Gardeners, help me turn my school rooftop into a sensory oasis of calm.
September 5, 2019 9:08 AM   Subscribe

I am a teacher at a high school in Vancouver. We have an area of the roof that was designed to be used as an outdoor classroom, but there are currently only a few picnic tables out there. Help me make it more attractive with plants that will survive both drought and very rainy conditions.

Here are the details:

• I have a dream of making this a sensory garden to promote mindfulness. I want things like plants you can see, smell, touch, and taste (not ALL of the plants need to have these qualities, but I want some). Maybe some bird feeders and a fountain too.

• There are a few raised garden beds but those are maintained by another teacher so I have to leave them alone.

• We are located in Vancouver, Canada.

• It is a very long but narrow space (see photos).

• We have a relatively small amount of money to dedicate to this (around $2500 CAD).

• It gets very hot up there in the summer (May-Sept.) and then rains nonstop during the winter months (Oct. – April). It snows occasionally but quickly melts.

• I don’t intend to plant anything out there until the Spring (unless I can plant certain things in the fall?).

• I can have the woodworking students build large planter boxes.

• I’ve already asked the school engineer and the roof can support a lot of weight.

• We can get free soil from the school board.

• I have people who can care for the plants over the summer holidays.

Some questions I have at this juncture:

What plants would work well in this environment?
Which plants would provide a good sensory experience?
Do planters all need rocks in the bottom or is a hole sufficient drainage?
I’d like to have plants that bloom at different time of the year so that there is always colour out there. What plants should I consider?
What else should I be thinking about?

As you can probably gather, I really have very little knowledge of how to go about this, but I’m really excited to learn about gardening and do this for my school. Thanks in advance!
posted by figaro to Home & Garden (18 answers total) 3 users marked this as a favorite
I find bigger containers do better in heat, they can stay damp. Many people have garden herbs to contribute. I would have an area of herbs, an area of grasses, and maybe an area of succulents.
When I plant large containers, I put twigs in the bottom and leaves to compost.
Small trees, like a Japanese maple can live in a large planter

Herbs: Sage and chives are perennial, thyme self-seeds, mints, including basil, grow well. There are many different mints- variety would be pleasant. Parsley is pretty rugged. Rosemary doesn't like to be frozen,but you roof will be getting residual heat from the building, and it is so fragrant. Lavender might do well. Lemon grass?

A good garden center or landscaper can help you choose locally-successful plants.

Now is a good time to pickup a couple of patio umbrellas and stands, which you'll have to assure are closed and secured in wind, maybe some resin or other comfortable outdoor chairs. Picnic tables are not that great.

I'll bet you could involve parents who would do a lot of the planting.
posted by theora55 at 9:32 AM on September 5, 2019 [1 favorite]

Do you have a local garden club? Those members can be of great help to you, and gardeners are among the most education-oriented and friendly people I know.

Once you decide what you want to create, I'd recommend breaking it into several stages that can be accomplished over more than one year. Sounds like a great idea - have fun!
posted by summerstorm at 9:46 AM on September 5, 2019 [1 favorite]

I'm in Vancouver too and perennials that do well in my garden include Azaleas (Which are great all year round and spectacular in the spring).
Hostas are superb for adding a burst of greenery from spring until winter.
Bulbs are a really great thing you can plant soon and you'll be rewarded with a beautiful bounty in spring!
I usually plant my bulbs end of September / beginning of October time.
Ferns are fab but again, more resplendent from spring onwards.
posted by JenThePro at 10:15 AM on September 5, 2019

My local Botanical garden has a sensory garden. Missouri Botanical Garden this page looks like it has informational links and an email address for their Therapeutic Horticultural team . (It's a neat garden .

My personal suggestions: bamboo wind chimes, some kind of smooth river rocks to touch, mint is pretty hard to kill and smells nice (and is edible), and those giant allium bulbs that get the huge purple ball flowers on them in the spring.
posted by Green Eyed Monster at 10:28 AM on September 5, 2019

Some sort of free-standing shade structure might be great both for shade and also as a bit of a rain barrier in the winter. Check with local boy scout troops - there may be some Eagle Scouts who are looking for a project to do for their final badge.

For more ideas on look and feel, also seek out "healing gardens". I think these might give you some ideas for the lushness you are seeking.

Many plants will do better being planted this fall if you can swing it - they'll get rain and be dormant most of the winter, and will wake up and get going in the spring.

