Agriculture and Food 7–12 · Years 11–12
Asexual propagation: rooting cuttings with and without auxin
Plant production (Preliminary): Plants and their commercial production
The idea
A stem cutting grows new roots and becomes a clone of its parent, and the auxin in rooting powder speeds root formation, which growers use to propagate plants true to type.
What you need
- parent plants of coleus (Plectranthus scutellarioides, the plant used in the SAPS auxin protocol) and of rosemary
- sharp secateurs or knife
- rooting powder containing the auxin indole-3-butyric acid (IBA), at the strength on the product label
- 50:50 perlite and peat (or coir), 40 small pots or a propagation tray with a clear cover
- spray bottle, labels, ruler
How to do it
- Take 20 cuttings of each species, 8 to 10 cm long, cutting just below a leaf joint and removing the lower leaves.
- Dip the base of 10 cuttings of each species in rooting powder and tap off the excess; leave the other 10 untreated.
- Insert all cuttings to the same depth in the mix, label them and cover them to keep the air humid, in bright indirect light.
- After 3 to 4 weeks lift each cutting gently and record whether it has rooted, the number of roots and the longest root length.
- Calculate the percentage rooted and the mean root number for each species and treatment, and compare the species.
What you should see
Treated cuttings root sooner and with more roots than untreated ones. Coleus roots readily even untreated, so its difference shows mainly in root number and length; the woody rosemary shows a larger difference in the percentage that roots. Rooted cuttings look like their parent because they are clones. The learner knows it worked when the untreated coleus cuttings still root, confirming that conditions were suitable.
What changes
- What you change
- rooting hormone (IBA powder or none) and species
- What you measure
- percentage rooted, roots per cutting, longest root (mm)
- What you keep the same
- cutting length and position on the parent
- mix
- humidity
- light
- temperature
- time before lifting
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- A cutting grows from a seed hidden in the stem.
- Plants grown from cuttings differ from their parent the way seedlings do.
- More rooting hormone always gives more roots.
Safety card
Hazards
- cuts from secateurs
- rooting powder irritates skin and eyes
- perlite dust
Controls
- cut away from the hand holding the stem
- gloves and eye protection for rooting powder
- dampen perlite and wear a P2 mask
Note
Plant hormone products: follow the label and NSW Department of Education, Chemical Safety in Schools (CSIS) 2021 Technical Update: Section 1 (general information for all staff) and Volume 2 Appendix D (generic risk assessment advice for each chemical). Complete a CSIS or RiskAssess site-specific risk assessment before the lesson.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
Sources
The pages the author read to write this activity.
- www.saps.org.uk/teaching-resources/resources/183/investigating-the-hormone-auxin-iaa-a-plant-growth-regulator
- www.nsw.gov.au/education-and-training/nesa/curriculum/tas/agriculture-stage-6-2013
- www.nsw.gov.au/sites/default/files/noindex/2025-03/agriculture-amended-st6-syl-2013.doc
- curriculum.nsw.edu.au/learning-areas/tas/agriculture-11-12-2026/outcomes
- education.nsw.gov.au/content/dam/main-education/asset-management/chemical-safety/5._Volume_2_Appendices.pdf