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.
Most 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 eat.
How can you solve this problem?
- Plan A: Buy two or more straight species viburnums (of the same species) 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: If you cannot find viburnums grown from seed, purchase two or more straight species viburnums (of the same species) from different nurseries that source plants from different growers.
- Plan C: Purchase different cultivars of the same species of viburnum. In the case of Viburnum dentatum, it is a bit more complicated – you must choose cultivars that are known to be compatible and bloom at the same time. For example, Viburnum dentatum ‘Blue Muffin’ is compatible with Viburnum dentatum ‘Little Joe.’
- Plan D: Purchase a cultivar and a straight species viburnum, of the same species, which are in bud or bloom at the same time.
Ask your local nursery or garden center to help you and local wildlife, 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