When looking for flowering shrubs, people often think about hydrangea, lilac, rhododendron or azalea, and viburnum. With its 80 or so species the genus Spiraea is quickly rising up to become a garden favorite. The species are easy to grow and maintain and there is a wide range of easily-available cultivars and hybrids on the market.
Spirea offers gardeners and designers endless possibilities in color, shape, texture, and form. Depending on which spirea you choose, they could be used as groundcovers, borders, hedges, and stand-alone specimens.
The Spiraea genus as a whole has a few distinct identifying physical features. Each is deciduous, mostly with narrow, oval-shaped leaves called lanceolate in botany. They all have many tightly clustered flowers with five sepals and five petals. These similarities are often as far as it goes when it comes to the genus. This is great news for designers and gardeners looking for variety in their landscapes.
Spirea, while also being invaluable ornamentally, is a marvelous plant ecologically. It feeds numerous pollinators and is a butterfly and moth lovers delight since the flowers will play host to the fluttering insects while they are in bloom. Take warning, though; spirea is not deer-resistant and is occasionally a last resort snack for these animals.
Medicinally and historically, spirea has played, and continues to play, an essential role in our society. Spiraea betulifolia was traditionally used both as a food and a medicine by the native Americans.
|Botanical Name||Spiraea spp.|
|Plant Type||Woody Perennial Shrub|
|Mature Size||1-20 ft. Depending on Species.|
|Sun Exposure||Full Sun|
|Soil Type||Loamy, Well Draining|
|Bloom Time||Spring to Late Summer.|
|Flower Color||Varies on species|
|Hardiness Zones||4-8, USA|
|Native Area||Varies on species, though all in Northern Hemisphere.|
Choosing an area that drains well and gets a fair amount of sun is essential for all spirea species. It's still important, however, to do your research when searching for a suitable species for your garden, as their care and condition requirements can vary considerably. The details below are general guidelines and not specific to any particular species.
The perfect time to plant spirea is just after the last frost in spring or right before the first frost in fall. Follow the usual guidelines for planting a shrub and dig a hole two times as wide as the container or rootball, and just as deep. Refill the hole and cover with a two-to-three-inch layer of mulch out to the drip line. Be sure to keep the mulch away from the stems to avoid damaging the shrub. If planning on a grouping, be mindful of the size at maturity and plant accordingly.
To achieve the best bloom production and foliage coloration, ensure that the shrub gets full sun.
Spirea prefers well-drained soil that has a neutral pH. Test the acidity level before planting and occasionally during the season to determine if soil amendments are needed.
Keep newly planted Spirea well-watered until they have established themselves. After this point, it is okay to taper off watering as it is only necessary when the soil is dry. This method is preferred because the genus has a tendency to develop root rot and overwatering can cause serious issues.
Temperature and Humidity
Spirea can be winter hardy down to 15o Fahrenheit. It is a good idea to check the individual species' details, but the general range is USDA 4-8, with some being a little bit pickier than others.
The Spiraea genus is not one that feeds heavily. If it is producing healthy and vigorous blooms, no fertilization may be needed. If feeding is required, it should only be done annually in the early spring with a slow-release fertilizer.
Popular Spiraea spp. Varieties
There are many different Spiraea species to choose from. Below are just a few popular choices, available for growing in North America.
- Birchleaf spirea (Spiraea betulifolia): While it has some summer interest in small white flowers, the real highlight is the show this shrub puts on during the fall with purple, orange, and red shades.
- Early Spirea (Spiraea thunbergii): Blooming early in the spring, this species offers three-season interest giving the most spectacular fall colors of purple, orange, burgundy, red and yellow.
- Japanese spirea (Spiraea japonica): This species is easily the most cultivated with endless sizes, forms, colors, and textures. One popular cultivar is 'Gold Mound'.
- Bridal wreath spirea (Spiraea prunifolia): Bridal wreath spirea is a large species compared to other in the genus. It can reach heights up to 20 feet if not pruned back. Bridal wreath spirea is named for the beautiful wedding wreaths traditionally made from its tiny white flowers. During autumn, reds, oranges, and yellows pop out of nowhere, setting the large shrub ablaze.