NATIVE PLANT ADAPTATIONS

Smooth Sumac – Okanagan native plant

HOW ARE NATIVE PLANTS BUILT FOR FIRE?

PONDEROSA PINE (Pinus ponderosa) is one of the clearest examples of a species built for fire.

Mature ponderosas feature thick, plated, corky bark, often several centimetres deep, that insulates the living cambium beneath from the heat of a passing surface fire. The cambium layer is the growth area of the trunk which annually produces new bark and wood in response to hormones.

Pinus ponderosa lower branches self-prune as the tree matures, lifting the canopy out of reach of ground-level flames, and their needles are held in tight, moisture-retentive bundles that resist ignition compared to the fine, resinous foliage of some other conifers.

Below ground, a deep taproot anchors the tree and taps moisture other species can’t reach, letting it stand through drought as well as fire.

Ponderosa forests historically burned every decade or two in low-intensity fires that cleared underbrush without killing the big trees, which is precisely why decades of fire suppression, followed by hot, fuel-laden fire seasons like this one, can be so devastating.

Today’s fires often burn hotter and higher than the ones these trees are built to shrug off.

SMOOTH SUMAC (Rhus glabra) has broad leaves with high moisture content that lack volatile oils found in many xeric plants.

Similar to Ponderosa, Sumac also shed their lower branches as they mature, creating a separation from ground-source fuels.

Sumac spreads by rhizomes, lateral roots that send up new stems some distance from the parent plant, and after a fire top-kills the visible shrub, those root systems resprout vigorously from buds below the soil surface, often producing denser thickets than existed before the burn.

MOCK ORANGE (Philadelphus lewisii) shares this resprouting strategy. Its root crown, the tissue where stem meets root, just at or below ground level, holds dormant buds that are protected from all but the most severe fires.

When top growth is lost, Mock orange resprouts from this crown, often flowering again within a few seasons, making it a valuable presence in post-fire slope stabilization and habitat recovery.

SNOWBRUSH CEANOTHUS (Ceanothus velutinus) has perhaps the most striking relationship with fire of all. Its seeds have such hard, impermeable coats that they can lie dormant in the soil for decades and, by some estimates, over a century, waiting for a cue they may never receive without fire.

The heat of a burn, in the range of roughly 80 to 95°C, scarifies that seed coat and triggers germination, while the fire itself clears competing vegetation and leaves a nutrient-rich ash bed behind.

The result is often a dense flush of Ceanothus seedlings in the first spring after a burn, acting as a nitrogen-fixing pioneer species that helps rebuild soil fertility for the plant community that follows. Snowbrush also resprouts from its root crown, giving it a second pathway back after the flames pass.

Snowbrush Ceanothus growing after forest fire
Matt Lavin | Wikimedia Commons (CC BY-SA 2.0)

For those of us practicing and promoting xeriscaping in the Okanagan, this fire season is a hard but useful reminder of why native, drought-adapted plants belong in FireSmart landscaping conversations, not just water conservation ones.

Species like these didn’t simply survive fire by accident– they built it into their life cycles over thousands of years in our valley.

As recovery begins in the areas affected by this month’s fires, Ponderosa pine, Sumac, Mock orange, and Snowbrush are reclaiming the burned slopes, evidence of these species surviving exactly as they always have.

DIG DEEPER –
For more information, read our blog post on Fire-smart Plant Choices and our in-depth page Okanagan Heat: Helping Your Garden Thrive

The Okanagan Xeriscape Association extends its thoughts to everyone affected by this season’s wildfires, and encourages residents to consult FireSmart BC for guidance on fire-resilient landscaping around homes.

Article by Sigrie Kendrick – a master gardener and executive-director of the non-profit Okanagan Xeriscape Association.

What Okanagan Gardeners Need to Know

Garden chives

Xeriscape Plants to Watch Around Dogs

YUCCA

Few plants say “xeriscape” quite like Yucca, with its architectural rosettes of stiff, sword-like leaves and towering flower spikes. It thrives in poor, rocky soil and needs almost no supplemental water once established making it ideal for Okanagan slopes and gravel beds. Unfortunately, all parts of the plant contain something known as steroidal saponins, and ingestion can cause vomiting, diarrhea, and lethargy in dogs.
The sharp leaf tips are also a mechanical hazard for curious noses and paws.

ALLIUM

The globe-shaped blooms of ornamental Allium are one of my favourite for adding structure and pollinator interest to a xeric border, and the bulbs are remarkably drought-hardy.

