Rooftop deck- Container plant plan advice

natural-sensSeptember 8, 2011

I am stumped on plant ideas for my friends swanky modern rooftop deck (I said I would help him out...). It is cedar with black and lime green accents (lighting fixtures and cushions). There is a ton of wood with the privacy screening, suana structure, pergola and bar. The little bit of vegetation we can squeeze in is going to go a very long way in rounding off the edges and cooling the feeling of the place off.

There are 3 planter boxes. One measures 2x2, the other 20"x20" and the other is 14"x2'

In zone 5b, third story city deck meaning intense winter winds and intense summer sun exposure. Irrigation equipped.

The pallette I am throwing around in my head is burgundy with lime green and silver splashes. But im open to whatever (2) plants will provide good structure and a graceful, soothing presence above all else.

So far I am considering-

Miscanthus Sinensis 'Morning Light' in the small planter that is largely protected from winds.

The other two planters though i'm stumped.

I have accepted the fact that I am best not trying to force an Acer Palmatum 'Bloodgood' into those conditions. I was drawn to it primarily for its dainty branch structure and trainable canopy.

I am thinking a tropical annual arrangement for one of the boxes centred around Canna Lilly and Sweet potato vine. Not sure though...

Please help. I am seeking ornamental tree and/or compact shrub suggestions to work with the above conditions. Evergreen would be great but not a Boxus. Specimen that are good as stand alones as I think I am forced to vary each planter box.

Anything helps, im stumped!


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You're looking for a perennial tree to winter outdoors on a rooftop deck in a really small container?
In zone 5? Which is probably more like a zone 3 under those conditions? Yikes!

If you don't want to consider annuals in the summer followed by decorative evergreen boughs in the winter covering spring bulbs,
how about junipers instead? I plant those with good success in an urn between two south facing garage doors in my severe climate, using
both spreading and columnar species. They tend to last 2 full years before needing replacement. Just select "attractive" and "inexpensive".

I've also had good luck creating sedum "tapestries" as perpetual container gardens but of course, there is no height nor winter interest if it is snow-covered. You would get the colour scheme that you're looking for though. Small consolation.

    Bookmark   September 8, 2011 at 2:21AM
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Over the years I have assisted city roof top gardeners growing plants in the situation described because they came to me for advise, often bringing pictures of their efforts to my nursery where we grew tough plants for adverse situations. Each garden presented different challenges, the toughest being dealing with cyclonic winds caused by wind circulating around buildings taller than their gardens.

Some plants to consider for wind and sun:

Shore juniper (Juniperus conferta)
Bayberry (Myrica pensylanica)
Artemisia "Powis Castle"
Armeria maritima 'Splendens'
Fairy rose
Gaura lindheimeri - keep deadheaded
Japanese maple...if a very small one is planted and allowed to fight the elements it will grow and thrive. Give it a try.

    Bookmark   September 8, 2011 at 1:59PM
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Acer Palmatum???? REALLY??? I thought it would dry out and wilt without question but I welcome the advice. Thank you.

Any varieties in particular? I am partial toward Bloodgoods but in general Japanese Maples did not do well during the heat wave in Ontario this year thus i am a little reluctant to try, but really a gentle nudge is all I need! I assume you recommend a young one as it will adapt better to the conditions and handle them better through maturity?

Thank you for the advice, any more is appreciated.

    Bookmark   September 8, 2011 at 11:37PM
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bahia(SF Bay Area)

