False spirea 'Sem'

Questions about false spirea 'Sem'

Does false spirea 'Sem' need sun or shade?

False spirea 'Sem' 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 false spirea 'Sem' grow in?

USDA zones 2 to 7. It is hardy to zone 2, which means it survives winter nights down to about −40 °F (−40 °C).

Above zone 7 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 false spirea 'Sem' flower in my zone?

In zone 5 it flowers late June to late July. As a summer flower it moves about half a week for every zone: earlier where it is warmer.

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 false spirea 'Sem' be planted?

3½ ft (100 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 4 ft (120 cm), so a group knits into one patch.

It grows 3½ ft (100 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.

How many false spirea 'Sem' plants do I need?

At 3½ ft apart, set out in staggered rows:

• 1 to fill 10 square feet (about 1 m²)
• 4 for a single row 10 ft (3 m) long
• 3 to fill a 4 × 8 ft bed on its own

In a mixed border, plant it as one, planted singly: it is the bed's structure, and everything else is arranged around it.

In the bed above, the planner used one in one group.

Is false spirea 'Sem' poisonous to dogs and cats?

No toxicity is recorded for dogs, cats, horses or people, according to NC State Extension.

"Not toxic" is not "edible": a pet that eats a lot of any plant can be sick.

Is there a native plant like false spirea 'Sem'?

False spirea 'Sem' comes from Central and Eastern Asia. These North American natives come closest to doing its job:

• Oakleaf hydrangea 'Pee Wee': the same job in a bed, the same flowering time and the same colour; 4 in narrower, bold leaves, not fine.
• Ninebark 'Tiny Wine': the same job in a bed and the same colour; 8 in taller, 4 in narrower.
• Snowberry: the same job in a bed and the same flowering time; 8 in taller, 8 in wider.

Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.

Do deer eat false spirea 'Sem'?

They may. NC State does not list it as resistant to deer or rabbits. Where they visit, protect it, or plant it among ones they avoid.

Will false spirea 'Sem' spread?

It spreads sideways, by runners or roots; the risk of it taking over is moderate. Suckers strongly and can form thickets. 'Sem' is more compact than the species, but it still needs paving, a root barrier or mown grass around it.

What flowers after false spirea 'Sem'?

False spirea 'Sem' is over by late July. These start as it finishes and carry the same spot on, so it never goes flat:

• Japanese anemone: from mid August to early October, 3 ft tall.
• Garden phlox: from mid July to early September, 3½ ft tall.
• Lilyturf: from early August to mid September, 16 in tall, to stand in front of it and cover its fading stems.

What does false spirea 'Sem' look like in winter?

False spirea 'Sem' drops its leaves and stands as bare branches. That is when to see its shape, and to prune it if it needs pruning.