If you can create a super tall trellis, hops are a fun plant to have, and easy to grow. Plant a rhizome in March. Give it about 10-12 feet to grow straight up. Hops will grow inches each day in the spring. They're most interesting over the summer, but they'll sprout in April/May so you'll get some time with them. And they'll still be around in the fall. They'll come back year after year - so little maintenance on your part.

Daffodils, crocuses, and tulip bulbs can be planted in the fall to have them pop up in the spring.

Definitely look at azaleas and rhododendron bushes - they're easy and pretty.

I've got a weeping blue atlas cedar that thrives in this climate. It can be trained, and is an interesting texture for a sensory garden (though quite prickly).
posted by hydra77 at 10:36 AM on September 5, 2019

Your enemy will be your plants drying out. What you need is a steady water supply and some kind of cheap drip irrigation set-up. It doesn't cost much at all and it can make all the difference. Unless you can easily get water up there it's going to be limited to some kind of xeriscaping project.
posted by Patapsco Mike at 10:46 AM on September 5, 2019

If you can manage the water requirements (or find items on this list or this one that do well in low-water), adding a few things for the local pollinators might be nice.
posted by jquinby at 11:09 AM on September 5, 2019

have your shop students build simple wood benches as well as planters!

also your roof could collect rain water in barrels during your substantial rainy season and stretch that into summer with a passive aqueduct/soaker hose system, making it less work to keep things alive when there are fewer staff. this will add to your startup cost but it's worth investigating if you can get rain barrels donated? unless you have running water up there, this will be a big obstacle otherwise. maybe there is a rebate or other community program for lower water use irrigation systems (there certainly are in TX) and you can teach your students about water conservation too?

Buchart Gardens is near you, it's one of the most spectacular gardens I have seen in the entire world and it's supposedly beautiful year round and they pull off the mix of color and sensory qualities you are looking for. Go for some inspiration (field trip?), see if they will let a gardener talk to you for free advice for educational outreach or if they have workshop hours for that kind of thing. They will be hands down the experts in the area on what grows best and they can advise what will best survive your extreme conditions on the roof. Also check if you have a university with an agriculture department nearby which would also be a source of potentially free expertise.

Your care requirements are tough because of the extremes created on the roof despite the ideal nature of British Columbia's climate. The roof will keep warmer in winter from the building radiating heat which is good, and covering plants in the event of light frost will extend your options a bit. you should carefully observe the pattern of sun during the entire day and figure out if you have corners that enter building shadow in the morning or afternoon or even all day. There are still many shade plants that will like the bright reflected light off the building but if you want fruits and vegetables, most need true full sun all day. Figure this out before you go buy anything, this will determine in large part what will work and it will be the first thing any expert will ask about after soil and drainage conditions.

re drainage yes all planters need holes, and the only exception would be if you grow some marsh plants that like to be very wet all the time
posted by slow graffiti at 12:23 PM on September 5, 2019 [2 favorites]

If you can reach out to parents, you may find some who have some expertise with this and would be willing to help. Or maybe even a local garden center would be willing to help out.
posted by ShooBoo at 12:25 PM on September 5, 2019

Perhaps your local Native Plant Society could help you to choose appropriate plants. If its members are at all like native plant society members I've met in other places they will probably have plenty of plants to donate and might even put together some workshops for you and your students.
posted by mareli at 12:50 PM on September 5, 2019

Roofs are often tough places to grow because of the exposure. I’d try to pick plants from Mediterranean climates including our local Garry Oak ecosystem that are used to most of the water coming in the cool season, but be wary of things that aren’t too frost hardy - it’ll be cold on the roof! The Garry oak ecosystems recovery team even has resources for school planting projects.

As far as Mediterranean plants go, I think lavender, rosemary, pretty much any cultivated cistaceae would do well.

This Vancouver plant list for roadway plantings will also have tough plant options that aren’t going to harm local ecosystems.
posted by congen at 2:19 PM on September 5, 2019

The roof is going to be drier, colder, and hotter than a garden on the ground. Vancouver has a lot of rainy days, but the actual amount of water we get isn’t especially high. The exposure to wind and sun is going to mean more plants are losing a lot of water. Having plants in pots as opposed to the ground means the soil will get hotter (and dry out faster) and colder than the actual ground. So choose plants with that in mind - like if you pick plants from the Garry oak ecosystem, choose the ones that like the exposed rocky bluffs, not the wetlands!

Oh, and make sure everything you plant anything in has drainage holes.
posted by congen at 2:30 PM on September 5, 2019 [1 favorite]

A couple other things -

Native plants are especially great for an outdoor classroom because most have traditional uses by local First Nations people.

