Of all the ways to grow plants without soil, wick system hydroponics is the most straightforward. No pumps to wire up, no timers to programme, no electricity from a circulating reservoir — just capillary action, the same physics that draws water up a paper towel when you touch one corner to a wet surface. For anyone curious about getting started with hydroponics but put off by the complexity of other systems, a wick build is the sensible place to begin: it costs next to nothing, fits on a windowsill, and teaches the fundamentals — nutrient solution, growing medium, pH — without a single moving part.
How a Wick System Actually Works
The principle is rooted in basic physics. Capillary action is the tendency of water to travel through narrow spaces against gravity, driven by the adhesive forces between water molecules and the surrounding material. Place one end of an absorbent cord into water and the other end into a dry medium, and moisture migrates upward until the system reaches equilibrium.
In a wick system, a reservoir of nutrient solution sits below a plant container. One or more wicks — lengths of absorbent cord — pass through holes in the container base and dip into the reservoir. As the growing medium around the roots dries out, capillary action draws more solution upward. Roots access water and dissolved nutrients from the medium rather than from any pumped flow.
Unlike active systems such as ebb and flow or deep water culture, a wick system has no mechanical components at all. Nothing moves except the liquid itself — which is both its greatest strength and, in certain situations, its most significant limitation.
What You Need to Build a Wick System at Home
A functional wick system requires just four things: a reservoir, a plant container, wick material, and a growing medium. Most of what you need is either already in the house or available inexpensively from a garden centre or general hardware shop.
The Reservoir
Any opaque, food-safe container that holds liquid will serve as a reservoir. Opacity matters because light encourages algae growth in nutrient solution, which you want to avoid. Common choices include dark-coloured plastic storage tubs, repurposed yoghurt pots for tiny builds, or lidded buckets for larger setups. The reservoir should be large enough to hold at least a litre of solution per plant — more if you want to go several days between top-ups.
The Plant Container
The container holding your growing medium and plant roots sits directly on top of the reservoir, with the wicks passing through small holes in its base. Net pots — the mesh cups used across most hydroponic systems — work excellently here because they allow the wick to thread through easily and give roots room to breathe. You can also cut holes in the base of a plastic pot. The container should nest into or sit snugly on the reservoir so the wicks reach the solution without hanging loose.
Wick Material
Choosing the right wick is one of the few places where a wick system can go wrong if you’re not careful. The material needs to be absorbent enough to draw solution steadily but not so dense that it becomes waterlogged and deprives roots of oxygen.
The most reliable options are:
- Nylon rope or braided nylon cord — resists rotting, draws moisture consistently, widely available from hardware shops. A common diameter is 6–8 mm.
- Felt strips — cut from a sheet of craft felt, these work well for shallow containers and are cheap to replace.
- Braided cotton rope — highly absorbent but degrades faster than nylon; suitable for short growing cycles.
- Strips of old cotton T-shirt — an improvised option that works for experimental builds, though longevity is limited.
Avoid natural fibres like jute twine or sisal. These decompose quickly in a moist environment, releasing debris into the reservoir and promoting bacterial growth.
As a starting guide, use one wick per net pot for small herbs, or two to three wicks per container for anything with a larger footprint. The wick should be long enough to reach the bottom of the reservoir and extend 5–8 cm into the growing medium above.
Growing Medium
Because there is no pump to oxygenate the root zone, choosing a growing medium that stays loose and airy is particularly important in a wick system. The medium needs to wick moisture upward readily while also allowing air pockets around the roots.
Good choices include:
- Coco coir — made from coconut husk fibre, coco coir is lightweight, holds moisture well, and wicks reliably. It is the most commonly recommended medium for wick systems.
- Vermiculite — a mineral that expands when heated, vermiculite has excellent capillary properties and is often blended 50/50 with perlite for wick use.
- A 50/50 coco coir and perlite blend — combining moisture retention (coco) with drainage and aeration (perlite) gives a balanced medium that suits most herbs and salad leaves.
Avoid clay pebbles (hydroton) as the sole medium in a wick system — their smooth, rounded surface does not wick water effectively over any meaningful distance.
Step-by-Step: Building Your First Wick System
The following build suits a single herb or small lettuce plant. Scale up by replicating the unit — a row of six jars on a windowsill is perfectly achievable.
- Prepare the reservoir. Choose an opaque container with a capacity of at least 1–2 litres. If your container is translucent, wrap it in dark tape or paint it with blackboard paint to block light. Fill it with pH-balanced nutrient solution (more on this below) to approximately three-quarters full.
- Prepare the plant container. If using a net pot, thread the wick cord through the mesh base. If using a standard pot, pierce two or three small holes in the base — large enough for your wick material, snug enough to hold it in place. Thread the wick through so that 5–8 cm extends upward into the pot and enough hangs below to reach the bottom of the reservoir.
