CORVALLIS, Ore. – As the hot summer days approach, you will want to keep an eye on the health of your landscape plants.
"Summer drought is normal in the Willamette Valley, so that will be an issue every year," said Neil Bell, a horticulturist with the Oregon State University Extension Service. "If there are a greater number of days in which the temperature exceeds 90 degrees, the stress on plants increases."
Bell offered the following advice to tend to your plants and conserve water when the mercury rises for extended periods of time:
- Water your landscape strategically. Water early in the morning when temperatures are lower. Water plants infrequently and deeply prior to and during drought. Saturate the area to a depth of 8 to 10 inches. For lawns, add one-half to three-fourths-of-an-inch of water per week, or let lawns go brown during the heat of the summer.
- Put the right plant in the right place. Design your landscape so that your plants won't compete with each other for shade and water. In other words, group plants with similar requirements for light and water in the same location.
- Prepare the soil adequately. Good quality soil helps retain moisture in times of drought. When you dig in, makes sure you can break up the soil easily, a sign that water can penetrate into the soil with no trouble. When air and water can't move through the soil easily, plants can experience problems with diseases and root growth. To build good quality soil, add organic matter such as composted yard trimmings, composted manure and leaves from deciduous trees.
- Mulch to conserve water. "Mulches are like putting a lid on a pot that's boiling and preventing it from evaporating quite as readily," Bell said. "They're not a substitute for irrigation, but they do help retain water in the soil." Place a 3- to 5-inch thick layer of mulch on the soil. Mulches could include shredded bark, bark chips or grass clippings. As these mulch materials decompose, organic matter is added to the soil.
- Choose plants that don't get thirsty in the summer. Some plants are so drought-tolerant that they only need winter rains to be happy and no irrigation at all during summer. Cold-tolerant varieties native to the Mediterranean region or native plants of the Pacific Northwest are good choices, Bell said. For groundcovers, these include Point Reyes ceanothus, also known as Ceanothus gloriosus, and carpet broom, also known as Genista pilosa. As for shrubs, Bell recommends the varieties below, which are followed by their scientific names:
- Dwarf Strawberry bush, Arbutus unedo Compacta
- Wild lilac, Ceanothus Victoria
- Rockrose, Cistus x hybridus
- Sunrose, Helianthemum nummularium
- Flowering currant, Ribes sanguineum
- Lavender, Lavandula spp.
For more information about mulching and gardening during a drought, view the following OSU Extension guides:
- Conserving Water in the Garden: Designing and Installing a New Landscape (pdf)
- Conserving Water in the Garden: Landscape and Lawn Care (pdf)
- Mulching Woody Ornamentals with Organic Materials (pdf)
Also check out the courses below from OSU's Professional and Continuing Education unit: