Posts Tagged: drought
• Your trees come first! If there just isn't enough water to go around, your lawn and flowers should be sacrificed instead. Trees are our most valuable landscape resource and take years to maximize their benefits (shade, cooling, habitat/ecosystem enhancement, carbon dioxide storage, etc.).
• Spread and maintain 2-4” of mulch around garden plants and trees (3-4” for wood chips, 2” for pebbles, decomposed gravel, etc.) keeping it a few inches away from tree trunks.
• Water early in the morning when soil evaporation is minimal.
• Control weeds. They compete with other plants for water.
• Avoid fertilizing. Nitrogen increases growth and the need for more water.
• Don't plant new plants during the summer when temperatures are highest. Even drought-resistant native and non-native plants need regular watering their first season.
During the drought, your trees should come first! Because many well-maintained trees don't reach their prime until their 4th or 5th decade, it's important to keep them watered during the drought and water restrictions. Older trees absorb higher levels of carbon dioxide, do a better job of cooling urban heat islands and providing shade. They also filter air and water pollutants, reduce soil and water erosion, provide habitat for wildlife, enhance privacy, beautify neighborhoods and parks, enhance property values, and even improve mental and emotional health. Trees are worth saving! The price of starting over is just too steep.
Recognizing early signs of drought stress is important because irreversible damage can occur that no amount of watering will correct. If you cash in your grass for a water district rebate, remember to water any trees that relied on water from the lawn sprinklers. This is because tree roots grow laterally quite a distance, often well beyond the dripline of the tree under the lawn. Over time, start watering them more deeply and less often to encourage deeper roots and enhanced stability.
Just a few deep waterings in mornings or late evenings with a garden hose during spring and summer can keep a tree alive, even during a drought. Keep the trunk dry and water from the mid-dripline outward. Apply a slow steady stream of water, moving the hose to another section of the tree every 1-2 hours. Another inexpensive way to water your trees is to encircle them with soaker hoses that connect to a garden hose. The soaker hose should be in concentric rings about one foot apart starting two feet away from the trunk for a larger tree, closer for a more recently planted tree with a more confined root system.
Check trees regularly for these common symptoms of water stress:
• Wilting or drooping leaves that don't return to normal by evening
• Yellow, brown or sometimes gray leaves that may drop from the tree
• Small new foliage and stunted overall tree growth
Other ways to reduce tree water loss include:
• Keep weeds out (they compete for water
• Maintain a 3-4” of organic mulch or 2” layer of inorganic mulch (pebbles, decomposed gravel) around your trees, starting a few inches away from the trunk outward.
• Avoid fertilizing since that increases their water need.
• Do only necessary pruning (to remove dead wood and any dangerous limbs that look like they might fail) since this stresses the tree and can increase its water need.
UC Resources at Your Fingertips:
Free Download Publications: https://anrcatalog.ucanr.edu
-Keeping Plants Alive Under Drought and Water Restrictions
-Sustainable Landscaping in California
-Lawn Watering Guide for California
-Use of Graywater in CA Landscapes -
CA Institute for Water Resources: http://ciwr.ucanr.edu/ (blogs, climate-smart ag, podcasts, etc.)
UC Cooperative Extension Master Gardener Program:
For more drought tips and help with your home gardening questions, contact a UCCE Master Gardener volunteer. Find your local program atucanr.edu/FindUs/
Our population of urban trees is shrinking! You can help turn this around by protecting your own trees and by planting new ones recommended for your climate and the conditions around your home. For more on this topic, please revisit my February blog for specific selection and care recommendations: https://ucanr.edu/b/~ZuB.
In addition, please encourage your city to plant a wide range of recommended species today for a healthier tomorrow. Why is this so important? Many of our current street trees are in the 11th hour of their lifespans. While some that were planted decades ago are simply aging naturally, in other cases, they are perishing prematurely due to poor selection and care. This leads to a downward spiral; trees not adapted to the climate they're planted in and not receiving proper care are much more susceptible to invasive pests (shot-hole borers, etc.) and diseases than are healthy, well- chosen and maintained trees. Even the loss of one front yard shade tree can significantly reduce shade, increase the surrounding temperature, and diminish energy savings.
Another reason we're losing our trees is due to the negative impacts of urban heat islands (UHIs) which shorten the lifespan of many species of trees dramatically. Some trees (even many natives!) just aren't able to withstand the higher temperatures (sometimes exceeding 20 degrees) they are subjected to due to UHIs.
What are urban heat islands and why should we care? Urban heat islands are caused by reradiated heat from paved concrete and (especially) asphalt surfaces.
And, our cities are growing and expanding. Very few Southern California residents reside in rural areas. Instead of living near pastures, field-filled crops, and forests that cool the surrounding area through evapotranspiration, the vast majority of us reside in warmer urban city centers. Conditions we expect our city trees to endure in 2021 are very different from even 20 to 30 years alone, let alone decades ago.
