The first time people see lettuce growing in water, the reaction is almost always the same: “that's chemicals”, “that tastes of nothing”, “that's all plastic”. Those objections deserve a concrete answer rather than a shrug.
Myth 1: “It's all chemicals”
True: you do add mineral salts to the water — calcium nitrate, potassium nitrate, magnesium sulphate (Epsom salt), monopotassium phosphate and trace elements. These are chemical compounds, and so is table salt.
Not true: that the plant is getting something it would otherwise never meet. Roots cannot absorb “organic” nitrogen from compost at all — soil microbes must first break it down into nitrate and ammonium. Hydroponics skips the middleman, but the molecule at the end of the road is identical.
| Salt in the solution | What the plant takes | Where it occurs in nature |
|---|---|---|
| Calcium nitrate | Nitrogen and calcium | Nitrate forms in every soil as organic matter decomposes |
| Potassium nitrate | Potassium and nitrogen | Saltpetre, wood ash, compost |
| Magnesium sulphate | Magnesium and sulphur | The mineral epsomite, spring and mineral waters |
| Monopotassium phosphate | Phosphorus and potassium | Phosphate rock, bone meal |
| Chelated iron | Iron | Iron is in every soil; the chelate is a synthetic carrier that keeps it soluble |
Staying honest: soil has buffering capacity — humus and clay hold excess and release it slowly. Forty or sixty-five litres of water have no such cushion, so a dosing mistake shows up within two days as brown leaf margins. That is why measuring EC is part of the job, not an optional extra (Nutrients).
Myth 2: “There are no vitamins in it”
Vitamin and mineral content in leafy greens is not set by the medium. It is set by cultivar, light, leaf age at harvest and the time between harvest and plate.
| Factor | Influence on leaf composition |
|---|---|
| Cultivar | Very large; vitamin C differences between lettuce varieties are measured in multiples |
| Light quantity (DLI) | Large; more light means more ascorbic acid and more dry matter |
| Leaf age and position | Large; old outer leaves differ clearly from the heart |
| Storage for 5–7 days | Clear decline; leafy greens typically lose 20–50 % of their vitamin C |
| Medium (soil or water) | Small and inconsistent; comparative studies point both ways |
So nobody can claim lettuce from water is “richer” — nor that it is poorer. What measurably changes is logistics: supermarket lettuce has three to seven days of harvest, cooling and shelf behind it, lettuce from a tower in your kitchen has zero minutes.
Myth 3: “Without soil there is no flavour”
Flavour comes from cultivar, light, temperature, freshness and solution strength. Soil is not an independent variable on that list.
- Bitter lettuce comes from heat, not from water: above 22–25 °C the plant bolts and the leaf turns bitter. Exactly the same happens in a garden bed.
- Tomatoes respond to EC — raised from roughly 2.5 to 3.5–4.0 mS/cm, Brix and flavour intensity climb while fruits stay smaller and yield drops. Bland supermarket tomatoes, by contrast, come from varieties selected for firmness and from chilling below 12 °C, at which aroma compounds disappear.
- And the other way round, honestly: herbs build more aroma under mild water stress. Basil in a continuously irrigated system can therefore taste milder than a pot on the windowsill.
Myth 4: “Plastic in your food”
- PETG is a copolyester, a relative of the PET used for water bottles. Bisphenol A is not in it — BPA comes from polycarbonate and epoxy linings.
- No phthalate plasticisers. PETG does not need them; its toughness comes from the polymer structure itself. Phthalates belong to soft PVC.
- Food-contact grade means compliance with Regulation (EU) 10/2011 for materials in contact with food; colourants and additives of unknown origin are ruled out.
- Heat is the real limit: PETG softens from around 70–80 °C, so tower parts go neither into a dishwasher nor under boiling water — lukewarm water and a brush are enough.
- The genuine weakness of 3D printing is not chemistry but the microscopic grooves between layers where biofilm settles; the answer is cleaning between cycles (Tower maintenance).
And a fair frame: plastic in contact with food is not specific to hydroponics — plant pots, irrigation hose, mulch film, the inner lining of tins and PET bottles are part of almost every food chain.
Myth 5: “It's artificial, GMO food”
Hydroponics is a growing method, not a breeding method. The seed you put into the tower is ordinary seed and may well be an heirloom variety saved from your own harvest; GM vegetable seed for home growing is essentially absent from the EU market.
But here is the part marketing copy skips: hydroponic produce cannot be certified organic in the EU. Regulation (EU) 2018/848 requires cultivation in living soil, so the organic label is off the table even if you never used a single plant protection product.
Where the real weak points are
- Electricity. A 5–10 W pump uses about 4–7 kWh a month, roughly one euro — but a long summer outage is a genuine risk.
- Water temperature. Above 24–26 °C the solution loses oxygen and root rot risk climbs; in summer that matters more than the fertiliser.
- Instruments. A pH and EC meter with calibration solutions costs 30 to 60 euros and needs recalibrating from time to time.
- Everything hangs on one reservoir. A pH mistake or a root disease hits the whole tower at once; in a dark winter you also need to ease back on the nitrogen dose.
Hydroponics is neither a miracle nor a con. It is growing in which you take on the responsibility that soil used to carry.