So you have moved to the Oregon coast or bought a summer house here-- by this I mean the real coast, by the ocean. Folks in the eastern parts of Washington and Oregon frequently refer to anything west of the Cascade mountains as "the coast." But conditions are radically different in the Willamette Valley than here on the actual coast-- and here is where guidance is lacking for the aspiring gardener.
Before you run to the local nursery, or worse yet, bring plants with you from the valley, you will want to spend some time assessing your site. I like to think of our neighborhoods in "zones," albeit not the USDA-type temperature zones. This has more to do with exposure to the ocean.
In the winter, we receive very strong winds mostly from the southwest, often extremely cold and pouring rain at the same time. Sure the whole northwest is rainy, but we receive more water than most other locations, especially near the headlands or by the foothills of the Coast range. The winter storms hit these barriers first, and dump a ton of moisture all at once. Wind is frequently in the 50+ mph range, and bad storms have brought us 80-100 mph winds. And yes, it does freeze here. Not as often as inland, but we get snow and freezing temps on occasion.
Summer is mostly comprised of dry weather (believe it or not) for months, with strong persistent winds from the north and fog laden with saltwater when the valley gets hot. Hence you might start the day with clear weather, and by noon the "marine layer" (fog) will have covered your coastal neighborhood. The deposit of salt on plants along with little moisture to wash it off or flush it through the soil, combined with drying winds, can be lethal for plants.
A new coastal gardener might then just want to throw up their hands in dismay. What will possibly survive all these challenges? Many plants grow exceptionally well here, but it's important to figure out what coastal-zone you are in.
If you are oceanfront, subject to the full force of winds and receiving plenty of salt-spray, your choices are pretty narrow. If you are a block or two back from the ocean, your choices widen considerably but realistically you should exclude some plants you might wish for. If you are some distance away, like "no way can I see the ocean from my house"-- you may be able to grow all kinds of climate-adapted plants, even vegetables.
Some good tactics to begin: go on walks of your neighborhood, and take notes or pictures. I like digital pictures, that way I can remember the plant I liked and also the setting in which it can grow. One almost-oceanfront place we cared for included a mature fig tree-- which likely would not have survived were it not for the shelter and warmth of 5-foot stucco walls on three sides of the tree (west-facing). Not only did it survive but produced a bounty of figs every year.
After you have toured the neighborhood, seek out a quality local nursery and bring your pictures or notes. The whole point of going to a good nursery, as opposed to a supermarket that sells plants in the spring, is to utilize the knowledge of the great people who work there. In a coastal nursery, the first question you will be asked is "how close are you to the ocean?" They don't want to sell you something that dies in a month, and they have plenty of experience with trial and error of all different plants in varied locations.
If you are close to the ocean, make note of any windscreens that might have been planted or built by the smart people who sold you the house, or the lack thereof. A nice big shore-pine on the southwest corner might obstruct a little of your view, but will provide needed shelter from winter winds if you are planting nearby. If you need to add wind shelter to your yard, consider that a permeable screen that allows wind to pass through somewhat will do a much better job than a solid one-- if the wind can't get through, it will swirl around the barrier and the result is more increased velocity when it gets to the plants. Yikes.
Be honest with yourself-- especially if this home is not your primary one. How often will you be here to visit? What time of year? Do you really want to pull weeds and prune things when you are on vacation? How will the plants get watered in the dry season? If you want a lush landscape and don't plan on doing the work, consider hiring a year-round garden service. They can also let you know when a tree has fallen after a windstorm and you might want to fix that roof. If you want to plant in summer, there must be a way to provide water to new plants. Just because it rains here in winter, don't assume things will be fine without water in summer. Drip on a timer system, or hire it out, but if you don't plan for this you can say goodbye to new plants.
Time of year that you visit might give you clues: if in spring/early summer, you might enjoy lots of rhodies and azaleas, with spring bulbs. If in mid-summer, hydrangeas, daylilies and beach roses will be in bloom along with many perennials and annual flowers. Fall will see the ornamental grasses send up their lovely seed-stalks and the tall sedums like 'Autumn Joy' display soft-pink flowers, to grace the few deciduous plants like vine maple whose leaves turn.
Finally, take some time to visit a mature public garden like the Connie Hansen Garden in Lincoln City. A place like this, carefully tended by volunteers and developed by an expert botanist, will provide you with equal parts information and inspiration. If you visit at different times of year you may discover new plants that never came to mind, and make new gardening friends in the bargain.
Next up: preparing your coastal garden for spring