But Allium species, including ornamental onion, along with garden chives and garlic, contain compounds that damage red blood cells in dogs, potentially leading to hemolytic anemia, a condition where blood cells burst within the bloodstream.

Bulbs are the most concentrated source of toxins, so dogs that dig, like mine, are at greatest risk. Symptoms may not appear for several days after ingestion, which makes it easy to miss the connection.

Bearded Iris

Bearded Iris requires minimal watering and rewards gardeners with a spectacular early-summer bloom but the entire plant is toxic.

Its rhizomes store enough moisture to shrug off dry spells but also contains irisin, a toxic compound that can cause drooling, vomiting, and diarrhea if chewed.

Most cases are mild, but dogs that make a habit of excavating garden beds should be kept away from Iris plantings.

Yews

Yew hedging is a familiar sight in Okanagan landscapes, prized for its dense, drought-tolerant evergreen structure and tolerance of poor soils and heat.

It is also one of the more dangerous plants on this list.

Nearly every part of the yew, apart from the fleshy red aril around the seed, contains taxine alkaloids that affect the heart and can be fatal in relatively small amounts.

Given how popular yew is in the Okanagan, gardeners with dogs may want to consider whether it belongs near an accessible yard, or whether a safer conifer substitute makes more sense.

Lavender

Lavender is a xeriscape mainstay for good reason. This perennial is fragrant, pollinator-friendly, and content with minimal irrigation.

Lavender contains small amounts of linalool, the consumption of which can cause vomiting, diarrhea, and lethargy in dogs.

Fortunately, most, but not all, dogs are deterred by the strong scent before they eat enough to cause a problem.

Yarrow

Yarrow, our tough, feathery-leaved native is a staple of Okanagan low-water borders.

Yarrow is only mildly toxic to dogs, typically causing vomiting, diarrhea, or excessive drooling if a significant quantity is consumed.

It’s a good example of how “toxic” covers a wide risk range, as yarrow’s risk is far lower than that of yew, but worth knowing all the same.

It should be noted that while almost all Ornamental grasses are non-toxic, Cordyline australis, often used as a centerpiece in annual plantings, is toxic to dogs.

Toxicity in plants exists on a spectrum, from mild gastrointestinal upset to genuine medical emergencies.

The dose your canine consumes matters, a dog that nibbles a leaf is in a very different situation from one that digs up and eats a bulb.

If you suspect your dog has ingested a toxic plant, contact your veterinarian immediately and try to identify the plant involved.

Creating a Dog-Friendly Xeriscape Garden

None of this means abandoning xeriscaping if you share your landscape with a dog.

It simply means being deliberate–

• Fence off higher-risk plantings,
• Choose dog-friendly xeric alternatives like Russian sage, Catmint, or Ornamental grasses for accessible areas
• Know your own dog’s habits.

PLANT OF THE MONTH- September

Salvia farinacea

Hardy only to USDA zones 8–10, ‘Unplugged White’ is grown as an annual here rather than a returning perennial, worth mentioning for gardeners planning multi-year xeric beds who may be expecting a plant that overwinters. Its appeal lies instead in season-long performance, with blooms appearing from late spring through the first hard frost. As an added bonus, this Salvia requires no deadheading to keep flowering, a genuine time-saver for busy gardeners.

Beyond its ornamental value, ‘Unplugged White’ is a strong pollinator plant, attracting bees, butterflies, and hummingbirds throughout its bloom period. It’s also deer-resistant, a practical consideration for many Okanagan properties browsed by visiting deer.

Give Salvia farinacea full sun to light shade and well-drained soil, and it will reward you with reliable structure and colour where many other annuals fade in the summer heat.

As a water-wise annual accent, rather than a permanent xeric structural plant, ‘Unplugged White’ pairs naturally with OXA’s perennial favourites, offering season-long white contrast against the likes of Berberis thunbergii ‘Rose Glow’ and Sambucus racemosa ‘Lemony Lace’.

Our Plant Database features more than 500 plants tested and ideally suited for the unique challenges of gardening in the Okanagan’s extreme climate, including the plants in this article.

GARDENING WITH NATURE

Article by Sigrie Kendrick

Good Intentions Need Good Practice

It is important to provide examples of meaningful ways to provide useful feed for pollinators such as bees.

There is no shortage of goodwill when it comes to helping pollinators. Gardeners across the Okanagan are increasingly aware that bees, butterflies, and other beneficial insects are under pressure, and many are eager to do something meaningful about it.

