Question
QUESTION: I want to construct a Clematis vine 搘all?on one end of an elevated concrete patio. There is an existing metal railing and I will construct a wire trellis above that. It will be approx. 10' wide and 6' high. Will I have any wintertime freezing problems if the vines are planted in large planters? How wide and deep should the planters be? How many plants will I need to cover the desired area?

ANSWER: Hi Buck,
Thanx for your question.  Where are you located?
thx,
Tom

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QUESTION: I'm located in Virginia's Northern Neck region, about 1 hour east of Richmond (the capitol) and 1.5 hrs southeast of Washington DC. I believe I'm in zone 7.

Answer
Hi Buck,
Thanx for the additional information.  We grow clematis here in Zone5/6 in 12inch deep pots about 18 inches wide.  We never have trouble with these although they are somewhat protected from direct northwind.  Our climate is a bit cooler than yours.  If you've got a 10 foot wide section, I would place perhaps, 5 planters at the foot of the trellis, one plant in each pot.  Side dress the plants with well-composted manure and water often in the summer to prevent them from drying out.  I hope this helps.
Tom