The easy way to plant and care for ageratum

Once only known for their blue flowers, ageratum has recently expanded out in terms of colour. Here's some ways to help your plants grow and flourish, no matter what colour you choose.

• Blue ageratums remain garden treasures, but now there are white ageratums.
• Innovative bicolours have medium blue flowers with contrasting white centres.
• 'Blue Horizon' and 'Blue Bouquet' produce a summer-long parade of blue flowers.

• Dwarf varieties are ideal plant partners for filling containers, edging beds and planting in front of taller flowers.
• For a bold effect, try massing these fluffy bloomers in groupings of 10 or more. Space the plants 15 to 20 centimetres (six to eight inches) apart.
• Ageratums are easy to mix with annuals of any colour.
• You can also tuck them between perennials to echo shades of blue and purple flowers.
• Use them to visually cool down hot bright orange and yellow flowers.

• It's easy to find ageratums in garden centres, discount stores, and nurseries as spring bedding plants.
• You can easily start seeds indoors eight weeks before the last frost.
• Use moistened, commercial sterile, soil-less seed starting mix. Lightly press the seeds, which need light to germinate, into the mix without covering them.
• Keep the soil moist and set the pots in a sunny window.
• When seedlings have two or three mature leaves, transplant them to individual pots.
• Set plants out after the last frost has passed. Keep the soil consistently moist for three weeks.

• Ageratums thrive in hot weather. But in locations where summers are very hot and humid, they prefer a little light shade.
• Watch out for too much shade, which can make these compact plants leggy.
• While prolonged droughts can wilt and weaken them, a deep drench of water will quickly revive agertums.
• Dwarf ageratums are willing to adapt to full sun or partial shade.
• Long-stemmed varieties bloom longer if you promptly remove old flowers.
• Vigorous dwarf varieties flower nonstop with occasional pinching off of old blooms.

• Dwarf varieties of Mexico and Central America truly resent a chill, and their leaves respond to frost by turning from green to black overnight.
• To get them through an early frost, cover them with blankets.

• Ageratums are usually pest-free, but can fall prey to two types of tiny sucking insects.
• Barely visible spider mites feed on the backs of leaves, giving the foliage a pale, stippled appearance. You may even be able to see their fuzzy webs.
• Whiteflies look like white gnats and will fly up in a cloud when disturbed.
• Pests can be dispatched by spraying the plant with a strong blast of water from a hose.
• You can also apply insecticidal soap, as directed. Use it in the evening, or on a cloudy day, to prevent sun-scorched leaves.

Agertums, thanks to modern innovation, can add splashes of colour to your garden. Be sure to watch out for pests and frost, however, as these plants can be difficult to maintain. But if you pay careful attention, you could be rewarded with wonderful colours.