- Fill with growing medium. Fill the plant container loosely with your chosen medium, threading the upward section of the wick through the material as you go. Do not pack it down — a loose fill preserves the air pockets that roots need.
- Position the plant container on the reservoir. The container should sit stably with the wicks hanging into the nutrient solution below. If there is a gap between container and reservoir, bridge it with a small platform (an upturned pot saucer works well) so the wicks are not under tension.
- Plant your seedling or germinated seed. Transplant a seedling grown in a rockwool cube, coco coir plug, or even a germinated seed directly into the medium. Nestle the roots into the medium, ensuring they have good contact with the moistened material.
- Position under light. Place the system near a south- or west-facing window, or under a grow light providing at least 12–16 hours of light daily. Most herbs and salad crops are happy with modest light levels.
- Maintain the reservoir. Top up the solution every few days and do a full change — empty, rinse, refill — every one to two weeks to prevent salt accumulation and microbial build-up.
Nutrient Solution and pH: Keeping It Simple
Even without moving parts, the chemistry of the nutrient solution still matters. Plants grown hydroponically receive all their minerals dissolved in water, so the solution needs the right balance of macronutrients (nitrogen, phosphorus, potassium) and micronutrients (calcium, magnesium, iron). Use a balanced, general-purpose hydroponic formula and follow the dilution instructions carefully — in a wick system there is no flushing action, so excess nutrients accumulate in the growing medium and can cause root burn. Start at half the recommended strength and adjust upward after a week. For leafy herbs and salads, an EC of 1.0–1.6 mS/cm is a reasonable target.
pH matters equally. Most leafy crops absorb nutrients most efficiently between pH 5.5 and 6.5. Check your solution with a pH test kit or digital meter before use, and adjust with pH-up (potassium hydroxide) or pH-down (phosphoric acid) drops as needed. UK tap water typically runs between pH 7 and 8, so you will almost always need to lower it slightly.
Best Crops for a Wick System
Not every plant thrives in a wick system, and understanding which crops suit it makes the difference between a rewarding harvest and a frustrating failure. The ideal candidates are low-demand plants that do not need large volumes of water quickly.
Herbs
Herbs are the classic wick system crop, and for good reason. Most culinary herbs have modest water requirements, compact root systems, and do well in small containers. A hydroponic herb garden built on wick principles can supply a kitchen with fresh leaves year-round. Particularly well-suited varieties include:
- Basil — fast-growing and productive under a windowsill grow light, basil thrives in the consistently moist but not waterlogged conditions a wick system provides.
- Mint — enthusiastic growers that actually benefit from the contained root space a net pot provides.
- Chives — hardy, minimal-fuss, and happy with less light than many herbs.
- Coriander — performs well in wick systems when temperatures are kept cool (15–20°C / 59–68°F); it tends to bolt in heat.
- Parsley — a steady, reliable performer that suits the slow, consistent moisture delivery of a wick.
- Thyme and oregano — Mediterranean herbs that actually prefer slightly drier conditions, making them ideal for a wick system that does not oversaturate the root zone.
Salad Leaves and Lettuce
Loose-leaf lettuce varieties and mixed salad leaves are among the easiest crops to grow in a wick system. They germinate quickly, mature in 30–45 days from seed to harvest, and cope well with the passive water delivery rate. Cut-and-come-again varieties — where you harvest outer leaves and allow the plant to continue growing — are particularly suited to the small scale of most wick builds.
Spinach and Rocket
Both spinach and rocket are shallow-rooted, low-demand crops that suit wick systems in cooler months. Like coriander, they prefer temperatures below 20°C / 68°F and bolt quickly in summer heat.
What to Avoid
Tomatoes, peppers, cucumbers, and courgettes are not suitable — they need far more water than capillary action can deliver, and their roots quickly outgrow a small container. For those crops, deep water culture or another active system is a better fit. Our guide to hydroponic systems for beginners covers the options side by side.
The Limitations of a Wick System
Honest gardening advice means being clear about what a method cannot do, not just what it can. A wick system is not a universal solution — its passivity is a genuine constraint in certain situations.
Water Delivery Rate
Capillary action is inherently slow and cannot be adjusted the way a pump output can. In warm conditions — above 22°C / 72°F — plants transpire rapidly and may outpace the wick, leading to wilting even with a full reservoir. If you grow indoors through warm UK summers without air conditioning, this is worth factoring in.
Not Suited to Larger Plants
The passive delivery rate cannot meet the demand of plants with large biomass. Fruiting vegetables require far more consistent water than a wick can supply, leading to underperformance or crop failure.
