I purchased this plant two years ago because I wanted something that would be vigorous, and then I heard it wasn't so great. This will be its third year and it only has one main stem. Should I discard it and get something new, and what would you suggest.

I don't know specifically about suberba. I have the regularJackmanii and it is vigorous.
Type 3 Clematis like to be cut back to about 12"in the early spring. Probably not too late to do in your area.Give some fertilizer and a drink of diluted epsom salts monthly too. If planted on an angle sometimes can get more stems. If you have done all these things and it is still doesn't meet your expectations, you can always plant another clem right beside it , even in the same large hole.

Our Jackmanii's are superb but they are not Jackmanii Superba. One grows so lush I have to cut it back a few times each summer.

WOW!

It backs up to one of the compost bins and that's why it's so lush.

do you currently have it in conditions that it doesn't like...? I would think two years would be a great start for establishing a good root system. the upper part of the stems should be in full sun and the roots need to be kept cool, by other plants or a fence or something. we use hostas planted around the base of our superba to keep its roots cool. we also fertilize ours with diluted organic 5-1-1 fish emulsion. its EXCELLENT for putting on growth prior to blooming. we also work in alfalfa meal into the surrounding soil once it starts putting on new growth. We've had our "Superba" not even two years now and its light years above and beyond any clematis ive ever owned! growth is so vigorous and the stems have already reached the top of the trellis its growing on and its about to take over! not that thats a bad thing, the more vigorous the better, the more flowers the better!! im just saying its not going to leave much room on top of the fence for the two other clematis plants (Henri & Gravetye Beauty) trying to catch up! ha

the pic below was taken on July 2nd of last year. it had only been in the ground 18 months at the time!

Good fertilizing advice. Yours looks SUPERB!

What a fabulous picture, Jason. Everything is so lush looking. How about more pictures of your gardens so I can be really jealous!!!

Yes to all those things about my J. Superba. One of the gals from the nursery where I bought is a Master Gardener, and she said hers did the same thing. Of the three people that she knew purchased it, only one had good luck. I am warning it that this is its last chance, so we will see!!!

Warning it??? ha, I like that! threaten it with some horsetail or something, that may help! don't know what to say about your bad luck with your superba. maybe purchase another one, see what happens with it; and keep this one going along with it...? I must say I couldn't be happier with mine. who knows, maybe this will be your lucky year!

pics of my other gardens can be seen here: The thread "Gold Bar, Washignton. Our Yard..." in Garden Photos forum

riverman, are you blessed with wonderful Washington weather? That might be the difference.

thanks!

sometimes its wonderful, on occasion, like on saturday. its actually pretty mild, as in, we don't have too many extremes. at least not on the west side. I think the difference however is we just try to grow stuff that's suited for our environment.

Yes, zone envy can be costly!

I actually rescued, from death (these were dying from lack of water even after I told cashier they needed watering) I went in store every week to check on them and the bees jubilee and ended up with 2 of each marked down 2/$12; had previously brought two at full price $12.99. I've never seen these in my area so had to get them. 😃

I never see deals like that! You knew what to look for

I agree! I was at Lowe's yesterday and their sale items were pathetic but a good buy for those who can nurse them back to health.