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Gargamel04
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Japanese Boxwood Hedge in smaller, raised planter boxes

Hello Gardening Forum,

I'm fairly new to home ownership and brand new to gardening. I live in Los Angeles, about 3 miles from the ocean, in a residential neighborhood. In an effort to privatize my backyard from the neighboring alley, I had some contractors build a planter trough in place of a rotting lattice fence on top of a 4-foot high brick wall. We were somewhat limited by the width and beginning height of the brick wall, but I was assured by a local garden store that I would be able to grow Japanese Boxwood into a formidable hedge over the course of a few years with what we had built.

I'm attaching pictures and will explain how they were arranged ...
IMG_0309.JPG
IMG_0005.JPG
Each plant is separated by 2.5 feet and has approximately 1 foot of soil depth. They were all purchased in 1 gallon nursery pots, so the existing root systems actually have a good 5-7 inches of potting soil beneath them. The trough is connected throughout its lower half, without interruption, so the roots of each plant can grow as far left and right as they please, until, of course, they run into those of their neighboring plants. The wood is treated to protect against termites, rot, and fungus. We also lined the inner walls of the trough with thick #30 roofing paper, which essentially guides water to drilled drainage holes on the bottom of the trough. These dump into the alley and seem to work quite well, as they typically begin evacuating water after about 20-30 seconds of watering the plants.

My concern here is that I can't seem to find any existing evidence of someone else trying to cultivate a boxwood hedge with this little depth. They're starting to grow a little after only about 3 weeks in the planters, but I still have some specific questions ...

1. Is 12 inches enough depth to get one continuous hedge reaching 3 feet in height? If not, how high should I expect them to grow?

2. Are the plants too far apart (2.5 feet), in light of the planter depth? *If so, I can easily reduce the separation and add more, as the roots have not yet begun to 'take hold' in the soil.

3. How should I be pruning these if my goal is to get them as wide and tall as possible?

4. How should I be pruning these if I wish to prioritize width over height, in the short term?

5. Am I insane to think that because each plant has plenty of space for its roots to grow laterally, that the hedge itself might mimic this root growth? In other words, will the plants grow less in the directions of the alley and interior of the yard, and more side-to-side, in the directions of their neighboring plants, because of the shape of their container?

6. I know that Boxwood are known for being slow, low-maintenance growers that can be pruned into just about any shape. However, if one were to wish to make them slightly faster growers, how would one go about this?

Those are my biggest concerns for now. Would love to get any and all advice, as well as any pictures if you've seen someone else try this before! Thanks!

Graeme

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rainbowgardener
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Re: Japanese Boxwood Hedge in smaller, raised planter boxes

I can't answer all of your questions, particularly the most crucial one of whether 12 inches is enough soil for your hedge. You didn't say how wide the planter is, which is relevant for the volume of soil. I know that boxwood is fairly shallow rooted, without a deep tap root. I think one of the things it means, because you are growing your hedge in a very limited volume of soil, is that you will have to fertilize your hedge regularly. In the ground, it could get nutrients from the soil, but your hedge will be totally dependent on what you give it. You will have to water frequently also. In a larger planter, the soil would hold water better. The smaller the container, the more frequently you have to water. I think essentially you are doing a form of large bonsai and eventually the growth of the hedge will be constrained by the size of the root system it can have.

Do you know the pH (acidity) of your potting soil? Boxwood is pretty picky about that. Boxwoods need well-drained soil with a pH between 6.5 and 7.0 (i.e. slightly acid). They don't like to stay wet. And they tend to suffer if they are in full, hot afternoon sun.

Q.2 your plant spacing is fine. You wouldn't want them any closer than that.

Q.3 &4 re pruning. The most crucial thing you need to know about pruning is that you need to prune it to a sort of wedge shape, slightly wider at the bottom than the top. If it is pruned in to round, square, or inverted triangle shapes where the base is narrower, then the leaves at the base will be shaded out, and will die off, leaving bare sticks at the bottom:

Image
https://www2.ca.uky.edu/agc/pubs/ho/ho55/f6.gif

Yew hedge should look about like this:

Image
https://msue.anr.msu.edu/uploads/images/ ... runing.jpg

Otherwise you will end up with something like this:

Image
https://palmbeachcountyextension.files. ... slide1.jpg

there are some extreme examples of this in my neighborhood: hedge shrubs that are very wide on top, but have just a couple inches of leaves and then three feet of bare sticks tapering in to the base. Ugly!

