Looking for suggestions for plants, either green or flowering, that would trail down a high cement retaining wall. Area is west facing, full sun, zone 7, not a lot of water, and a very narrow planting space.
Any chance you give more info so we can give you proper ideas rather than list plants that wont grow in some situations like shade, wet soil or wrong temps.
Once you give this info then there could be many, many plants more suitable for your needs.
Best wishes, WeeNel.
newmarket, I'm wondering what kind of irrigation you're planning for that area if any? Also, are there surrounding plants? I suggest picking a plant that matches others in the area. I potted catmint and placed a few in our West garden but the catmint's "English garden" look didn't match the tropical look of the area.
Catmint will do well in a sunny location but it only trails one or two feet. I placed six pots of catmint over a giant tree stump from an evergreen tree that was cut down this year and the mint trails beautifully over the unsightly stump. It prefers to be watered every few days, but still remains green if watered once a week. Cut it down at the end of spring and it will rebloom and you could get 6 months of lavender flowers which I think would look attractive atop a retaining wall.
There are a couple varieties of trailing rosemary that could be a good option, rosemary likes full sun and doesn't need a lot of water. It would help to see the space though--it can get a bit on the large side so it may get a little too big for the narrow planting space. You could also consider a number of different vines--assuming they don't have anything to climb up they will tend to trail down over the wall instead and they'd be good for a narrow planting space.
Years ago I saw a photo of a home in no. California. It had a very tall wall that went from ground level up maybe 10 or 12 feet to a terrace. The planting area looked to be about 14-18 inches wide and was planted with creeping rosemary that extended almost down to the ground. The blurb along with the photo said the area was "totally maintenance free once established, except for a periodic trimming at the base of the wall." I wanted to build a wall just so I could duplicate that look...grin
Creeping Rosemary isn't hardy for colder zones, not sure about Zone 7, may be borderline but you'd lose it in a colder year. I think it's OK down to 16 degrees, like regular Rosemary and Bay. Too bad, I've seen lots of it in LA and it's gorgeous.
What about vinca, either minor or major? That would definitely hang down quite a distance. Another option is to add vines in, like Clematis for instance, which would add wonderful color and drama. Is there any way to add irrigation? If not, maybe a honeysuckle, one of the newer ones, they can take tough conditions. Also if they get too long you can prune them and they'll just bush out more.
When I lived in Southampton, LI, which was then zone 6 but has now been reclassified as zone 7, I lost it every year. But I knew other people in the general area for whom it lasted many years. That's why I said borderline, I suppose it's a question of microclimates, like with so many other plants.
I would imagine the Rosemary and other herb type of plants would suffer from too cold against a wall especially IF the wall gets freeze into the materials used for building the wall, its the opposite of summer when you can grow fruit against walls as the sun heats the walls up like a radiator but deadly for plants requiring cooler conditions.
I would be inclined to look out for plants that grow upwards when grown against a wall, like Clematis, climbing roses can be grown tumbling over walls as they were in Elizabethan times, you need to research the type of Rose for that, some evergreens like Jasmine, Passion flower (hardy types) Abutilon ,Berberis
You would have to check out those plants for hardiness etc, you would also have to prep the soil very well for growing things in situ and will be there for many years, you would need to make allowance's for irrigation as plants that grow close to any type of wall or structure get very dry roots due to the heat generated from the wall,
IF you have not began to build the wall, maybe you could consider at the building stage to make planting holes / pockets for smaller plants that hang down and you can use a variety of shades of green, purple, white and many other colours, I saw a wall with plantings like waves made from pockets, easier to maintain and very attractive to boot.
Perhaps a visit to the book store or library could give you further ideas of planting a wall as believe me there are many ways, plants and materials you can use, the material can decide the planting too, so look carefully at the whole job to hand.
Good luck, WeeNel.
You could also look into some vines. Many are usually planted at the bottom of the wall, and allowed to climb, so I am not sure how well they will do when they are asked to climb down a wall.
For a colder zone you might look into something like Parthenocissus. One of these is the 'Ivy' that the 'Ivy League' colleges are nick-named for. I am sure they are fine into zone 7.
If it is at all possible to irrigate the area a bit better for the plants' first 2-3 summers that would get it going better than ignoring it, and allowing just natural water to irrigate it. If you can get the roots deeper as soon as possible it is more cold tolerant, and more drought tolerant.