The Pacific Northwest summer has arrived! The sparkling sun on the Salish Sea waters, bright, beautiful flowers blooming in our gardens, zucchini and tomatoes ripening, what’s not to like? Increasingly our summer weather window has widened on each side of the few months we are used to feeling the heat, making June and September hotter and drier than what used to be our normal weather for this time of year. In theory this sounds great until we are dealing with the daily realities of managing our plants and keeping them hydrated and thriving. That is the goal after all – to have a healthy garden.
What does it mean to have a healthy garden in our changing climate? We now encounter record heat at difficult junctions in the garden’s life, like a hot spell in early June when new leaves on our plants are not sun hardy and whose thin cuticles make them vulnerable to sun scald. Or when we find ourselves weary from watering more often beginning in June instead of July and trying to practice water smart techniques at the same time?
Let’s break it down; what is changing and how can we adapt our practices to make our gardens manageable so they can be healthy and we can in turn enjoy them!
Climate Change and Our Gardens
The Pacific Northwest is classified as a maritime climate which means we have the blessing of having cooler summers and warmer winters than by contrast a region in the mid-west of the United States. Our weather is modified by mountain ranges, and especially the Salish Sea including Puget Sound which keeps us from baking all summer and staying frozen all winter. The changing climate of earth is affecting this and we are already experiencing more dramatic weather events which include the following:
- Heavier winter rains rather than the drizzle we associate with the PNW during winter months – potential for floods, erosion, pollution events from stormwater.
- Hotter weather – more extreme heat events in the summer like high temps in June when plants are not hardened off yet – June, July, August, September all are experiencing hotter weather overall.
- Warmer weather during the winter which can exacerbate rainfall events and snow pack loss, affect pest populations, noxious weed populations, and change phenological partnerships between plants and pollinators.
How does this translate to what is going to happen in our gardens?
Heavier rainfall can compact soil, inundate our lawns, erode hillside gardens, wash away nutrients from soil, and wash nutrients into local waterways causing pollution and algal bloom which affects fishes and amphibians. It makes timing on maintenance more difficult if our soil is still water logged when we want to mow, start our veggie gardens, or plant a new tree.
Hotter weather in the summer scalds leaves, causes water stress, and makes it hard to start seeds in a garden bed, as plants cope with increased transpiration from their leaves and soil drying out more quickly. Drought and long term dry weather can affect large trees and shrubs which have benefitted from our now not so common June gloom which helped recharge ground water and support large plants through what used to be two months of drying weather.
Warmer winter weather can affect snow packs, leading to more runoff and complicate heavy storm events. Nutrient loss increases, leads to less available water for summer watering which is also seeing an increase in need, and can stretch the number of generations of plant pests so we have more pests during the growing season. Noxious weeds benefit from increased carbon-dioxide in the atmosphere and can be harder to control, and plant phenology partners of pollinators and flowering plants may become misaligned leading to lack of fertilization in our fruiting plants.
It is predicted that warmer weather will be seen in all seasons but will see a slightly larger temperature increase during the summer months. Extreme heat events are also predicted to be more frequent as we traverse the 21st century. Projected PNW Climate Changes
AgWeatherNet from Washington State University has launched a new app which can help growers in Washington State mange their fruiting crops and assess risk for quality and sunburn risk for their crops because of the changes we are seeing.
What do we do to adapt to these changes?
Rainfall Adaptation
- Pay attention to the weather reports! Get real time weather from a weather station near you: https://weather.wsu.edu/
- Mulch open areas of soil, if you can’t add more plants, to prevent compaction and prevent nutrient loss and keep winter weeds down
- Add more plants to garden beds to break up rainfall, prevent compaction, introduce roots to hold soil in place and to soak up water
- Plant evergreen plants which continue to photosynthesize over the winter and provide more cover for the ground, they will help use ground water and are especially good at breaking up rainfall – and they shelter wildlife as well
- Assess plant placement – if you have areas which get water logged convert them to plantings which can handle wet winter feet – native plants are adapted to wet winter and dry summer settings
- Build rain gardens where soil drains well, install cisterns, build rock filled trenches, to slow rainwater on the land down and prevent erosion and nutrient loss and pollution events from storm drains
- Remove lawns from water soaked areas and convert to native plantings
- Avoid walking on water logged soil to avoid compaction
Hotter Summer Weather Adaptation
- Pay attention to the weather reports! Get real time weather from a weather station near you: https://weather.wsu.edu/
- Use drought resistant plants in your landscape – many PNW native plants succeed through dry weather – try phenotypes of northwest natives from further south like Douglas Fir from southern Oregon
- Keep like water need plants in the same area of your garden beds to make watering easier
- Mulch garden beds of all types to lower evaporation, keep moisture in your soil and cool the soil down
- Make sure plants are well hydrated by checking the soil at root level depths after watering and assess how often you need to water to keep roots cool and moist – once you know your plant’s setting it is easier to follow a watering schedule
- Avoid small containers in sunny areas of your garden unless you are prepared to water them daily
- Set up containers for success – group them together to make them easier to water, install drip irrigation systems, use amended soil with water holding properties, water in the morning to hydrate for the day
- Use tree gators, which wrap around the trunk of a tree and drip water out the base, on valuable smaller trees to keep them slowly hydrated during the driest months
- Use automatic sprinkler timers which have sensors to monitor real time weather
- Avoid using sprinklers at high noon – early morning is ideal to prevent evaporation and if you have to water at night use soaking techniques to avoid wetting leaves which can increase some leaf disease issues
- Water lawns slowly and deeply to get roots hydrated deeper into the soil – 1/2 inch per week – allow to go golden but avoid heavy traffic on dry lawns
- When an extreme weather event is predicted and there is danger of scalding leaves set up shade cloth over vulnerable plants
- Do not prune in high heat events – shaded interior leaves will burn when exposed to bright sun – this is getting harder to do in June for shrubs like Rhododendrons
- Provide water for wildlife – birds benefit from clean and cool water in shallow bowls, bees and butterflies need water too – make mud puddle areas, create bee baths with small water filled containers filled with rocks or colorful marbles
- Assess plant placement – make sure the garden setting has not changed significantly from removal or addition or growth of other plants that will stress your plants out
Warmer Winter Weather Adaptation
- Assess your garden for noxious weeds and remove them to prevent competition with your desired plants
- Grow a diverse garden with plants that bloom in as many seasons as possible with lots of overlap to increase food for pollinators and other beneficial insects – less than 5% of insects in your garden have adverse affects on your plants – most are benign or beneficial in pollinating flowers and eating or parasitizing plant pests
- Know what plant pests are in your garden and what their life cycle is – aim to prevent them from getting to your plants or how to remove them without chemicals
- Stay on top of plant pests – be aware if you have beneficial insects aiding your efforts to control aphids or others and encourage their presence by planting flowers that particular beneficial insect is attracted to
- Keep a journal noting phenology events – when did you first see black bean aphids, or green aphids on your roses, when did you see the first imported cabbage worm butterfly, or the first lady beetles or hover flies, what types of bumble bees are in your garden and are they nesting there – note changes from year to year to see patterns
- Call or email the Garden Hotline or access our resources page for more information
We are all going to be living with the changes happening to our planet and because life on earth is resilient we can help support the beautiful northwest flora and fauna in the ways we manage the landscape.