Bougainvillea on Roof Terrace

mermeremail

Hello! 

I have a rooftop terrace in zone 10 with a 40 foot long fence along which I would like to plant bougainvillea that will fill out and climb to form a beautiful occlusive wall. I'd like the height to be around 8 feet ultimately. I want to build a 40 foot long planter with the same wood as the decking along the fence line for this purpose. 

Can anyone please tell me how deep and wide I should make this planter? (Or at least the cubic foot of soil volume I should aim for). Also, how far apart should I plant the starts? 

Any other recommendations for the planter specific to bougainvillea? I know it needs good drainage. I'd like this planter to last as long as possible. 

Many thanks. 

Iamweedy

This is a UK based forum. Where do you live? I don't think bougainvilia would survive anywhere in the UK outside a heated conservatory.  I don't quite know how USA zones might work.

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Valley Gardener

If you live somewhere hot and dry,as I did for several years,you will find they don't need much to keep them happy! Ours grew in awful sandy soil,and it wasn't very deep.The only thing I would say,is you will have to do a trim every week,as they grow like mad,and have very vicious thorns,i have had many a deep scratch from them!
As Iamweedy says,they will fill a greenhouse in this country,and I did see one growing in a pot once in an old folks home.
It would be interesting to know your location? Good luck.

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mermeremail

Thank you all. I am in Spain, but no one in the Spanish gardening forum I had joined could help with the soil volume/depth needed for them to do well in planters on a hot roof terrace. I figured it was worth a shot! Never know who's lived where in the past.  

We're just going to build a long planter 40 cm wide and 60 cm deep and put one plant every 5 ft or so. We'll see how it goes after a few years of growth (with regular trimming indeed, and training/pinning up the wall). The numbers are only very loosely based on what I've seen for some other climbers while reading around. 

Blue Onion

Have a building inspector have a check over your terrace and ensure there is structure to support the weight of the soil weight when wet (plus full grown plants).  Reading around online, it looks like they quite like being potbound, so they should be pretty happy up there.  A wood planter would probably be best, lined with plastic, to help keep the soil a littler cooler/insulated than, say, metal.  It looks like they like well drained soil, so build you planter up on blocks with regular holes along the bottom to aid drainage.  

Obelixx

I don't think you need to risk the weight of a long trough, not to mention the cost of filling it with growing medium and the difficulties of watering evenly.  You should be able to get one to grow perfectly well in a good sized pot (min 60 x 60 x 60cms) and then train it along you trellis structure.

Here's what the RHS says, but bear in mind it is aimed at UK gardeners so interpret as necessary - https://www.rhs.org.uk/advice/profile?PID=816

Nollie

Your plan, in principle, sounds fine, but your elevation is important as well as what zone you are in - zones are crude instruments. I used to live in zone 10 but couldn’t grow Bougainvillea successfully because I was 700m above sea level. However if your neighbours grow it...

They don’t need very rich soil, and use lightweight materials at the bottom to aid drainage, such as chunks of polystyrene insulation, anything to lighten the load, and don’t overwater.

I would second the cautions about load bearing. Do you know how the roof terrace is constructed? If it’s an old house or block with a traditional elm beam, cal and cane structure, be very careful! If it’s the more modern concrete beam and raciones, you might be ok.