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Street trees provide much value in urban and suburban environments. They provide a refreshing contrast to streets and buildings, and add identity and character to communities. They provide shade and reduce temperatures during summer and seasonal color at different times of the year.

Although street trees have become an integral part of communities throughout California, the fundamental planting requirements that are needed to achieve long term success have been widely underestimated. From a horticultural perspective, many street trees have been planted in paved areas that are far too small for good root and trunk development. Additionally, these areas are often difficult to irrigate and there are many problems associated with litter, roots, damaged pavement and branches that grow into vehicular lanes. Ironically, when these issues and difficulties arise, the tree is viewed as the source of the problem. While it is important to continue the practice of planting street trees, better planning and adequate space is necessary. The lists of suggested street trees include the minimum size planting area recommended for each species.

Above: Lagerstroemia indica

Deciduous Street Trees S M L PF IG

Albizia julibrissin + cv Silk Tree • • M 1 Bauhinia x blakeana Hong Kong Orchid Tree • • M 1 Bauhinia variegata + cv Purple Orchid Tree • • M 1 Calodendrum capense Cape Chestnut • M 1 Cassia leptophylla Gold Medallion Tree • • M 1 Catalpa species Catalpa • • M 1 Celtis species Hackberry • • M 1 Cercis canadensis + cvs Eastern Redbud • M 1 Chionanthus retusus Chinese Fringe Tree • M 1 x Chitalpa tashkentensis + cvs Chitalpa • M/L 2 Fraxinus angustifolia + cvs NCN • • M 1 Fraxinus velutina + cvs Arizona Ash • • M 1 Ginkgo biloba + cvs Maidenhair Tree • • M 1 Gleditsia triacanthos + cvs Honey Locust • M 1 Jacaranda mimosifolia + cv Jacaranda • • M 1 Koelreuteria bipinnata Chinese Flame Tree • • M 1 Koelreuteria elegans NCN • M 1 Koelreuteria paniculata Goldenrain Tree • M 1 Lagerstroemia fauriei x indica + cvs Crape Myrtle • • M 1 Lagerstroemia indica + cvs Crape Myrtle • • M 1 Liquidambar formosana Chinese Sweet Gum • • M 1 Liquidambar styraciflua + cvs American Sweet Gum • • M 1 Liriodendron tulipifera Tulip Tree • • H 1 Lysiloma watsonii var. thornberi Feather Bush • • M/L 2 Parkinsonia species + cvs Palo Verde • • M/L 2 Pistacia chinensis Chinese Pistache • M 1 Platanus x acerifolia + cvs London Plane Tree • • M 1 Prosopis glandulosa Texas Honey Mesquite • • M/L 2 Prunus cerasifera + cvs Purple-leaf Plum • M 1 Pyrus calleryana + cvs Callery Pear • M 1 Quercus palustris Pin Oak • • M 1 Quercus virginiana Southern Live Oak • • M 1 Robinia x ambigua + cvs Locust • M 1 Robinia pseudoacacia Black Locust • M 1 Sapien sebiferum Chinese Tallow Tree • M 1 Sophora japonica Japanese Pagoda Tree • M 1 Tabebuia chrysotricha Golden Trumpet Tree • M 1 Tabebuia impetiginosa Pink Trumpet Tree • M 1 Ulmus parvifolia + cvs Chinese Evergreen Elm • • M 1 Zelkova serrata Sawleaf Zelkova • • M 1 S = Small - Minimum 5 ft. x 5 ft.

M = Medium - Minimum 10 ft. x 10 ft. L = Large - Minimum 12 ft. and more

Below: Quercus agrifolia

Above: Afrocarpus gracilior

Plant Lists

Street Trees

Like all plants, trees depend upon their roots to obtain moisture, nutrients and oxygen to sustain growth. Trees become diminished in size and are more vulnerable to drought and pollution when root growth is restricted by compacted soils and limited space.

Roots develop best in soils that have a balance of moisture, nutrients and oxygen; they do not grow in areas where any one of these conditions are lacking. Roots will grow under paving or adjacent to structures when poor conditions are present. Over time such roots can become quite large and cause damage to paving or structures.

