A trellis for a climbing hydrangea? Were you aware that climbing hydrangea can reach more than 80 feet? Decumeria Barbara Ann is cousin of CH that gets to be around 40 feet or so.

@luis_pr On either side of the climbing hydrangea, there are Italian cypress trees that are currently around 50 feet tall. So nature provided some additional trellis material. The white formal trellis behind the container here is to help any vines establish, including (maybe) a Clematis.

Climbing hydrangea is self adhesive on solid, slightly rough surfaces like tree trunks or walls. I don't think it would climb your trellis, especially if it’s plastic, or your Cypresses satisfactorily. And I’ve mentioned elsewhere that using climbers on Cypresses is a bad idea imo. You reduce the light on their foliage and end up with die back. I also don’t think your pot is large enough to sustain two Clematis and a Hydrangea.

@floral_uk z.8/9 SW UK The trellis will allow us to keep the plant off the fence and a neighbor's shed. We don't want the plant to adhere to those things. The trellis also looks beautiful and everyone who sees it stops to comment on its huge size and beautiful shape.

I am replacing boring Italian cypress foliage with something that is beautiful and interesting and imposing. Those are tradeoffs, and I think I am choosing the right side of that decision.

I agree the Clematis probably should not go in the pot.

@tsugajunkie z5 SE WI ♱ That's a beauty, and amazing job keeping it trimmed.

IMO, pairing the two is a very poor decision. The hydrangea grows slowly, has the potential to get very big and very heavy and is almost impossible to grow on a trellis. It doesn't vine.....it supports itself by producing rootlets along all the stems. These rootlets adhere and attach themselves to wide, flat and moderately textured surfaces - a wooden fence, a brick or stone chimney, the side of a garage, a tree trunk, etc. It will NOT be supported by a trellis regardless of how attractive it is nor will it be supported by the foliage of a Italian cypress. And then there is the issue of trying to prune a clematis that is entangled with a hydrangea.........what a headache!!

The pot and trellis are great for a clematis.....maybe even two. And they will gladly grow up and into the cypress. But find a more suitable location and support system for the hydrangea. It just won't work under the conditions you describe.

“We don't want the plant to adhere to those things.”

See gardengal’s response. Adhering is how climbing hydrangea climbs. It is not capable of climbing without sticking and it can’t stick to smooth plastic. I was not criticising your trellis. It’s just not suitable for what you want it to do. As to replacing ‘boring cypress foliage’, even if it could somehow scramble up the cypress it would shade it out. This might not be noticeable in summer, but in winter there would be just be bare Hydrangea branches hanging off dead cypress branches.

@gardengal48 (PNW Z8/9) Again, the trellis will allow us to steer the plant away from the fence and towards the woody plants where we want them to grow vertically. I don't care at all if the Hydrangea cannot stick to the trellis. The more important question is whether Climbing Hydrangea can use an Italian cypress to climb. If it cannot that is a problem.

I originally did want to use two Clematis with different colors on each side of the pot.

@floral_uk z.8/9 SW UK Climbing Hydrangea might end up being evergreen in our moderate zone 9b Mediterranean climate, but if not then its twisting woody vines would not be awful to look at for three months a year.

"The more important question is whether Climbing Hydrangea can use an Italian cypress to climb. If it cannot that is a problem."

Then you have a problem. The hydrangea will attach itself to bare wood but it won't attach to just foliage. Or the thin, needled branches and stems of the cypress. And the weight of the hydrangea attempting to grow through these thin branches will cause them to splay out and look messy and unkept.

It is just not a good idea.

@gardengal48 (PNW Z8/9) Climbing Hydrangea can grow up the trunks of trees, as in the attached photo. Italian cypress has 50 feet of trunk available to grow on.

Do you have a photo showing what the kind of splaying that you are anticipating looks like?

An Italian cypress with 50 feet of bare trunk?? Never seen one and if it was that bare, would assume it to be dead or very close to it!!

Sure, the hydrangea can be grown on trees. I grew one on a 80'+ Doug fir in my old garden. But its lowest branch was probably 20' above the ground and with a 5' circumference, there was more than enough bare wood for the hydrangea to take hold. Much like arborvitaes, Italian cypress have branching from the ground up. And with very fastigiate or upward growing branching. Splaying is when these branches are pulled away from the vertical by weight, like with snow loads or a heavy vine. They almost never go back upright without tying them back to the trunk.

@westes Zone 9b California SF Bay At the risk of offending I will say this. You have a plan & vision in mind & want it to work & to be blessed by the plant gurus that so kindly give us their advice & input. They are telling you, with very strong reasons, why your vision is not achievable. You can listen & take their advice, or you can go on to implement your plan anyway. I would not want to be the one to have to pay to have my Italian cypress dug up & removed because I killed it with a climbing hydrangea.

