White alternative for Alchemilla Molis

Question

After 20 years, I'm somewhere close to getting a garden I'm happy with but I now need to undo a plant choice I made 20 years ago: Alchemilla Molis.

The problem:

I need a plant that provides the benefit of Alchemilla Molis (good ground coverage, attractive foliage for a long period) but without the downsides (invasive, laborious dead-heading, sprawls over the lawn) for the front of a border that is a better fit for my colour scheme (I really don't like the lime green flower heads).

Note: in the picture the day lilies and perovskia are not yet in bloom and the alliums, tulips, cherry blossom and clematis have been and gone; there are some red leaf heuchera at the front swamped by the alchemilla.

I want a perennial plant or low growing shrub with a lot of long lasting white flowers to 'lift' the whole planting scheme, low enough to plant in a mass at the front of the border.

In my front garden I have Hydrangea Runaway Bride, which would be ideal for this job if I could keep it small (eventual height I believe is 1.2m/4 ft, which is too high.) Would it be possible to keep it small? Or is there an alternative that does the same job?

The front of the border gets a fair amount of sun (west facing garden); soil is clay but it's been improved for 20 years so is pretty friable; location is Gloucestershire, England. I would expect to water plants until they're well established, but hope not to do afterward -- that border has never dried out in 20 years.

Answer 1

If you are okay with a deciduous plant, I can recommend Calamintha nepeta 'Montrose White' (and ONLY this cultivar). Montrose White is sterile, so once it starts flowering (mid-July in zone 5 US), it doesn't stop until frost. Before then, it forms a nice, very neat mound of glossy medium-green foliage (other calamints are very sloppy—like catmint in form—but not this cultivar). It's well-behaved in that it doesn't spread at all, just clumps out a bit each year. Its only drawback from your point of view may be that the flowers are small (somewhat like a white 'Walker's Low' catmint) held in relatively loose panicles. They do, however, make an impact when planted en masse. Here's a little more information, written by a well-respected horticulturalist in southern Wisconsin (US).

UPDATE

Given that Monstrose White is not available in the UK, I can change my recommendation to Marvelette White. This is a 20cm tall Fleuroselect winner that is called "permanent flowering" from Jelitto Seeds, so it is available in the UK. Seems to be a European replacement for Montrose White. There is also a blue cultivar, if you're interested.

Answer 2

How about a potentilla (shrubby cinquefoil)? It's a low-growing shrub, and some cultivars will give you white flowers from spring through autumn, e.g. Potentilla fruticosa 'Abbotswood'.

Answer 3

The short answer to keeping a hydrangea small is no, it won't flower, and the same is true of finding a low growing white flowering plant that will flower all summer long, there isn't one. Iberis sempervirens flowers white and is evergreen, but flowers early, around March April; Helianthemum varieties follow on up to mid/end of June, and there are some white flowered varieties, but they prefer as much sun as possible. The problem then is, there's nothing from July onwards that's white flowered and low growing till we get to September/October, when Liriope muscari monroe white flowers in short spikes. Liriope also has other variegated leaf forms, with purple flowers in late summer - these will look quite bright at the front of the border.

Perhaps an alternative solution therefore is to select a plant based on its foliage rather than its flowers - Helianthemum The Bride has white flowers and grey foliage, and after the flowers have gone, the foliage will still give a pale look at the front of the border. Other grey leaved plants that are relatively low growing: Convulvulus cneorum with white flowers around May; dwarf forms of lavender and Santolina chaemycyparis, which has yellow flowers if you let it flower - I usually clip mine back to keep a tidy rounded shape two or three times a year, which often means few or no flowers, but I grow them for their foliage anyway.