While I am not totally sure that there isn't some question about invasiveness with the English hollies in the PNW, the American holly cultivars should be just fine. If you want berries, you will need to plant male and females of the appropriate varieties - if you aren't too enamored of berries, then plant what you can find. If you don't want a "Great Wall" - depending on the length of ground you want to plant, then planting a mix of hollies and other evergreens would give a "Tapestry Hedge" effect. There are also madronas, ceanothus, etc., as well as California bay, but I have forgotten a lot of the plants I once knew - it's been almost 9 years now since I moved from San Francisco! If you want others, there are cedars, thujas, chaemacyparis, cryptomerias, clumping bamboos, camellias, Rhodies, loropetalums, possibly pittosporums, possibly podocarpus, and various viburnums (check as some have made the invasives listings in other parts of the country). 'Hope those give you a place to start looking. If you can plant a hedge of double or triple thickness, then the front row doesn't HAVE to be evergreen, and can include deciduous, flowering shrubs and trees, just to give additional interest. The Sunset Garden Book should have a listing of good, evergreen hedge plants (it's a very good book anyway, so you probably should have a copy if you don't already), and there should be any number of books available through your local library to look things up in. As well, here is always Google and the rest of the search engines. You can also try your local county extension agent, as he/she should know what will grow well in your area - try looking under gov't offices in the phone book - there should be an office in the county seat.

Generally no runoff or leaching issues with Roundup, but if you're right on a wetland or in a riparian zone then you might want to consider using the aquatic formulations but you'd need a commercial applicator's license to buy those. It's not the Roundup itself but the surfactants that run off and get into water bodies. The aquatic formulations are used for controlling things like purple loosestrife and yellow flag iris and they have different surfactants. Cutting off the flowers will reduce the amount of seeds produced but may not reduce the seedling population. Two things to consider: A, the plant will try to re-flower unless you cut it just as seeds are setting, and maybe even then. B, most plants produce way more seeds than will be able to germinate and turn into seedlings. Reducing the number of seeds set won't necessarily reduce the number that germinate and turn into seedlings. You'd have to get nearly all the potential seed to significantly reduce the number of seedlings. But it's worth trying, definitely. Just maybe not right now, it may be better to wait a little longer so the plants have less time to put out new flowers.

Some large evergreens for shade would be 'Nellie Stevens' Holly, Leyland Cypress and Western Arborvitae. The traditional Arborvitae 'Emerlad Green' do need a lot of sun and do not tolerate shade. Leylands are a bit fussy. They do tend to dry out quickly due to their shallow roots and dislike for windy conditions. If you water them in well especially for the first season and get them to take they will be alright but again they can be difficult. The western Arborvitae is the new substitute for the Leyland, takes shade and is much hardier in our region. Skip Laurel and Leatherleaf Vibernum are also nice selctions but only reach about 15 feet. The Skip Laurel is evergreen and the vibernum is semi-evergreen. Both have more of a natural form verses the evergreens which are more pyramidal shaped. Hope this helps!

it grew back a bit slower than anticipated. ==>>> it sounds like the base issue.. is that you were expecting instant gratification .. and that doesnt always work.. in the garden ... its genetics dictate how fast it will grow back ... you will not change said genetics with fertilizer .. and IMO ... shrubs and trees NEVER need fert ... it has been there a very long time .. and done .. apparently.. very well ... without such.. so what could it be lacking ... these are not production crops that might 'use up' the soil .. the same could be said .. with water ... again.. its was doing so good.. you had to whack it down... what makes you think it now needs water ... on some level ... you might be trying to love them to death .... trying to get them to grow faster ... imo ... the best thing you can do.. is just be patient .. and let them do their thing ... it might be interesting to do a soil test.. and see if anything is lacking in the soil.. and react accordingly .. and you might do a perk test.. and find out what your soil is.. and how it drains and if there are any water issues .. but again.. all that said.. they were vigorous and over grown ... so i suspct.. nothing is lacking in regard to those plants ... be patient.. ken ps: if you gave if fert a few months ago .. i do not recommend double dosing them ... by giving them more ... if you take vitamins.. would taking twice as many.. be of any value???