Bougainvillea Cuttings in Monsoon: Rot, Leaf Drop and a Blame on Hormone
A nursery in Nashik takes 200 semi-hardwood bougainvillea cuttings in the first week of June. Each cutting is 15 cm long with four nodes, the lower leaves are stripped, and the cut end is dipped in 2,000 ppm IBA powder. Cuttings are inserted 5 cm deep in river sand inside an open-sided shade net with 50% shade. Intermittent mist runs for 10 seconds every 10 minutes from 9 a.m. to 6 p.m. There is no bottom heat and no fungicide treatment. After three weeks, 65% of cuttings have dropped their leaves, about 40% have black, soft bases, and only a few show roots. The sand feels saturated and algae are growing on the surface. Night temperature is 24–26°C and daytime humidity stays above 85% because of monsoon conditions. The nursery owner wants to blame the IBA powder and switch to a stronger hormone.
1. Diagnose why rooting failed. Link each symptom to a likely cause and explain whether the IBA powder is the main problem.
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The symptoms point to an environment and sanitation problem, not the IBA powder.
- Black, soft bases in 40% of cuttings indicate basal rot from a waterlogged medium and no fungicide protection. River sand alone holds a perched water table, and mist every 10 minutes keeps it saturated. Bougainvillea cuttings need air at the base.
- 65% leaf drop is consistent with anaerobic stress and ethylene buildup in a continuously wet medium. The monsoon already gives high humidity, so frequent mist adds little benefit and keeps leaves and stems wet.
- Few roots follows from lack of oxygen in the medium. Root initiation needs respiration; saturated sand inhibits it even when temperature is warm enough.
- Algae on the surface confirms continuous moisture and nutrient presence.
- The IBA dose of 2,000 ppm is within a normal range for semi-hardwood bougainvillea cuttings. A stronger hormone will not fix rot and may increase callus without roots.
A 50% shade net is reasonable, but open-sided monsoon shade with no ventilation control keeps humidity near saturation. The main correction is drainage, aeration, mist control and sanitation.
2. Design a revised propagation protocol for the next batch, covering cutting selection, medium, hormone, sanitation, and misting.
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Cutting selection. Take healthy, stocky semi-hardwood shoots, 12–15 cm long with 3–4 nodes, about pencil thickness. Make a clean angled cut just below a node. Remove lower leaves and keep two or three upper leaves, cutting large leaves in half to reduce water loss.
Medium. Use a free-draining mix such as 50% cocopeat plus 50% perlite, or 1:1:1 cocopeat:perlite:vermiculite. Pasteurize or treat the medium, and use trays with drainage. Do not use river sand alone.
Hormone. Keep IBA at 2,000–3,000 ppm as a quick dip or powder. Do not increase the dose blindly; the problem is not hormone concentration.
Sanitation. Sterilize blades between batches. Dip cuttings in a labelled broad-spectrum fungicide and drench the medium according to label directions. Remove and discard rotting cuttings promptly.
Environment. Provide bottom heat of about 22–25°C at the base if possible. Aim for 70–80% relative humidity, not continuous saturation. Mist for 5–8 seconds every 10–15 minutes during the day, less at night, and let leaves dry between cycles. Use a ventilated propagation tunnel rather than open monsoon shade, and start with 50–70% shade.
Record keeping. Record mist intervals, temperature, humidity and fungicide dates so results can be compared.
3. How would you assess success at six weeks, and how would you harden off and pot the rooted cuttings?
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Assess success. At six weeks, gently tug 10 random cuttings. Resistance indicates roots. Lift a few to check that roots are 3–5 cm long, white and branching, and that the base is firm, not black and soft. Count rooted cuttings and calculate the percentage. Reject any cutting with black basal tissue.
Reduce mist. Once roots are visible, cut misting to two or three short cycles a day for 5–7 days. This encourages the plant to take up water through roots rather than leaves.
Harden off. Move the trays to 50% shade, then gradually increase sunlight over 7–10 days. Apply a dilute balanced liquid feed at low EC. Avoid sudden full sun, which can scorch soft leaves.
Potting. Pot into a free-draining nursery mix, water thoroughly, and keep under 50% shade for another week. Space pots for airflow. Label the batch and keep it separate from older stock so any rot problem does not spread. A realistic target after correction is 70–85% rooting, not 100%.