Ever wonder why those terrific native viburnums you planted are not producing fruit? You are not alone. It’s one of the frustrations of gardening ecologically in a world where “cross pollination” is rarely mentioned at local nurseries or garden centers (and forget about the big box stores!). Some plants, although deemed self-fruitful, may need a “pollinator partner” to bear fruit reliably.
Although potentially self-fruitful, native viburnums are actually pretty self-incompatible and typically require cross-pollination for good fruit production. Two genetically different plants of the same species should be planted in reasonably close proximity. And, those genetically different plants must be in bloom at the same time so that visiting insect pollinators can do their job.
Unfortunately, nurseries and garden centers rarely explain this (or may not even know this) and may tell you to simply buy two of the same viburnums they have on hand (which may turn out to be genetically identical). Later, you wonder why the plants don’t bear fruit – a great disappointment if you want to provide fruit for birds and other wildlife, and in the case of some viburnums, like Nannyberry (Viburnum lentago), fruit that you can enjoy.
How can you solve this problem?
- Plan A: Ask a nursery for straight species viburnums that have been grown from seed – these will be genetically diverse. In contrast, plants that have been propagated from cuttings will be genetic clones. Unless the nursery has grown the plants themselves, they may not know whether the plants have been grown from seed or from cuttings.
- Plan B: Purchase straight species viburnums from different nurseries that source plants from different growers. Try to buy plants in bud or in bloom so that you know that the various plants will flower at the same time.
- Plan C: Purchase cultivars that are known to be compatible and bloom at the same time. An example: Viburnum dentatum ‘Chicago Lustre’ is compatible with Viburnum dentatum ‘Blue Muffin.
- Plan D: Purchase a cultivar which is in bud or bloom at the same time as a straight species viburnum.
Ask your local nursery to help you and other gardeners by selling “paired plants” for those species needing cross-pollination, including our beautiful native viburnums.
Happy gardening from Kim Eierman at EcoBeneficial!
Photo: Fruit of Nannyberry (Viburnum lentago)
Photo credit: Flickr_Andrey Zharkikh