Control a suckering shrub

[Janet Macunovich 32]

JG wrote to us wondering whether to cut her snowberry bush to the ground, "or what!"

 

We answered her and told her we'd post it here so others might make suggestions. Here goes - our answer and room for your added experience!

 

Controlling suckering shrubs

 

People often ask us how to keep suckering shrubs in check, to keep small things like:

dwarf flowering quince (Chaenomeles japonica)

dwarf fothergilla (F. gardenii)

dwarf grapeholly (Mahonia aquifolium 'Compactum')

thimbleberry (Rubus odorata)

 

ash-leaf spirea/Ural false spirea (Sorbaria sorbifolia)

kerria (K. japonica)

snowberry (Symphoricarpos species)

Virginia sweetspire (Itea virginica)

 

These shrubs are all capable of becoming wide-ranging thickets. Often when they get out of bounds the urge is to whack them to the ground. You can do that but I think it is better to thin the canes plus dig to remove all the unwanted runners.

 

My reason for restraint is that the foliage on existing canes casts cooling shade on the roots. Buds on the runners which could develop into new canes tend to remain dormant in cool soil. It is only when a runner reaches beyond the mother plant's shade that the warmer soil triggers its buds and new shoots grow upward.

 

Cut a suckering shrub all the way down and you give every bud the cue to grow. The thicket comes back thicker.

 

Virginia sweetspire before its annual thin-and-dig

 

Same shrubs 30 minutes later. Notice all the rooted sections in the background, my dig-outs.

 

Take out only the oldest canes, removing 1/3 to 1/2 of the canes. The remaining canes will still create enough shade to deter root-bud growth.

When  you begin:

 

Cutting with loppers, right to the ground:

 

After thinning, I position my fork outside the circle of canes, turn the fork so it's aligned radially to the center of the plant, insert the tines, loosen and pop up roots there. I trace those runners back into the shrub's crown and nip them off there.

I fork and nip all the way around the perimeter of each shrub.

 

Each rooted runner (arrows) could become a new shrub. Look again at the pile of runners in the background of the second photo. I could start a nursery with so many excess plants!

 

Here is our example shrub, thinned and relieved of its runners.

 

It's more work than many like to do but if you choose to grow a suckering plant, this works. We love Virginia sweetspire enough to do this. We enjoy its clean green summer look and gorgeous fall color.

 

A blooming note: The first group at the top of this post blooms on old wood in spring or very early summer. The second group blooms on new wood. Although every one of these plants will quickly grow back if simply be mowed to the ground in late winter or spring, those in the first group would not bloom that year.

 

Some people tell me "Oh you can't cut it in spring, it won't bloom." I say, "If that's so, why are there seed pods on this first-year cane I just took out?"