The use of root barriers to help prevent root damage by street trees can be successful under some conditions. Barriers placed continuously along the edge of a sidewalk in a linear parkway can be a deterrent to root growth of smaller trees by redirecting the direction of the roots away from the pavement. Encircling trees with root barriers is not recommended; trees become rootbound and even lead to the failure of the root barrier itself.

The use of structural soils holds promise for trees planted in many urban and suburban areas to reduce damage by tree roots and increase the health and vigor of the trees. Structural soils consist mostly of crushed gravel with some topsoil. These soils enable sufficient compaction to support sidewalks and pavement, while providing increased space and structure to hold moisture, oxygen and room for root development. Even with structural soils, it is necessary to excavate the largest area possible for each street tree to have the greatest soil volume to sustain healthy growth.

Above: Brahea edulis

Below: Washingtonia filifera, Palm Springs

Evergreen Street Trees S M L PF IG

Afrocarpus gracilior Fern Pine • • M 1 Agonis flexuosa + cvs Peppermint Tree • M/L 2 Brachychiton populneus Kurrajong Bottle Tree • M/L 2 Callistemon citrinus Lemon Bottlebrush • • M/L 2 Callistemon viminalis + var. Weeping Bottlebrush • M/L 2 Casuarina cunninghamiana River She-Oak • M/L 2 Cinnamomum camphora Camphor Tree • • M 1 Cupaniopsis anacardioides Carrot Wood • M 1 Eriobotrya deflexa Bronze Loquat • M 1 Eucalyptus ficifolia Red-Flowering Gum • M/L 2 Eucalyptus torquata Red Cap Gum • • M/L 2 Geijera parviflora Australian Willow • M/L 2 Hymenosporum flavum Sweetshade Tree • M 1 Laurus nobilis Sweet Bay • • M/L 2 Lophostemon confertus Brisbane Box • • M/L 2 Magnolia grandiflora + cvs Southern Magnolia • • M 1 Maytenus boaria Mayten Tree • M 1 Melaleuca linariifolia Flaxleaf Paperbark • M 1 Melaleuca quinquenervia Cajeput Tree • M 1 Melaleuca styphelioides Prickly Paperbark • M 1 Metrosideros excelsus N. Z. Christmas Tree • • M/L 2 Photinia x fraseri NCN • • M 1 Pinus brutia var. eldarica Afghan Pine • • L/VL 2 Pinus canariensis Canary Island Pine • • M/L 2 Pittosporum rhombifolium Queensland Pittosporum • M 1 Quercus agrifolia Coast Live Oak • • M/L 2 Quercus ilex Holly Oak • • M/L 2 Quercus suber Cork Oak • • M/L 2 Rhus lancea African Sumac • M/L 2 Schinus terebinthifolius Brazilian Pepper Tree • M/L 2 Stenocarpus sinuatus Firewheel Tree • M 1

Palms S M L PF IG

Archontophoenix cunninghamiana King Palm • • M 1 Brahea armata Mexican Blue Palm • • M 1 Brahea edulis Guadalupe Palm • • M 1 Butia capitata Pindo Palm • • M 1 Livistona australis Cabbage Palm • • M 1 Livistona chinensis Chinese Fan Palm • • M 1 Phoenix canariensis Canary Island Date Palm • • M 1 Phoenix dactylifera Date Palm • M 1 Syagrus romanzoffianum Queen Palm • • M 1 Washingtonia filifera California Fan Palm • • M 1 Washingtonia robusta Mexican Fan Palm • • M 1

Below: Platanus racemosa

Below: Magnolia grandiflora

Above: Eucalyptus viminalis

Above: Pinus canariensis

Parkways and medians often provide an opportunity to establish some of the most significant plantings throughout urban communities. These areas can be planned to have more space where the use of larger sized trees can achieve dense visual screening and a forested landscape quality. Importantly, these landscapes offer some of the best opportunities to function as carbon banks and to capture airborne pollutants. Areas that are richly planted with large growing trees will sequester more carbon from the atmosphere than sparsely planted ground covers and shrubs. Additionally, more particulate matter carried in the air can become collected on leaf surfaces of such abundantly planted landscapes. Additionally, these environmental benefits will be optimized when such trees are selected according to their natural adaptability to the local climate conditions. Once established, these trees can often survive and grow without reliance on high amounts of supplemental water.

Plant Lists