Biome: Hot Aspects

Caesalpinia gilliesii requires the most blasting hot locations.

Its surprising in our climate that heat is as big of an issue as it is. But there are scores of sunburned and toasted plants littering our city by the end of summer. We average just 2.o” of rain during June-August and you have to take into account reflected heat. That could be heat emanating from an asphalt street such as occurs in a hellstrip or the accumulated heat of a hot wall. Both can conspire to fry plants. Luckily, we grow a LOT of plants adapted to excess heat. These plants won’t fry on the first day above 95ºF. Some plants revel in reflected heat, they come from hotter climates and need warmth to both bloom and to ripen wood for winter. That means it receives enough heating calories to ensure winter hardiness. Currently, Portland averages 14 days above 90ºF per year. By the next decade that number will have more than doubled. Part of gardening with climate change is to anticipate those effects and adapt to them. Increasingly, we will be considered a  hot summer climate. We should garden accordingly.

Climate Adapted Plants for Gardeners in the PNW

Agastache 'Lilac Moon'

Agastache ‘Lilac Moon’

Cool bicolored Hummingbird Mint that has masses of flowers that appear from orange buds which quickly change to luminous light lavender when open. To 20″ tall and forming a clump this very, very, long blooming perennial is delightful for hummingbirds, bees and butterflies. A soft pastel coloration that pairs wonderfully with light yellow flowers and even blue. Great in seasonal containers. Blooms non-stop from June to October. Do not remove flower spikes as new flowers will appear continuously from the same spike. Rich, WELL DRAINED soil with light, consistent summer water. Its best to water Agastaches consistently during their first year in the ground- to establish a large root system. Ideal on slopes- to assist in drainage in winter. Double dig soil to incorporate lots of oxygen in the soil.  One of our favorite introductions. An amazing combination of flower colors on a single plant. Do not cut back until new growth has flushed out in spring and all threat of a hard freeze has passed.

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Agastache ‘Berry Princess’

We believe this to be a cross inheriting some of the coloration of A. auranticus as well as A. cana. To 28″ tall this clump forming, everblooming perennial brings bright red buds that open to purple flowers. The colorful combination lasts all summer into autumn. New flowers are born on the same spikes so do not remove. Moderate consistent water through the first summer to establish. Double dig soil to incorporate oxygen into the soil and aid in irrigation to the roots. Established plants get by with a little less. Loved by hummers and  pretty decent cutfower as well. Full all day sun for best performance, will not be quite as floriferous in part shade. Sweetly scented foliage is an extra benefit. To 18″ wide and slowly increasing. Excellent on berms as well as slopes. Mulch in fall.  Small rosette of winter foliage is protected by the previous years defunct stems. Prune these away after all threat of a hard freeze has passed.

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Agastache 'Electric Punch'

Agastache ‘Electric Punch’

One of our all-time best introductions ‘Electric Punch’ is a floral powerhouse of a hummingbird mint with exceptional adaptation to our cold and wet winters. Rising to 34″ tall in bloom, a clump can become enormous in rich, WELL DRAINED soil with light, consistent summer water. Also, accepts no water but with interruptions in bloom. Incorporate plenty of oxygen into the soil and slopes are ideal. Do not remove flower spikes during the season- new orange aging to pink flowers appear from the same inflorescence. Best to wait until spring to cut back the previous seasons defunct stems. Moderate deer resistance. Agastache are best watered well for their first season, in subsequent years they will use much less.

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Agastache 'Mandarin Dream'

Agastache ‘Mandarin Dream’

This is our selection of an improved form of the species Agastache auranticus. It has deeper orange flowers on taller stems and exhibits excellent winter/cold/wet hardiness. To 30″ tall, the vivid blooms erupt from June to October. Tightly clump forming perennial whose tall wand-like stems require more horizontal room as well. Hummingbird Mint excels in very well-drained soils with consistent, light summer water. Full sun- you can fudge in light shade and still get results. Remove the previous seasons spent stems in March. Agastache are plants that like oxygen in the soil and they often seed themselves happily between large stones. They appreciate soil that is rich but permeable at all times. We advise to wait until March to remove the previous year’s stem. The hollow stems that remain over winter actually provide oxygen to the roots. If you cut them back too early (Fall, winter) you also leave the new growth at the base unprotected from the elements. So, the stems should remain to both give the plant oxygen and protect the next seasons clump of foliage. Double dig the soil heartily and add a little compost and even pumice if your soil is stingy. Water regularly for the first season to establish a large root system which will require less H20 in subsequent years. This is a vibrant orange that mixes well with deep purples and blues.

