Wick System Window Box Herbs

At a Glance

How This System Works

A wick system is one of the simplest forms of hydroponics. Nutrient solution sits in a reservoir below the planter, and cotton or nylon wicks draw the solution upward into the growing medium by capillary action — the same way an oil lamp wick draws fuel to the flame.

In this build, a long window box planter sits on top of a matching reservoir tray. Wicks threaded through drainage holes in the planter reach down into the nutrient solution and keep the growing medium consistently moist. There are no pumps, no timers, and no electricity needed for water delivery.

Why a window box? The 36-inch length provides room for 8–10 herb plants in a single container, making it the perfect kitchen-window herb garden. The slim 12-inch depth fits on most windowsills or can be mounted with standard window box brackets.

Materials List

Our philosophy: Use what you already have. Hydroponics does not require store-bought equipment. People around the world grow food this way using recycled containers, scraps of fabric, and seeds saved from last season's harvest. The links below are for convenience if you prefer to purchase, but we encourage you to improvise with what is available to you.

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Containers

A 36-inch window box planter with drainage holes and a matching drip tray or reservoir. Use what you have: any long, narrow container works. An old gutter section, a shallow storage bin, or even a wooden box lined with plastic. The reservoir underneath can be a matching tray, a second container, or a baking sheet with raised edges. If you want to buy a dedicated tote for the reservoir, a 10-gallon dark storage tote works well.

Wick Material

Cotton or nylon wick cord is the engine of this system, and it is the easiest thing to find for free. Cut an old cotton t-shirt into 1-inch strips, grab some cotton shoelaces, or use cotton rope from the hardware store. Even strips of felt work. Wick systems are all about simplicity, so use whatever cotton material you have. If you prefer a spool, cotton wick cord (50 ft) is convenient.

Net Cups

2-inch or 3-inch net cups for each planting position (optional, you can also plant directly in the medium). Use what you have: small plastic cups with the bottoms cut out and holes poked in the sides. Or skip them entirely and just plant into the perlite. If you want to buy them, 3-inch net cups (25-pack) keep things tidy.

Growing Supplies

Starter plugs: Small sponge pieces or cotton balls hold herb seeds until they sprout. You can also buy nursery herb transplants and skip the seed-starting step. If you want plugs, Rapid Rooter plugs (50-pack) are a reliable option.

Nutrients: This is one item you need to purchase. Herbs growing in perlite need dissolved minerals in the water. A single kit lasts for months since herbs are light feeders. A General Hydroponics Flora Series (3-part kit) is the standard choice.

Monitoring

A pH/EC meter ensures consistent nutrient delivery. pH test strips from a pet store work fine for a window box herb garden. If you want more precision, a digital pH and TDS meter kit gives you exact readings.

Additional Materials (no affiliate link)

• Perlite and vermiculite mix (50/50), lightweight growing medium that wicks well
• A 36-inch window box planter with drainage holes (available at any garden center)
• A shallow tray, second planter, or custom reservoir that fits beneath the window box
• Herb seeds or small nursery transplants
• Window box mounting brackets (if wall-mounting)

Tools

No power tools required:

• Scissors for cutting wick cord
• Drill with 1/4-inch bit (if planter needs additional drainage holes for wicks)
• Measuring cup or syringe for nutrients

Build Instructions

Step 1: Prepare the Reservoir

The reservoir sits beneath the window box and holds the nutrient solution. Options include:

• Matching drip tray: Many window box planters come with a drip tray — use this as the reservoir
• Second planter: An identical window box without medium, set below the growing box
• DIY reservoir: A shallow plastic storage container (at least 36 inches long, 2–3 inches deep)

The reservoir should hold at least 1–2 gallons of solution.

Step 2: Prepare the Window Box Planter

Ensure your window box has drainage holes along the bottom. If not, drill 8–10 holes spaced 3–4 inches apart using a 1/4-inch drill bit. These holes serve double duty — they let wicks pass through and prevent waterlogging.

Step 3: Thread the Wicks

• Cut 8–10 pieces of wick cord, each about 10–12 inches long
• Thread one wick through each drainage hole so that:
  • 4–5 inches hangs below the planter into the reservoir
  • 5–6 inches extends upward into the planter, fanned out
• Space wicks evenly along the length of the planter

Wick tip: Before first use, soak wicks in water for 10 minutes. This primes them and ensures capillary action starts immediately.

Step 4: Add the Growing Medium

Fill the window box planter with a 50/50 mix of perlite and vermiculite:

• This blend is lightweight, retains moisture, and wicks nutrient solution effectively
• Fill to about 1 inch below the rim of the planter
• Do not pack the medium tightly — loose fill allows better wicking

Why perlite and vermiculite? Perlite provides aeration and drainage while vermiculite holds moisture. Together they create the ideal wicking medium. Avoid soil — it is too dense and will clog the wicks.