I've worked on my share of roof top gardens as well, but never in as severe a climate as yours. I would beg to differ with Nandina on the suitability of a Japanese maple in the location as you've described it, I doubt it will ever look good. You don't say how deep your planters are, if you don't have sufficient depth and width of soil in these planters, anything that can't tolerate frozen soil at the roots will not survive the winter. That greatly limits the selection of woody or evergreen plants. In general, whatever you end up using, I'd suggest that your automatic irrigation system provide up to twice daily watering for a few minutes each cycle for best plant/root health. In general the deeper the soil depth you can provide, the greater possibilities for larger sized healthier growth. You might also consider using portable pots that can be set inside the permanent planters which would allow switching things out seasonally more easily
If you're interested in red foliaged small trees, you might do better with Berberis thunbergeri cultivars or Cotinus coggygria cultivars as being far more sun/wind tolerant. Another cool looking accent shrub/small tree for you might include Poncirus trifoliata 'Flying Dragon'
I'd suggest you use some hardy succulents in the mix such as Serum spectabile or S. rupestre Angelina, Sempervivums, grasses hardy to your zone. If you'd be willing to consider duoble potting your containers and bringing them inside in the winter, you could plant some truly sun/heat/wind tolerant plantings using architectural succulents such as Hesperaloes, Aloes,Agaves, Dasylirions, Echeverias, etc. These could thrive in the more temperate months outdoors and be brou__ght into a greenhouse or sun porch for the winter, and you could plunk into fall/winter seasonal accents in their place if you still needed something out there in winter, or maybe just park some cut greens and cut colorful branches such as Cornus stolonifera or willows for winter.

I would stay away from any plants up there that can't stand up to the wind and hot sun and some drought stress. So no big or soft leaved plants that will wind burn.

    Bookmark   September 9, 2011 at 1:38AM
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Over the years I have studied root structures of plants/trees/shrubs including those in Zone 5 where the prevalence of Verticillium wilt very often kills Japanese maples. Thus I have had the opportunity to slowly excavate and study dying JM's root growth. Much to my surprise the bulk of the roots plus feeder roots are just under soil surface and well within the ground freeze zone and yet the trees survive. It was this observation many years ago that encouraged me to experiment, growing them in fairly small planters subject to winter freezing, in heavy winds, in heat. When dealing with such adverse conditions if one plants a very young JM and allows it to struggle there is a strong probability that it will survive and develop an acceptable, dense shape. I will not discourage our OP from trying.

    Bookmark   September 9, 2011 at 11:01AM
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bahia(SF Bay Area)

I appreciate the thoughtful response, but my personal experience with map maples here in California is that they will always exhibit leaf tip burn when exposed to such tough conditions, which detracts from how they could look under better conditions. It would also be highly dependent on regular, consistent irrigation to never let it dry out, not a quality one looks for in a small planter on an exposed roof top. Why set someone up for such a continuous battle when there are better adapted/less needy choices out there. If someone has their heart set on this tree, and is still willing to grow it knowing the risks, go for it. I hate to see how poorly they can look after one hot windy day in the ground here locally, when they are forced to contend with full hot sun and wind, and don't have enough available ground moisture to cope. Container grown specimens are affected to an even greater degree. I can only assume that greater average humidity in summer back east does compensate for these sun/wind effects we see in California, but I don't think a roof top small planter growing maple would show the same tolerance and not look stressed. If there were s more wind protected spot with dappled shade or only early morning sun, and you're prepsred to kee up with constant watering, good results are more likely. Just my personal west coast experience here, where I'd equate a JM's preferences more in line with that of a Hydrangea or Rhododendron.9

    Bookmark   September 9, 2011 at 12:46PM
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marquest(z5 PA)

Your description is....'swanky modern rooftop deck'

I would go with a tropical theme since you want to go with Cannas for the summer. From your description it sounds like what I see when I vacation on tropical islands. To get that look I would plant..

Hardy Bamboo
Yucca, Yellow Color Guard
In the summer I would plant colorful leaf Cannas, coleus and Ornamental Banana plants.

In your zone you will not be out there in harsh conditions in the middle of winter. If there is a view from a window in the winter time I would just buy some winter greens and put in the boxes. But the Yucca and Bamboo are winter structural plants.

That is my vision. LOL

I know I have a magazine around somewhere with a pic. When I find it I will post the pic.

    Bookmark   September 9, 2011 at 11:33PM
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