Answer: Your Blue Muffin viburnums are self-fertile and will set berries whether you have a single plant or a whole garden full of viburnums. I think the lack of berries is due to plant immaturity or weather conditions during the blossom period. Although they are self-fertile, they need a little help from flying insects to transfer the pollen. So, if it was very wet or very cold during their bloom period, insect activity could have been nil, which would account for very few berries. Give your plants a chance to mature a little, and hope that the weather is clear and warm during blossoming - if so, you should have a bounty of berries next year.
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