Everything You Need To Know About Growing Ageratum

Written by Joel SImon in Annuals

Planting ageratums will give any garden or landscaping the pop it needs with its spiky blooms.

Ageratum is an annual plant that is native to Mexico with four varieties that are native to the United States and about 60 different varieties.

Also commonly known as floss flowers, they are a member of the aster plant family that are hardy plants that can take a drought, they can handle some shade, and they don’t get messed with by deer or rabbits.

PLANTING AGERATUM

Ageratums can be sown straight into the soil or started 8 to 10 weeks before the last frost in a cardboard seed starting tray.

They need full sun but they will do fine in partial shade with slower growth and fewer blooms.

Once sown, they take 7 to 10 days to germinate.

Dwarf varieties should be planted about eight inches apart and with other varieties, they should be planted about one foot apart.

They grow best in hardiness zone 10 and 11 with the soil pH ranging between 5.8 through 6.2.

For best results, it is recommended before planting ageratums to till compost into the soil which is known as amending the soil.

This will provide nutrients to the soil, helps with water retention, and will help to keep the soil loose which will make it easier for the roots to grow.

AGERATUM USES

Ageratums are typically used by gardeners in flower beds, rock gardens, raised garden beds, in potting containers, as a border, along pathways, or in mass as a display.

FERTILIZING AND WATERING

Ageratums are not heavy feeders therefore mixing in compost every year is good enough for them or use can use a homemade liquid fertilizer that is well diluted.

When applying fertilizer, it is best to apply it between the base of the plant to the tips of the branches. This area of the plant is known as the drip line.

If the leaves are turning yellow and the soil is moist enough then they need to be fertilized.

Ageratums require constantly moist soil when they are becoming established but afterward, they require about one inch of water per week.

They tend to wilt quickly if the soil is allowed to dry out.

MULCHING

Mulching ageratums will help the soil retain water which will reduce the amount of time it takes to water them.

The thickness bed of the mulch is best between 1 to 2 inches thick and may need to be reduced if you live in a moist and rainy climate or if you are is getting more rain the usual.

The mulch will also help with weed control which is important because they don’t compete well with weeds.

It is best to add new mulch every year as the older mulch breaks down.

BLOOMS

Ageratum Blooms

Ageratum has spiky ball-shaped blooms that are mostly different shades of blue but they also come in red, purple, pink, and white that appear from June until the first frost.

Their blooms attract bees and butterflies in large numbers.

Ageratums don’t require deadheading because the plant will rebloom on its own until the first frost.

If the blooms are allowed to go to seed then they will sprout next year, if you don’t want this to happen remove the wilted bloom before it produces seeds.

PRUNING

When ageratums are young the new growth can be clipped off to encourage the plant to bush out which will increase the number of blooms.

PROPAGATING

If you would like your ageratums to return the next season then you can let some or all of the blooms go to seed.

The seed can be collected or allowed to fall to the ground to sprout the following season.

PESTS

Ageratums don’t have many pests to worry about but there are a few to watch out for.

DISEASES

Ageratums that are planted close together can develop mold and mildew issues during times of high humidity.

If this is the case then pruning and preventive measures may need to be taken.

VARIETIES

Most varieties of ageratums are hybrids with different heights and shades of color.

BLUE HORIZON AGERATUM

Blue horizon ageratums are an F1 hybrid, meaning that it is the first generation that is different from the parent plant.

  • Plant size – grows to about 30 inches tall and 8 inches wide
  • Drought tolerant – yes
  • Blooming colors – purplish-blue
  • Bloom attracts – butterflies and bees
  • Foliage – spade-shaped foliage with jagged edges that grow to about 2 inches long
  • Deer resistant – yes

HAWAIIAN ROYAL AGERATUM

Hawaiian royal ageratum is known for its long-lasting blooms that appear in early spring.

  • Plant size – grows to about 6 inches tall and 8 inches wide
  • Drought tolerant – yes
  • Sun exposure – full sun to partial shade with fewer blooms
  • Blooming colors – blue
  • Bloom attracts – butterflies and bees
  • Foliage – spade-shaped leaves with jagged edges that grow to about 2 inches long
  • Deer resistant – yes

SOUTHERN CROSS AGERATUM

  • Plant size – grows to about 2 feet tall
  • Drought tolerant – yes
  • Sun exposure – full sun to partial shade with fewer blooms
  • Blooming colors – pale blue and white
  • Bloom attracts – butterflies and bees
  • Foliage – spade-shaped leaves that grow to about 2 inches long
  • Deer resistant – yes

RED FLINT AGERATUM

  • Plant size – grows to about 3 feet tall and 1 and a half feet wide
  • Soil pH – 5.8 through 6.2
  • Drought tolerant – yes
  • Sun exposure – full sun to partial shade with fewer blooms
  • Blooming colors – red
  • Bloom attracts – butterflies and bees
  • Foliage – spade-shaped leaves that grow to about 2 inches long
  • Deer resistant – yes

DONDO WHITE AGERATUM

  • Plant size – grows to about 2 feet tall and 1 foot wide
  • Drought tolerant – yes
  • Sun exposure – full sun to partial shade with fewer blooms
  • Blooming colors – white
  • Bloom attracts – butterflies and bees
  • Foliage – spade-shaped leaves that grow to about 2 inches long
  • Deer resistant – yes

BLUE BLAZER AGERATUM

Blue blazer ageratums are an F1 or first-generation hybrid with improved uniformity and earlier blooms.

  • Plant size – grows to about 6 inches tall and 8 inches wide
  • Drought tolerant – yes
  • Sun exposure – full sun to partial shade with fewer blooms
  • Blooming colors – blue
  • Bloom attracts – butterflies and bees
  • Foliage – spade-shaped leaves that grow to about 2 inches long
  • Deer resistant – yes

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Joel SImon

As a kid, Joel found enjoyment in caring for the many houseplants he grew up with, learning how to transplant them safely, cloning them, and more. At about the age of 10, he wanted to see if he could sprout an orange seed from a store-bought orange and ended up using it as a science experiment in a school project. Throughout the many years of gardening, he has helped many friends and family set up their food and botanical gardens. After years of caring for plants, he was talking with other gardeners and discovering old methods of farming and botanical gardening. Joel has decided to share his knowledge for others to enjoy as he has for many years.

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