Heat Tolerant Plants of the Pacific Northwest

Landscape designers have a new concern, as do gardening gurus and nurserymen:  understanding the heat tolerance of our native and cultivated plants. This past summer was a pressure cooker, not only for drought but also for a week of intense temperatures. This affected people, plants and animals. Plants help to cool the planet, yet in an ever-changing climate, what plant goes where? A landscape designer with a strong knowledge of plant and tree temperature tolerance can help assure you of a successful outdoor habitat.

 Some of the old rules apply when specifying and selecting plants for drought and heat, but not all of them, such as “the larger the leaf, the less sun and heat a plant can tolerate”. We still need to pay attention to the micro-climate from the urban heat of asphalt and concrete to the surrounding tree canopy. Intense heat can be hard on many plants even when adequately watered. Also, overly wet roots can be damaging for many plants especially conifers-when heat is intense their water uptake often shuts down.

Fleshy leaves, such as sedums and agaves tend to store more water in their cells. A plant such as a large leaved Rhododendron or a Camellia japonica may have thick leaves but they are not fleshy—they took a real hit last summer, especially if their micro-climate was baking. They also appreciate water. For trees, deep water is the best way to prepare for hot weather, especially during drought. Yet, depending on their micro-climate, even though deciduous tree leaves can burn in extreme heat and leave an undesirable specimen– rest assured, if they are well established, most of them should leaf out in the spring, that is, if they were watered deeply.

In general, heat tolerant plants thriving in a sunny location have very small leaves or are fleshy, but not always.  Some are very drought tolerant and others are not. Established plants fair better. Also, many of these plants are hummingbird and bee magnets.

Heat Tolerant Plants and Trees:

Agave varieties

Blue fescue grass-Festucca glauca (water a bit)

California lilac-Ceanothus varieties, both large and groundcover type, native and non-native.

Coyote bush-Baccharis-native to southwestern Oregon

Douglas Fir-Pseudotsuga menziesii

Dogwood tree-Cornus tree varieties (water deep)

Epilobium (Zauchineria)- california fuchsia varieties, native and non-native

Heath-Erica (also known as heather-water a bit)

Heather-Calluna (water a bit)

Hens and Chicks-Sempervirens

Huckleberry, evergreen-Vaccinium ovatum (native and in the shade)

Lavender cotton-Santolina varieties

Japanese false Camellia-Stewartia (water deep)

Kaminski milkwort-Polygala c. ‘Kaminski’ (water a bit)

Lavenders-Lavendula varieties

Manzanita-Arctostaphylos varieties, both large and the ground cover kinnickinnick, native and non-native. These appreciate good drainage, planted in a quarter-ten gravel/soil mix.

Oak-Quercus Northwest natives (water deep)

Oregon grape (The tall one)-Mahonia (native and in the shade)

Pine-Pinus, especially Northwest native pines such as lodgepole (contorta) and Ponderosa

Red hot poker-Kniphophia varieties

Rockrose-Cistus varieties

Rosmary-Rosemarinus varieties, large and small

Russian sage-Perovskia varieties

Sedum varieties

Smoke tree-Cotinus varieties

Snowberry-Syphorocarpus alba (native and in the shade)

Strawberry tree-Arbutus unedo varieties

Sunrose-Helianthemum (water a bit)

Juniper-Juniperus varieties, all trees and shrubs

Yucca varieties

  • In addition, roses and peonies seem to be an exception to the rule—they survive and bloom even with burnt leaves. Hydrangeas and deciduous blueberries cooked and many ferns, native and non-native took a hit. Native sword fern, in the shade performed fairly well.

The Lawn-Less Yard

Creating a lawn-free garden can be a challenge. Turf grass lawns are nice for kids to play on, but they are not always necessary for play. Especially if there is a park, woodland or schoolyard nearby. Lawn maintenance is constant whether you are paying for a lawn service of doing your own mowing. In the growing season mowing is required weekly. If the lawn has been rained on, mowing can create a muddy mess. Turf grass will struggle and thin due to a lack of sun and/or poor draining. In some situations it never looks good no matter what you do. These photos of gardens devoid of lawn may provide some insights for alternatives to the standard turf.

Drought Tolerant Plants for Portland, Oregon

Contrary to local garden geek beliefs (myself included), this year of unprecedented drought has brought to light that many plants thought to be drought tolerant, are certainly not. This includes Hebe, Crocosmia (Montbrecia), Rudbekia (black-eyed Susan) and Echinacea (purple coneflower).

I have composed my own drought tolerant list based on my observations in established gardens this year. They are listed according to drought tolerance in the sun or shade.

