Plants
Floss Flower
Ageratum houstonianum · Asteraceae
Floss flower is the classic for blue bed edgings: its fluffy, pompom-like flower clusters in blue-violet sit so densely that the low varieties read as a continuous ribbon of colour — from May until the first frost. Its German name, liver balm, comes from old herbal medicine and has nothing to do with the modern bedding plant. We buy our bedding stock compact and full of buds at the Veiling Rhein-Maas.
- Light
- Sunny to lightly part-shaded.
- Watering
- Regular — evenly moist, without waterlogging.
- Care level
- Easy
- Botanical
- Ageratum houstonianum
Ageratum houstonianum comes in two stature classes: low bedding varieties such as Blue Mink or the Hawaii series stay compact at fifteen to twenty-five centimetres and are the classic edging; tall cutting varieties like Blue Horizon reach sixty to seventy centimetres and are popular with us as a summer cut flower.
The blue-violet of floss flower is valuable in design because true blue is rare in the bed. Classically it is paired with yellow marigolds — the complementary contrast positively glows. Neighbourhoods with white sweet alyssum, silver foliage or pink begonias read more calmly.
The fluffy flower clusters consist of dozens of tubular florets and are a good nectar source for butterflies and bees. Because the plant pushes new blooms tirelessly, the ribbon of colour stays closed with little effort; just pick off spent heads occasionally so no brown tufts spoil the picture.
As a Central American it needs warmth and is absolutely frost-tender — it has no business in the bed before the last spring frosts. It likes nutrient-rich, evenly moist soil in full sun; under drought stress it stops flowering but forgives quickly after a good watering.
An important safety note: floss flower contains pyrrolizidine alkaloids, which damage the liver in larger amounts. It is purely ornamental — not for nibbling children or grazing pets, and despite its German name absolutely unsuitable for tea or home remedies.
Is Floss Flower toxic to children and pets?
- Children
- Toxic
- Cats
- Toxic
- Dogs
- Toxic
Floss flower contains pyrrolizidine alkaloids that are toxic to cats, dogs and children and can damage the liver in larger amounts. Keep the plant out of reach and, despite its misleading German name, never use it internally.
Typical symptoms: After ingestion: vomiting, diarrhoea, loss of appetite; liver damage possible with repeated intake of larger amounts.
In an emergency:call the German poison control centre in Bonn on +49 228 19240 (24/7) — for pets, contact an emergency vet directly. This information does not replace medical or veterinary advice.
Overview: toxic & non-toxic plants for cats, dogs and children
Care
- 01A fully sunny, warm spot; also flowers in light part shade, but more loosely.
- 02Keep evenly moist — drought stress halts flowering.
- 03Nutrient-rich soil and a feed every two weeks.
- 04Pick off spent, browned tufts regularly.
- 05Plant out only after the last spring frosts; absolutely frost-tender.
- 06Grow out of reach of pets and small children.
Frequently asked
- Where does the German name liver balm come from?
- From old herbal medicine: related species were once used for liver complaints. The modern bedding plant Ageratum houstonianum must be strictly separated from that — it contains liver-damaging pyrrolizidine alkaloids and must never be used internally.
- Is floss flower toxic to cats or dogs?
- Yes. Its pyrrolizidine alkaloids can cause digestive upsets in cats and dogs and, in larger or repeated amounts, liver damage. Plant beds and boxes with floss flower out of reach of nibbling pets.
- Does floss flower work as a cut flower?
- The tall varieties such as Blue Horizon, yes — freshly cut they last a good week in the vase and give summer bouquets a fluffy blue-violet texture. The low bedding varieties are too short-stemmed for that.
- How long does floss flower bloom?
- Continuously from planting in May until the first frost — hence the botanical name Ageratum, roughly „not ageing“. The prerequisites are a warm, sunny spot, even moisture and occasionally picking off spent blooms.