The question is not whether to act, but how to act effectively. When it comes to pollinator support, good intentions need to be matched with good practice, and good practice begins with understanding what pollinators actually need.

Swallowtail butterfly on Weigela

Prioritize Native Plants for Pollinators

Asters
Photo by Sigrie Kendrick

Provide Blooms Throughout the Growing Season

The Okanagan is home to a remarkable diversity of native flora that serves pollinators across the season.

Early-blooming species like Pulsatilla vulgaris (Pasque flower) and Geum
triflorum (Prairie smoke) bridge the hungry gap of early spring, offering high-quality pollen at precisely the moment when emerging queen bumblebees and solitary bees need it most.

As the season progresses, plants like Balsamorhiza sagittata (Arrowleaf balsamroot) and Penstemon species carry the load through late spring and early summer by supporting both generalist and specialist bee species.

Mid-season support can come from Gaillardia aristata (Blanket flower), and Linum lewissi (Blue flax).

Later-season bloomers such as Monarda fistulosa and various Asters along with Solidago (Goldenrod), are critical for bees building winter reserves.

A garden that staggers bloom times across this full season is doing far more for pollinators than any single showpiece plant ever could.

Pollinator paradise in an Okanagan garden
Photo by Judie Steeves

Think in Sequences, Not a Single Peak of Bloom

Wooly Thyme pathway
Photo by Judie Steeves

Group Plants to Make Foraging Easier

Groupings matter too. Pollinators forage more efficiently when plants are massed rather than scattered. A cluster of five Echinacea is far more useful than five individual plants of five different species dotted randomly across a bed.

When planning or replanting, think in drifts of perennials, generous sweeps of the same plant that a bee can forage systematically before moving on.

Give Pollinators Places to Nest and Overwinter

Nectar and pollen are essential, but pollinators also need places to nest, overwinter, and raise young.

Roughly 70 percent of native bee species are ground-nesters, requiring patches of bare or sparsely vegetated soil in a sunny, well-drained location.

Leaving small areas of the garden unplanted or selectively clearing mulch from a south-facing slope can make a meaningful difference.

Other species nest in hollow stems or pithy wood, so leaving dead stalks standing through winter rather than cutting them to the ground in autumn is one of the simplest and most effective habitat actions available.

Provide Water for Pollinators

Water access for pollinators is often overlooked. Consider adding a shallow dish with pebbles or marbles for bees to land on. A regularly refreshed water source adds another layer of support, particularly during the dry Okanagan summer.

Avoid Pesticides Where Possible

PLANT OF THE MONTH- August

by Sigrie Kendrick

Limonium latifolium, Sea Lavender

A Cloud of Colour for the Dry Garden

If you’re looking to add texture without adding to your water bill, Limonium latifolium deserves a spot on your shortlist. Commonly known as sea lavender or broad-leaved statice, this perennial in the Plumbaginaceae family hails originally from the coasts of southeastern Europe. Surprisingly, its heat and drought tolerance make it a natural fit for the hot, dry summers of the Okanagan.

The plant forms a low, leathery rosette of broad, dark-green leaves close to the ground, from which wiry, branching flower stems rise in mid-to-late summer. These stems erupt into hundreds of tiny lavender-blue blooms, creating an airy, cloud-like haze that seems to float above the foliage. It’s this misty texture rather than any single showy flower that makes sea lavender so valuable in a xeric border, as it softens the sharper forms of companion plants such as Yarrow (Achillea millefolium) or ornamental grasses without competing for water.

Leonora Enking | Wikimedia Commons (CC BY-SA 2.0)

Our Plant Database features more than 500 plants tested and ideally suited for the unique challenges of gardening in the Okanagan’s extreme climate, including the plants in this article.

Have You Ever Watered a Plant…  and It Still Wilted?

Have you ever watered a plant, found the soil still damp, yet watched the leaves wilt anyway?

That plant may not be thirsty– it may be suffering from heat stress.

As Okanagan summers become hotter and heat waves last longer, gardeners are discovering that watering alone isn’t always enough. A plant also needs to be able to tolerate prolonged periods of high temperatures. And that’s where Heat Zones come in.

Rudbeckia ‘Goldsturm’ and a variety of sedum in the OXA demonstration garden during the 2023 extreme heat.  Photos by Judie Steeves

Hardiness Zones vs. Heat Zones

Most gardeners are familiar with Plant Hardiness Zones, which tell us how well a plant can survive the coldest temperatures of winter. A lack of cold hardiness in plants generally results in dramatic winter kill.