Oxygen Limitation
Active systems oxygenate nutrient solution through pumps, sprayers, or air stones. A wick system does none of this — the growing medium must supply the oxygen roots need. If the medium becomes compacted or waterlogged, roots suffocate. This is why root rot is a genuine risk in poorly built wick systems: stagnant, underoxygenated conditions are precisely the environment that Pythium and similar pathogens favour.
Nutrient Accumulation
Without a pump’s flushing action, salts from the nutrient solution accumulate in the growing medium over time. Regular reservoir changes and occasional plain-water flushes of the medium keep this in check — something active systems handle more automatically.
How a Wick System Compares to Other Passive Methods
The wick system’s nearest passive relative is the Kratky method, which is even simpler: plant roots hang directly into a static reservoir with no wick. As the solution is consumed, an air gap forms below the container base, providing oxygen to the roots.
A wick system offers slightly more control over moisture delivery and suits containers where roots cannot easily reach into the reservoir — shallow trays and multi-pot windowsill setups in particular. Kratky tends to work better for lettuce in single bottles or jars where roots can dangle freely. Both are excellent first steps into the broader world of soil-free growing, sharing the same appeal: no electricity, no moving parts, no specialist knowledge required.
Troubleshooting Common Wick System Problems
Plants Wilting Despite a Full Reservoir
Check the wick first — over time, mineral deposits or biofilm reduce capillary efficiency. Remove and rinse it, or replace it entirely. Also check that the medium has not compacted around the wick. If the wick seems fine, measure the EC of your solution; too high a concentration creates osmotic stress that prevents roots from absorbing water normally.
Algae in the Reservoir
Green or brown slime indicates algae growth caused by light reaching the nutrient solution. Ensure the reservoir is fully opaque and reinforce any gaps around the plant container with dark tape. Do a full change and rinse once algae has established.
Slow or No Growth
Slow growth despite adequate moisture usually points to insufficient light or an imbalanced nutrient solution. Revisit the nutrient concentration and pH — both too high and too low a pH lock out specific minerals, showing as deficiency symptoms even when nutrients are present.
Smelly Reservoir
An unpleasant odour suggests bacterial or fungal activity, more likely when temperatures are high or the reservoir has gone too long between changes. Empty, scrub with a weak hydrogen peroxide solution (3%), rinse thoroughly, and refill. Increase the frequency of full changes going forward.
Frequently Asked Questions
What Is the Best Wick Material for a Hydroponics Wick System?
Nylon rope, braided cotton cord, and felt strips are the most reliable choices. Nylon is particularly popular because it resists rotting, draws water steadily, and is widely available. Avoid materials such as jute or natural twine, which decompose quickly in a moist reservoir and can introduce bacteria to your nutrient solution.
How Many Wicks Do I Need per Plant?
For most small herbs grown in individual net pots, one wick per plant is sufficient. Larger plants or those in bigger containers may benefit from two or three wicks to ensure enough moisture reaches the roots. As a rule, if the growing medium is drying out faster than expected, adding an extra wick is the quickest fix.
Can I Use Tap Water in a Wick System?
Yes, but with caveats. UK tap water is generally safe for plants, though it can be high in calcium and magnesium in hard water areas. Check your local water hardness: in soft-water regions, tap water is fine. In hard-water areas, consider using filtered or collected rainwater to avoid mineral build-up in the growing medium over time. Always let tap water sit uncovered for a few hours before use to allow chlorine to off-gas.
How Often Should I Change the Nutrient Solution?
Top up the reservoir every few days as the liquid level drops, and do a full change — emptying and rinsing the reservoir — every one to two weeks. This prevents salt build-up from nutrients and reduces the risk of algae or bacterial growth. In warmer conditions, change it closer to weekly.
Why Are My Plants Wilting Even Though the Reservoir Has Water in It?
Wilting despite a full reservoir usually points to one of three issues: the wick has become saturated or clogged and is no longer drawing moisture upward effectively; the growing medium has compacted around the roots, restricting airflow; or the nutrient concentration (EC) is too high, causing osmotic stress that prevents roots from absorbing water. Check the wick first — replace it if it feels slimy or stiff — then measure the EC of your solution with an inexpensive meter.
Summary
Wick system hydroponics is the gentlest on-ramp into soil-free growing. It runs on capillary action alone, costs little to build from household materials, and produces genuine harvests of herbs and salad leaves without any technical setup. Its limitations are real — it cannot meet the water demand of large or thirsty plants, and it requires attentive reservoir management to avoid salt build-up and algae — but for a windowsill herb garden or a first experiment with hydroponic growing, those limitations rarely matter. Get the wick material right, choose a light-blocking reservoir, use coco coir or a coco-perlite blend, and keep the nutrient solution fresh — everything else is observation and adjustment.