Needmore Bamboo Co.
 
                                             
   
  Phyllostachys viridis - Boy, if I lived about 150 miles farther south this would be my favorite bamboo.   In the spring following the only winter that was mild enough to allow the Viridis culms to survive, the grove produced some canes that were 1.75 inches in diameter and the average size for the grove was more than 1 inch.  Unfortunately the next winter was sufficient to kill back all of the culms again and the following spring the new canes were mostly under an inch, with a couple approaching 1.25 inches in diameter.   Still, it is a beautiful grove to admire with the very bright green, upright culms and attractive leaf form.   
   Viridis tends to produce lots of culms which can translate into lots of work in the spring as I have to spend many hours cutting down and dragging off the entire grove of dead canes. This spring I chopped off every small shoot that came up, probably 300 or more, so that I would have less work the following spring.   But the bamboo waited until I wasn't paying attention and I now see hundreds of new small canes that came up after my culling. Viridis has been a relatively slow spreading Phyllostachys, and has been easy to control.   At one time this bamboo was named Phyllostachys sulphurea due to its tendency to have the leaves all turn golden yellow in the fall, and there remains confusion - particularly in Europe - over the name of this bamboo and the 'Robert Young' form which has yellow canes.  My grove has never shown the yellow leaves and I wonder if it is due to the culms not surviving winter and therefore not exhibiting mature behavior.  Apparently some clone of Viridis has been flowering in parts of Alabama for a few years now and even though mine came from that area I have not yet seen any signs of flowering.  Probably solid most winters in zone 6b and warmer this is not a zone 5b/6a bamboo unless you don't mind the annual dieback/cleanup.   I have also observed that Viridis culms break very easily under snow/ice loads which creates additional maintenance issues.

    Viridis is a beautiful bamboo (I've noticed that I have more photos of this one than any other) and can be rewarding to grow in my area if you have other, hardier species but the subspecies 'Houzeau' & 'Robert Young' both top kill every winter for me.   Although they do come back each spring with new culms, the culms remain small and I am reducing the space allotted to them.   I suspect that 'Houzeau' may gain some hardiness and size up so I'll keep an eye on it, but there are just too many other species of similar coloration that are much stronger in my area. 'Robert Young' has lemon yellow canes with random green striping and 'Houzeau' is a green cane with a yellow sulcus.  The similarly colored forms of Phyllostachys aureosulcata are significantly more rewarding to grow and will attain much greater sizes - if you want brilliantly colored culms go with them instead.  
    I estimate that Viridis can hold green leaves to about +3F while 'Robert Young' can start to show damage at +10F and is usually top killed at around +5F despite ratings of it being hardy to -5F , the 'Houzeau' form is a bit hardier than 'Robert Young' but has not yet wintered over for me.   Despite the allure of the 'Robert Young' form, I would not recommend it north of zone 7.		  
                                             
         
                                             
                       
Viridis shoots
                
                                             
                     
                                             
                       
Viridis culms
                
                                             
                     
                                             
                     
                                             
                   
                                             
               

Winter damage, Spring renewal

              
                                             
                         
           
                         
       

Garden hose diameter rhizome
        
                         
                                             
                 
                                             
                 
                                             
             
'Houzeau' mini-grove & 'yellow-groove' culms
           
                                             
                     
                                             
                 
Yellow culm 'Robert Young'