But cold isn’t the only stress a plant has to survive– summer heat leaves its own mark, just less obviously. The effects of heat stress on a plant occur at the cellular level, resulting in wilting, dieback, and flower damage. The effects often mimic drought stress but with wet soil.

Fewer people know about Heat Zones. Developed by the American Horticultural Society (AHS), Heat Zones are based on the average number of days per year when temperatures reach or exceed 30°C

While hardiness tells us whether a plant can survive winter, heat zones help us understand how well it can cope with prolonged summer heat. Plants may wilt, leaves may scorch, flowers may fade, or stems may die back– even when the soil still contains adequate moisture.

That’s because extreme heat affects how plants function, making it difficult for them to keep up with water loss during prolonged hot weather.

Plants chosen with heat tolerance in mind for the full sun setting in the UnH2O demonstration gardens

Why Heat Zones for Plants Matter in the Okanagan

That doesn’t mean every plant rated below Heat Zone 5 will suddenly fail. It does mean that heat tolerance is becoming an increasingly important consideration when choosing plants for Okanagan gardens.

How OXA Rates Heat Tolerance

Plant growers and horticultural references may provide heat zone ratings to indicate a plant’s tolerance to summer heat. Rather than asking gardeners to interpret those numerical ratings, OXA has translated them into simple, easy-to-understand categories in our Plant Database: Poor, Fair, Good, and Excellent.

These simplified ratings make it easier for Okanagan gardeners to compare plants and choose species better suited to today’s hotter summers. They are included in the Notes section for individual plants.

Every plant in OXA’s Plant Database is rated to withstand at least AHS Heat Zone 6, which gives a buffer for the Zone 5 designation.

Plants with a Poor heat-resistance rating may already struggle during our hottest summers, while those rated Fair, Good, or Excellent are generally better equipped to cope with prolonged heat.

Article prepared by Okanagan Xeriscape Association, with contributions from Mark Godlewski

Learn More

Heat tolerance is just one of many factors to consider when selecting plants. Soil conditions, exposure, irrigation, and winter hardiness all play important roles as well.

Explore OXA’s Plant Database to compare heat resistance ratings, or return to our companion guide, Okanagan Heat: Helping Your Garden Thrive, to learn more about creating climate resilient landscapes for the future.

PLANT OF THE MONTH- July

by Sigrie Kendrick

Buddleia davidii, Butterfly Bush

For xeriscapers seeking a compact, drought-tolerant shrub that pulls its weight for pollinators, Buddleia davidii (Butterfly bush) ‘Buzz Hot Raspberry’ deserves a close look. Bred as part of the dwarf Buzz series, this cultivar tops out at just 3 to 4 feet, making it a great choice for smaller water-wise beds where a full-sized butterfly bush would overwhelm the design.

The appeal for pollinators is substantial. From early summer through fall, ‘Buzz Hot Raspberry’ produces long, fragrant, cone-shaped flower spikes in vivid magenta-pink. This nectar source draws honeybees, bumblebees, hummingbird moths, and a wide range of butterfly species, including swallowtails and red admirals. Once established, the plant asks for little except full sun, sharp drainage, and only occasional supplemental water, making it a fantastic addition to a drought-tolerant landscape.

A caveat belongs alongside the praise. While Buzz cultivars are marketed and bred for reduced seed production compared to the wild species, Buddleia davidii itself is documented as naturalized and locally invasive across parts of British Columbia, including sensitive Garry Oak ecosystems on Vancouver Island. Unlike a handful of confirmed sterile cultivars on the market, Buzz series plants are not verified seedless so responsible placement matters. Prompt deadheading before seed set, avoiding proximity to natural areas or waterways, and monitoring for volunteer seedlings are worthwhile practices for any gardener choosing this shrub.

Used thoughtfully, ‘Buzz Hot Raspberry’ can be a vibrant, high-reward addition to a contained residential xeriscape bed. Gardeners prioritizing ecological caution, however, may prefer to substitute native nectar shrubs such as Ceanothus velutinus or Philadelphus lewisii, which offer comparable pollinator benefits without the risk. of naturalization 

Our Plant Database features more than 500 plants tested and ideally suited for the unique challenges of gardening in the Okanagan’s extreme climate, including the plants in this article.