Mountain sandwort
Arenaria montana · Caryophyllaceae
A dense, dark green mat of tiny leaves that disappears under round, pure white flowers in late spring, each one large for so small a plant.
- Size
- 4 in tall, 16 in wide
- Zones
- 4 to 8
- Light
- Full sun to part sun
- Flowers
- Mid May to late June
- Pets
- Not checked
- Job in a bed
- Carpet
A bed built around mountain sandwort
The planner designed this bed around mountain sandwort when this page was made: a 12 × 6 ft (3.7 × 1.8 m) English border in zone 6, full sun. It chose the other plants from the 966 that suit those conditions, and says below why mountain sandwort stands where it does.
The plants
- 1 Mountain sandwort × 21, white
- 2 Sea thrift × 7, pink
- 3 Little bluestem 'The Blues' × 5, tan
- 4 Stiff goldenrod × 3, yellow
- 5 Dwarf English boxwood × 1, dark green leaves
- 6 Butterfly weed × 3, orange
- 7 Star of Persia × 2, purple
- 8 Hyacinth × 7, blue
Why this plant
- The only open bowls. The others are globes, spires and flat plates. Shape reads at a distance, where colours blur.
- A classic partner for sea thrift. Both are on this plan. A pairing gardeners have proved outranks a general rule.
- The only white. White sits between stronger colours and calms them.
Why here
- Under the taller plants. It runs back between them as living mulch: there its job is to cover the soil, not to be looked at.
- 21 plants in 5 groups (5, 5, 5, 3 and 3). Seen again further along, the same plant ties the bed together.
- Beside sea thrift. A recognised partner: the planner puts such plants together where it can.
Why now
- In flower for six weeks. From mid May to late June.
- Part of the bed's peak. With sea thrift and star of Persia in late May: 3 kinds at once. No week has more.
- One of three evergreens. They are what the bed has to show from November to March.
Planned as an English border: 7 of the 7 groups (100%) are drifts, longer along the bed than they are deep. Mountain sandwort repeats along the bed to tie it together. Cool colours (pink, purple and blue) with yellow and orange as the warm notes, and white and tan to calm things between them.
The planner's own design check: 12 Excellent, 5 Good. It flags one thing to watch: Nothing on this plan is highly poisonous or an aggressive spreader.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where mountain sandwort goes in a border
At 4 in it belongs at the front of a bed. In the planner's ten height classes it is ground-hugging (up to 6 in).
Its job: carpet. A groundcover planted in threes and fives to cover the soil: along the front, and just behind it.
It drapes over the edge of a wall or path and softens stone. Unlike most alpines it wants steady moisture, with drainage, so it suits the front of an ordinary border.
- Spilling over walls and path edges
- Rock gardens
- Between paving stones
What to plant with mountain sandwort
Plants recorded as good partners for it, and what each pairing does:
- Sea thrift: in flower together for five weeks, from mid May; tall enough (8 in) to stand behind it.
- Candytuft: in flower together for two weeks, from mid May; tall enough (10 in) to stand behind it.
- Dalmatian bellflower: in flower together for four weeks, from late May.
Questions about mountain sandwort
Does mountain sandwort need sun or shade?
Mountain sandwort grows in full sun (6 or more hours of direct sun a day) and part sun (4 to 6 hours of sun, including some afternoon sun).
It wants ordinary well-drained soil, of average fertility, and a good soak in dry spells.
What zones does mountain sandwort grow in?
USDA zones 4 to 8. It is hardy to zone 4, which means it survives winter nights down to about −20 °F (−29 °C).
Above zone 8 it struggles: the zones measure winter cold, but a plant's top zone usually means the summers are too hot or the winters too mild for it to rest.
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does mountain sandwort flower in my zone?
In zone 5 it flowers mid May to late June. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.
| Zone 4 | Late May to late June |
|---|---|
| Zone 5 | Mid May to late June |
| Zone 6 | Early May to late June |
| Zone 7 | Early May to mid June |
| Zone 8 | Late April to mid June |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should mountain sandwort be planted?
12 in (30 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 16 in (40 cm), so a group knits into one patch.
It grows 4 in (10 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many mountain sandwort plants do I need?
At 12 in apart, set out in staggered rows:
- 12 to fill 10 square feet (about 1 m²)
- 11 for a single row 10 ft (3 m) long
- 38 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as threes and fives, along the front and just behind it.
In the bed above, the planner used 21 in five groups.
Is there a native plant like mountain sandwort?
Mountain sandwort is not native to North America. These North American natives come closest to doing its job:
- Three-toothed cinquefoil: the same job in a bed, the same size, the same flowering time and the same colour; wants dry soil.
- Mountain avens: the same job in a bed, the same flowering time and the same colour; 4 in wider.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
What flowers after mountain sandwort?
Mountain sandwort is over by late June. These start as it finishes and carry the same spot on, so it never goes flat:
- Black-eyed Susan: from mid July to mid September, 24 in tall.
- Butterfly weed: from late June to early August, 24 in tall.
- Carpathian bellflower 'Blue Clips': from late June to late August, 8 in tall.
What does mountain sandwort look like in winter?
Mountain sandwort keeps its dark green leaves all winter, so it is one of the plants that hold a bed together from November to March, when the perennials have gone.
In these guides
- Low plants for the front of a border
- Groundcover plants
- Evergreen perennials, ferns and grasses
- Plants for a white garden
Every fact on record
- Type
- Perennial (groundcover)
- Size
- 4 in (10 cm) tall, 16 in (40 cm) wide
- Plant
- 12 in (30 cm) apart
- Height class
- Ground-hugging (up to 6 in)
- Place in the bed
- Front
- Flowers
- Mid May to late June; open bowls; white
- Leaves
- Fine texture, evergreen; dark green
- Shape
- Mat-forming, clumping
- Hardy in
- USDA zones 4 to 8
- Light
- Full sun, part sun
- Soil
- Average, well-drained
- Water
- Moderate
- Feeding
- None needed
- Family
- Caryophyllaceae
Not yet checked against an outside reference: its figures rest on general horticultural knowledge. Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.