Step 5: Mix the Nutrient Solution

Follow the instructions on your hydroponic nutrient concentrate:

• Use clean, room-temperature water
• Mix to half strength for herbs (herbs prefer lighter feeding)
• Target pH: 5.5–6.5
• Target EC: 0.8–1.2 mS/cm

Prepare 1.5–2 gallons of solution for the initial fill.

Step 6: Fill the Reservoir

Pour the nutrient solution into the reservoir tray until it is 1.5–2 inches deep. Set the window box planter on top of the reservoir. The hanging wicks should be submerged in the solution. Within 15–30 minutes, you should see moisture wicking up into the growing medium.

Step 7: Plant Your Herbs

You can plant from seed or transplant small nursery starts:

From seed:

• Make small depressions in the perlite/vermiculite surface, 3.5–4 inches apart
• Place 2–3 seeds per spot, cover lightly with medium
• Mist the surface with a spray bottle until wicking action fully saturates the medium

From transplants:

• Gently rinse all soil from nursery transplant roots
• Create a hole in the medium large enough for the root ball
• Place the transplant and backfill with perlite/vermiculite
• Arrange 8–10 plants along the length of the box

Step 8: Position and Light

• Place the assembled system on a south-facing windowsill for maximum sunlight (6+ hours daily)
• Alternatively, mount with window box brackets at window height
• If natural light is limited, supplement with a grow light positioned 6–8 inches above the plants

Nutrient Guide

Herbs are light feeders. The wick system delivers a steady, gentle supply of nutrients.

Reservoir top-off rule: Check the reservoir every 2–3 days. When the level drops below 1/2 inch, refill with fresh nutrient solution at the same strength. Unlike Kratky, there is no air gap to maintain — the wicks regulate moisture delivery to the roots.

Crop Suggestions

Planting layout suggestion (36-inch box): Place 8 plants spaced 4 inches apart, starting 2 inches from each end. Put taller herbs (dill, basil) at the back and shorter herbs (thyme, chives) at the front.

Estimated Cost

Tips & Troubleshooting

General tips:

• Harvest herbs regularly by cutting stems just above a leaf node to encourage bushy growth
• Replace wicks every 2–3 months as mineral deposits can reduce wicking efficiency
• Rotate the window box 180 degrees weekly so all plants get even light
• Mint is very aggressive — consider giving it an end position or isolating it in its own pot

Maintenance Schedule

Daily

• Quick visual check: are all herbs upright and green?
• Ensure the window box is stable on the sill or brackets

Every 2–3 Days

• Check reservoir level — refill with fresh nutrient solution if below 1/2 inch
• Inspect wicks — make sure they remain in contact with the solution

Weekly

• Harvest herbs — regular trimming keeps plants bushy and productive
• Check pH of the reservoir solution and adjust if outside the 5.5–6.5 range
• Rotate the planter for even light exposure

Monthly

• Flush the growing medium — pour plain pH-adjusted water through the planter to dissolve mineral buildup, then resume normal nutrient solution in the reservoir
• Inspect wicks for mineral clogging — replace any that feel stiff or are no longer drawing moisture
• Prune any woody or overgrown herbs to rejuvenate growth

Frequently Asked Questions

How long do wicks last in a hydroponic window box?

Cotton wicks typically last two to three months before mineral deposits from the nutrient solution begin to clog the fibers and reduce wicking efficiency. You will know it is time to replace them when the growing medium feels dry on top even though the reservoir is full, or when the wicks feel stiff and crusty rather than soft and flexible.

Can you grow herbs indoors in a wick system without a sunny window?

Yes, but you will need to supplement with a grow light. Herbs like basil and cilantro need at least six hours of strong light per day to grow well, and a small LED grow light mounted six to eight inches above the window box and run for 14 to 16 hours daily will produce results comparable to a south-facing window. Without adequate light, herbs will become leggy and produce weak flavor.

Why is there white crust forming on top of my wick system growing medium?

The white crust is mineral salt buildup from the nutrient solution, which is normal in wick systems because water evaporates from the surface and leaves dissolved minerals behind. Flush the growing medium once a month by slowly pouring plain pH-adjusted water through the perlite until it drains out the bottom, which dissolves and washes away the accumulated salts before they reach levels that can harm your plants.

Is a wick system better than a Kratky jar for growing herbs?

Both methods work well for herbs, but they have different strengths. A wick system with a window box is better if you want to grow many herbs in one container with consistent moisture delivery, while individual Kratky mason jars are simpler to set up and make it easy to move or replace a single plant without disturbing the others. The wick system requires periodic wick replacement, while Kratky requires managing the air gap as the water level drops.