is one of those simple “kitchen hacks” that looks too easy to be real — but it actually works when you do it the right way.
The problem is… most people try it once, the potato turns slimy, the water smells bad, or nothing sprouts at all.
So in this full guide, you’ll learn the exact jar method that produces strong roots and healthy slips (sweet potato shoots) — without mold, without rot, and without wasting your time.
Why Grow Sweet Potatoes in Water?
This method is popular because it:
✅ starts growth fast (sprouts in days)
✅ doesn’t require soil at first
✅ makes it easy to monitor roots
✅ produces multiple slips from one sweet potato
✅ works indoors on a kitchen counter
It’s one of the easiest ways to start a sweet potato garden — even if you have limited space.
What You Need (Simple Setup)
To do the jar method correctly, you only need:
- 1 healthy sweet potato (firm, not wrinkled)
- 1 glass jar (mason jar works best)
- 3–4 toothpicks
- clean water (filtered is best)
- bright window (indirect light)
Optional but helpful:
- a small bit of hydrogen peroxide (for rot prevention)
- paper towel to wipe slime if needed
The #1 Mistake That Makes Sweet Potatoes Rot in Water
Most failures happen because people put the wrong part of the sweet potato in water.
✅ The bottom end goes in water.
❌ The top end stays out.
How to identify the bottom end:
- usually wider and slightly rough
- more “pointy” or root-looking
- sometimes has tiny root bumps
Top end:
- smoother
- more rounded
If you put the top end down, it often delays sprouting or causes rot.
The Jar Method (Step-by-Step)
Step 1: Choose the Right Sweet Potato
Pick a sweet potato that is:
✅ firm
✅ uncut
✅ no bruises
✅ no soft spots
✅ no black mold patches
Avoid sweet potatoes that already feel watery or smell odd.
Step 2: Insert Toothpicks the Right Way
Insert 3–4 toothpicks around the middle of the sweet potato.
This creates a stable “suspension” so it sits in the jar without sinking.
✅ toothpicks should go about 1/2 inch deep
✅ evenly spaced so the potato balances
Step 3: Fill the Jar With Water (Correct Level)
Fill with water so only the bottom part sits in water.
✅ only 1 inch (2–3 cm) of the bottom should touch water
❌ do not submerge half the potato
This is the secret to preventing slimy rot.
Step 4: Place Near Bright Indirect Light
Put the jar near a window with:
✅ bright indirect light
✅ stable temperature (18–26°C)
Avoid direct sun all day — it can overheat the jar and spoil water faster.
When You’ll See Sprouts + Roots
If the setup is correct, typical timeline:
✅ Day 3–7: small sprouts begin
✅ Day 7–14: roots start growing down
✅ Week 2–4: strong slips grow taller
Some varieties are slower, especially in winter. Warm rooms = faster growth.
The Water Change Rule (So It Doesn’t Smell or Rot)
This is what makes or breaks the method:
✅ change the water every 2–3 days
✅ rinse jar quickly
✅ refill with clean water
If you leave old water too long:
❌ bacteria builds up
❌ water turns cloudy
❌ sweet potato turns slimy
❌ roots rot
The “Clean Root Boost” Trick (Safe Optional)
If rot starts or water clouds fast, use this safe trick:
✅ add 1 teaspoon hydrogen peroxide (3%) per jar
Only once every 7–10 days.
It helps reduce bacteria and keeps roots clean.
Do NOT use bleach. Never.
How to Harvest Slips (The Right Way)
After slips reach:
✅ 4–6 inches long (10–15 cm)
You can remove them.
How to remove slips safely:
- twist slip gently at the base
- pull it off cleanly
- place slips in water (separate jar)
- let them grow roots for 5–10 days
Once slips have roots:
✅ plant into soil
This is how gardeners multiply sweet potatoes easily.
How Many Slips Can One Sweet Potato Make?
A healthy sweet potato can produce:
✅ 5 to 20 slips
depending on size, variety, and warmth.
That’s why this method is so powerful — one potato can become many plants.
Best Soil After Water Rooting (For Fast Growth)
Once slips root, plant into:
✅ loose, airy soil that drains well
Best mix:
- 50% potting soil
- 30% compost
- 20% perlite or sand
Sweet potatoes hate heavy wet soil.
Common Problems (And Fixes Fast)
Problem 1: Sweet potato gets slimy
✅ solution:
- change water daily
- wipe slime off
- reduce water level (only 1 inch)
- add peroxide once
Problem 2: No sprouts after 2 weeks
✅ solution:
- move to warmer location
- confirm correct bottom end
- switch potato (some are treated to prevent sprouting)
Problem 3: Roots are short and brown
✅ solution:
- water is old → change more often
- keep jar clean
- avoid direct hot sun
Problem 4: Mold near toothpicks
✅ solution:
- lower water level
- dry the top part
- move to airy location
FAQ (6 Questions + Answers)
1) Can you grow sweet potatoes fully in water?
You can start them in water, but for real sweet potato tubers you need soil. Water method is mainly for rooting and growing slips.
2) How long does it take for sweet potatoes to sprout in water?
Usually 3–14 days depending on temperature and potato variety.
3) Why did my sweet potato rot in the jar?
Most common reasons:
- too much of the potato was submerged
- water wasn’t changed often
- jar was kept too warm in direct sun
4) Can I use a store-bought sweet potato?
Yes, but some store potatoes are treated to stop sprouting. If nothing happens after 2–3 weeks, try an organic sweet potato.
5) Should the sweet potato be peeled first?
No. Keep skin on. Peeling increases rot risk.
6) How do I know when slips are ready to plant?
When slips are: ✅ 4–6 inches long
✅ have roots in water after removing
Then they’re ready to plant in soil.
Final Takeaway
If you want the jar method to actually work:
✅ use a firm sweet potato
✅ bottom end in water (only 1 inch submerged)
✅ suspend with toothpicks
✅ bright indirect light
✅ change water every 2–3 days
✅ harvest slips when 4–6 inches tall
✅ root slips in water then plant in soil
This method is simple, clean, and works indoors — and it can turn one sweet potato into many plants.