ETA - i also would not want to be your neighbor who has to worry about their shed being enshrouded by your hydrangea.

@gardengal48 (PNW Z8/9) So your point is that the Hydrangea will pull the branches of the Italian Cypress from vertical to closer to horizontal, which is likely to look ugly? I am just trying to understand your point, in language I can understand.

@KW PNW Z8 The neighbor is thrilled about what I am doing, and I am going out of my way to protect the back side of their shed.

I am not looking for a blessing. I am looking for an education. I need a certain amount of detail to understand the points that are being made. Please allow me to just ask the detailed questions so I can understand the objection.

@westes Zone 9b California SF Bay Yes, okay. We all process info differently & communication that’s not in person is challenging.

The neighbour being thrilled is not really an argument since they presumably haven't had the information given to you here. I feel we've offered plenty of detail as to why we think this is a bad idea. I would suggest now that you just go ahead and see what happens, since you've already planted the Hydrangea and seem very attached to your plan. Maybe it'll surprise us.

nb There are evergreen climbing Hydrangeas (seemannii and serratifolia.) but if you are talking about petiolaris, and that's what yours looks like, it is deciduous, wherever you live.

Your picture of a Hydrangea climbing a tree hasn't posted.

@floral_uk z.8/9 SW UK I did not say I was going to keep this here. I want to understand the point that Gardengal made regarding "splaying". I asked a clear question below. I am asking someone to explain what splaying will look like in my case. Explain it to me like I am five years old.

The photo is attached below, but Gardengal's point was that the Hydrangea likes to climb exposed trunks, not thin branches.

"Splay" means to open up outward. Like this:

Not a good look.

@gardengal48 (PNW Z8/9) Okay, you convinced me. I'm going to replant the Hydrangea at the base of a tree with a large length of exposed trunk.

Are we agreed that a Clematis is much less likely to weigh down the Italian cypress branches and cause splaying?

I am glad you dropped the idea of growing the hydrangea on the cypress.

Clematis vary considerably in size and weight. I always start them on a trellis, even if the point is to grow them into a shrub. One that is 20-30’ as stated above, will have enough weight that it may splay branches, plus it may create enough shade to kill some of the cypress foliage, leaving permanent bare spots. Are you willing to risk permanent damage to your cypress?

@NHBabs z4b-5a NH Climbing hydrangea matures into a heavy wooded vine, so I definitely see how that might force splaying. Clematis seems like a much lighter vine. The bottom four feet might get woody, but the vines up to 20 or 30 feet on a large Clematis seem less likely to force an established woody branch to splay out. If you have a photo showing it actually happening with a mature Clematis, you could convince me. If it does start to happen, then cutting the vine at the bottom would quickly put an end to that branch before the damage gets too severe.

This is a photo of a Clematis montana that Gg48 has shared on this forum. A clematis like this can have a lot of weight, and I find it difficult to believe that it won’t damage the plant that it has buried. In my part of the world, where few if any clematis survive above the snow line in bad winters, they are largely herbaceous in growth and have a limit to how large they get during our relatively short growing season. But in areas with less severe winters they do develop woody stems and some can get quite large.

Ultimately, they aren’t my cypress and I do not care if you damage them. I can only tell you what I would do if they were mine.

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@NHBabs z4b-5a NH Gardengal's photo shows a Clematis covering a tree in a shroud, but in that photo there is no splaying. I am open to your idea, but I am just asking for some evidence. I understand Gardengal's point about the Hydrangea because it forms stiff woody vines that will not play nice with anything they surround. Clematis seems like a much tamer plant, and as I said the remedy is a couple of snips with the sheers. It should be possible to stop splaying of the Italian Cypress early in that process, if it even happens.

I don’t know what the plant is under the montana, so who knows what it is susceptible to. As I said, your plants, but splaying and shading out foliage are a risk. Take that risk if you want. I am not going to expend energy looking for a photo that doesn’t exist because most folks wouldn’t do that combo. You can post photos of your splaying or half bald cypress in 5 or 10 years.

In GG’s picture the conifer is not an Italian Cypress, which have a different growth habit and are particularly prone to splaying. And since the tree is completely hidden you cannot possibly tell there is no splaying. People have already said that clematis vary widely in size but if you want one which will reach 20 - 30 feet you are talking about the big ones.

It is getting dark here, there is not much light under my C montana and it’s hard to get at for a photo but this is one of its multiple stems (and not the thickest). Not exactly amenable to ’a couple of snips with the shears.‘

The less vigorous Clematis would be more appropriate but they will not reach the height you want, particularly since part of the routine maintenance to keep them well clothed top to bottom is regularly cutting them to the base.

