When to prune shrubs and trees - Santa Cruz Sentinel

ON GARDENING

When to prune shrubs and trees

Single white Camellia (Camellia japonica). There are thousands of cultivars of Camellia japonica in cultivation, with many colors and forms of flowers. Despite its common name, it is native to China, not Japan. From December to February, it opens with pure white single flowers with a bunch of yellow stamens in the center that emit a light, sweet scent. When blooming is over, there is new growth of glossy, deep black leaves that fade to deep green. This specimen could be a related species, Camellia sasanqua, also in the Tea plant family (Theaceae). PHOTOS COURTESY OF TOM KARWIN

English climbing rose (Rosa ‘Graham Thomas’). This vigorous, upright climber grows 5-8 feet tall and wide, and features large, intensely fragrant bright yellow double blooms in clusters on arching canes. Blooms well from spring to fall. Leathery, dark green foliage. It was introduced into the United Kingdom by David Austin Roses Limited in 1983. The cultivar was named after the legendary rose horticulturalist Graham Thomas.

Lilac ‘California rose’ (Syringa vulgaris). Native to the Balkan Peninsula, this plant is widely cultivated for its scented flowers in Europe (particularly the north and west) and North America. Syringa vulgaris was first formally described by Carl Linnaeus in 1753 and published in “Species Plantarum.” The specific epithet “vulgaris” is Latin for “common” (in the sense of “widespread”). A member of the olive plant family (Oleaceae). This cultivar, a hybrid, is sometimes referred to as Syringa x hyacinthiflora ‘California rose.’

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January is a highly beneficial time to prune trees and shrubs because this is the dormant period for many plants in coastal California. This column provides specific recommendations for the Monterey Bay area’s Mediterranean climate.

This column image gallery includes blooms of one plant (a rose) to be pruned this month and others that should be pruned in late winter or early spring for best results. These images are from plants in my garden, taken during their blooming time. Plants are appealing visually in bloom and interesting botanically in dormancy.

Best general practices

• Prune deciduous trees and shrubs when they are dormant and leafless, as their structure is more visible, and pruning wounds heal faster in cool, damp conditions.

• Avoid pruning spring-flowering shrubs heavily, as you may remove flower buds set the previous year. Light shaping is fine.

• Use clean and sharp pruning tools to ensure clean cuts and reduce disease risk.

• Sterilize tools between plants, especially if pruning trees or shrubs showing disease signs.

• Check for nesting birds or wildlife before pruning.

• Use proper safety gear and ladders when necessary.

• After pruning, consider adding a layer of mulch to retain moisture and regulate soil temperature, but keep it away from the base of trunks and stems.

Tree pruning

Remove dead, diseased or damaged branches when pruning deciduous landscape and fruit trees. For the next step, thin the tree’s crowded areas to improve air circulation and sunlight penetration. Then, remove crossing or rubbing branches to shape the tree’s structure and strength.

Pruning evergreen trees involves different steps. Remove any dead or damaged limbs, but avoid heavy pruning. Evergreens do not regenerate well from cuts into old wood.

When considering trees in the Citrus genus (oranges, mandarins, lemons, grapefruits, pomelos, limes and others), remove any deadwood and branches that block sunlight from the canopy’s interior, but avoid heavy pruning at this time of the year. Pruning encourages the development of new growth that could be damaged by frost. Even a brief frost in the Monterey Bay area could hurt young new growth.

Shrub pruning

Consider these categories of shrubs: deciduous, evergreen, spring flowering and summer flowering shrubs.

January is ideal for pruning deciduous shrubs, including the popular roses (hybrid teas, floribundas, grandifloras) and hydrangeas.

The fundamental approach to pruning roses involves cutting canes to 12-18 inches high, removing old wood and leaving three to five healthy canes. For more detailed pruning, participate in local pruning workshops (see “Advance your gardening knowledge” below).

When considering hydrangeas, prune summer-blooming varieties lightly to improve shape and remove dead wood. Do not prune spring-blooming hydrangeas at this time of the year unless they are overgrown.

