Pruning Deciduous Spring-flowering Shrubs

The best way to prune deciduous spring-flowering shrubs is to use thinning cuts. Shearing, heading back and pollarding are specialized pruning methods often used by mistake on deciduous spring-flowering shrubs.

These three pruning methods are useful in specialized situations. However, using them on deciduous spring-flowering shrubs only gets in the way of the shrubs’ natural positive features and requires unnecessary work. Goals in pruning deciduous spring-flowering shrubs are to encourage eye-catching bloom for the coming year and to enhance health and vigor.

Problems result when traditional shrubs begin to overwhelm foundation area spaces and hedge areas. Habitual shearing is one method repeatedly used to maintain optimal sizes. Results are bizarre looking and unhealthy plants. (Photo #2) Preferable to shearing is planting modern introductions that are smaller than their normal-sized relations and often labeled as dwarfs. (Photo #1)

When to Prune Spring-flowering Shrubs

• Prune immediately after flowering. Shrubs that bloom from March through May usually form flower buds during summer months for next season’s flowers. “Flowering on old wood” is the traditional way of expressing this type of flower bud development.
• Pruning deciduous spring-flowering shrubs in early spring or late fall, when leaves are absent, allows meticulous correction and thinning of the plant’s branching habit. In situations like these, structural change to the shrub is more important than spring flowering. Few to no flowers are produced during the next flowering season.

How to Prune Spring-flowering Shrubs

Thinning cuts require skill, patience and time, but are well worth the resulting beauty and vigor of pruned shrubs. Thinning cuts can reduce the size height and spread, or crown density of shrubs while retaining their natural shapes. Thinning cuts also are less conspicuous than those left from heading back or shearing. They close and heal rapidly and completely. There are two ways of using thinning cuts:

• Remove entire older woody, less productive and dead branches from the shrub base at their points of origin. This opens the interior of the shrub to air and light. Some experts suggest removing ¼ to 1/3 of woody canes each year. (Photo #3)
• Cut the length of vigorous branches just above an outward-facing lateral bud that is large enough to take over as the terminal bud. This prevents growth of crossing branches and enhances the shrub’s natural shape. New growth occurs naturally along the remaining branches.

Shrub Types

Plant professionals usually divide shrubs into two groups based on form and growth habit:

• “Cane growers” are multistemmed shrubs that grow from new shoots (canes) at the plant base. These plants are usually fountain-shaped with a natural, free-flowing habit. They grow easily, often reaching mature size in three years.
• Here is a partial list of examples:

1. Deutzia spp. and cvs. (Deutzia) (Photo #4)
2. Forsythia spp. and cvs. (Forysthia )
3. Hyperium spp. and cvs. (Some but not all St. John’s Wort)
4. Kolkwitzia amabilis (Beautybush)
5. Philadelphus spp. and cvs. (Mock Orange)
6. Potentilla spp. and cvs.
7. Rubus spp. and cvs. (Ornamental Brambles)
8. Spiraea spp. and cvs. (Some but not all Spiraeas / Bridal Wreath / Bridal Veil)
9. Syringa meyeri and cvs. (Meyer Lilac)
10. Viburnum spp. and cvs. (Some but not all Viburnums)
11. Weigela spp. and cvs. (Weigela)

• “Tree-like growers” are those that grow from a strong structural frame that persists throughout the life of the shrub. Changing these natural patterns is time-consuming and often a frustrating undertaking.
• Here is a partial list of examples:

1. Corylus spp. and cvs. (Hazel)
2. Hamamelis spp. and hybrids (Witch Hazel)
3. Potentilla spp. and cvs.
4. Spiraea spp. and cvs (Some but not all Spiraeas / Bridal Wreath / Bridal Veil
5. Syringa vulgaris and cvs. (Common lilac cultivars)
6. Viburnum spp. and cvs (Some but not all Viburnums)

Rejuvenation

Most cane growing shrubs that are overmature respond well to removal of all canes at ground level. Accomplish early in the season (February-April) so new growth has a full growing season to mature. A full flowering season is lost, but the result is a newly invigorated shrub. (Photo #5)

Hard Annual Pruning

Use only shrubs recommended below or in regional pruning handbooks to take advantage of this pruning method.

• Colored stems: Cut shoots in early spring to within 2 to 3″ of ground level on shrubs to produce striking summer and winter displays. Flower display is lost with this pruning.

1. Cornus alba‘ Bud’s Yellow’
2. Cornus baileyi ‘Bailey’s Red Twig Dogwood’
3. Cornus sanguinea ‘Winter Flame’
4. Cornus sanguinea ‘Bloodtwig Dogwood’
5. Cornus sericea / Cornus stolonifera ‘Cardinal’
6. Cornus sericea / Cornus stolonifera ‘Red Twig Dogwood’
7. Kerria japonica (Japanese kerria)

• Juvenile leaf forms or extra large leaves: Prune to low leaf buds or sturdy framework to promote displays. Flower display is also lost with this pruning.

1. Catalpa bignondioides ‘Aurea’ (Golden-leaved Catalpa trained as a shrub)
2. Corylus maxima ‘Purpurea’ (Purple-leaved filbert)
3. Cotinus coggygria ‘Golden Spirit’™ (Yellow-leaved Smokebush)
4. Cotinus coggygria purpureus (Purple Smokebush)
5. Photinia x fraseri (Red-leaf Photinia)

More Information

American Horticultural Society Pruning & Training: A Fully Illustrated Plant-by-Plant Manual. 1996. Bricknell, Christopher and David Joyce. ISBN 13: 9781564583314. .Dorling Kindersley. New York, NY 10014