I've attached a link to a recent thread that discusses online sources. Some are better than others (customer service, plant quality, selection) so do your research first. Jackmanii is a very popular and common clematis, so you shouldn't have much difficulty in locating one :-) It should also very likely be available at local retail nurseries or garden centers, eliminating the need for ordering and associated shipping costs.

Most clematis prefer at least 6 hours of sun to thrive and bloom well, but partial shade is doable. The heavier or longer the period of shade, the less flowering is likely to occur.

Here is a link that might be useful: online clematis sources

gardengal;

Thank you for the info. It was very helpful. I will stop by at our local nursery and see if they have it. You pointed out a good point, if its a common Clematis, i would think any nursery would carry them and I don't have to pay the crazy shipping for it.

Thank You again.

They say to plant them 2 inches deeper than the soil level in the pot.

I like Brushwood Nurseries www.gardenvines.com and also Klehm's Song Sparrow www.songsparrow.com but the first was out of Polish Spirit so picked mine up from a subvendor at amazon.

I'd rather buy online even if a little pricier as it's too much running to hit so many places now locally, and they seldom have what I want. Like Blue Columbines. So I am trying to start my own from seeds.

I looked for Blue Columbines last year too. Didn't find any!

Silver Star Vinery is one of my favorites. I miss Chalk Hill as a source. Some varieties do better in partial shade than others (my Pink Fantasy blooms very, very well in ps). My Jackmanni is in full sun so I don't know how it is for ps, but it is on this list for clematis that can handle less light. Recommendations for Partial Shade or North Wall (list from Chalk Hill Nursery):
Alabast
alpina cultivars
Andromeda
Asao
Bees Jubilee
Bella
Blue Gem
The Bride
Carnaby
cartmanii Joe
Comtesse de Bouchaud
C.W. Dowman
Daniel Deronda
Dawn
Dr. Ruppel
Edith
Elsa Spath
florida Plena
florida Sieboldiana
forsteri
General Sikorski
Hakuba
Henryi
H.F. Young
John Warren
x jouiniana Praecox
Ken Donson
Lady Northcliffe
Lasurstern
Lemon Chiffon
Lilactime
macropetala cultivars
Marie Boisselot
Masquerade
montana cultivars
Moonlight
Mrs. Cholmondeley
Multi-Blue
Nelly Moser
Peveril Pearl
Pink Cameo
Pink Fantasy
Roko Kolla
Silver Moon
Souvenir du Capitaine Thuilleaux
Special Ocassion
Twilight
Victoria
Viticella cultivars (includes Jackmanni)
Will Goodwin

Silver Star Vinery. 'Nuf said!

I have blue columbines. Would be happy to send seeds when they are ready. I seem to have taken multiple photos of every plant in my yard but the columbines. They are dark blue with a touch of purple and they hold their blooms up about two feet or more. I've sent seeds to others and they bloom true.