Welll, I did this by accident lol. That arbor in another post that has my Rooguchi on it? Well, on the other side of the arbor I had planted a jackmanii. It grew somewhat slowly and weakly (although I admit to extreme neglect!) and in the third year I thought it was a goner. On impulse I bought a Romantika and plopped it in the same area. Turns out the jackmanii was NOT dead, just mostly dead, and came back, right alongside the Romantika. That was just last year (and they did okay but still on the small side) so I'll have to see how they both do this year. I'll try to remember to update later in the season if you still haven't decided by then! But I would think they'd do well as long as there is enough room - how large is largish lol?

:)

Dee

P.S. Don't plant a Rooguchi there haha!

i cant imagine why it would matter... no matter if they are close kin of not.. or any other plant in the world ... why would you think it would be an issue...

if you tried to plant a clem in the middle of a huge clump of grass .. i would expect you would have watering issues.. sooner or later.. but if you started with babes all around.. i would think they would grow peacefully together until ones roots took over ...

there are some super killer/competitors... but they are pretty far and few between ... but your true Allelopathy plants are rather rare ...

all that said.. i cant imagine one clem killing another clem...

ken

https://duckduckgo.com/?q=allelopathic+plants&t=ffab&ia=web

" i cant imagine why it would matter... no matter if they are close kin of not.. or any other plant in the world ... why would you think it would be an issue... "

It certainly can be an issue, especially if we are dealing within the confines of a not huge obelisk. First, there are pruning issues. Inevitably the two clems will become entangled and if they are not of the same pruning group, one or the other is not going to be pruned correctly for best appearance and performance.

Second, there are size issues. Vining clems range in size from 6-8' to 25' or more and you can bet hard money that the big guy will outcompete and eventually smother the smaller one, so a need to be cognizant of mature sizes and select those that are comparable.

Finally, clems can develop very large and extensive root systems so want to allow each enough space in the ground to develop fully without too much interference from its neighbors.

It is a situation that should warrant some forethought before just plunking down 2 random clematis selections immediately adjacent to each other. The difference between a bit of a jungle and a thoughtfully planned out garden. 🤗

why would you think it would be an issue...

Off the to of my head it could be the case that "close quarters" planting could result in increased competition for soil nutrients, sunlight and water

It is a situation that should warrant some forethought before just plunking down 2 random clematis selections immediately adjacent to each other.

As I had written in my original post, both clems would be of the same group (and yes both would be of similar stature).

The difference between a bit of a jungle and a thoughtfully planned out garden.

I do my best in a very established but small garden :).

" I do my best in a very established but small garden :). "

You most certainly do!! My comments were primarily directed at ken's "what possible issue " statement and the implication from another comment that any clems planted together will be fine. Maybe, maybe not.

All good 'gg' :)

(Each off season I muse about changes to make in the garden)