Biome: Oregon Coast

Sweeping views from Cape Disappointment on the Oregon coast.

The Oregon Coast is a great place to garden but it has distinct differences from our inland gardens. More than 70″ of rain a year, the modifying influence of the water with less arctic cold and almost no true heat. Most of the coast is Zn8b-Zn9b- we’ve amassed a large collection of plants that thrive on the mild and wild Oregon coast. Lack of summer heat means that some plants are not as hardy to cold- Camellias and Loropetalum are examples. Locate these plants in the warmest possible locations. Wind is a perennial issue too Remember that exposed gardens will be impacted by N/NW winds in spring and summer but the biggest windstorms arrive from the SW.

Salt spray and sandy soils

Salt spray is an issue very close to the strand. Salt tolerance is part of the perameters when we list a plant for the Oregon Coast. One of the boundaries to gardening close to the beach is soil. Sandy soils that drain instantly, lack nutrients are are almost always acidic. Its best to stick with plants that are adapted to these challenging substrates. I list individual plants that are recommended for sand. Two groups of plants that deserve greater recognition on the coast are Callistemons (Bottlebrushes) and Grevilleas. Both are adapted to very poor soils but don’t flinch in more well developed soils. They also sport considerable deer resistance and that includes elk.

Hard freezes are rare but cold near the coast range

Beach side communities hardly ever see a very hard freeze and highs below freezing are very rare. Just inland it gets colder quite quickly. Remember this when planting closer to the coast range. Often it can be one zone colder as well as lack heat for plants to harden for winter. On the ocean most gardens are zone 9a or warmer within 2 miles of the beach.

Garrya elliptica is native to the Oregon coast.

Less drought, more cool and wet

The season of real summer drought is somewhat muted on the coast. The rainy season begins earlier and ends later. Consistent low temperatures and high humidities mitigate the lack of rain. Also, the coast can be slow to heat in spring time, often lagging behind hotter inland gardens. Heat waves on the coast can be intense but they seldom last more than a day and often only several hours of one day if offshore flow is brief. Somewhat backwards cool air advects north during and after a heat low moves inland. That is the coastal fog moves from south to north at the end of a coast heatwave. These brief soaring temps and low humidity are seldom harmful to plants and cause more worry for the gardener than plants.

 

Climate Adapted Plants for Gardeners in the PNW

Abutilon x 'Smoked Salmon'

Abutilon (Callianthe) x ‘Smoked Salmon’

A tender abutilon that is best considered an annual but boy howdy is it one of the best flowering maples that we’ve ever seen. Compact growing to 3′ x 3′ in a season at the largest. Profuse, huge flared pendant flowers are the color of smoked salmon on the interior and a distinctively darker orange on the outside. Its a great effect. Full sun and rich well-drained soil with regular irrigation. Excellent container plant that blooms non-stop with little intervention.  Not hardy below about 25ºF.

Xera Plants Introduction.

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Abutilon x 'Tangerine Scream'

Abutilon (Callianthe) x ‘Tangerine Scream’

A relatively hardy and massive blooming Abutilon that we named for its small but vivid tangerine orange flowers. A tall grower, easily reaching 4′ in the ground in a single season. Excellent in containers in full sun but be warned it gets big, fast. In the ground it has been a great performer. It requires a very protected location- between shrubs that will protect the base or near a house wall- under those conditions it will freeze back below about 20ºF but will be able to return from the base. And don’t be discouraged in spring if this plant looks dead- just water, water, water, in April-June and you’d be surprised at the vigorous recovery that will take place. It helps if it is in rich, well drained soil. Hummingbirds love it. Excellent performance at the Oregon Coast where it will seldom be bothered by cold and can bloom nearly year round.

Xera Plants Introduction.

