Ageratum
Ageratum houstonianum · Asteraceae
The gardener's calendar
Ideal time to plant ageratum: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.
ID card
- Common name
- Mexican Ageratum
- Family
- Asteraceae
- Form
- Annual herbaceous plant
- Mature size
- 20 to 60 cm in height
- Flowering
- June to October (blue, pink or white flowers)
- Foliage
- Deciduous (annual)
- Growth
- Fast
- Hardiness
- Frost-tender (grown as annual)
- Origin
- Mexico and tropical regions of the Americas
- Soil type
- Fertile, well-draining, slightly moist
Care
Regular watering
Keep the soil moist but never waterlogged. Water as soon as the soil surface dries slightly, about 2 to 3 times per week depending on climate. During heat waves, increase watering frequency. Avoid wetting the foliage to prevent fungal diseases.
Light and exposure
Ageratum prefers full sun to partial shade. It flowers best with 6 to 8 hours of sun daily. In very hot regions, light afternoon shade protects from excessive summer heat.
Pruning and pinching
Pinch young plants early in their growth to encourage dense branching and a compact form. Regularly remove spent flowers (deadheading) to stimulate continuous blooming. Light pruning during the season rejuvenates the plant.
Moderate fertilizing
Apply a balanced, diluted fertilizer every 2 to 3 weeks during growth and flowering. Excess nitrogen encourages foliage at the expense of flowers. Potassium boosts abundant flowering.
Soil preparation
Prepare a rich, light, well-draining substrate high in organic matter. Incorporate quality compost or potting soil. This plant appreciates fertile soils but fears root asphyxiation from compaction.
Disease prevention
Watch for powdery mildew and downy mildew if conditions are too moist. Ensure good air circulation between plants. Spider mites can appear indoors in dry conditions; mist the air around plants to prevent infestations.
Did you know?
Mexican ageratum owes its name to the Greek words "a" (not) and "geras" (old age), because its flowers remain colorful for a long time without fading. In the 19th century, Victorian horticulturists widely adopted it for ornamental gardens in Europe, appreciating its prolonged flowering and unique blues among annuals.
Where to buy it
Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.
Add this plant to my garden →Plants from the same family
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- YarrowAchillea millefolium
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- SneezewortAchillea ptarmica
- Canadian goldenrodSolidago canadensis
- WormwoodArtemisia absinthium
Tips generated and checked by Viridia — adapt them to your local climate.