We have a neighbor with some sketchy guests and are incorporating a "zombie screen" into our permie design plan for our 10 acres on the North Olympic Peninsula zone 8b. Koppen is Csb I believe. Mediterranean completely dry summers and wet winters. Doesn't get below 15oF.
This hedge is going to be over 300 linear feet.
I'd like some help brainstorming species that would provide a visual (not wind) screen that would max out at 10-15' or less(nice view of the mountains there) and preferably stay green year round for us, provide bee forage, bird habitat, etc. I'd like it easy to maintain this with yearly mowing with tractor brush hog on inside of hedge which will remain a perimeter tractor path around a field.
One plant that would be great for us is Ceonothus (sp?) as it's nitro-fixing, evergreen bee forage. Native species that make a great hedge here are Nootka Rose and Snowberry mixed and although they're not evergreen they make a visual screen eventually up to 8-10'.
But I'd like a righteously polycultural hedge so hit me with more species suggestions!
Feijoa sellowiana, aka guava, aka guavasteen, aka pineapple guava, might work. Their lowest recommended temp. is 15 degrees F. and upper temp ideal is 70 to 80 degrees. However, I live in zone 9a where summer temps are routinely in the 90's. This week they've been in the low 100's. My guava looks as good as it did in the blush of spring.
Guavas are evergreen, can reach, at maturity, a height of 8 ft. and a similar spread. They are easily kept in check with pruning. They bearfruit which I personally find quite tasty. They suffer little from disease or pests and deer don't care much for them.
I am planning a hedge around my garden and I expect to have up to 10 guavas in it.
There is a nice description of guava on the Calif. Rare Fruit Growers page, crfg.org.
With 300 ft to plant, unless you are wealthy, you probably would do well to choose plants that you can propagate easily from cuttings. Evergreen is tough unless you choose something like clumping bamboos. Not sure how hardy guavas would do unless you get a lot of heat in the summer. Elderberries grow about that tall, send up shoots and spread, produce great fruit for people (choose good cultivars) and birds, easily propagated. Highbush cranberry would probably do well and is also about 8-10'. Wild plums will sprout from twigs stuck right in the ground. Serviceberries are native and get about 10'. Filberts. Might also consider coppicing willows (outstanding for bees)--if you grow the right kinds you can sell the rods produced each year to basket weavers. willows Some gooseberry varieties. I'm no help on evergreens though.
Some of the evergreen hedges do great with slight pruning, like yews and boxwoods.
I have some osmarea burkwoodi that are evergreen. Attract bees and smell great, plus don't need lots of water. My zone is similar to yours but hotter in summer.
Mine are 20 years old and about 9 ft with only slight pruning.
THe pineapple guava might not reliably fruit for you, but it should survive. The flowers are beautiful and delicious. It reliably fruits for us in Portland, but we get a lot more heat.
Another one to think about is silver berry Eleagnus x ebbingei. I call it the fall daphne. It is amazingly fragrant, and then it blesses us with edible berries in April! Yes it is evergreen and nitrogen fixing.
There are some citrus that might work for you-Thomasville Citrangequat is one that has worked well here. Tastes like limes.
Boxwood is the obvious choice for a thick, evergreen hedge and it's easy to propagate by cuttings. But it doesn't really offer any of the other characteristics you are interested in.
There are some hardy varieties of Rosemary that might work there. Evergreen, bees love Rosemary blooms, and although not high in useful calories it makes a tasty addition to numerous dishes. Some varieties get 8-10 feet tall and I've seen them growing in Zone 8b.
My opinions are barely worth the paper they are written on here, but hopefully they can spark some new ideas, or at least a different train of thought