Hydroponics for beginners: growing plants without soil at home

What is hydroponics?

In soil, roots search for water and nutrients. In hydroponics you hand them both directly: the roots hang in, or are regularly wetted by, water that already contains dissolved plant food. An inert material such as clay pebbles or rockwool only holds the plant upright; it feeds nothing.

Because nothing comes from the medium, everything the plant needs must come from you: a complete hydroponic fertilizer, enough light and oxygen around the roots. Get those three right and leafy greens and herbs often grow faster and cleaner than in pots.

Main system types

Home systems differ mainly in how roots get oxygen. For a first try, the Kratky method is the easiest: no pump, no electricity, no timer. The plant drinks the solution down over weeks, and the growing air gap above the water supplies oxygen to the upper roots.

What you need

• An opaque container with a lid: a 1-gallon jar wrapped in foil or paper, a dark plastic tub or a painted bottle
• A net pot 2–3 in wide, sitting in a hole cut in the lid
• Growing medium: clay pebbles (rinsed) or a rockwool cube
• Hydroponic fertilizer (a complete formula, not regular soil fertilizer); follow the label for dose
• A pH meter or pH test kit, and pH up/down solutions if needed
• Seeds or rooted seedlings with the soil washed off
• Measuring cup and clean water

Setting up a Kratky jar step by step

1. Wash the container, lid and net pot with warm soapy water and rinse well.
2. Make light-proof: wrap or paint the container so no light reaches the solution.
3. Cut a hole in the lid so the net pot sits snugly with its rim resting on the lid.
4. Start the seed in a moist rockwool cube or sow it among clay pebbles in the net pot.
5. Mix hydroponic fertilizer into room-temperature water exactly as the label says.
6. Check the pH and adjust it toward the range on the fertilizer label (often about 5.5–6.5, estimated).
7. Fill the container so the solution just touches the bottom of the net pot.
8. Fit the lid and net pot, place it in light and do not top up to the brim later: let the level fall so an air gap forms for the roots.

Best plants and timings

Fast, leafy crops do best in a jar. Times below are from planting a seedling to first harvest under good light (estimated).

Light: window or LED

Hydroponics removes soil, not the need for light. A south- or west-facing window giving at least 6 hours of direct or very bright light works for lettuce in spring and summer. In winter, or for basil, a full-spectrum LED grow light gives far better results: hang it about 6–12 in above the leaves (check the lamp's guide) and run it 12–16 hours a day on a timer.

Leggy, pale, leaning plants mean too little light. Keep light off the solution itself: light plus nutrients equals algae.

pH and EC made simple

pH shows how acidic the solution is. Roots can only take up all nutrients within a band; for most leafy greens and herbs this is roughly 5.5–6.5 (estimated). Always use the range your fertilizer label gives.

EC (electrical conductivity) shows how strong the nutrient mix is. Leafy greens usually like a mild solution, about 0.8–1.6 mS/cm (estimated); fruiting plants want more. If you do not have an EC meter, simply follow the label dose and do not add extra "to make it grow faster": too strong a mix burns roots and leaf tips.

• Mix fertilizer into water first, then measure pH.
• Adjust pH in small drops and stir before measuring again.
• Check once or twice a week in a Kratky jar.

Water changes and cleaning

In a Kratky jar with a single lettuce, you often do not change the water at all: the plant uses most of it by harvest. If the level gets very low early, add a little solution mixed at half strength, but leave the air gap in place; never drown all the roots again.

In DWC and larger systems, replace the whole solution every 2–3 weeks (estimated) or as your fertilizer label suggests, because nutrients get used unevenly. Between crops, empty everything, scrub containers and net pots with soapy water, rinse thoroughly and let them dry. Clay pebbles can be washed, soaked and reused; rockwool is single-use.

Common problems and fixes

Food safety and hygiene

• Use clean drinking-quality water and wash hands before handling plants and roots.
• Keep fertilizer and pH solutions labelled, closed and out of reach of children and pets; wear gloves if the label says so.
• Never use food containers that held chemicals, and never mix fertilizer in kitchen cookware.
• Rinse harvested leaves in clean water before eating and discard any plant with slimy rot or mold.

⚠️ Hydroponic fertilizer and pH adjusters are not food. Measure them only as the label instructs and store them away from food.

Frequently asked questions

Plants that grow well in hydroponics

LettuceBasilSpinachMintStrawberryParsleyCorianderChives