Q5. I don't believe the shape of the roots will have anything to do with the shape of your shrubs, which depends on how you prune. Even though the roots are constrained in one dimension, the plants will continue to grow out evenly in all directions. But boxwood is the most common topiary hedge. You can shape it how you want.

Q6. It grows at the speed it grows. Despite what you think, you really don't want it growing fast on top right now. What you want is for it to be growing good root systems. Gardeners need to cultivate patience.
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rainbowgardener
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Re: Japanese Boxwood Hedge in smaller, raised planter boxes

duplicate post

Gargame, it really doesn't help to post the same question in a bunch of different sections (even though they are relevant). People aren't seeing each others answers then and it can get very confusing.

Applestar, I replied to this in the Container Gardening section, before I saw the other two. Trees, Shrubs, Hedges seems like the most appropriate. Maybe merge all these there?
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Re: Japanese Boxwood Hedge in smaller, raised planter boxes

Done! :wink:
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Gargamel04
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Re: Japanese Boxwood Hedge in smaller, raised planter boxes

Sorry about that. New to the forum and was assuming that the different categories would have different experts roaming. If it's any consolation, I lost my entire response to the second post in the merger. Here's the abbreviated version.

The planters are about 8 inches wide, so I believe that means the volume per plant is 1.66 cubic feet. Please let me know if that provides any clarity in terms of the plants' ability to form a contiguous hedge or the hedge's potential height.

I'll figure out a way to get the soil's pH and post it here for further guidance or direction to another discussion, if that's cool. Same goes for fertilizing. I gave each plant Sure Start initially, which I'm told keeps the soil fertilized for the first two months or so. Any direction in terms of fertilization after that is appreciated. I'm confident I can keep up with the water situation.

In terms of the hedge shape, do you think it matters that this particular set of plants is raised up so high, with the morning sun hitting it from the alley side (east) and the afternoon sun hitting it from the yard side (west)? It actually doesn't get terribly hot here (rarely at or above 80) but they'll certainly get plenty of sunlight. I suppose that may just be something I have to keep an eye on as they get more dense.

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Re: Japanese Boxwood Hedge in smaller, raised planter boxes

Oh! I'm so sorry! I just hate it when all the well and carefully thought-out comment disappear into the Internet ether for whatever reason and I feel bad that I may have caused yours to get lost that way :(

We may have been on-line, working on the same thread at the same time, and maybe I beat you to the submit button. :o

The window did go blank in an odd way ...and at some point my browser crashed, I'll have you know. :| (...though actually this us probably unrelated... It would kind of interesting if it could be tested though 8) )
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Gargamel04
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Re: Japanese Boxwood Hedge in smaller, raised planter boxes

Nahh, it's my fault. You'd think by now I would know to copy my text within these submission boxes before hitting reply. There's something about the long ones that causes them to get 'disappeared' easily!

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Re: Japanese Boxwood Hedge in smaller, raised planter boxes

You are going to be totally dependent on some kind of emitter irrigation system and you can expect to need to water daily with such a small soil reserve in the long California dry season.
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Gargamel04
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Re: Japanese Boxwood Hedge in smaller, raised planter boxes

That hasn't really appeared to be the case so far. Even on the really warm , sometimes hot, dry days we've had over the past few weeks (it's dry most of the winter here too) the moisture meter I'm using is showing way over the ideal saturation mark for a couple of days after watering. Here's the weather from the month of October, to illustrate ...
Screen Shot 2015-11-10 at 8.31.09 AM.png
I was also a little skeptical of what the meter was telling me, so I dug down in between a couple of the plants and the soil was quite damp. That was just one day after watering, but I do think it indicates that my gauge was working correctly. I know they don't like it too soggy, but the entire length of the planter really does drain immediately upon watering, so I can't imagine the drainage needs to be adjusted.

Not trying to be contradictory without making a point, but I'd love any feedback based on that information. It's actually supposed to warm up again later this week, although there has been a lot of talk about torrential downpours and "El Nino" this particular winter.

That actually brings up another question - are there steps to take if it rains like crazy and the soil gets way too soggy?

Thanks again for everyone's input. I wish I had found this forum a month ago!

Graeme

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