Seaside Daisy Erigeron karvinskianus (Erigeron mucronatus)

Seaside daisy throws out wiry, branching stems covered in small daisies that open white and age through pink to a dull red, so a healthy clump carries every stage at once from spring until the cold sets in. It seeds itself freely into wall cracks, gravel joints and step risers where nothing could be planted deliberately, and that habit is the entire point of it. It is used spilling over rendered retaining walls, softening the edge of a gravel drive and filling the awkward strip between paving and a fence.

Tough, undemanding, and a plant with a caveat

It comes from Mexico and Central America, and it takes coastal exposure, salt laden wind, thin soil and gravel with no trouble at all. Drainage is what it wants; anywhere water sits, it sulks. The failure mode is not death but decline: left unsheared, a clump goes woody, opens up bare through the middle and flowers less each year until it is a ring of thin stems around nothing. It needs a hard cut, not a tidy up. The caveat is the seeding. Erigeron karvinskianus is naturalised in parts of southern and eastern Australia, so keep it well away from bushland boundaries, creek reserves and rural fence lines, and deal with prunings and stray seedlings rather than letting them travel. In a courtyard, on a wall or in a paved city garden, its wandering habit is a feature. On a bush block boundary it is a liability. It is happiest in a crack, a wall joint or a gravel bed and merely acceptable in a well dug border, where richer conditions push it into leaf and it flops open earlier in the season.

The spiller that flowers, next to the one that does not

The obvious comparison is licorice plant, which fills the same edges and baskets with silver felted foliage and no flower worth keeping. Choose Helichrysum for foliage colour and a plant that stays roughly where you put it. Choose Erigeron if you want flower over a long season and you are happy for it to place itself. On flat ground where you want cover rather than spill, kidney weed makes a dense mat that takes light footfall, which Erigeron will not do. The two work together, the daisy in the vertical joints and the dichondra across the ground. Put simply, plant the Erigeron if you want it to colonise and the Helichrysum if you do not.

The hard shear that keeps it flowering

Shear the whole plant back hard in late winter, to a few centimetres above the crown, before new growth starts. This is the single job that decides whether the plant looks good, and it is done with hedge shears rather than secateurs. A second lighter shear after the main summer flush brings on another wave and cuts down the seed set. Feeding is close to unnecessary and mostly counterproductive: rich soil and regular fertiliser give lush foliage, fewer flowers and a floppier plant. A light dressing of compost in spring on poor ground is as far as it needs to go.

Choosing a size

This plant is available in 5 sizes, from 68mm up to 175mm, priced from $16.95 to $20.95 per plant. The size shown is the pot the plant arrives in, which is the rootball, not the height of the plant. These are younger plants, priced for planting in quantity, and they establish quickly once in the ground. Not sure which to choose? Read our guide to when to plant in Australia.