Lesson guide · Lesson 7 · Grades 3–8 · 6 min

Growing without soil

How a plant can grow in water with no soil, and what does soil's jobs instead.

Open the lessonPrintable worksheet

Students will

  • Explain hydroponics as growing plants in water with plant food mixed in, and no soil.
  • Name what does each of soil's jobs in a hydroponic tub: holding the plant, bringing water and food, bringing air.
  • Explain why roots in water still need air.

New words

hydroponics
Growing plants in water with plant food mixed in, and no soil.
net-pot
A small cup full of holes that holds a plant up. Roots grow out through the holes.
reservoir
The tub that holds the water and plant food.

Talk about it

If you grew plants on a spaceship, which of soil's jobs would be hardest to replace?

Check questions and answers

  1. What is hydroponics?

    • Growing plants in water with plant food, and no soil (answer) Right. The water brings the food straight to the roots.
    • Growing plants in very wet soil Not quite. Hydroponics uses no soil at all.
    • Growing plants with no water Not quite. Water is the main part. It carries the food.

  2. There is no soil. What holds the plant up?

    • A net pot (answer) Right. The cup holds the stem, and the roots grow through its holes.
    • The bubbles Not quite. Bubbles bring air. Look at the cup in the lid.
    • The roots float it up Not quite. Something at the top holds the plant in place.

  3. Why does a tub of water need bubbles?

    • Roots need air to stay healthy (answer) Right. In soil, air sits in tiny gaps. In water, bubbles bring it.
    • Bubbles make the water warm Not quite. Bubbles bring something roots need to breathe.
    • Bubbles push the food out Not quite. The food stays in the water. Bubbles add air.

Sources

  • Dunn, B. Hydroponics. Fact sheet HLA-6442. Oklahoma State University Extension, 2025.
  • Nelson, M., G. Langellotto, and L. Nackley. Hydro hints: What is hydroponics? EM 9453. Oregon State University Extension Service, 2025.
  • Hart, C. Home Hydroponics (handouts). University of Illinois Extension.
  • Gatiboni, L. "1. Soils & Plant Nutrients." In Moore, K. A., and L. K. Bradley, eds. North Carolina Extension Gardener Handbook, 2nd ed. NC State Extension, AG-831, 2022.
  • Accessible Gardening: Hydroponic Gardening. Green Thumbs, Healthy Joints, West Virginia University, 2011.
  • Kratky, B. A. Three non-circulating hydroponic methods for growing lettuce. Acta Horticulturae 843: 65-72, 2009. Copy hosted by the University of Hawaii CTAHR.
  • Hoagland, D. R., and D. I. Arnon. The Water-Culture Method for Growing Plants without Soil. Circular 347. University of California College of Agriculture, Agricultural Experiment Station, 1938.
  • Singh, H., and B. Dunn. Electrical Conductivity and pH Guide for Hydroponics. Fact sheet HLA-6722. Oklahoma State University Extension, 2017.
  • Johnson, K. Growing without soil: Getting started with hydroponics at home. Good Growing blog, University of Illinois Extension, 2026.