Wick Hydroponic System — Passive Capillary

Quick answer

Wick hydroponic systems use capillary action through a fiber wick to draw nutrient solution from a reservoir into media surrounding plant roots. There is no pump, no timer, and no power requirement. The system is suitable only for low-water-demand crops — lettuce, herbs, and microgreens — and fails the moment you try to grow anything that transpires heavily [RHS-HYDRO-01].

Parameters

How it works

A reservoir of nutrient solution sits below a media-filled grow tray or container. One or more wicks pass from the reservoir up through the media. Capillary action — the same physics that pulls water up a paper towel — draws solution along the wick fibers, wetting the media surrounding the wick. Roots grow into the moist zone and take up nutrients [RHS-HYDRO-01].

The wick continuously delivers solution at a rate set by the wick's capillary capacity, the media's water-holding ability, and the plant's transpiration demand. There's no active control — the system self-regulates by physics.

Wick material

Wick choice determines the maximum delivery rate:

• Cotton braided rope. Highest wicking rate, biodegrades in 6–12 months. Hobby favorite.
• Nylon rope. Slower wicking, lasts indefinitely. Commercial choice where available.
• Felt strips. Wide surface area, moderate rate, easy to install.
• Synthetic monofilament. Does not wick. Avoid [GROWER-LOGS].

Pre-soak the wick in water before installation; dry wicks can air-lock and fail to start capillary flow.

Best crops

Wick systems work for:

• Lettuce (all types)
• Basil, mint, parsley (small specimens)
• Arugula and baby greens
• Microgreens (extremely well-suited)
• Small house plants

The system fails for:

• Tomato, pepper, cucumber (transpiration exceeds wick capacity)
• Strawberry (variable demand exceeds passive supply)
• Anything taller than 30 cm [CORN-CEA-01].

How wick differs from Kratky

Both are passive, but the mechanism is different:

• Wick: capillary action through a fiber, media-based, no air gap above water.
• Kratky: static reservoir with a roots-and-air dual zone, no media for roots beyond initial net cup [KRATKY-ORIG].

Wick allows you to top up the reservoir without disturbing the plant. Kratky requires the air gap to develop naturally as plants drink, which means you don't top up — you start with the full reservoir.

Failure modes

• Wick air-locks. Dry wicks fail to start flow. Pre-soak.
• Plant outgrows wick capacity. Lettuce at maturity in a hot room can exceed a single cotton wick's delivery. Add wicks or accept slow growth.
• Algae in reservoir. Light exposure to nutrient solution. Use opaque reservoirs.
• EC concentration at root zone. Without flush cycles, salts concentrate at the wick exit point. Flush or replace media every 4 weeks.
• Reservoir runs dry. No alarm, no pump status. Check weekly [OSU-NUT-01].

EC management

Wick systems struggle with EC control. Because the system has no active recirculation, evaporation from the media surface concentrates salts at the top. Counter this by:

• Keeping EC modest (under 1.4 for leafy crops)
• Top-watering with plain water once weekly to flush the surface
• Refreshing reservoir solution every 2 weeks [OSU-NUT-01]

What we recommend

Wick systems are a beginner-friendly entry point for understanding hydroponic principles, and they work genuinely well for microgreens, basil, and small lettuce plantings. Use cotton wicks, perlite or perlite/vermiculite media, EC 1.0, pH 6.0, and a 5 L opaque reservoir per 4-plant setup. Refill water weekly, replace full solution every 14 days. Don't try to scale wick — the moment you want production volume or fruiting crops, switch to DWC, NFT, or Dutch bucket. Wick is for hobby, education, and crops that don't transpire much.