Vine maple

The only native oak of British Columbia and Washington and the principal oak of Oregon - a slow-growing, deeply tap-rooted deciduous tree with deeply lobed, rounded-lobe glossy leaves and a broad, rugged, rounded crown. It is the keystone of the Pacific Northwest oak savanna, providing acorns and cover for deer, small mammals, and birds. Notably drought-adapted: it wants dry summer soil and resents irrigation.

The western counterpart of eastern flowering dogwood - a small deciduous tree of the Pacific coast with horizontal, tiered branching and a rounded-to-conical crown. Its showy spring "flowers" are actually a tight central cluster of tiny purple-green true flowers ringed by six large white petal-like bracts (eastern flowering dogwood has four). Elliptic dark green leaves color yellow to orange to red in fall, and the 1/3-inch fruits ripen to showy bright red or orange that feed songbirds, squirrels, and deer.

Subalpine fir (Abies lasiocarpa) is the narrowest conifer in western North America and, for most gardens, the wrong tree. It is a timberline species: the US Forest Service silvical account puts its climate at a mean July temperature of 45 to 60°F, with more than 24 inches of precipitation of which much falls as snow, on ground that is frozen or under snow for a large part of the year. Bring it down the mountain into a hot summer, a humid one, or a polluted one and it sulks, thins and dies, and it does so slowly enough that people keep watering it. The Lady Bird Johnson Wildflower Center calls it a spire-like evergreen of 30 to 50 feet with stiff horizontal limbs branched to the ground, and that spire is the whole ornamental argument - a crown so narrow it can be a fifth as wide as it is tall, which is a snow-shedding adaptation rather than a nursery selection. At and above treeline it stops being a tree at all and grows as krummholz, low sprawling mats scoured by wind, and reproduces by LAYERING: a branch pressed into the ground roots and becomes a new stem, so a single tree can leave behind a ring of clones that mountaineers call an atoll. Two honest problems follow it down into cultivation. It is slow and, for a conifer, short-lived and structurally weak - thin bark, persistent dead branches, easily windthrown - and its pest list is serious: balsam woolly adelgid (Adelges piceae), introduced from Europe and the most destructive insect on this species in the Cascades, and the western balsam bark beetle (Dryocoetes confusus), which together with Armillaria root rot drives the mortality complex that has killed subalpine fir across large areas of the Rockies. Like every true fir it carries its cones UPRIGHT on the upper branches, dark purple ripening brown, and those cones never fall whole - they shatter on the tree and leave a bare central spike standing on the branch, which is the single quickest way to tell an Abies from a Picea at a glance.

Rocky Mountain juniper (Juniperus scopulorum) is the western counterpart to eastern redcedar, and the two are confused constantly - with good reason, because where their ranges meet across the Great Plains they hybridise freely and intermediate trees are genuinely hard to name. Start with the caveat: Missouri Botanical Garden has no species-level page for it at all, only cultivar entries, and the species is the wrong plant for a hot humid climate. The Lady Bird Johnson Wildflower Center is blunt about it - drought and salt spray are fine, high humidity and high night temperatures are not - so this is a plant for the dry interior west and the plains, not the Southeast. What it offers there is unusual. It is a narrow, slow, drought-hard tree of dry rocky foothills, 30 to 50 feet on a good site and often far less, with shredding red-brown bark, blue-grey scale foliage, and high tolerance of caliche and limestone - the mirror image of the acid-soil hollies in this batch. It is dioecious like them, so the waxy blue-black cones appear only on female trees with a male nearby, and those cones are cones rather than fruit, taking about 18 months to ripen. It also lives an extraordinarily long time: the Jardine Juniper in Utah is over 1,500 years old and a New Mexico specimen counted 1,888 rings. The hard restriction is cedar-apple rust, for which it is an alternate host - do not plant it near an orchard.

Balsam fir (Abies balsamea) is THE Christmas tree of the northeast and, for most gardens, a tree to admire rather than plant. Missouri Botanical Garden is unambiguous about why: the species is native to cool climates and is not recommended for planting in the hot and humid summer conditions south of USDA Zone 5, it is generally intolerant of urban pollution, and MBG explicitly does not recommend it for its own St. Louis climate. Wikipedia puts the same limit the other way round - it wants a mean annual temperature near 40°F with consistent moisture, and low moisture combined with high temperature is what stops the range. This is a boreal tree. It runs from Labrador and Newfoundland west to Alberta and south to Minnesota, Wisconsin, New England and New York, then survives in the Appalachians only by climbing, hanging on at 2,500 to 5,000 feet as far south as Virginia and West Virginia. Where it does suit the climate it is superb: a narrow aromatic spire of 50 to 70 feet and only 15 to 25 feet wide, clothed in flat blunt needles 0.6 to 1.2 inches long, dark green above with two chalk-white stomatal bands beneath and twisted at the base so they lie in two horizontal ranks either side of the shoot. Two features are worth learning by hand. The young bark is smooth and grey and studded with RESIN BLISTERS that spray when punctured - no spruce or pine does that - and the erect cones, 2 to 3 inches and dark purple, ripen brown and DISINTEGRATE on the branch in September, dropping their scales and leaving a bare central spike standing on the twig. A fir cone is therefore something you almost never find whole on the ground, which is the single fastest way to tell Abies from Picea. That resin is also the reason this tree has a place in the history of optics: Canada balsam, the oleoresin tapped from those bark blisters, dries to a transparent mass with a refractive index near 1.52, effectively the same as crown glass, so it worked as an invisible glue for cementing lens elements and became the standard mounting medium for microscope slides from about 1830. It was phased out during the Second World War for polyester, epoxy and urethane adhesives, which do not yellow and have far better thermal and solvent resistance. The honest catch list is long: balsam woolly adelgid, spruce budworm (this is the budworm's preferred main host), bark beetles, spider mites in hot spells, cankers, heart rot, root rot, needle rust and twig blight, plus heavy deer browsing, shallow roots that make it wind-firm only in a stand, and a working life measured in decades rather than centuries.

The signature evergreen oak of the California coast and foothills - a broad-canopied tree with dense, dark, holly-like leaves whose spiny-toothed margins curl under, and a short, often massive trunk. The Lady Bird Johnson Wildflower Center documents it growing 20 to 50 feet high and wide, with old specimens reaching 100 feet and living for centuries. A keystone wildlife tree: its acorns and dense canopy feed and shelter Oak Titmouse, scrub and Steller's jays, chestnut-backed chickadee, and roughly 30 other bird species, and it is a larval host for three duskywing and sister butterflies.