Pruning viburnum trilobum #372766

Asked October 25, 2016, 9:39 PM EDT

I have a 3 yr. old Bailey Compact Viburnum which has not bloomed nor set fruit yet. It does not show strong fall color. What would be the best method to encourage the shrub to bloom, set fruit and show good fall leaf color? When is a good time to prune it? Does it bloom on old wood or new wood? It receives very good, strong sun most of the day. Otherwise the 6 ft. shrub seems to be doing well. Thank you for your consideration. Sydra Krueger

Bay County Michigan

Expert Response

Hello Sydra,
There are a few things that can reduce flowering, and of course if you didn't get flowers you will not get the fruit that results from the pollinated flowers.

Here are some things to check-
Viburnums flower on old wood. Don't prune anything but diseased, dead  or damaged branches for one full year. Then  you can choose to not prune  at all or only prune lightly after the usual flowering time- watch other viburnums in your area  around late May to June. Pruning in early spring or late fall will prune off the flower buds. The flower buds are set for next year during summer. And of course, if you prune off faded flowers then you won't get fruit from those flowers.

Be sure you are not putting down nitrogen fertilizer, or allowing lawn fertilizer to get to the shrub by way of your application spreader or by lawn water run-off. Too much nitrogen encourages lots of leafy growth but not many flowers.

Consider planting another viburnum. Cross pollination from another shrub  helps produce more fruit, once you have flowers.

Lack of fall color can be due to too much shade, too little water, or - more rarely- the shrub was mis-labeled at the nursery( some viburnums have a 'poor yellowish' fall color). Or you just have an individual that doesn't produce the fall color. Even among a species or cultivar some individual plants vary from the norm. This variation can also explain why you aren't seeing flowers- some viburnums only produce flowers sparsely.

Once the plant flowers, a failure to set fruit can be caused by a late hard frost, or a lack of pollinating insects. Cold, wet weather can keep the pollinators away.

Stress on the plant can prevent bloom. Viburnums like moist, well-drained soil conditions, so keep the soil moist during drought times by watering slowly all around the root zone. Check the soil moisture by digging a narrow hole down at least 6 inches. If your soil is clay you have to water carefully so as not to force all the air out of the soil. Mulch around the plant with 3 inches deep of organic mulch and keep it pulled back so it doesn't touch the stems.

Three years in the ground is about right for a transplanted shrub to have developed enough roots to start producing well. Next spring may be its year to bloom for you. Thank you for using Ask an Expert.

Laura Sheffer Replied October 26, 2016, 11:56 AM EDT
Thanks so much for answering. Now I know it blooms on old wood...hopefully, I will see bloom and fruit set next season. I do have a Blue Muffin Viburnum and a smaller Tomentosa in the garden as well, which were planted in 2016. I am also a Master Gardener in Bay County, MI. Having gone through that program has really helped me understand the plant world much better! (& I'm an Iowa farm girl! haha.) I will not prune that plant for another year or so. It may need height control eventually. Our son, who studied horticulture at MSU tells us, "Things just grow here." I don't have to encourage my garden very much, weeding and pruning are my main chores. Have a restful winter and a blooming spring! Sgk
The Question Asker Replied October 26, 2016, 12:54 PM EDT
Great, glad to hear from anothe MG. FYI there is a vibrunum trilobum called 'Compactum' which is sometimes confused with 'Bailey's Compact' and that one doesn't have good fall color according to my reference. So, I hope you have the Bailey!
Laura Sheffer Replied October 26, 2016, 1:08 PM EDT

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