Rodger: Great points....cannas are a plant in which one of the viruses that affect them can be seed transmitted. When we first tested cannas over a decade ago, some had as many as four different viruses. One by one, we are finally getting most of them cleaned of virus. totototo@telus.net wrote: > On 10 Sep 2009, at 21:55, Tony Avent wrote: > > >> unless the virus causes a significant problem such as disfigurement of vigor >> loss, most folks never suspect a problem. It's only the plants that show >> symptoms that cause gardeners to get upset. >> > > The real issue isn't infection with this or that virus in particular, but the > gradual infection of a plant by a number of viruses. Individually, none of them > would amount to much of a problem, but as the virus titer goes up (i e when a > plant is progressively infected with an more and more viruses), vigor declines. > This is the usual explanation why old cultivars propagated by vegetative means > ultimately disappear or become so fussy to grow that only a few enthusiasts can > give them the attention they require to stay alive. > > Tissue culture methods have been used to clean up a surprising range of plants, > ranging from show auriculas on the verge of extinction to Cosmos > atrosanguineus, formerly a very rare plant, today sold widely in 4" pots. > > But there's an even more insidious problem: those vigorous plants that tolerate > viral infections and then act as typhoid Marys, infecting other nearby plants > via transmission by aphids, leafhoppers, and uncleaned garden implements. > > There are some mysteries in the world of commercial bulb production. The little > narcissus 'Tete a Tete' is entirely virused, yet sold very, very widely. You > would think that someone would put it through tissue culture to rid it of its > virus(es), but evidently it has sufficient vigor as is that the producers can't > be bothered. > > Another mystery is the horribly virused form of Crocus kotschyanus that is > sold. Its flowers are so deformed that it has no garden value at all, yet this > crocus is quite easy from seed, and seedlings reveal its true beauty. I always > thought of it as a rather small-flowered crocus until I obtained some seedlings > from a naturalized patch of it that has spread by seed. > > If all you are growing is common garden plants, the issue of viral infection > can be ignored, but if you are growing species grown from seed, you must be > much more careful. One rule of wisdom applies to lily growers: if you wish to > grow the species from seed, then you must not grow any of the hybrids in the > Dutch bulb trade because they are one and all virused and will infect and > destroy the less robust species. > > As for transmission by seed, I believe there are a few plants where this > happens, but for the life of me cannot recall which genus. > > > > -- Tony Avent Plant Delights Nursery @ Juniper Level Botanic Garden 9241 Sauls Road Raleigh, North Carolina 27603 USA Minimum Winter Temps 0-5 F Maximum Summer Temps 95-105F USDA Hardiness Zone 7b email tony@plantdelights.com website http://www.plantdelights.com/ phone 919 772-4794 fax 919 772-4752 "I consider every plant hardy until I have killed it myself...at least three times" - Avent