Posts Tagged: riverside
“To forget how to dig the earth and to tend the soil is to forget ourselves.” Mohandas K. Gandhi, World leader, political ethicist, lawyer
“Everything that slows us down and forces patience, everything that sets us back into the slow circles of nature, is a help. Gardening is an instrument of grace. ” May Sarton, Poet “
"May our heart's garden of awakening bloom with hundreds of flowers.” Thich Nhat Hanh, global spiritual leader and activist “If you have a garden and a library, you have everything you need.” Marcus Tullius Cicero, Roman philosopher
"The importance of encouraging our children in outdoor work with living plants is now recognized. It benefits the health, broadens the education, and gives a valuable training in industry and thrift. The great garden movement is sweeping over all America, and our present problem is to direct it and make it most profitable to the children in our schools and homes. — Van Evrie Kilpatrick, 1918, in “The Child's Food Garden”
As the above quotes so beautifully proclaim, interacting with nature, whether passively (viewing plants) or actively (gardening, etc.) offers many positive benefits. In fact, the link between horticulture and health and well-being has been scientifically documented for centuries. In 1812, psychiatrist, professor, and Declaration of Independence signer Dr. Benjamin Rush reported that patients participating in gardening activities had better mental health outcomes than non-gardening counterparts.
Many additional papers were published throughout the 1800's documenting benefits of active participation in gardening. More recently, positive links between simply viewing plants through a window or even on a television, movie, or exercise apparatus screen have been reported in peer-review journals. A groundbreaking study in this area was published in 1984 by environmental psychologist Robert Ulrich (Ulrich, 1984) who compared post-operative patients recovering from gall bladder surgery who had views of landscape plants to recovering patients who had the same surgery in the same facility with views of a brick wall. Patients with landscape views had fewer surgical complications, shorter hospital stays, required fewer analgesics, had better moods, and even fewer derogatory remarks by medical staff in their daily records.
Since 1984, dozens of other studies have documented similar positive outcomes resulting from both passive and active engagement with nature and plants. These include improved physical, mental and emotional health; environmental benefits; and community and societal benefits. Recent literature reviews that summarize these findings include:
- An overview of 77 peer-reviewed journal articles (Howarth, et. al., 2020) identified 35 positive outcomes linking physical and mental health and well-being to active and passive horticultural interactions. doi: https://10.1136/bmjopen-2020-036923
-A meta-analysis (Soga, 2016) of 22 studies identified several positive mental health outcomes related to gardening including mood, group cohesiveness, cooperation, pride, well-being, and more. https://doi.org/10.1016/j.pmedr.2016.11.007 -
An overview of 45 peer-review studies (Shepley, et. al., 2019) identified links between properly designed and maintained urban green spaces and crime, gun violence, and the overall safety and cohesiveness of low-wealth urban neighborhoods. https://doi.org/10.3390/ijerph16245119
- A review of 120 papers (Crus-Piedrahita, et. al., 2020) reported public health benefits from urban horticulture activities in the global North. Thirty-two papers had a specific focus on social cohesion and/or social capital. https://doi:10.1016/j.glt.2020.10.001
-Alizadeh (2019) synthesized research regarding the environmental benefits of urban plants, highlighting their vital roles in combating climate change, cooling urban heat islands, providing habitat, removing air and water pollutants, enhancing soil health, and more. https://www.researchgate.net/deref/https%3A%2F%2Fdoi.org%2F10.1108%2FIJCCSM-10-2017-0179
Enjoy your garden! Enjoy a day in nature.
I've been interested in surface temperatures of various living and non-living surfaces in our inland Southern California cities with increasingly hot urban heat islands for some time. Results are in! Use of dark asphalt, synthetic turf,
What can you do?
Take care of your trees, shrubs, groundcovers, and lawns, which cool the environment substantially. In the same experiment, the coolest scenario was the surface temperature of a lawn growing in the shade of a mature tree. Remember that, through transpiration, living plants cool the environment while non-living surfaces do not.
If you're tired of your high maintenance lawn, think about alternative groundcovers that have similar effects (see suggestions below). While cool season lawns like tall fescue and ryes are high water-requiring plants, warm season lawns like Bermuda, zoysia, and buffalograss are more drought-resistant. Our studies have found that it's not the lawns and groundcovers that waste the water, it's the uneven coverage (low distribution uniformity) of most sprinkler systems, coupled with not applying the right amount of water at the right time. This holds true for even the most drought-resistant native and non-native groundcovers irrigated via sprinklers, as well.
Plant drought-tolerant groundcovers
There are dozens of groundcover species that are both drought and heat-tolerant suitable for California gardens.
Here are just two examples:
Creeping thyme (Thymus serpyhllum) They are both drought resistant and do well in the heat. Fragrant flowers add a special touch to a meandering path to a secret backyard garden (below left).
Rosemary (Rosmarinus prostratus) Some rosemary species are low-growing groundcovers. It is great for rock gardens, growing to only 6 inches tall. It produces purple flowers in the summer and attracts pollinators and can be used for culinary purpose (below right).
trees cool urban heat islands
• 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.
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.