Science 7–10 · Year 9

Asexual reproduction by cuttings: rooting success as an investigation

Science understanding: Biological sciences

PracticalLow risk

The idea

A piece of a plant can grow into a complete, genetically identical plant, and the conditions that favour rooting can be tested with a controlled comparison.

What you need

Softwood shoots from an easily rooted plant (coleus, geranium, mint or basil), enough for ten 5 to 10 cm cuttings per treatment
Clean secateurs or scissors, pots of moist propagating mix, labels
Clear plastic bags or a propagator lid, and a warm spot at 18 to 24 °C out of direct sun (the RHS softwood cuttings guidance gives 18 to 24 °C bottom heat and says a plastic bag somewhere warm will do)
A ruler and a sheet for weekly observations

How to do it

Cut shoots 5 to 10 cm long just below a leaf joint, remove the lower leaves and pinch out the soft tip, as the RHS advises.
Set up two treatments of ten cuttings each, differing in one factor: covered with a bag against uncovered, or two leaves left against four.
Push each cutting into moist mix, water, and place all pots together at 18 to 24 °C. Take the cuttings in spring or early summer, when the RHS says softwood material roots readily, and ventilate bagged cuttings for 10 minutes at least twice a week as the RHS advises.
Each week for four weeks record which cuttings are alive and, at the end, tip each out and record whether roots are present and the longest root length.
Calculate rooting percentage per treatment and the mean root length of rooted cuttings.
Evaluate the comparison: did the two treatments differ in only one factor, and is a difference between two groups of ten cuttings large enough to trust, or should the class pool its results?
Pot up the rooted cuttings and note that each is a clone of the parent.

What you should see

The RHS gives about two to four weeks for softwood cuttings to root. Covered cuttings are expected to wilt less and root more often than uncovered ones, because the bag keeps humidity high while there are no roots to replace lost water. The learner knows it worked when rooted cuttings show white roots at four weeks and the rooting percentages of the two treatments have been compared using the pooled class results.

What changes

What you change: Humidity cover, or number of leaves retained
What you measure: Rooting percentage at four weeks; longest root length
What you keep the same: Parent plant
Cutting length
Mix and pot
Temperature and light
Watering

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

A cutting is a seed of the plant; it is a piece of the parent and genetically identical to it.
Plants only reproduce sexually.
Roots grow from the leaves.

Safety card

Low riskLearners carry it out

Hazards

Secateurs
Potting mix dust (Legionella risk)

Controls

Cut away from the hand
Moisten mix before use, wear gloves and a mask, follow the warnings on the potting mix label and wash hands afterwards, as healthdirect advises; open bags outdoors

Note

No hazardous chemicals; record a RiskAssess risk assessment for the activity as school procedure requires.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science 7–10 Syllabus (2023)SC5-GEV-02 SC5-WS-03 SC5-WS-04 SC5-WS-06
Australian Curriculum v9AC9S9U02AC9S9I02AC9S9I04AC9S9I06

Sources

The pages the author read to write this activity.

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