I like the native yuccas that flower at about 4 feet. There is another, around here, that flowers at 6-8 feet that I like less. If there are no kids or pets, Opuntia humifusa is native and spectacular for a while in early Summer. Goldenrod is native, does not cause hay-fever, but any showy flowers attract bees. Woodlanders sells a rare shadbush, perhaps from Nantucket,that, I think, would spread and stay low. Beachplum is classic but can get 8 feet high, and I don't like the look, except in bloom.I am unsure whether Kalmia would tolerate salty mists. Low growing junipers like J. conferta 'Silver Mist' could fill in around.

How tall an ornamental grass are you wanting? Pennisetum alopecuroides/fountain grass grows to about 2-2 1/2 ft. in height. Kalamagrostis/feather reed grass grows to about 5 ft. in height but doesn't have (in my garden anyway) the lovely fountaining habit--it remains pretty much vertical right into the fall. I'm assuming you have sandy soil but if it's not, that might widen your options. You might Google ornamental grasses and check out those that prefer moist, sandy soil or else visit Santa Rosa Gardens' website and review the recommended growing conditions for their fairly-extensive selection of ornamental grasses. I will comment that my own experience has been successful but limited to only those named above. The only variety I've grown that prefers shade is Japanese sedge grass. That said, there are several available cultivars + I have mine growing in full shade, part shade, part sun and all are thriving. As for a perennial that might suit your needs, I'd look at those that might thrive in your situation. Here are a few suggestions to get you started: Armeria/sea thrift Agastache/hummingbird mint Alchemilla mollis/lady's mantle Athyrium/fern Anemone hupensis/Japanese anemone Chelone lyonii/turtlehead Cimicifuga racemosa/black snakeroot Dicentra spectabilis/bleeding heart Hellebore/Lenten rose Hydrangea Pulmonaria/lungwort, Bethlehem sage Tricyrtis hirta/toad lily Trollius ledebourii/Chinese globeflower There are likely lots of others but these have been reliably hardy in my Z6 garden. Best of luck to you! Here is a link that might be useful: Santa Rosa Gardens

clematis are listed as being toxic to dogs, and so are rose of sharon's, not to mention ROS's are not even vines... which defeats the purpose of the poster question... now allbeit, most plants listed as "toxic" to dogs won't kill your dog outright... most are not toxic to the extreme point... but they're still not "good" for your dog to digest if they do chew on 'em... they could cause diarreah, nausea, or they could have more none visible effects that take time but maybe hard on their kidneys, or other functions within their body, slowly killing or weakening them over time... the poster said they were in search of a plant that's NON-toxic... and hardy kiwi's are a climbing vine that is just that, NON-toxic; and best part, if you plant just males you won't even have to worry about the fruits at all... plant a female in your garden, and you get mini-kiwi's you can use in smoothies and such... i'm actually planting a bunch around our chain link fence myself this spring for the same purpose... keep the dogs from getting distracted so easily by everything around 'em... like i said in my above post, i too had alot of trouble finding a true non-toxic "vine" to hide our fence, esp. one that could surely thrive in my zone (6B) with no worries... now hardy kiwi's are not found on either list by the ASPCA, but i assure you that they are non-toxic... a perfect hardy "true-vine" for someone attempting to "hide" their chain link fence... (i'm going with the "artic beauty" types)... Here is a link that might be useful: ASPCA's list of plants toxic and non-toxic to dogs...

Good point about the slope-I really should have done better in geometry! So far the pittosporum seems most appealing since it won’t drop any fruit. i would think that I’d have to plant more than one to achieve a continuous hedge but it does appear to be a fast grower so definitely a contender