Understanding Plant Hormones for Better Growth

By Nina Walsh · October 1, 2026

The Five Key Plant Hormones

Plant hormones, or phytohormones, are chemical messengers that control every aspect of plant growth and development. Understanding these hormones helps gardeners make better decisions about pruning, fertilizing, and stress management.

Auxins

Auxins control cell elongation, root initiation, and apical dominance. They are produced in shoot tips and flow downward. When you pinch off the top of a plant, you remove the auxin source, which releases lateral buds and creates bushier growth.

Practical Application

Rooting hormone powder contains synthetic auxin (IBA). Dip cuttings in it to speed root formation. Pinching stem tips removes apical dominance and encourages branching. Bending branches downward redirects auxin flow and promotes flowering.

Cytokinins

Cytokinins promote cell division, delay senescence, and stimulate shoot growth. They are produced in root tips and flow upward. The balance between auxins (from shoots) and cytokinins (from roots) determines whether a plant grows roots or shoots.

Gibberellins

Gibberellins promote stem elongation, seed germination, and flowering. They are responsible for the stretching growth of seedlings reaching for light. Dwarf plant varieties often have reduced gibberellin production or sensitivity.

Ethylene

Ethylene is a gas that promotes fruit ripening, leaf abscission, and flower senescence. It is why a ripe banana speeds up the ripening of nearby fruit. Ventilation reduces ethylene buildup and extends the life of cut flowers and stored produce.

Abscisic Acid (ABA)

ABA is the stress hormone. It triggers stomatal closure during drought, promotes seed dormancy, and helps plants survive winter. Overwatering can reduce ABA levels, making plants less resilient to sudden stress events.