I have a few Phyllostachys species that haven't been doing too well with growth. They aren't increasing in height as I had expected them to. I would like to describe my methods of caring for my plantings and ask the more knowledgable 'boo growers on the forum what I should do to get better growth and winter above ground survival. I would appreciate any and all advice!

- this is/was their third summer and growing season, they were planted spring of '06

- they receive a high nitrogen granular fertilizer in early spring and again in mid summer given as per package instructions (for grass) and have not exhibited any signs of burn

- they are planted in full sun and watered once a week if rain is lacking/leaves begin curling

- the soil is a clay loam (not well drained nor soggy)

- they were mulched with ~5-6 inches of chipped wood/branches at planting time and have been refreshed as needed. I extend the mulch about one and a half feet past the perimeter of the outer-most canes

- they have received no winter protection to this point

- I'm in USDA zone 6a with an average winter minimum temperature of -4.8F based on the past 58 years of climate records from a local weather station that is only a few miles from my house/plants

- despite the avg. min. temp. of -4.8F, it only drops below 0F for an average of 3.7 days each winter

- we usually get a good amount of lake effect snow in the average winter

Here's my winter track record for reference as well as the height increases for each since their planting in spring of '06:

P. rubromarginata - loses a couple canes and all leaves on surviving canes, grew from 4 to 6 feet

p. nuda - loses all canes in winter, grew from 3 to 6 feet

p. nigra 'Henon' - loses all canes in winter, has remained at 3 feet

p. atrovaginata - loses half its canes in winter and all its leaves on the surviving canes, grew from 3 to 5 feet

P. aureosulcata 'spectabilis' - planted spring '07, complete top kill this past winter, has remained at 3 feet

P. dulcis - planted spring '07 and was completely killed

Would wilt-pruf be my best bet for winter protection on my bamboo? Would I have to re-apply it monthly? Lastly, would fencing in each clump of canes and wrapping the fencing in a couple layers of burlap be as effective as wilt-pruf spray?

Thanks all for the help!