Three star jasmine in upper deck planter?

[digalot]

Hello,

I live in Victoria and would like to build a large container on a second floor deck that will hold three "star jasmine" vines.

This weekend we picked up three:
Trachelospermum jasminoides japonicum "star Jasmine", with grower tag stating adult height 6'-8'. (Clearview Horticultural Products Inc.)

The purpose for this planting is to provide evergreen privacy screening for a deck railing 14' long by 4' high. This height may eventually be increased to 5'.

I'm hoping you may have suggestions regarding a few concerns that will help these vines in the long run, and avoid root pruning if possible.

The container will be situated in the middle section of the span with vines trained along horizontal wires. Also I realize that considerable structural reinforcing will be needed below the deck.

Anyway I was wondering...

- What size container would be ideal to hold three of these vines, and is a depth of 18" sufficient? This is a long term set-up and I hope to avoid root pruning if possible.

- I'm concerned about winter freezing of the root mass. The cedar box will have a fiberglass liner, so the cedar will be more decorative. Is it a possibility to include 1" blue foam sheet in the box construction, or does the whole box have to be covered with something each winter?

- What type of wire should I use for training the vine on? I thought of copper as this may be good outside, as far as corrosion, but will it harm the vine?

Thank-you for all your help,
Digalot

[Gnome]

digalot,

Hello and welcome to the forum. I know nothing of the species you are using but I do have a few thoughts on the project in general.

What size container would be ideal to hold three of these vines, and is a depth of 18" sufficient? This is a long term set-up and I hope to avoid root pruning if possible.

That would probably be deep enough but if they grow well eventually they will need to be root-pruned. I'm not sure how long it would take but eventually they will. I don't know how you will be able to re-pot if the tops are fixed and not movable. Ideally you should move up through a series of smaller pots but from the description of your plan that may be impractical.

A soil that will not collapse and compact is essential for such a long term planting, luckily that is just the sort of soil (actually soiless medium) we use in bonsai culture. Older trees can go for five years or longer without re-potting due the the specialized medium that is used. If you use a denser, more water retentive soil, such as conventional potting soil, I'm afraid that it will compact over time. I feel that is the price you must pay for a long term planting. look [url=https://www.helpfulgardener.com/forum/viewtopic.php?t=3422]here[/url] for basic information.

The cedar box will have a fiberglass liner, so the cedar will be more decorative.

I hope you are planning to allow for drainage. Nothing will kill most potted plants faster than waterlogged soil. The coarse medium described in the thread I linked to will require frequent and thorough watering, especially after the roots completely colonize the container.

Is it a possibility to include 1" blue foam sheet in the box construction, or does the whole box have to be covered with something each winter?

Your plan sounds good but you should include a sheet in the bottom to insulate from the cold air under the deck. Also include a sheet on the top as well, during the winter of course. The plant you are using and your climate will dictate if that is sufficient.

Norm

[digalot]

Thanks Norm for all the suggestions. I still have to research it further, but I like the ideas you've given me.

Cheers,
Jim

[Jess]

I think you will find that the plant grows a bit bigger.....20ft! I even checked the company you mentioned online just in case by some miracle they had bred a dwarf form or something but it also says 20ft. (6m)
https://www.homeofclematis.net/Trachelos_majus.html

[Jess]

Oh and before you ask, japonicum and majus are the same one.

[digalot]

Well it looks like the growers tag has been made incorrectly.
Thanks for the update. I'll send them an e-mail.

Any ideas on the planter box dimensions?

Thanks
Jim

[Jess]

I think for a start you would have to reduce the number to 2 at the most and even then they would more than than adequately cover.

Most climbers like a deep rootrun....not this one apparently;

However, this particular evergreen climber seems to manage rather well in a container (preferably a wooden tub) as long as it is at least 18in deep and wide. It responds by becoming woodier, shrubbier, and climbing rather less, but nevertheless produces an abundance of beautifully scented flowers over a long period.

Copied that from a site with answers from the RHS so it must be good!

[digalot]

Thanks for the info Jess. :-))
Can't help it, I like the "old school" smilies.

I'll just plant two.

Cheers,
Jim