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Acacia covenyi

An exciting shrub/small tree with paddle shaped blue evergreen phyllodes for foliage and in late winter to early spring a massive display of luminous yellow flowers. I’ve always loved Australian wattles so it was with great excitement that we decided to grow this striking plant. Moderately fast growing to 16′ tall and 8′ wide forming either multiple or a single trunk. The bark is chocolate brown and smooth. Very few Australian Acacias will thrive in Portland,  its just about 5 degrees too  cold in our coldest years. This one is different, (a few species will live for 4-6 years before they finally succumb to Jack Frost. Acacia pravissima etc.) This, however, is the cold hardiest  that we have grown. It is hardy to just below 10ºF for brief stints- good enough for long term survival. This is a rare limited endemic to the high mountains of New South Wales but is popular as a garden subject the world over.  The small, fluffy,  balls of electric yellow flowers foam among the blue leaves – incredibly pretty. Full sun and a protected location – against a south facing wall is ideal for a very pretty fun to grow tree. Once fully open the flowering stems may be cut for long lasting bouquets. Blooms on wood from the previous season, prune if needed after flowering has ended. Light consistent water to establish . Not fussy about soils and happiest in full, all day sun. Protect from subfreezing east wind. Bloom time is concurrent with several earlier Ceanothus  (‘Blue Jeans’, ‘Dark Star’, ‘Concha’) and creates a vivid early spring  yellow and blue display not soon to be forgotten. Drought adapted when established. Not bothered by deer/elk- not entirely sure about rabbits- if they are profuse in your neighborhood it wouldn’t hurt to protect the plant with chicken wire when young. Beautiful year round and spectacular in bloom. AKA Blue Bush.

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Acacia spectabilis

Mudgee Wattle or simply showy wattle this is an extremely pretty small tree that requires a very protected location to thrive. Blue/green bipinnate leaves are intricate and pretty. In very late winter to early spring a stunning show of electric yellow puff ball flowers. It covers the whole tree weighing down the limbs in full bloom. To 12′-15′ tall in rich to average soil and it absolutely requires full sun. Excellent against a south facing wall. The flowers truly are showy and glow from quite a distance. Native to New South Wales and southern Queensland on table lands. Cold hardy to at least 18ºF- it should take colder temperatures if sited correctly. As with all Acacias it is extremely fast growing when young. Consistent summer water. Loved by hummingbirds and insects in general. This special small tree can begin its life in a spindly way. Full sun and regular water strengthens this growth. Excellent, and best adapted for the Oregon coast. It adapts to life on sand (with supplemental water) as well as well developed soils. Not bothered by deer. The large delicate leaves are blue/gray and are pretty year round. This Acacia is not as cold hardy as Acacia covenyi and is hardier than Acacia pravissima. Following bloom long dusty purple seed pods contrast against the blue/gray foliate. Bark is black to dark brown. Inland it is considered experimental.  Eastern Australia.

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Acaena 'Blue Haze'

Acaena ‘Blue Haze’

The blue form of New Zealand Burr with finely divided pinnate evergreen foliage that forms a vigorous creeping ground cover. In summer 3″ stems support round white flowers that appear for several weeks. Easy to grow dense-growing plant to 3″ tall and covering up to 3 square feet in a year. Rich, well drained soil with regular summer moisture to speed growth and keep the appearance fresh. Best in part shade to shade- seems to resent hot sun and permanently dry positions. Excellent for a fast cover that blocks weeds and roots as it grows- perfect erosion control for steep shady slopes. Plant on 1′ centers for a fast cover. Adaptable to dry conditions when established.

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Acaena inermis 'Purpurea'

Acaena inermis ‘Purpurea’

Such a good good plant. The purple-foliaged New Zealand Burr covers the ground in pinnate dark purple foliage. Low spreading evergreen ground cover for full sun to part shade in rich, well drained, moisture retentive soils. Avoid compacted dry soils- it will die out. Instead provide an annual mulch of compost- put it right over the leaves and let the foliage grow up through it. This will give you a dense spectacular ground cover of purple with blue tints. Excellent as an understory in containers as well. In summer sporadic 4″ stems support spiky maroon orbs- these are the flowers. Best as a small scale ground cover, 3’x 3′ is reasonable. It will flow around low shrubs such as Hebes and around paving stones. Regular water.  New Zealand.

