Spirea (Spiraea) – The Complete Guide

From majestic spring bloomers to beguilingly fragrant groundcovers, the multifaceted genus of spirea shrubs fulfills horticultural design dreams.

Are you wondering how to cultivate this hardy, deciduous ornamental shrub in your garden? Here you can find all the information you need to know.

Planting Spirea

The optimal time window for planting spireas, commonly known as meadowsweet or steeplebush, is open from August to October. Alternatively, you can plant the spirea bush in the thawed soil in the spring.

While meticulously weeding and raking the soil, soak the root ball in water until no more air bubbles rise. Dig a spacious planting pit and enrich the excavated soil with compost and horn shavings.

Then unpot the young spirea and plant it in the center. The previous planting depth should be preserved as much as possible. Consolidate the substrate with your hands, spread a layer of foliage, and water the plant.

Finally, the spirea should receive a planting pruning. To do this, shorten all the shoots by half to two-thirds.

Care Tips

Properly planted, spireas rarely require any horticultural attention. In order for the opulent abundance of flowers, the dense foliage, and the beguiling fragrance to unfold, the following cultivation measures are important:

  • Water the woody plant regularly during dry periods.
  • After initial fertilization in spring, mulch with compost, leaves, or grass cuttings every 2-3 weeks.
  • Treat potted plants with liquid fertilizer from April to August.
  • Prune spring bloomers immediately after blooming.
  • Prune summer bloomers in late winter or early spring.
  • Winter protection is advisable in the year of planting as well as for spireas in tubs.

Provided that you plant a spirea shrub in spring, sufficient water supply during the summer comes into focus.

In contrast to planting in the rainy autumn, during the dry season, you can not avoid a regular walk to your spirea with a watering can in hand.

Which Location is Suitable for Spirea?

Among its outstanding attributes is the flexible attitude to site conditions. The spirea shrub thrives splendidly in sunny to semi-shady locations and will not let you down even in light shade.

The ornamental shrub spreads its roots in any normal garden soil, which may as well be calcareous. The only thing it does not want to be bothered with is waterlogging.

The Right Planting Distance for Spireas

In order to determine the ideal planting distance, please take a look at the expected growth height and width.

Since the genus comes up with dainty dwarf varieties to mighty flowering towers, we have compiled recommended distances for popular species for you:

  • Astilbe (Astilbe): 40-60 inches (100-150 cm) planting distance
  • Nippon spirea (Spirea nipponica): 20-24 inches (50-60 cm) planting distance
  • Japanese spirea (Spirea japonica): 12-16 inches (30-40 cm) planting distance

When measuring the planting distance, please keep in mind that the majority of spirea species thrive approximately as wide as they are tall.

In addition, many shrubs have a rapid growth rate of up to 20 inches (50 cm) per year, so that apparent gaps are filled within a short time.

When is Flowering Time for Spirea?

Cleverly combined, the lavish spireas blossom adorn gardens and balconies from spring to fall. For your reference, we have listed the flowering times of popular species for you:

Thunberg spirea (Spiraea thunbergii): flowering from April to May
Astilbe (Astilbe): flowering time from mid-May to the end of June
Nippon spirea (Spiraea nipponica): flowering time from June to July
Japanese spirea (Spiraea japonica): flowering time from July to September

Pruning Spirea Properly

Equipped with a robust pruning tolerance, you can easily keep the growth of spireas under control with pruning shears. The blooming season defines the ideal time for pruning.

Cut back spring-flowering species immediately after blooming, while summer bloomers should receive a pruning in late winter.

Don’t be afraid to cut back shoots that are too long during the growing season. Pruning itself follows this sequence:

  • Shorten shoots by up to two-thirds, as desired.
  • Thoroughly thin out the entire shrub.
  • Cut off shoots that are pointing inwards or rubbing against each other.
  • Cut branches that have fully blossomed for vase decorations.

Place the scissors just above an outward-facing node. You can identify such a node as a slight bump under the bark. This pruning encourages the plant to branch briskly at this point for a bushy habit.

Watering Spirea

Although the spirea shrub tolerates short-term drought, consistent soil moisture encourages growth and flowering.

If the soil surface dries out, water the plant in the early morning or late evening. To avoid interfering with flowering, refrain from overhead watering.

If you are cultivating the wonderfully fragrant flowering beauty in a container, check the moisture content of the substrate every few days by thumb-testing. If the top inch (2-3 cm) feels dry, water immediately on the root disc.

Fertilizing the Spirea Properly

Starter fertilization in March/April will get the growth going with spirea.

Work some compost with horn shavings into the soil superficially. Alternatively, you can use a nitrogen-rich mineral-organic fertilizer.

Subsequently, the frugal spirea shrub proves grateful for a mulch layer of leaves, lawn clippings, or compost. For spirea in a container, we recommend regular applications of liquid fertilizer from April to August.

Overwintering Spireas

Spireas are completely winter-hardy and require no precautions for overwintering. Only in the year of planting, do we recommend spreading a layer of foliage on the root disc, as frost hardiness has not yet fully developed.

For specimens in containers, the following measures are useful:

  • In the fall, wrap the planter with bubble wrap, jute, or fleece.
  • Place a block of wood or a polystyrene plate underneath.
  • Cover the substrate with straw, autumn leaves, or coniferous twigs.

Where sufficient space is available, relocate spirea in a pot to frost-free winter quarters. Water the plant occasionally so that the root ball does not dry out completely.

Propagating Spireas

With the long list of its convincing advantages, the spirea shrub continues seamlessly in terms of propagation. We have compiled proven propagation methods for you here:

  • In early summer, pull down saplings to the ground and dig in the middle part until an independent root system is formed.
  • During summer, cut head cuttings and nurture them in a pot with a lean substrate.
  • In September, cut cuttings, plant them in the ground and allow them to root.
  • Sow the seeds behind glass or directly in the bed.

Is Spirea Poisonous?

The charming spireas deserve a special place in any family garden. Since the opulent ornamental shrubs are not poisonous, they do not pose any health hazard.

Good-naturedly forgiving of many a beginner’s mistakes, the spirea is considered an ideal candidate for awakening the joy of amateur gardening in interested children.

Beautiful Varieties

  • Bridal wreath (Spirea arguta): A dreamlike spring bloomer in bright white and impressive presence. The height of growth is 60-80 inches (150-200 cm).
  • Spirea Triumphans (Spiraea billardii): The bright red cob flowers adorn the shrub from June to July. The growing height is 60-80 inches (150-200 cm).
  • Japanese Meadowsweet ‘Anthony Waterer’ (Spiraea bumalda): A breathtaking summer spirea with ruby-red umbel flowers until September. The height of growth is 24-40 inches (60-100 cm).
  • White Japanese spirea (Spiraea albiflora): A dainty dwarf spirea that wraps itself in white flower clouds from July to September. The height of growth is 20-28 inches (50-70 cm).
  • Japanese spirea ‘Golden Princess’ (Spirea japonica): Wonderful play of colors thanks to pink summer flowers above golden-yellow leaves. The growth height is 16-20 inches (40-50 cm).