One of the first shrubs we planted at JLBG in the late 1980s was the giant snowball bush, Viburnum macrocephalum sterile form. Today, this amazing selection of the Chinese native species, tops out at 25′ tall. In April each year, it puts on a truly indescribable show, as you can see from our new April photo below. If that’s not enough, it re-flowers as heavily in the fall. I can’t imagine a sun garden without this. There are also sterile “snowball” forms of several viburnum species, but this is by far, the largest. Hardiness Zone 6a-9b.
Beautiful!
I’ve seen where many fertile viburnum are not self-fruiting and require a related species for cross-pollination to produce berries. Others say having three or more the same viburnum cultivar also increases fruiting. Guidance on the web is a little thin here. It gets a little complicated as you see below.
For example, for the v. rhytidophyllum x v. pragense hybrid leatherleaf viburnum ‘Allegheny’, would you need either straight parent species v. rhytidophyllum or v. pragense for optimum cross-pollination? Or could you use the popular cultivar “Decker’ that is a hybrid cross of v. rhytidophyllum and v. utile? And would it follow that Decker could then cross-pollinate both with Allegheny and a nearby v. burkwoodii, a hybrid of v. carlesii and v. utile? I told you it gets complicated.
Some nurseries advise in general that any other viburnum that has overlapping bloom period will do as a cross-pollinator, but it doesn’t seem to be that simple. I ask because I’m in the process of creating a mixed viburnum screen and several groupings, and would like to have the ‘right viburnum in the right place’ for the long-term. I’m planting a wide variety of viburnums, including leatherleaf, doublefile, snowball, Korean spice and arrowwood.
Lastly, though many viburnums are ‘non-native’ and thus suffer the wrath of native-purists, the flowers obviously attract pollinators and the berries of viburnum are highly prized by cardinals, robins, cedar waxwing, thrushes and mockingbirds, among others. And I say we need more thrushes, don’t you?
Thanks,
Greg
I’m not aware of a comprehensive study on which viburnums pollinate which others. Our Viburnum settigerum sets fruit on it’s own, but our Viburnum sieboldii never set fruit until we planted one near several other hybrids.
Keeping with the spring theme of ‘new life and re-birth’…..
Earlier in the season to facilitate cross-pollination of my leatherleaf viburnums I placed one flowering Pragense Viburnum (in a 5gal container) in with a linear screen of flowering Allegheny Viburnums that I had planted last fall. The 8 Alleghenies are 3-5ft tall x wide and spaced 10 ft. apart over 80-90ft. I moved the flowering Pragense each week to openings near each end of the screen/hedge to ensure pollinators had similar access to both species, so one end of the screen was not biased over the other. All viburnum flowered strongly and are now full of developing fruit. It was not exactly a well designed scientific study with all the usual requisite controls, but the key takeaways show that having just one related species (Pragense) within 40ft of Allegheny, plus having more than 3 of the same species within an 80ft radius resulted in ‘abundant fruitfulness’. Another observation with the Allegheny viburnum was that certain plants flowered significantly later (by 2 to 3 weeks), these plants were also later to leaf-out. This suggested transplant shock or other stressor while in pots set certain plants back a few weeks. It will be interesting to see if they all are in sync by next spring. _Greg
Will these Giant Snowball Viburnums flourish in deep South Georgia? I like them, but I don’t see them growing in our area. I don’t even remember seeing them in the botanic gardens at Georgia Southern or at the Coastal Botanic Gardens in Savannah.
It’s generally listed as fine in Zone 9, so it should be worth a try there.