The good news is that, through proper tree selection and care, we can be a part of the solution. In fact, trees offer many benefits that offset the impacts of UHIs. Cities with larger tree canopies are a testament to this fact and have fewer adverse impacts from UHIs than do cities with low tree canopies. Trees reduce the impact of UHIs by shading parking lots, buildings, and vehicles), deflecting the sun's radiation, and cooling the atmosphere through evapotranspiration. Trees also absorb and store carbon which lessens the impacts of pollution from fossil fuels. A well-tended mature landscape tree can absorb 40 tons of carbon over its lifespan.
The solution? Augment our current urban tree palettes with heat, drought, and pest-resistant native and adapted non-native species. A case in point of a native tree in trouble is our beautiful Joshua trees (Yucca brevifolia) which are dying off in their namesake National Park and seeding 500 or more feet higher elevation than parent plants. Planting trees that withstand UHIs today is crucial for tomorrow.
We are well on the way to identifying landscape tree species that can remain healthy under adverse urban conditions. In our study examining the performance of 12 species of underplanted but promising landscape trees, several candidates are standing out for their heat, drought, and pest resistance.
Landscape trees provide shade, cool urban heat islands, reduce interior energy use and related costs, provide habitat for pollinators and wildlife, and beautify our communities. They also help clean our environment by absorbing carbon dioxide emitted by vehicles and other producers of fossil fuels.
Taking care of our urban trees is an important way to maximize these benefits. Unfortunately, their average lifespan in our cities is less than 1/4 of their potential due to poor selection and care. You can help enact change and increase the health, longevity and canopy coverage of our urban forests by encouraging your city leaders, local non-profit organizations interested in ‘green cities' arborists, landscape architects, nursery growers, HOAs, and concerned citizens to register for our free ‘Trees for Tomorrow Start Today' workshop (via Zoom) on Tuesday, March 9, 2021 (8:15am – 3pm).
Please reach out to your city leaders and local ‘green industry' professionals to encourage their attendance and participation. While the workshop is free, registration is required through this secure link: http://ucanr.edu/u.cfm?id=264
A bevy of speakers including certified arborists, horticulturists, planners, water district personnel and other non-profit and green industry representatives will discuss the benefits of urban trees; recommended practices for their selection and care; how to avoid hazardous trees that damage property and structures; and share success stories resulting from partnerships through cities, non-profit organizations, the green industry, HOAs, and street tree committees.
A highlight of the workshop will be the opportunity for attendees to participate in breakout sessions that cut across professions and interest groups (city planners, community service directors, arborists, landscape architects, landscapers, water district managers, HOA managers, golf course superintendents, nursery growers, UC master gardeners, concerned citizens, etc.) to enact positive change regarding tree selection and care.
Thank you for sharing this opportunity to help ensure a healthy future for our children's children with your city leaders and decision-makers.
In the meantime, here are some tree care tips to ‘start the conversation' between now and the workshop:
• Select trees that perform well in your climate. The Sunset Western Climate Zone maps are more precise than USDA zones for our warmer climates. Trees should also be selected based on their adaptation to the ‘micro-climate' in each particular landscape, as well (shade, proximity to buildings, space needs below as well as above ground, soil type, water source, etc.)
• Plant trees the same depth they were in their container in holes at least 2-1/2 times wider. Do not add compost or organic matter to the hole. This practice can result in circled roots that never grow laterally out of the confines of the dug hole.
• Remove any tree ties that are cutting into the trunk or branches of your trees. If trees must be staked due to windy conditions, make sure that the ties are loose enough to allow trees to gently flex in the wind. This helps trees develop the necessary lower trunk strength and stability to support the tree as it matures. Over time, you may be able to completely remove the ties and stakes once the lower trunk becomes stronger and self-supporting.
• Keep all plants and mulch several inches away from tree trunks.
• Keep tree trunks dry. They should not come into contact with water from sprinklers or hoses.
• Regularly water newly planted trees but water mature trees infrequently and deeply. Watering too often reduces the level of oxygen in the rootzone and can lead to waterlogged soils prone to crown and root rots. During fall, trees require only about 15% of the water they require in the summer.
• Prune trees only as needed and avoid topping them. Invest in the services of a credentialed and knowledgeable professional to correctly care for your valued trees. Find a list of International Society of Arboriculture Certified Arborists in your area here: https://www.treesaregood.org/findanarborist.
Drought Update........How to Save Your Plants Under Drought and Water Restrictions......and Use Graywater!
California is in the midst of the worst drought in decades. But you can save your valued trees and landscape plants by following a few simple principles. Watering mature trees deeply just once during mid-summer will keep most species alive, especially if there is a three inch layer of mulch on the top of the soil to keep evaporation down. Be sure to water outward toward the dripline of the tree rather than near the trunk. Keep weeds out of your garden; they will win the water fight. Don't fertilize your landscape during the drought and avoid ripping out your current landscape in the middle of summer to replace it with a drought tolerant one; young plants require more water than established landscapes, and more frequent irrigations. For more information on how to reduce water use in your landscape and garden and to learn more about using graywater from your washing machine to irrigate your landscape click on this link. http://cesanbernardino.ucanr.edu/Drought_Resources/ Janet Hartin, Environmental Horticulture Advisor, University of California ANR Cooperative Extension, San Bernardino, Riverside, and Los Angeles Counties.