2015 Extreme Drought Tolerance List

Shrubs and Trees for Sun

Acer griseum-paper-bark maple
Acer rubrum-red maple
Arbutus unedo ‘Compacts’-dwarf strawberry tree
Actostaphyllos varieties and natives-manzanita
Carpenteria californica-Sierra bush anemone (native to Calif)
Ceanothus thrysiflorus-California lilac (native to Southern Oregon & Calif)
Cistus purpurea and other varieties-rockrose
Cotinus coggygria varieties-smoke tree
Cupressus-Some cypress
Lagerstromeria indica-crepe myrtle
Lavendula varieties-lavender, English & Spanish
Lonicera varieties-Honeysuckle shrub & vine
Nandina varieties, especially ‘Sienna Sunrise’, ‘Moyer’s Red’ & ‘Plum Passion’.
Rosemarinus varieties-rosemary
Roses-shrub and rambler
Senecio greyi varieties-ragwort

Perennials for Sun

Achillea varieties-yarrow varieties
Aescelpis-native milkweed varieties, butterfly weed
Artemesia varieties-wormwood
Erisimum linefolium varieties-wallflower
Kniphofia varieties-red-hot poker
Penstemon rupicola-rockery penstemon
Salvia varieties-hardy salvia or sage varieties
Santolina varieties-lavender cotton
Sedum varieties-stonecrop  and of coarse,  Yucca varieties

Shrubs and Trees for Shade

Camellia japonica & sasanqua
Choysia varieties-Mexican orange ‘Sundance’ & ‘Aztec Pearl’
Elaeanagus varieties-silverberry, Russian olive
Leucothoe varieties-drooping & Sierra
Lonicera varieties-shrubs
Mahonia varieties-Native Oregon grape and others
Ribes sanguineum-red flowering currant (native)
Sarcococca varieties-sweet box
Thuja plicata-Western red cedar (native)
Vaccinium ovatum-evergreen huckleberry (native)

Ferns, Groundcovers, Perennials and Sedges for Shade

Carex oshimensis ‘Evergold’-’Evergold’ variegated Japanese sedge
Dryopteris seteferum-Alaska fern
Epimedium varieties-barrenwort
Oxalis oreganum-native shamrock plant
Polystichum minutum-western sword fern (native)

Plant Densely, Tread Softly

Bark dust is not a groundcover. It is a type of mulch. Its purpose is to deter weeds and reduce evaporation. It is temporary until new plants cover the soil. Groundcover plants eventually knit and cover the bare earth holding moisture for themselves and the planting layers above them.

Layered and dense plantings provide habitat, visual interest and shade. If you prefer a more sparse planting arrangement keep it simple with 2 or 3 shrub varieties, well spaced, but with a dense groundcover. Dense plantings are beneficial to the soil, their roots breaking up clay and encouraging beneficial microbial activity in the soil.

Just as medical science has uncovered the good bacteria in our bodies, soil scientists have discovered wondrous activity underfoot. Soil mycorrhiza is a fungus that has a symbiotic relationship with plant roots-it is an important part of soil and plant life. A soil wasteland of bark dust with little in the way of plant life is basically dead soil especially if it has been tilled, scraped or re-graded. Tilling exposes soil mycorrhiza to air and heat destroying the soil’s microbial life.

It can take years to renew damaged soil but it can be done with the proper compost and plants. Letting leaves lie can help build better soil. Ground beetles and sow bugs feed on dead leaves breaking them down into smaller particles that enrich the soil. Salamanders can slink unseen under damp leaves. Fallen leaves provide cover for nesting bumblebees.
As with the vast unknown under our oceans and in our heavens, beneath our feet there is a whole other world.


‘The Soil Will Save Us” by Kristin Ohlson

“The Know Maintenance Perennial Garden” by Roy Diblik

Winter Flowers in the Pacific Northwest

In so many areas of the country, particularly in the North, Winter can be dreary in the garden. Interest is derived from twiggy and grassy texture, colored dogwood twigs, foliage variations, berries and the lovely peeling bark of some trees. Here in the Pacific Northwest we do have plants that bloom in the winter. Our winters are soggy and wet but they are usually mild in temperature.  Many of us tend to ignore our gardens in the Winter. Add a winter- blooming plant on the path  where you travel to your door or outside your windows. Many of these plants attract  winter migrating hummingbirds at a time when they need nectar the most. On warmer days the hibernating bees will wake up to gather pollen. But don’t be fooled with the birds and the bees. We have a way to go until Spring.

