Garden Detective: Timing tricky for moving rhododendron, hydrangea

11/23/2013 12:00 AM

11/22/2013 10:30 AM

Can you please tell me the best time to move a rhododendron? And how about moving hydrangeas?

– Nancy McGagin, West Sacramento

Many shrubs can be moved in fall or winter. But spring-blooming shrubs can be tricky. Disturbing them now can impact their spring flower show.

For evergreen varieties of rhododendron, transplant in spring (after the bush has finished flowering and frost danger has past) or fall. Either time, the weather is milder and plants are less stressed.

For deciduous varieties, early spring is the best time for transplanting up until the bushes leaf out.

When transplanting, carefully remove the bush from its old container or spot in the ground, gently untangle roots and spread them out. Cut any broken or encircling roots (common in container plants). When replanting, keep the top of the bush’s root crown level at or slightly above soil level. Make sure to water well and deeply.

According to Sacramento County master gardeners, the ideal location for a rhododendron in our area is a site with filtered sunlight, but not heavy shade. Locations on the east or north side of the house or fence are the next best. Taller plants can create dappled “shade” for the smaller ones. They prefer acid soils with rich organic matter and excellent drainage. Mulch around the plants to help keep the roots cool and conserve moisture.

But try to plant away from mature trees. Tree roots give too much competition for moisture and nutrients, and the plants will suffer.

Hydrangeas can be moved during winter while dormant. You may want to prune the plant back before moving, but this will cost some blooms.

Pruning hydrangeas is a common issue for local gardeners. There are many types of hydrangeas, say UC master gardeners, and the timing of the pruning depends upon whether the hydrangea blooms on current or previous years’ growth.

The mophead varieties, Hydrangea macrophylla, are the most common and have large, globe-shaped flowers. These bloom on previous years’ growth or “old wood.” Pruning in late fall or early winter will eliminate the bloom for next spring.

Hydrangeas need little pruning except to deadhead or to remove dead stems. To encourage a particular shape, prune right after your bush blooms.

Older hydrangeas may benefit from some rejuvenation pruning. This involves removing about one-third of the older stems down to the ground to allow light to penetrate to the center of the shrub and to encourage replacement limbs. This can be done in the summer or in the winter, at the expense of some blooms.

Fertilizing is not necessary, but the plants will respond to an application of a slow-release, balanced fertilizer during the spring growing season. Apply per label instructions. Mulching is a good practice as it helps hold in moisture around the roots and the decaying organic matter adds nutrients to the soil.

No more Weed-Hoe

Alert reader James Shattuck noted that Monterey Chemical no longer makes Weed-Hoe, a recommended remedy for crabgrass mentioned in a recent Garden Detective column. He hopes to save some gardeners frustration as they search for this product.

“Readers should know this information as they may be calling around to Home Depot, OSH, etc., looking for it,” he said.

A possible alternative is Spectracide WeedStop for Lawns with Crabgrass Killer, available at Lowe’s. This herbicide kills a broad spectrum of lawn weeds, but also can affect ornamental plants near the turf. Don’t use around lawn trees.

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