Plant the same seeds in two gardens and they may grow very differently. A fair test can find out why.
Key idea
A plant's growth depends on its genes and its surroundings: light, water, nutrients, temperature and space. Genes set what is possible; conditions decide how much of it happens.
Why it works
Seeds from one parent plant share most of their genes. If they grow differently, the difference must come from their surroundings. Two different varieties given the same care show the opposite: a dwarf pea stays short beside a tall pea, because their genes differ. Most traits depend on both.
Worked examples
Worked example: Read the chart
How much taller, on average, were the plants with 12 hours of light than those with 2 hours?
- 12 hours: 23 cm. 2 hours: 6 cm.
- $23 - 6 = 17$.
Answer: 17 cm taller.
Worked example: Genes or surroundings?
A tall variety of corn grows short in poor, dry soil. Why?
- Its genes allow tall growth.
- Poor soil and too little water limited it.
Answer: Both: the genes allow tall growth, but the conditions held it back.
Common mistake
Thinking a plant's size is decided by genes alone, or by care alone. Genes set the range; light, water, nutrients, temperature and space decide where in that range the plant ends up. Check: did the plants share genes, or share conditions?
Try it with the Food Garden Planner: it suggests what to grow for your space and climate, and when to plant it.