Fall Color in the Pacific Northwest

Fall color can vary depending on the weather and where you live. Trees that are stressed may color-up early just from the lack of water. This year in the Pacific Northwest the autumn foliage is pretty astonishing. We typically show a lot of yellow foliage but this fall, after a very warm summer, there is an abundance of reds!

In addition to foliage color there are many plants that bloom in the fall, providing late pollen for bees and nectar for hummingbirds.

Our native vine maple offers a variety of fall color.

Japanese false camellia tree, (Stewartia pseodocamellia ), is known for its autumn color, exfoliating bark and white flowers in spring. This tree has it all and it is small and not prone to damage from wind or snow.

Red maple (Acer rubrum) is the tree that contributes the greatest to New England’s famous fall color. This tree is tough and takes both wet and drought. It is no longer on the City street tree list due to its popularity. By diversifying our street tree plantings we can prevent disease from spreading.

Camellia sasanqua ‘Apple Blossom’ blooms from fall into winter and provides late pollen that bees need for wintering over. It also attracts hummingbirds, even with a light dusting of snow!

Beauty berry (Calicarpa b. ‘Profusion’) berries provide a color that is seldom seen in the fall.

The soft yellow foliage of this Japanese katsura tree (cercydiphyllum japonicum)stands out against an evergreen background and the red of a sourwood tree (Oxydendrum arboreum).

One of the very best large shrubs for fall color is the smoke tree ‘Grace’ (cotinus coggygria ‘Grace’). They are almost a coral color.

The dwarf strawberry tree (Arbutus unedo ‘Compacta’) has both fruit for birds and other critters and flowers for hummingbirds.

Nyssa sylvatica, the Tupelo Tree has some of the best fall color of any tree.

Oak leaf hydranga (a very large shrub) can have fall color ranging from red to plum.

This Persian ironwood tree is just starting to turn. It is known to be the most reliable fall color, whatever the weather.

Maryhill Museum: Art in the Garden

This summer I stopped at Maryhill Museum on the way up to Wenatchee. I had not been there in years. The new wing and grounds are inspiring with the backdrop of the Columbia Gorge. Outdoor sculptures set against against cliffs, river and sky is a awe-inspiring must see. A show at the museum featured James Lee Hansen. (I took sculpture classes from him at PSU back in the late 70′s.) What a fantastic journey he has led in his life of making art. He is known as one of the most prolific sculptors in the Pacific Northwest.Seeing this show stirred up all my thoughts of sculpture in the garden, placement and mass. Human-sized pieces seem to work best unless you can elevate a piece to eye level.  Although the pieces are abstract, they are filled with symbolism and history for both the artist and the viewer.

An added benefit of the Museum was a tour on July 12th of James Hansen’s home, garden, gallery and studio in Ridgefield, Washington. I am amazed at the amount of work that he has produced.


The  photos of sculptures are at Maryhill, James Hansen’s home. Note the windblown pod is not his work but it is fun to see.

A Garden Design Review

This garden will be featured in ANLD’s Garden Tour June 28, 2014.

Donna Giguere provided a complete redesign of our property (hardscape and plantings), helped us find a landscape contractor, and assured proper installation in both the front and back yards. We live in a 110-year-old house in the inner city of Portland. Donna’s design struck the right balance between a clean, modern look that still complements the historic architecture of our home and neighborhood. Our contractor, Patrick Handley was very skilled at working with a variety of materials used to create this garden.
One of the major problems was that we often could not find street parking near our house. We are avid bicyclists and own one car. We needed to carve out a parking space in our 38 foot wide lot that met the city setback and looked nice. The parking space created a steep slope that required retaining walls and rainwater mitigation but it looks great. We also added a ramped path for the ease of moving bicycles and trash cans.
In the backyard there were 2 trees, dead sod, and a dilapidated deck. That was it. A place to BBQ, dine and relax was desired. The new deck provides a cooking space. The patio addresses dining and relaxing by the fire-pit. The large gas fire-pit, centered on the kitchen doors, may also be viewed from the kitchen. A gravel space is for relaxing in the hammock under the great magnolia tree. A Mondo grass lawn provides a cool place for the dog to sprawl.

Some features of our new landscape are all of the rainwater is handled on-site through the employment of a rain garden swale, drywells and a permeable paver parking space. There is no lawn and the plantings are low in maintenance. This garden clearly displays how much versatility can be created in a small space.

