Hi, I have been gardening in the Boise area for about 8 years now. It's actually not too difficult of a climate to garden in, so long as you have access to irrigation water. Another thing that you might want to think about is protection from wind, If you're in a suburban back yard, it is not as much of an issue, but if your garden is more exposed, the wind can be pretty tough on plants. The sun can also be pretty intense, so where you may have wanted to maximize sun/heat on the "wet side" of Oregon, that's not always the case over here. For instance, I established a garden on the south side of the house this spring, and while the eggplants, sweet potatoes and okra are all thriving, it is proving to be too much for the hops, and they are getting kind of bleached and singed from the intense sun and heat. There is very little that can't be grown in this climate though. Artichokes are the only thing that comes to mind (and citrus of course) that I haven't been successful with.

I still fight with container citrus trees (and in-ground young trees) in our hot 100+ weather. The in-ground trees do certainly get sunburned badly (not just the young leaves that haven't hardened off from Spring) and the recently planted ones in ONLY the West direct sunlight will sit for an entire year+ before showing growth (these are all properly planted, in raised beds). Ones in partial shade or morning only light do much better and typically show growth in the first spring. The containers are by far the worst. I've been forced to pot-in-pot on every single one: there is no container mix (gritty, 511, or bagged soil) that can adequately protect roots in direct summer sunlight. The soil temps are easily 100+ around the edges. Yes, black containers are the worst. Supposedly painting black plastic white will drop surface temps 15 degrees. Besides pot-in-pot (best with 1" of largest bark chunks separating each container), I do have success with wrapping the containers with the foil backed bubble wrap (radiant barrier); alternatively, just burying the container can work extremely well (but careful as roots will leave the container or nearby roots invade). Overall, I think burying has worked best (easiest?) if you don't have root worries. However, I do also have to put shade cloth over them. The cloth went up for me mid-June (early heat waves here in central CA). The shade cloth exception: mature trees. If there is a GIANT canopy (very well established tree), this is less important as the outer leaves do protect the interior leaves and bark enough from burning up. That's why you can't compare entire groves of mature citrus trees in hot weather to container or young in-ground. You can't say "citrus are high heat tolerant trees, there are groves of them in 110F weather, heat isn't an issue". It very much is an issue until the tree is very mature and established. IIRC, all other conditions in place (nutrients, humidity, leaf temps) root temps are ideal growing at 90F but quickly shut down and burn up just over 100F+. Leaf temps shut down photosynthesis somewhere above 115F or so -- which means the majority of photosynthesis occurs is the morning sunlight. It's not ideal to only exposed them in afternoon, but /shrug I have some that are only afternoon exposed due to limited space.

Amongst the best palms for the PNW would be the Windmill Palm, Trachycarpus fortunei, which is the palm in the pool photo. Other species of this genus to look for would include the more refined leaf form of T. wagneriana or T. takil. A smaller growing fan palm that is also perfectly hardy is the Mediterranean Fan Palm, Chamaerops humilis. There is also a lovely silver leafed version, C. humilis var cerifera. You might also be interested to try growing one of the hardier feather palms, such as Butia capitata, the Pindo Palm. Other subtropical plants that are often used in PNW gardens for a tropical effect would include the various Phormium hybrids, Cordyline australis hybrids and cultivars, and Beschorneria yuccoides. The silvery foliage of Astelias, which much resemble Phormiums in habit, are also quite hardy for Seattle, and would include the larger growing Astelia chathamica 'Silver Spear', and others such as A. nervosa 'Red Gem' or similar. Fatsia japonica is always a reliable tropical looking foliage plant. Usually not quite hardy as year round perennials in all but the mildest PNW locations, but great as temperennials, the Abutilons of all colors are great filler plants. Bergenia was already mentioned, but this is a great foliage plant that also blooms in late winter, and is fully hardy, coming from Russia. Winter deciduous subtropicals such as the various Hedychiums are also great, such as H. gardnerianum, H. flavescens, H. greenei. Cautleya spicata is also quite nice, and is quite colorful with summer blooms of red and yellow, and will even bloom in a fair amount of shade. My favorite Canna varieties for tropical flair would have to include the very tall growing C. ehemannii, which can get 10 feet tall, and has smaller rose red pendant flowers that cleanly drop off when done blooming. If you want dramatic foliage that is the equal of a Gunnera, you might also consider planting the Rice Paper Plant, Tetrapanax papyriferus, but this will probably be killed back to the roots in winter in most PNW locations. Melianthus major is another great foliage plant, but will often be killed back to the roots outside USDA zone 9a conditions. As to Acanthus, you should also look for the attractive A. spinosus, which has distinctive looking leaves. Acanthus does perfectly well in full sun in more coastal locations that don't get the baking summer heat of interior Oregon, but in its native Mediterranean habitats it will also quite willingly grow in full sun locations as well. In dry summer locations, it will go summer deciduous, and come back into growth with fall rains. In irrigated gardens, the yellowing, heat damaged foliage can simply be pruned off, and it will often push new foliage immediately if watered and fertilized, or can be allowed to wait until it cools off and starts raining again.

Mull, Oregon is a beautiful state, great place to live. To pull off mangoes, and other tropicals you are going to need a greenhouse. If you are on a budget, you can build one from easy to find parts for a decent price. You can get away without a heated greenhouse. Using methods like pools of water, and composting inside the greenhouse. If you are adventurous, you can even build a greenhouse into the ground, and use the ground to keep temps warm in the winter. I had some resources for DIY greenhouses, however my main computer with the links is down atm. If you do some googling you can find all you need.