How and when to rejuvenate old shrubs and prune hydrangeas

How and when to rejuvenate old shrubs and prune hydrangeas

I recently wrote about selective pruning, an important maintenance practice used to remove broken, damaged, and diseased branches from trees and shrubs. Selective pruning is used to improve their shape, control size, and increase air circulation to discourage disease. But there is another, more risky method of pruning – rejuvenation pruning – and if it is warranted, now is the ideal time to do the job.

Rejuvenation pruning is the severe cutting of overgrown or unproductive (healthy) shrubs. This method should be used when shrubs become overgrown, have too much open space in their centers, or simply decline and fail to grow, fruit or flower. The goal is to force the plant to replace older, weaker stems and less productive branches with new, strong ones. It’s radical, but when all is said and done, it’ll be like owning a brand new factory.

Do not attempt rejuvenation pruning on evergreen shrubs with needles. They should never be pruned beyond their needles, i.e. no cuts should be made on bare wood. Likewise, do not completely cut back shrubs that grow from a single trunk. Renewal pruning is for shrubs that send up multiple stems straight from the ground.

To rejuvenate your shrubs and shrubs, you have three options:

1. Cut the entire plant by cutting it to the soil line. This method requires a certain level of intestinal fortitude because, let’s face it, it can be nerve-wracking cutting a mature plant to the ground. Waiting for it to grow back while looking at a gap in your landscape isn’t fun either, and the time it takes to grow back can vary greatly, depending on the type of shrub. But this method will provide the most consistent results.

2. Cut all branches to unequal heights in one session. Start by removing broken, crossed and diseased branches at their bases, then stand back and visualize the overall size and shape you want, and prune each remaining stem or branch, some long and some shorter, making each cut just above the front of a side branch or bud. From these shoots new external growth will be stimulated.

3. Remove a third of the plant’s branches every year over a period of three years, starting with the oldest and least productive. This is the least risky method, as well as the least intrusive to your landscape, but you need to remember to follow through and complete phases two and three over the next two years.

Renewal pruning is well suited for canning plants such as:

For beautyberry

For “burning bush” Euonymus

For choke berries

For Cotoneaster

For forsythia

For lilac

L. Sandcherry purple

l Redtwig dogwood

For Rose of Sharon

to. Viburnum

Hydrangea pruning instructions

There are five types of hydrangeas, each with its own requirements. Be careful, as pruning at the wrong time will risk a season without blooms.

For large hydrangeas (mopheads and lacecaps): Prune in late summer, as soon as the flowers fade, but not after September. Remove weaker stems from the base of the plant, being careful to keep several stems of old wood, which will produce buds for next year’s flowers. You can prune now too, but it will cost you flowers this year.

For Hydrangea ‘Grandiflora’ (Hydrangea Smooth): Cut to the ground in late winter/early spring. If the plant has survived the winter well and you want it to grow even better, perform light selective pruning and cut the branches at different heights.

For Hydrangea paniculata Grandiflora (Hydrangea paniculata; Peegee): Simply remove spent flowers; Weaken or shrink last year’s growth in late winter/early spring.

l Hydrangea quercifolia (oak leaf hydrangea): Remove dead wood from the base of the plant in early spring.

For Hydrangea anomala petiolaris (climbing hydrangea): Unruly vines can be shortened in summer. Otherwise, pruning is rarely necessary.

The right tools

The best pruning tool for the job depends on the size of the stems or branches to be cut:

l Use hand shears for stems up to 1/2 inch in diameter.

l Use pruning shears for stems that are between 1/2 inch and 1 inch in diameter.

l Use a pruning saw for stems that are one inch in diameter or larger.

Canning plants, such as the red dogwood bush, are well suited for rejuvenation. (Dreamtime/TNS)

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