Making Forsythia (and Other Shrubs) Bloom

April 8, 2009 | By | Comments (5)

As always, the generous Grump is here to answer your most perplexing garden questions. Here’s one about forsythia from Pam Nichols:

Hi! I have three large forsythia that are about 20 years old.  They are in full sun and have not been trimmed in a couple of years.  The last two years they have had no blooms (well, maybe three flowers in all).  What am I doing or not doing wrong?  Help!

Forsythia

If your shrubs are 20 years old, I would say they are prime candidates for a technique called renewal pruning. This involves in cutting 1/3 of the oldest, woodiest canes to the ground every year for three years. Do this immediately after the forsythia finishes blooming. This will remove the old, tired growth and promote new, vigorous growth with lots of flowers. Don’t prune in summer, fall, or winter or you’ll cut off flower buds for next spring. In 3 years, you’ll have brand new shrubs.

Some people advocate renewing shrubs like forsythia (also called yellow bells) by cutting them completely to the ground after they bloom. I think this is a little drastic, unless your shrubs are very overgrown.

Renewal pruning can also be used to rejuvenate the following shrubs:

1. Beauty bush (Kolkwitizia amabilis)

2. Fuzzy deutzia (Deutzia scabra)

3. Dwarf flowering almond (Prunus glandulosa)

4. Japanese kerria (Kerria japonica)

5. Lilac (Syringa sp.)

6. Spirea (many kinds)

7. Weigela (Weigela florida)

8. Winter honeysuckle (Lonicera fragrantissima)

9. Mockorange (Philadelphus sp.)

COMMENTS

  1. Are You Ready For Spring? – The Daily South | Your Hub for Southern Culture

    […] depends on the plant. If it blooms in the spring on growth made the previous year (azalea, lilac, forsythia, spirea, loropetalum, ‘Nikko Blue’ hydrangea, Lady banks rose, etc.) and you prune now, […]

    January 31, 2013 at 9:01 am
  2. Grumpy Gardener

    It’s really tough. Most weedkillers don’t work, because mature violets develop thick fleshy roots that don’t die. One product that has worked for me to some extent is Ortho Max Poison Ivy Killer. You have to mix it up and brush it on the leaves, because it will kill any green thing it gets on. The surest solution is to dig up the violets. It’s a royal pain, I know, but it works.

    June 2, 2009 at 11:45 am
  3. Donna

    How do I kill wild violets in my lawn?

    June 2, 2009 at 11:14 am
  4. Grumpy Gardener

    The common butterfly bush (Buddleia davidii) blooms on new growth, so you prune it back in winter or early spring. However, Buddleia alternifolia blooms on growth made the year before. So you want to prune it after it finishes blooming, not before.

    April 9, 2009 at 1:09 pm
  5. Phillip

    Great advice, I think my beauty bush needs this. Can you tell me the proper way to prune a Buddleia alternifolia?

    April 8, 2009 at 7:18 pm

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