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Agastache 'Rainbow Sorbet'

Agastache ‘Rainbow Sorbet’

One of our larger growing introductions this is a flowering machine with large individual flowers that open pale orange and senesce to pale pink. Overall this is a pastel flower palette. To 36″ tall and as wide in full sun and well drained soil with light, consistent summer water. Agastaches are excellent as container subjects- they will accept the most cramped roots and still perform. Wait until March to remove the previous years spent stems. Give this guy room. Hummingbird nirvana. Good winter hardiness.

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Agastache 'Xera Flame'

Agastache ‘Xera Flame’

Our selection of a compact and free flowering cold hardy Hummingbird mint with intense dark orange flowers. Blooms June to October and they rise on spikes to 18″ tall. Does not flop- great for smaller spaces. Regular summer water in well drained, enriched soil. Excellent on slopes which improves winter drainage which increases cold hardiness. Full sun to very light shade. Irresistible to pollinators. Blooms appear from the same spikes all season- do not remove. Wait to cut it back until spring. Then remove dead top growth to make way for the new growth that is pushing from below.

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Agastache pallida ssp. neomexicana

Agastache pallida ssp. neomexicana

Cute flowering hyssop that makes a clump of strongly vertical stems clad at the tips with soft mauve/purple flowers. A boon to pollinators as well as hummingbirds. Blooms June to October continuously from the same spikes. To 18″ tall and barely half as wide. Agastaches like light soil. Double dig the soil well to incorporate oxygen and apply a handful of all organic fertilizer at planting. This will establish the plant much faster. Excellent performance on slopes where it achieves the drainage that it likes. Middle of the border or massed in a meadow- this easy to grow perennial performs for a long time. Do not cut back until after Valentine’s Day. Consistent water for the first summer then light water in subsequent years. Excellent performance in mixed container plantings. Moderate deer resistance. Foliage is sweetly pungent.

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Agave americana 'Medio Picta Alba'

Agave americana ‘Medio Picta Alba’

Tender <sigh> but perhaps the most spectacular variegated Agave. It makes a great container plant for LARGE containers. To 5′ x 5′, it grows a little slower in containers. Make sure it’s sturdy and well built too because this puppy has been known to grow so vigorously as to shatter its own home. Use well drained cactus mix and add a handful of all organic fertilizer. Move to a freeze free environment such as an unheated garage if temperatures threaten to drop below 20ºF. Otherwise move it to a dry place for winter- under a south facing eave is ideal. Move it back out in the open when rain dwindles.  Light summer water will speed growth. Leaves on this form are blue on the edges with a dramatic pure white stripe down the center. Wow.

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Agave bracteosa

Far and away the easiest Agave to cultivate in our climate and the handsome contorted sage green leaves are free of a deadly spike at the tip. Don’t be fooled, though. The leaves are lined in fine serrations that can cause a cut if you rub your person against them. To 3′ tall and as wide for very well-drained soils in full sun to very light shade. Amend the soil with pumice to sharpen drainage if needed. Ideally adapted to slopes. Good dimensions as a large focal point in a rock garden or clustered into clumps in the gravel bed. Accepts the highest reflected heat. Light summer water speeds growth. Often produces offspring from the base. These can be detached and replanted when its truly warm. Bold mature clumps are breathtaking. Wonderful life in hellstrips. Obviously deer resistant, but the tips can be brittle so handle them with care when planting. Excellent year round appearance and texture.

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Agave harvardiana

Agave harvardiana

Spikes! A very upright and pokey Agave with steel blue/gray foliage that forms large rosettes. To 3′ across eventually this cold hardy Agave demands excellent drainage but is worth the effort. VERY well drained soil- amend with liberal amounts of pumice and gravel. Excellent on a slope. Plant with the rosette tilted to shed winter water. Makes new pups happily and they will often come up quite a distance from the parent plant. To 3′ tall when up and established. Great in containers that you protect from winter wet. Move to a covered place in fall- a south facing eave is sufficient. Cold hardy below 0ºF- when established. Best to plant in March or April so that it has the longest possible season to develop a root system going into its first winter. Light summer water to none. High deer resistance.

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