Evergreen shrubs also can be pruned in January. Prune lightly to maintain shape, remove dead or damaged branches and avoid cutting into old wood that will not sprout new growth.

Evergreen flowering shrubs include spring-flowering and summer-flowering varieties.

Limit the pruning of spring-flowering shrubs to removing spent flowers or light shaping. Examples include camellias, azaleas and lilacs. These should be pruned in after they finish blooming. Avoid heavy pruning in January and schedule heavy pruning for late winter to early spring to preserve buds.

When pruning summer-flowering shrubs, cut back in January only to maintain size and remove old flowering stems. These shrubs benefit from pruning in late winter to early spring to encourage strong new growth and maximize summer blooms. Examples include butterfly bush (buddleia), tree mallow (lavatera) and crape myrtle (lagerstroemia).

Semi-tropical shrubs are sensitive to frost. Coastal California can experience mild frost through February, so pruning these shrubs in January would be too early. This can encourage tender new growth that may be damaged by cold weather. Examples include bougainvillea, lantana and fuchsia. After the danger of frost has passed, prune such shrubs in February or early March. The emergence of new growth in early spring signals a good time for pruning.

Similarly, other shrubs that might sustain frost damage, such as flowering maple (abutilon) and woody types of salvias, are best pruned in late winter to cut back frost-damaged stems and encourage fresh spring growth.Generally, check whether the shrub produces flowers on old or new wood. Old wood bloomers should be pruned after flowering, while new wood bloomers can be pruned in late winter.

Special pruning cases

When considering coastal wind-prone plants, such as Monterey cypress or ceanothus, shape plants to maintain a strong structure resistant to wind damage and remove branches that create sail-like profiles.

Lightly prune Mediterranean and drought-tolerant shrubs, such as lavender, sage and cistus, to remove spent flowers and old growth. Avoid cutting into woody stems.

Winter is ideal for hard-pruning vines, such as wisteria and grape varieties (genus Vitis), to control size and promote flowering or fruiting. Cut back wisteria to two or three buds per spur. When pruning grapevines, remove 85-90% of the previous year’s growth to help the grapevine maintain its structure and distribute the fruit load.

Advance your gardening knowledge

The Monterey Bay Rose Society has announced its annual rose pruning classes. American Rose Society consulting and master rosarians will demonstrate how to prune roses for beautiful spring results. They will discuss fertilization, watering, pesticides and other rose gardening subjects. No reservation is needed, and these events are free of charge.

The society has scheduled the following dates for the classes:

• Jan. 11-12 at 10 a.m., Monterey Bay Rose Society Display Rose Garden at the Santa Cruz County Fairgrounds, 2601 E. Lake Ave., Watsonville (use livestock entrance).

• Jan. 18 at 10 a.m., Alladin Nursery & Gift Shop, 2905 Freedom Blvd., Watsonville.

• Jan. 25 at 10 a.m., San Lorenzo Garden Center on 235 River St., Santa Cruz.

• Feb. 8 at 10 a.m., Alladin Nursery & Gift Shop, 2905 Freedom Blvd., Watsonville.

Contact secretary Janey Leonardich at 831-722-7958 for more information.

This week in the garden

A pruning planning project for this week: inventory the trees and shrubs in your garden and make two lists — plants that should be pruned in January and those that should be pruned in late winter or early spring.

Clean and sharpen your pruning tools to ensure clean cuts and reduce disease risk.

Pursue the pruning schedule to prepare plants for the blooming seasons.

Enjoy your garden!

Tom Karwin is a past president of Friends of the UC Santa Cruz Arboretum and the Monterey Bay Iris Society, a past president and Lifetime Member of the Monterey Bay Area Cactus & Succulent Society and a Lifetime UC Master Gardener (Certified 1999-2009). He is now a board member of the Santa Cruz Hostel Society, and active with the Pacific Horticultural Society. To view photos from his garden, visit facebook.com/ongardeningcom-566 511763375123. For garden coaching info and an archive of On Gardening columns, visit ongardening.com for earlier columns or visit santacruzsentinel.com and search for “Karwin” for more recent columns. Email comments or questions to gardening@karwin.com.