How does soda bottle hydroponics work? Bottle hydroponics turns a 2-liter soda bottle into a wick garden. Cut the bottle, invert the top into the base, thread a cotton wick through the cap, and fill the top with coir. Colorado State, New Jersey Agriculture in the Classroom and the Edible Schoolyard all use this no-pump design.
Key takeaway: Bottle hydroponics uses an inverted bottle top, a cotton wick and coir; capillary action feeds roots.
| Part | What to use | Why | Source |
|---|---|---|---|
| Container | Clean 1- or 2-liter soda bottle with cap | Top is grow tray, base is reservoir | Colorado State, NJ AITC |
| Wick | Cotton strip, rope, yarn or felt | Moves solution by capillary action | Colorado State, NJ AITC |
| Medium | Coconut coir, perlite, vermiculite or cotton | Absorbs and holds moisture | Colorado State, Edible Schoolyard |
| Light cover | Black paint or aluminum foil on base | Blocks light that feeds algae | Colorado State, Edible Schoolyard |
What Do You Need for Bottle Hydroponics?
A bottle, a wick, a medium and nutrients. Colorado State Extension lists a clean 2-liter bottle with cap, a fibrous wick, coconut coir or perlite, a soluble fertilizer, black spray paint, duct tape, scissors, a ruler and a marker. It notes a pump or air stone can be added but the system grows without one.
How Does a Bottle Hydroponics Wick Work?
Through capillary action. Colorado State Extension explains that water adheres to the wick fibers and is pulled upward, much as a paper towel soaks up a spill, with no moving parts. That steady upward flow keeps the medium moist so roots can draw water and nutrients. Our wick system hydroponics guide covers larger versions.
How Do You Build a Soda Bottle Hydroponics System?
Cut, invert, wick and fill. New Jersey Agriculture in the Classroom cuts the top off about 4 inches (10 cm) down, at the bottle’s shoulders, while Colorado State cuts about 8 inches (20 cm) from the top. The Edible Schoolyard says to cut just below the curve so the plant has room.
- Rinse the bottle and mark a line just below the shoulder.
- Cut along the line and tape the sharp edges.
- Cut a hole in the cap and thread the wick halfway through.
- Fill the base with nutrient solution, keeping the cap above the liquid.
- Invert the top into the base so the wick hangs in the solution.
- Pack moist coir around the wick and sow seeds.
- Cover the base with foil or paint to block light.
Which Plants Grow Best in Bottle Hydroponics?
Small, low-demand plants. Colorado State Extension says the wick system works very well with plants that need less water and nutrients, such as rosemary, lettuce and greens. The Edible Schoolyard says a 2-liter garden can produce a head of lettuce, spinach or basil within a few weeks. New Jersey Agriculture in the Classroom uses lettuce seed.
Try a variety from our little gem lettuce hydroponics guide.
What Nutrients Should You Use in Bottle Hydroponics?
A dilute soluble fertilizer. Colorado State Extension uses Miracle-Gro. New Jersey Agriculture in the Classroom waits until true leaves appear, since seeds carry their own food, then mixes 1/4 teaspoon (1.2 mL) of soluble plant food and 1/8 teaspoon (0.6 mL) of Epsom salt in a 2-liter bottle of water.
The Edible Schoolyard adjusts tap water to pH 6.0 to 6.5 before adding nutrients, noting most tap water reads 7.0 to 8.0.
Why Should the Bottle Be Covered?
To stop algae. The Edible Schoolyard explains that algae, like plants, thrive on water, nutrients and light, so letting light hit the reservoir invites growth that looks and smells unpleasant. It recommends wrapping the bottle in aluminum foil, while Colorado State paints the bottom black. See our algae in hydroponic reservoirs guide.
How Do You Maintain Bottle Hydroponics?
Top up and flush. Colorado State Extension says to replace water and nutrients as the level drops and flush the medium with clean water every 2 weeks. New Jersey Agriculture in the Classroom keeps the bottle about half full and expects small lettuce leaves in about 10 to 14 days.
How Many Seeds Should You Plant per Bottle?
Three or four. The Edible Schoolyard sows 3 to 4 seeds together because fresh seed usually germinates at 80 to 95%, which improves the odds that at least one sprouts. It plants them 1/8 to 1/4 inch (3 to 6 mm) deep in coir and covers them so they sit in darkness.
FAQ About Bottle Hydroponics
Do I need an air pump?
No. Colorado State says an air stone is optional.
Can I use a 1-liter bottle?
Yes. New Jersey Agriculture in the Classroom allows 1- or 2-liter bottles.
What if I use clay pebbles?
The Edible Schoolyard says to start seeds in a plug or rockwool cube first.
When should nutrients go in?
New Jersey Agriculture in the Classroom adds them once the first leaves appear.
Is it good for kids?
Yes; all three sources are classroom or home lessons. Also see our Kratky method guide.
Sources
- Colorado State University Extension — Hydroponics: Wicking Soda Bottle System
- New Jersey Agriculture in the Classroom — Soda Bottle Hydroponics: Growing Plants Without Soil
- The Edible Schoolyard Project — 2 Liter Bottle Self Watering Container
- Photo credits (Wikimedia Commons, edited with titles): Hydroponic lettuce @ Plaine des Cafres 03 by Rémih (CC BY-SA 4.0); Water fills a plastic bottle at an outdoor tap in a garden setting by Shixart1985 (CC BY 2.0); Mason Jar with Screw Top by Dwight Burdette (CC BY 3.0); Dahlias started indoors by F. D. Richards from Clinton, MI (CC BY-SA 2.0)