I really don’t know what else we can say. Since you do not accept what is almost certainly well over a century of knowledge and experience as ’evidence’, why don’t you just plant your Clematis and gather some evidence you’re happy with?

@floral_uk z.8/9 SW UK How would you feel about a Clematis in this location if it was a variety that did not grow above about 15 feet?

No problem at all. It could be trained around the trellis and needn’t get onto the cypresses at all. Or, since it would be pruned down regularly, even if it did scramble into the trees, it wouldn't get the chance to smother them.

I totally agree with floral.

How would Boston Ivy and Climbing Fig do on an Italian Cypress?

Badly.

Boston Ivy would have the same problems as any other huge, vigorous, heavy vine. Weight, light obstruction and bare all winter, following a heavy fall of large leathery leaves in autumn. And it also climbs by holdfasts on a solid surface not tendrils or twining.

I have no experience of climbing fig, but afaik that too climbs by sticking flat to a solid substrate, not by twining. And its tiny, overlapping green leaves would be lost in the green tree foliage. Imo it would need a clear contrasting backdrop to show off the form.

You say ’and’ rather than ’or’. Even if they survived together, BI would completely hide the fig. Neither has showy flowers.

@floral_uk z.8/9 SW UK At this point my hopes for "and" look dashed, and I am ready to look for "any" plant that works well with the Italian Cypress. A smaller Clematis appears to be the only plant that people will not protest against.

If you have the appropriate climate Tropaeolum speciosum looks stunning on a conifer, especially yew.

@floral_uk z.8/9 SW UK Tropaeolum speciosum is available here only as seed. It's a nice looking plant.

Would these tall pine trees be good candidates to have Climbing Hydrangea at the base? They are about 60 feet high and it would be easy to clear the base up to about 25 feet. Paging:

@floral_uk z.8/9 SW UK

@gardengal48 (PNW Z8/9)

@NHBabs z4b-5a NH

@tsugajunkie z5 SE WI ♱

A small H petiolaris is not expensive. How about just buying one and trying it out?

I’m curious about the feasibility of planting anything larger than something in a 4” container at the base of a large established tree. Wondering how far away from base of tree planting hole would need to be in order to be able to dig a deep enough hole for plant. And, would the plant & tree compete for water?

@KW PNW Z8 I would use a raised bed. I doubt you would have much luck in our native soil, and established tree roots make that problem worse. I am not sure what the Climbing Hydrangea's root system looks like at maturity. At what point does it outgrow the raised bed?

@floral_uk z.8/9 SW UK I already have a Climbing Hydrangea. This entire thread has been about finding the right application for it.

So, if you already have one it’s even cheaper for you. Just plant it and see what happens. I would not put a raised bed over the tree roots.

@floral_uk z.8/9 SW UK How would a tree even know that there is a raised bed *above* its buried roots? If anything this would be seen as a source of increased water for the tree, as the water drains out of the raised bed? I realize my earlier suggestion to build a raised bed using the bottom 18 inches of the trunk itself as part of the raised bed is a separate case, and risky.

Increasing the soil level over a tree's root system as little as just a couple of inches effectively smothers the roots, depriving them of oxygen. If over enough of the root system, it can be fatal but even a small area will stress the tree unnecessarily.

@gardengal48 (PNW Z8/9) Facts matter and in this case some simple math should make clear this is not an issue.

A mature pine that is 60 feet tall has a root system that is already about 40 foot diameter if you draw a circle around the base of the tree (20-foot radius). The surface area of such a circle is 1257 square feet.

My raised bed has a diameter of 3 feet. That means the surface area is only about 7 square feet.

So my raised bed occupies less than 1% of the surface area of the roots of the pine tree. Even if you change my numbers to something more conservative, it seems unlikely that said pine tree is going to suffocate.

If the example was instead that a five-foot-high pine tree had a raised bed built all around it with a 10-foot diameter, then clearly the entire root system of the small pine tree is potentially affected. You just have to look at the facts of the specific case.

"You just have to look at the facts of the specific case."

You didn't provide the "facts of the case" so I had no idea of just how large this raised bed may be. Still, the premise remains that creating a raised bed regardless of size on top of the root system is not doing the tree any favors.

I'm done here. I don't really need nor do I care for your lectures. You seem determined to do what you want to do despite any suggestions to the contrary, so go for it.

@gardengal48 (PNW Z8/9) I am not lecturing. I am agreeing with the point you are making in general, while providing some specific facts specific to my case.

And in the big picture, you advised me to not put Climbing Hydrangea on the Italian Cypress, and I followed your advice.