Pruning Large-Leaved Rhododendrons

Pruning Large-Leaved Rhododendrons

Any rhododendron is suitable for woodland or informal use where a reasonable amount of space is available. Here it is only necessary to arrange the planting so that the robust growers do not over-crowd those of relatively restricted growth.

It is around the foundations of the home, spots of limited area or the rockery that the choice is limited to the smaller-leaved and dwarfed types. Wise selection in the beginning will eliminate the need for most of the pruning. There are, however, times when pruning is justified and essential.

Large-leaved rhododendrons are the most difficult to prune but only for the lack of understanding. These plants put out their first growth in a flush that terminates with a rosette of leaves. Generally in the colder areas of the East and North the flush varies from 4 to 10 inches, but more often around 6 inches. On young plants, two flushes per year are the rule. On older plants that set flowers freely, it is the rule that one flush is made followed by a flower bud. This latter is due to both a natural reduction in vitality after the juvenile stage is passed and the use of tremendous energy in blooming which delays the commencement of growth.

Large-leaved rhododendrons may be pruned anytime without harming the plant, but there are times that are more expedient. These plants, with few exceptions, retain their leaves two years. This means that on young plants there will be four rosettes of leaves and fewer on older plants. It is permissible to prune back to any of these rosettes, depending on how drastically it is desired to prune. Always make the cut about a quarter of an inch above the rosette. The flush of growth will burst out from the auxiliary buds of the rosette.

The most favorable time to prune when there are no flower buds is in the early spring just before growth begins. If done at this time, the growth cycle is least disturbed, and bud set the same season will be uninhibited. In so pruning, it is important to cut back every terminal or watch when growth begins. The terminals left uncut commence growth earlier usually with a long single shoot. These single shoots should be pinches off when the new growing tips are abut an inch long. This will encourage multiple branching from that terminal. This step is important in shaping or reshaping a plant. Cutting back develops a heavily branches, sturdy shrub. If this is done when the plant is abut 3 feet or less, it can eliminated future need for pruning.

Pruning old rhododendrons presents a different problem. When old rhododendrons become unthrifty in appearance, the cells in the vascular bundles have become hardened or plugged and no longer function normally. Any revitalizing to be accomplished must be done on new wood, supplied by drastic pruning. This is best done in the spring or early summer but spring preferred.1

One method is to cut the plant down to several inches above the ground. This is more successful with those having multiple stems coming up from the ground. In hybrids, which often have one stem, they may sometimes die from this. A less drastic means is to reach down into the shrub and cut out about one-third of the old wood. Do this for a period of about three years. In this way, there remains sufficient leaf surface to supply nutrients for reestablishment of new shrubs.

Photo by Andrea44

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OnJanuary 23, 2013, posted in: Seasonal Tips by

When is the right time to trim Viburnum?

When is the right time to trim Viburnum?

Viburnums are shrubs favored for landscaping, hedges and lawn specimens. Depending on the variety, they thrive in U.S. Department of Agriculture plant hardiness zones 2 through 9. Although viburnums do not require pruning, trimming them can help them maintain a specific size, create healthy growth and increase the number of blooms. It is helpful to know what time of year to trim the plants to avoid decreasing flower production.

Trimming Basics

Trimming is another name for pruning. There are different methods of trimming including pinching, heading and shearing. Using the pinching method to trim a viburnum means removing the tips of growth shoots. Heading involves cutting a section of branch back to healthy branch material or a bud. The shearing method means trimming back most of the outer growth shoots. All three of these methods encourage new plant growth. Shearing creates hedge-like growth with very little interior growth. A fourth method – thinning – means trimming back branches to their point of origin from another branch. This method does not result in new growth.

Viburnum Growth

Although viburnums have lovely foliage, most varieties are grown for their flowers or colorful fruit. With the exception of thinning, viburnums will develop new growth wherever they are cut. The flower buds set on new growth in late summer or early fall. The buds develop throughout the winter and open the following spring. This means that no matter when a viburnum is trimmed, it still has to wait for new growth in early spring and bud set in late summer or fall before it will bloom the following spring.

Trimming for Appearance

Different parts of a viburnum bush can be trimmed at different times of year. Throughout the year, trim back any suckers that appear at the base of the plant. Suckers do not add to the appearance of the bush, and may divert needed nutrients. If you are training your viburnum to a tree shape, thin back any side growth by pinching back any new shoots that appear on the sides of the trunk. Perform other trimming from winter to spring while the viburnum is dormant. Trimming during this time will help you avoid cutting the next season’s flowers, as long as you don’t cut budded areas. You can also trim flowering branches immediately after the flowers have wilted, as these branches will not set buds until the following summer. However, do not trim these branches if the viburnum has showy fruit, as the plant needs the old flowers to set fruit.

Trimming for Pests and Diseases

Remove dead or diseased branches at any time. Use the heading method to cut these branches back to healthy branch material. Viburnums with dense interior growth may be susceptible to fungal infections, especially if they are growing in shady areas. Thinning out the interior of the bush will improve airflow within the plant and help prevent fungal growth. This type of thinning can be done at any time, as viburnums rarely develop flowers in the interior of the plant. Viburnum leaf beetles are a common pest of viburnums. Trimming off infested branches is one of the best ways to eliminate this insect. Destroy egg-laying sites and future larvae by cutting off the branches in the winter or early spring.

Source: SF Gate
Photo by wlcutler

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OnJanuary 23, 2013, posted in: Seasonal Tips by

Aerate your lawn this spring

Aerate your lawn this spring

Now that spring is on the way it’s a great time to think about your lawn.


Aeration is the process of removing plugs of soil from your lawn. This creates spaces for air, water and nutrients to penetrate into the soil and promotes the growth of beneficial microorganisms. It also increases water absorption and reduces surface runoff.

Aeration is essential for compacted soil. Signs of compacted soil are: bare patches standing water after rain decreased grass vitality.
To test for compacted soil, stick a screwdriver or pencil into the soil. If the soil is compacted this will be difficult to do.

Aeration is also essential to reduce thatch problems. Thatch is that tough layer of dead organic matter between the lawn and the soil. When thatch becomes too thick, it blocks water and nutrients from getting to the soil.

Avoid aerating when your soil is very dry. Wait until after it has rained or water deeply the day before you aerate. Spring and fall are the best times to aerate.

It is a great idea to add high quality grass seed after aerating. Topdressing can also be done.

Aerators can be rented or lawn care companies can provide this service.

Contact us today about aerating your lawn.

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OnJanuary 23, 2013, posted in: Seasonal Tips by