The style of the garden in the front yard is a fusion of Modern and Craftsman. A bio-swale, the absence of lawn, the simple planting style and plant selections are a considered Modern element. The dyed and molded concrete walls and acid etched concrete steps are reminiscent of an older time to meet the style of the 1908 home.
In the backyard most of the garden elements are clean and geometric evoking a Modern Style. Rustic elements do intersect though as seen in the rough stone corner of the fire-pit and the Craftsman Style gate. The deck, created of 100% Timbertech PVC with cedar flows into the yard. The deck has multi-purpose platforms that can be used for seating, pots or for serving. The very old large trees (sycamore maple & saucer magnolia) and the borrowed view of the brick condos neighboring the garden add a sense of history.
We like that our garden has year-round beauty with leaf color and textural variations to create interest. For ease of maintenance, perennials are at a minimum. This is a garden for serenity. Small grasses are a favorite. We appreciate anything that flowers in the winter such as the Camellia sasanqua ‘Shi-Shi Gashira’ espaliered against the back fence. A few blueberry bushes and evergreen huckleberries provide some nibbles. With the tall close-set homes and large trees there is not much sun in this garden. Beside the front porch there is enough sun for a small vegetable garden. Notice the “lawn” in the front parking strip of Leptinella squalida (brass buttons). This works well as long as it is confined.

We are truly happy with our new space and love to relax and entertain there. I have recommended Donna to admiring neighbors and friends and will continue to do so.

Mother’s Day Gifts: A Plant That Endures

We often give blooming plants for Mother’s Day but if it’s a pot of tulips or a greenhouse forced lily or mums, after a while they wither away and look downright sad.  What about small plants that will look good in a pot year after year? She can also plant them out in the garden when they outgrow their pots. Some of my all- time favorites for the Pacific Northwest are: Heucherella ‘Sweet Tea’, Lonicera nitida ‘Twiggy’ and Carex oshimensis ‘Everillo. Put these 3 together in a large patio pot for year-round color and interesting textural  contrast. This combination can take some shade so if she has a covered patio, all the better.

In a sunny situation you might try a Yucca ‘Bright Edge’ with Sedum ‘Angelina’ and Sempervirens ‘Old Copper’ (hens & Chicks). This combination can withstand extremes so if she forgets to water they’ll be sure to survive. Again, she’ll have year-round interest and textural interest.

Go ahead. Impress your Mom!

Top 7 Spring Garden Ideas for Portland

Want easy and practical gardening tasks can you do to spruce up your garden this spring?

  1. If you have a lawn edge it, especially along the planting beds. Alternatively, get rid of your lawn. If you have trees remove any lawn beneath them-they will perform better.  For shaping your lawn, large broad curves and/or straight lines work best. Think of a distinct shape like a bean, oval or a rectangle. Little jogs and small shapes look messy.
  2. Work on your pathways initially by accessing their lines-do they make sense?  What is their purpose? Are they for traveling quickly, taking out the trash or for leading the eye and creating a serene walk? Where will they drain or are they permeable? Paths may be  gravel with edging, stone, concrete, pavers or tree grindings. Gravel paths should be at least 30 inches wide-I recommend 1/4 minus (with fines) and nothing else. Here in the Pacific Northwest the most available gravel will be crushed basalt rock since access to large quantities of granite gravel is difficult and expensive here.
  3. Widen your beds! You’ll have better air circulation and less pruning. Planting beds should be at least 36 inches deep, unless you have a structural obstruction. If your beds have to be skinny, select plants that stay small.
  4. Remove the plants that are not performing well. If you have tried to revive them for 3 or 4 years and nothing is working, relocate them,  give them away, or turn them into compost. Try a native plant in their place. Native plants aren’t perfect either but they do take less care and if sited correctly, thrive on neglect.
  5. Create a planting design in layers. There should be a tree canopy, large and small shrubs, lower plantings such as perennials and ground covers. Access the plants’ mature size yet be aware that by planting densely you will be deterring weeds (less sunlight reaching the ground) and preventing evaporation (reducing irrigation).  Using native plants will attract native pollinating insects and birds. You’ll be doing something good for our fragile ecosystem especially if you live in an urban environment.
  6. Clean up the patio and outdoor furniture or find something new to you. Site a bench for the best view or create a meditative relaxing spot for your own “time out”. A few outdoor pillows here and there will brighten things up.
  7. Mulch your beds for weed suppression and water retention. Mulch can be a variety of materials depending on your gardening style. The most common mulch is bark dust-hemlock bark does not have slivers. You may also use compost as mulch-it will enrich your beds but may not suppress weeds as well as other mulches. Tree grindings from the chipper work well too but they are fresh and do pull nitrogen from the soil-a gardener that I know uses mushroom compost under the grindings to offset the nitrogen loss. 1/4 ten (washed) gravel makes a good mulch especially for plants that hate wet feet such as heaths and heathers.

Get outside!