Many shrubs and trees have better survival if planted in the fall, esp if they’re sold bare root. Many bulbs and perennials must be planted in the fall.
posted by congen at 2:48 PM on September 5, 2019

I have no idea HOW, but could you rig up some sort of rain capture device that waters the plants when it's not rainy?
posted by Weeping_angel at 4:40 PM on September 5, 2019

Arbutus saplings/ seedlings can be had (I know Arts has them) for <$40.

Native species with very limited natural distribution (mostly just the South interior coasts of the Straight.

They're hardy (but yes, the larger the planter, the larger thermal mass available to buffer against weather extremes - if it's a bad winter, you can mulch/ insulate them), gorgeous visually. Broad dark waxy leaves - lighter on the underside, smooth brown new bark with fine striations, red and grey cracked open textured old bark. They flower and berry, too.

They thrive with lots of sun, tolerate rocky soil, and don't require a ton of water.

They can attract bees during flowering season, though, and birds during the last half of fruiting season. But leaf-fall are very sturdy and happens mostly after desiccation and is resistant to rehydration (and rotting) so cleanup is very easy.

I love Arbutuses; they're BC's naturally growing bonsai aspire to be BC's natural Arbutuses.


If you have an area with really poor sunlight, consider building a poly greenhouse (mostly to maximize humidity - and maybe an advanced/ volunteer Shop project to maximize inclusivity) and try growing all kinds of native ferns from our rainforests. Pretty sure provincial parks prohibit the public from harvesting plants for transplant, but I know in cub scouts that we were allowed to harvest plants to use on scout camps. If you can figure out the legal side, a "collect specimens" fieldtrip could be pretty cool - figuring out how to create different conditions required to keep them alive and thriving.

The direct comparison is that this is an easier analogue to the massive commercial orchid business.

If we're talking about business, depending on how amazing your bio department is, plant tissue culture (PTC) is fairly low barrier - at least compared to everything else. PTC is the backbone that drives commercial/ industrial agriculture and has a high-tech R&D application, too. PTC also branches out into general TC - which in biomed is mostly mammalian tissue, either primary (difficult, limited) or immortalized (trivial) but can also involved "tamed" insect tissue/ cells.


Herbs grow quickly and can be fun; donate some to home ec or something. Mint does very well in our climate, especially if you give them lots of water. Cilantro and spring onions also do well. Basil, I've found, seems to do better partially shaded. Rosemary is very hardy.

If there is plenty of sun, you have some really good soil, and give them plenty of water, cherry tomatoes can do very well in hot summers.

Hops are very cool - but require tall trellises to grow properly, might be a safety hazard. The species most closely related to hops is cannabis, but as this is school property and minors, that isn't going to fly. Grapes are also another very BC thing, but takes years to set up properly.


I hope that you have running water up there and good drainage - I'd ask facilities or maintenance if you want a successive series of traps up there so the drainage system doesn't get clogged; it's going to get messy/ dirty once you put rotting vegetation into play and I hope you have good people who're willing to help clean up.

You'll probably want a good power-washing once a year.
posted by porpoise at 8:04 PM on September 5, 2019 [2 favorites]

Herbs are usually cheap and easy to grow and can offer some wonderful sensory experiences. For hardiness and something that stays lovely long into the fall, I really enjoy decorative grasses. There will be many choices if you google for decorative grass for Vancouver. I would also google for what grass might be considered an invasive species in the area because, yeah, they are often so easy to care for that they jump the fence! Grass will often enter a dormant phase when things get hot and dry and will come out of it just fine. They are very easy to propagate, in late winter, you literally take a spade and jab the clump into many clumps and replant. For very little money and effort, you could have planters full of fragrant herbs and swaying grasses that rustle in the wind. You could even try out a wildflower mix intended for the area to add a bit of color and, yeah, really easy and pretty.
posted by Foam Pants at 10:26 PM on September 5, 2019 [1 favorite]

Counterintuitively, planters don't drain as well if you put a thick layer of coarse material like gravel or twigs in the bottom because it creates a perched water table - the finer material holds on to the water and there is less gravitational force to pull excess water out of the pot. It also reduces the water holding capacity, which is important in summer. Drainage is very imortant in climates with cold wet winters.
posted by gray17 at 11:22 AM on September 6, 2019

Wow, thank you so much everyone! You've all given me a lot to think about and some new dreams and ideas. I will try and remember to post some "after" photos when it gets closer to summer holidays!
posted by figaro at 3:29 PM on September 9, 2019

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