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Acanthus mollis 'Hollard's Gold'

Acanthus mollis ‘Hollard’s Gold’

Bear’s Breeches is a standard perennial in our region for dry shady environs. And though the bold foliage is amazing we’ve been drawn to this form which turns it up a notch. Nearly 3′ long bold leaves are imbued with gold changing to acid green as the season continues. In early summer the fantastic white/mauve/grey chalice-like flower spikes rise to 4′ tall. Forms imposing clumps quickly in rich to average, well drained soil with light, consistent summer water. Takes dry conditions well and will actually resort to summer dormancy in extreme conditions. Evergreen to about 20ºF. Low deer resistance. Shines in the deepest shade. A very permanent plant that will live for decades.

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Acer circinatum

Acer circinatum

Vine Maple is perhaps our most beautiful native maple. Found from SW British Columbia to Northern California in the Shasta area. Its a pervasive understory tree throughout the western part of the state. It derives its name from its almost vine like habit in shade. This winding and sun seeking component leads to the most graceful natural forms. In full sun it is a compact, multi-trunked shrub. In autumn in both habitats it turns to shades of fiery orange and yellow and red. Vivid against the pure green trunks and stems.  One of the most dramatic places you will see this shrub is at 4500′ on Belknap crater on McKenzie Pass where it lives among the lava. In early fall the brilliant colors of the maples contrasts wonderfully with the black lava. Its very hot and very dry but  its also very high in elevation. The symmetrically serrated round leaves rival any Japanse maple. In shade established trees get by with little summer water. In the sun irrigation is welcome. Rich to average soil with regular applications of mulch. To 16′ tall in shade and again quite a bit shorter in full sun- very wide in shade. Avoid the reflected heat of south facing walls. This shrub/tree belongs on the north side or under substantial shade. Some deer resistance. Excellent underplanted with native ferns and Gaultheria. A common native that should be a more common ornamental. Tiny red flowers turn into sunny orange samaras by autumn and persist past the leaves.  Avoid very dry shade of un-irrigated over hangs. This is a semi-mesic maple.  Oregon native plant

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Acer glabrum ssp. douglasii

Rocky mountain maple or locally also known as Douglas maple is our form of a widespread and sweet small tree that ranges from the Yukon in Canada  to the highest  mountains of  northern Mexico. Our local variety is found in all of the mountainous parts of the state. This demure tree is the least planted of our native maples and deserves much more inclusion in our gardens. In the coast range it is found primarily above 2000′ and it can even be found lower in the Cascades. It follows the spine of the Ochocos in eastern Oregon up into the Blue mountains and Wallowa Mountains in the far north east. Rarely pole straight in stature its often multi-trunked and single trunked trees are in the minority in the wild. Ours are single trunks but multiple stems do not take away from the fresh green leaves and pretty to stunning fall color. The familiar maple leaves can achieve anything from dull yellow to shots of vermillion. Depending on the weather and tree. Soft gray bark.  To 25′ tall moderately fast. Tiny green flowers morph into rosy hued samaras in autumn. Regular water for the first several years. This tree does appreciate rich soil that retains moisture in the Willamette Valley. Excellent woodland tree or even more appropriate on the edge of a stand of trees where it receives at least half a day of sun. The most recent years stems are often sanguine red, nice contrast with the grass green elegant leaves. The most striking fall color is achieved with more sun. A mesic maple that often follows water courses or lines wet ground.  Single trunked trees are conical shaped and multi-trunked forms are more rounded and spreading. Deciduous.  Avoid blasting heat and  drought. Oregon native plant.

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Achillea millefolium, common yarrow

Achillea millefolium

This is the green foliage form of our wild yarrow. A rambunctious, easy to grow evergreen perennial for rough sites in well drained soil in full sun. Continuously from spring to autumn ‘umbels’ of pure white flowers rise 18″ above low spreading aromatic, finely divided ferny foliage. Most often it is green with variants that have gray foliage from time to time. Low water perennial that can even be used as a lawn substitute. A single plant spreads to several feet wide. Moderate deer resistance.  Butterflies oh the butterflies.This is a pioneer perennial and will often out compete less robust native perennials. Its best use is as a contained weed. It is great for pollinators Individual plants rarely persist more than 3 years.  Oregon native plant.

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