Help for out of control Clematis!

This photo of my Clematis trellis tells the tale. It is about seven feet tall, and there are several different types growing there. Most are prunning group 2. I say most because I am not sure of everything that is there. Friends and neighbors have transplanted some of their plants here because they were not doing well where the were. The trellis needs repair as the plants are pulling it over. There are tons of buds on it now, so I really don't want to do anything until most of them bloom. When is the best time to cut them back so we can repair the trellis, and get rid of some of the dead growth? How far can I cut them back without damage?
Any advice would be greatly appreciated.
Thanks,
Lisa

Lisa...ahhh "what a tangle mess we weave" says your clematis and time has most definitely come to fix their support and to rejuvenate them...I would wait until all the blooms are done and then prune all the many vines down to about 2 feet...also...do you fertilize?..I noticed your clematis seems to have yellowish leaves or is that the pic?..They might be lacking in Magnesium is why I bring this to your attention and if so it's a rather quick fix.....you can mix about 4 tbs of Epsom Salts in a gallon bucket and mix well and then pour some around each vine and water in well..this should "Green-up" your clematis in the future...Jeanne
ps..don't forget to give your clematis either rose or tomato fertilize at the same time you do your Epsom Salts..they'll love you for it

Thank you so much, Jeanne. I just called DH to bring home the Epsom Salts. I do fertilize, but the leaves do look yellow to me also. We have had so much rain in the last few days that some of my plants are showing some unusual signs of wilt...very unusual for western NY. I have noticed now that many more of my other (more organized) Clematis are a little less green than usual. Will the epsom salts be OK for the roses that they are growing with?
Thank you again for your help. I will do exactly as you suggest.
Lisa

Yes epsom salts are good for most plants.....they love it!

Thank you, Dawn..I am mixing some up right now..
Lisa

too much water.
prune back seriously after blooming and fertilize with a balanced formula.

also meant to add as the plants reemerge next spring consider moving some of them to a different trellis. and then you can spread out your vines and train them as they start out for a controlled "big show" of clems!

Too much rain can most definitely be the culprit 'causing your leaves to yellow....ROSES adore Epsom Salts...I have tons of roses and use my Alfalfa Tea on them and my roses and it contains Epsom Salts..Jeanne

all good advice, but if the ground is drowning, wait till it dries out a bit to use any fertilizers. we had some downpours this spring and i found that i could not help the plant till the soil got less waterlogged.
more clems die from overwatering than underwatering so don't make it worse in the short term by applying lots of epson salt water and fertilizer. wait til the hydration is needed and will be utilized.

Thank you so much Guru and Jeanne. I do plan to wait until we dry out before I do anything. It rained again last night! I am now going to dig up a penstimen that is going to die if I don't try to dry it out. The thing is we have great drainage, and it is still not enough!
Thanks again for the advice and ideas.
Lisa

Good News! The Penstimon are OK. I planted the poor things the day before the rain started, and they really looked bad last night. Today they are coming back...
Thanks again,
Lisa

Glad to hear it Lisa...Keep us in the loop and hope everything turns out ok...Jeanne

Rain rain go away.....I guess sometimes we feel like singing it when we are getting too much of it.

humm -
just heard acid loving plants also like used tea.
Ive been making green tea for the summer heat and using these leaves -
would be so fashionably 'green'
- but not worth the effort if it turns my plant brown!

Any one heard of this??

tea, compost water and such can not hurt the plant. however, i always caution to put on the ground outside of the area of the stems. it's farfetched, but as a habit, not putting stuff on the stems makes sense and is a good practice with clems in my experience. safe, not sorry. and if the tea has been sweetened, personally i would not use it unless it has been decomposed with other compost as the sugar could draw ants and insects.