Shrub Spotlight for May
SPRING Flowering versus SUMMER Flowering Spirea
Every month, The BIG Oak will spotlight a specific shrub type or shrub topic to examine further. Here is a look at the difference between spring and summer flowering spirea for May:
Spring Flower Spirea
The Main Difference = Outside of an earlier flowering time, spring flowering spirea will produce flowers on “OLD WOOD”, or tissue from last year’s growth. This means that once spring flowering spirea are done flowering in May / June, they will set buds for next years’ flowers. Pruning for these spirea must be done right after flowering, otherwise, flower buds for the next season could be removed during pruning. Reducing the overall size of a spring flower spirea in late fall will remove most or all of the flowers for the next growing season.
Common Types
Snowmound spirea (3-5 feet high / wide, white flowers)
Bridal’s wreath spirea (5-7 feet high / wide, white flowers, also known as Vanhoutte Renaissance)
Tor spirea (3-4 high / wide, white flowers), type of Birchleaf spirea
Pink Sparker spirea (3-4 feet high / wide, pink flowers), type of Birchleaf spirea
Glow Girl (gold leaf version of Tor spirea)
Typical Tor spirea in June in Minnesota.
Summer Flowering Spirea
The Main Difference = Outside of the later flowering time, summer flowering spirea flower on “NEW WOOD”, or tissue from the current year. This means that once summer flowering spirea are done flowering in July, they COULD be lightly pruned to encourage a second flowering or left alone until late fall (or the following spring). Because they will flower on new tissue, the timing of pruning has some variability.
Common Types (White Flowers)
Japanese White spirea (2-3 feet high / wide)
Common Types (Pink Flowers)
Alpine Spirea (1-2 feet high / wide, compact, good for ground cover)
Anthony Waterer (3-4 feet high / wide, deeper pink)
Goldflame Spirea (2-3 feet high / wide, golden foliage)
Goldmound Spirea (2-3 feet high / wide, yellow foliage)
Neon Flash Spirea (2-3 feet high / wide, deeper pink flowers)
Little Princess Spirea (2-3 feet high / wide, very dense form)
The Big Oak Favorite
Double Play Blue Kazoo (2-3 feet high / wide, white flowers, bluish foliage)
Bonus comment regarding spirea pruning from The Big Oak = Do not prune spirea more than once per season. Overpruning can greatly reduce the lifespan of spirea shrubs. Prune once during one of these time periods in Minnesota:
Early April (cut back in half or fully rejuvenate)
Mid to late July (light shearing of flower heads to encourage a 2nd flowering)
Late Fall (cut back or fully rejuvenate)
Summer flowering spirea about 30 days following a light shearing in July to encourage a 2nd flowering.
The picture below shows the typical difference between spring and summer flowering spirea. Spring flowering spirea (red arrow) tend to be wilder and flowing versus the “ball” shape summer flowering spirea (blue arrow). Since flowering is the main reason to have spirea in the landscape, pruning should help enhance the flowering for both types.
Snowmound spirea (spring flowering) is indicated with the red arrow, while Goldflame spirea (summer flowering) is indicated with the blue arrow.
Double Play Big Bang spirea.
Bonus comment from The BIG Oak = Utilize Double Play Big Bang instead of Goldflame or Goldmound spirea. They will have pink flowers with yellowish / red foliage with a better performance.
