Seattle is better known for its rainy climate than searing temperatures, and it's a local joke that our summer begins on July 5th (the day after we huddle around bonfires to stay warm as we celebrate Independence Day). So when we hit well over 100'F for several consecutive days last week there was an initial sense of disbelief rapidly followed by concern as neither our homes nor our gardens are set up for Texas-type conditions.
While I did design my garden with drought tolerance in mind, it was assuming our typical weather pattern that would gradually build from the 70's to the 90' over the course of a few months, giving everything a chance to adapt and newly planted annuals time to get established. This year not only did we hit a record-breaking temperature of 109'F in Duvall, I wasn't even at home to water during that time.
Surprisingly the damage was relatively minor, with only a few things showing leaf scorch and no dead bodies. Hydrangeas took the hardest hit, specifically two that have been placed in the shadow of a young paperbark maple which will eventually cast afternoon shade but whose canopy is still too small to be effective. Other hydrangeas did fine – not even any wilting, so my mulching and 'right plant-right place' must be working.
What really shocked me was how well my annuals did. I knew those in containers that were fitted with drip irrigation would fare reasonably well and was also confident that most succulents and silver leaved annuals such as licorice plant (Helichrysum ) and wormwood (Artemisia) wouldn't be fazed, but what about the others?
I'm a fairly recent convert to zinnias, never having liked the jellybean 'Profusion ' series, finding them gaudy, too short for cutting, and having less-than-exciting foliage. That all changed when I saw a display of Benary's giant coral zinnias a few years ago – especially when I discovered that they were reputedly deer resistant and drought tolerant. For the past two years I grown a color blend that Renee's Garden produces called Apricot Blush. This is also a taller variety and the many shades from pale apricot to tangerine are playful without being brash. I only planted these out in June so they had relatively little time to establish before being tested by fire – yet they not only continued to bloom, they bloomed prolifically and show no sign of leaf scorch at all.
The same can be said for a compact variety that was new to me this year; Profusion Red Yellow Bicolor. This compact, well branched variety fades to the most delicious shades of orange, coral and pink. I struggled to control slug damage during June when they were first planted but otherwise these have not only been trouble free they have been quite exceptional performers.
I grew both these zinnia from seed in early spring.
Tobacco plants (Nicotiana spp.) have been a favorite of gardeners for decades and I have grown many different species and varieties, but the jasmine tobacco (Nicotiana alata) is my favorite. At 4-feet-tall this is excellent for the middle of the border where the tall spikes of starry white flowers create a diaphanous effect, yet the faded blooms do not distract from the display. Be sure to site these where you can appreciate the seductive jasmine fragrance that is released in the evening.
The large green basal leaves may need slug protection when the plants are young but these annuals are fast growers and seem to out-compete the pests quickly. Rabbits and deer rarely bother these although a friend in eastern WA commented that for the first time deer had browsed hers this year, possibly because they were planted alongside their usual route through the garden and also because "deer pressure is pretty intense this year probably due to the dryness of the fields and woods nearby".
I expected these to be fried after our excessively high temperatures and lack of water – but they were in full bloom and showed no signs of damage from the intense sun. Remarkable.
Incidentally, these have self-seeded from plants I grew in the same spot last year! Maybe that helped them get a deep root system earlier which helped them thrive?
Yes, your grandma knew what she was doing when she planted sweet alyssum (Lobularia maritima) in her garden. Sweet fragrance, deer-resistant, rabbit-resistant, attracts pollinators, blooms for months, and is drought tolerant. I wasn't sure how it would fare last week but when I returned from my trip it had almost doubled in size, was in full bloom and showed no signs of wilting or sun scorch. The variety I purchased this year was Wonderland White – I'd be curious to know if other varieties would do as well.
Incidentally, I usually buy these as young plants but my mum grew them every year from seed. I'd love to have your tips on growing these from seed if you've been successful (one of those random things I wish I'd asked Mum when I could).
Other Notable Superstars
A perennial in warmer climates, tall verbena (Verbena bonariensis) self-seeds in my garden but the 'mother plant' typically dies after just one year, hence my reason for including it here as an annual. It allows for some exciting yet serendipitous combinations – I'm never quite sure where it will pop up from one year to the next, but I always love the see-through scrim effect it creates in the garden and unwanted babies are very easy to thin out or remove.
Thriving in Mediterranean conditions its survival was not a surprise to me but I've included it in case you have been curious. The smaller variety 'Lollipop' also does well in these harsh conditions.
Deer-resistant, rabbit-resistant, and gives you free plants – a winner!
There are many species and named varieties of Sage (Salvia) and some which are annuals in my garden may well be woody perennials for you. I find the larger hybrids e.g. Wendy's Wish, Amistad, Embers Wish to offer exceptional value in both containers and the landscape plus the hummingbirds love them. This year I have added two of the Skyscraper series to a patio bed and both came through the heatwave and lack of water without a hitch even though one of them was only planted two weeks beforehand.
Share your ideas
Which annuals have you discovered to be reliably heat tolerant and able to withstand up to one week without supplemental water? I'd love to know.