Watering in an era of climate change

hand holding a garden hose spraying water

When thinking of Oregon, a lush, diverse, green landscape with wet winters and comfortable dry summers may come to mind. With the last heatwave, and another one fast approaching, we are beginning to see the start of a new normal. Continual heat waves are going to shift and shape Oregon’s landscape. Gardening in this new era will bring challenges. Having an understanding of plants and how they use water will make it easier to know how to care for your own garden and what to expect in coming years should this pattern of excessive heat and dryness continue.

Preparations before, and correct actions during, a heatwave are essential to help native landscapes survive extreme weather. Following are a few key things to keep in mind about watering during a drought.

In preparation for a heatwave, watering weekly to a depth of at least six inches will help your plants develop deeper root systems that will stay cool and moist in deeper layers of soil.  More frequent shallow watering causes plants to develop shallow root systems, because roots don’t need to grow deeper to reach water. Shallow soil lacks moisture and root protection provided by deeper soil layers. Selecting native plants will help ensure your landscape survives extreme heat, as well-selected native plants are typically more adapted to our droughty summers.

Understanding the source of your water during a drought will help with management of your landscape. If your water comes from a city or town, reaching out to utilities is the best way to figure out how much water you’re able to use. Utilities will also advise on managing household water, which will be equally important during a heatwave emergency. If you’re using well water, an understanding of the depth of the well will help determine how much water you will be able to use. Shallower wells are more susceptible to droughts than deeper ones, but deeper wells take longer to recover after droughts so being aware of that is important too.

Focusing on watering trees and shrubs instead of grasses and perennials will also be more effective long-term than keeping a green lawn. Trees and shrubs are important for maintaining overall landscape temperature and health. They provide cooling shade and food for wildlife during heatwaves and also contribute to overall watershed health, by preventing soil erosion. When rain does return, trees and shrubs, with their extensive root and mycelium network, will help protect the soil from erosion and nutrient loss by binding soil to the land.

Retaining moisture is just as important if not more important than creating it. With this in mind, using a heavy layer of mulch – one to two inches deep around flowers, and three to four inches deep for shrubs and trees – will help keep soil moist for longer and also protect shallow root systems.

Creating shade for native plants will also decrease leaf burn and help create temperature relief on hot days. When temperatures do start to moderate, the immediate urge may be to prune off dead leaves, but try to resist! As hard as it may be to look at burnt leaves and brush, leaving them on the plant will create natural shade and retain moisture for longer.

Being patient and watering plants based on their need for water after a heatwave is important to help plants transition back to wet winter weather and to help them rest and come back again the following spring.