I would have guessed that caroleoh has arrowwood viburnum (Viburnum dentatum). These pretty much stink in flower, and they bloom late spring/early summer here. About the only viburnums that bloom later are Viburnum nudum and its clones, which have a bit sweeter scent but not in the range of the spice girls like Viburnum carlesii and her offspring. brandon7: harryshoe may be reluctant to relate the rancorous or rancid, but I can tell you the range of smells of over 100 different species and clones that have a home here. I will not speak for him and his guests, as I don't find 'Winterthur' objectionable olfactorily. I do have a problem with Viburnum dilatatum, unfortunately, which is one of my favorites for overall performance. Reproductive fluids is as near a description as I can match it with. gardengal48's mention of old sweat socks fits nearby. I've even heard some reputable plantsmen attribute that to the odor of fallen leaves of some species. Go figure. Beauty is in the eye of the beholder, and fragrance - well, that's a rhinoceros of a different color.

While we wait for an expert, I'll give you my opinion. I have at least a dozen types of viburnums and have grown them for about 20 years - at one time I thought I would try to grow them all, but I've scaled back my plans due to lack of space and the increased number of varieties on the market. If they are multi-stemmed, with several trunks coming out of the ground, you may have MUCH better luck removing 1/3 of the main stems to the ground instead of heading back the shrub. Trimming all stems to give a haircut is not going to be very good for your viburnums' eventual shape and is going to require at least annual repeat performances on your part. Removing 1/3 of the shrub can be done for 3 years in a row and followed up with an occasional removal of the tallest couple of branches. It should result in better shaped and more natural looking shrubs. By cutting some stems to the ground, you'll be encouraging the new growth to appear at the base of the plant, not at the top, and you won't have to worry that you may be removing all of next year's potential flowering stems. Also, with this treatment, you may even find that these shrubs perform well enough that you may want to keep them - right where they are.

Yes, viburnums are not caning shrubs and so the 1/3 removal method is not applicable. Dirr, in his treatise on viburnums, states: "Viburnums do not require heavy-handed, butcher-shop type pruning. Tidying and shaping with hand pruners is best. Pruning viburnums should be an exercise in retraint". Since nearly all viburnums flower on old growth, any pruning that may be required should be done immediately after flowering. But since 'Summer Snowflake' flowers pretty much non-stop through summer, that may be hard to achieve :-) You may be able to encourage denser growth by cutting back some exterior shoots to right before a node -- this typically will prompt budding of new shoots from the node. FWIW, there is a mature SS shrub at my nursery that is easily 15' tall and about 10-12' wide. I doubt it has ever seen pruning shears nor does it need to. I might look to other reasons why your shrub's growth is rangy and sparse - poor soils, too much shade, insufficient moisture?

Sorry for getting to this so late. Maybe OP is still around? For all species of multi-stemmed shrubs, the all-around best treatment is occasional to yearly renewal pruning. In this type of pruning, you select for removal the oldest, stoutest and most mature "canes", which you cut at ground level or as near to ground level as you can, without dinging up the remaining more juvenile stems. By doing so, you are favoring the more vigorous younger stems, which will help with flower/fruit production in many cases, as well as helping to keep the plant a bit more manageable. This is not easy work by any means, but it will allow an older shrub to remain youthful and vigorous more or less indefinitely. +oM