Aster lateriflorus 'Horizontalis', Aster vimineus 'Horizontalis', Solidago lateriflora 'Horizontalis' and Symphyotrichum lateriflorum 'Horizontalis'



Common name/s ?

Calico aster 'Horizontalis' and horizontal aster.

Skill rating



North America.

Type of plant ?

Deciduous, herbaceous perennial.

Hardiness zone ?

RHS zone


EGF zone


USDA zone


Eventual size

To 60cm height by 45cm spread.

Growth rate ?

Moderate, will reach full size in 2 to 5 years.

Shape it grows into

Upright, branching herbaceous growth.

Season/s of interest

Flowers from late summer through to autumn.

Where to grow it

Happy in full sun or part shade.
Prefers well drained to moist soil.

Happy in any soil type and any pH. Prefers a fertile (nutrient-rich) soil. Will tolerate exposed conditions, but won’t thrive in a north facing position.

Aster lateriflorus var. horizontalis


This branching perennial has a compact structure of crossing, slender stems with small, dark green leaves which may become coppery-purple in autumn. In autumn masses of small, daisy-like flowers appear which have slim white bracts and darker pink centres (which are the actual flowers).

What to use it for

A great choice for late summer/autumn colour in beds and borders. A good choice for a wildlife garden as both birds and butterflies enjoy the nectar from Aster flowers.

How to look after it

Benefits from being divided; if you wish to keep the plant as vigorous as possible you can do this annually.

How to prune it

You can deadhead through the flowering season if you wish, to keep the plant looking tidy. In autumn, once the flowers have faded, cut the whole plant down to ground level.

In late May you can carry out the ‘Chelsea chop’, pruning back your aster to promote a greater number of flowers, later flowering and a more compact plant.

How to propagate it

Asters should be divided regularly to keep them vigorous, and this will also provide additional plants for free. Divide the crowns with a spade or two forks back to back in spring; you can separate them into single shoots to be replanted separately. They should flower in the same year.

Seeds can be collected in the autumn and sown in spring at 15°C. They should germinate in a fortnight and flower after two years’ growth.

Basal shoot cuttings can be taken in spring, or stem cuttings if there isn’t sufficient basal material. They should be rooted in a propagator or mist bench, hardened off and grown on in a cold frame.

Common problems

Asters are susceptible to powdery mildews and wilts. They may also be infested by strawberry mites, aphids, caterpillars, froghoppers, chrysanthemum eelworms and slugs.

Other useful information

The name ‘Aster’ derives from the Latin for ’star’.

One legend explaining why it received this name (other than because of the star like shape of the flowers) is that the plant arose when the Greek goddess of justice, innocence and purity, Astraea, looked at the earth and cried because she couldn’t see any stars. The aster flower then grew out of the soil where her tears fell.

This Aster has been given the Award of Garden Merit by the RHS.