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Few trees can match the stately elm as its branches
raise in graceful arcs above our streets, creating a
ceiling that changes with each season. Silver
samaras emerge in the spring with the pale green
of bud break. The canopy fills to a dark green as
the shade brings relief from the hot summer
streets. Fall brings golden yellow foliage that glows
against the dark trunk and branches.
The majestic sculptures of trunks and branches
display their twists and turns as winter reveals the
clear blue sky. Tunnels of streets are created in the
intertwined mesh of branches and the city becomes
a garden where elms bring life to the urban core.
Elms in SacramentoElms enjoy a rich history in Sacramento as the most popularoriginal street tree planted through the end of the 19th century.In addition to their availability, rapid growth, elegantappearance, tall height, and generous shade, elms were favoredfor sentimental reasons as they reminded early Sacramentosettlers of their east coast home towns which were also plantedwith elms. By 1900 Sacramento had already become a “City ofTrees” thanks to the fast growing elms and the efforts of thecity council and civic leaders.
The elms suffered setbacks in 1938, 1941, and 1950 whencatastrophic windstorms toppled many of the largest and moststately elms and led to the cutting back and topping of manythat remained. Along with the rest of the city’s trees, the elmsbegan to see a reduction in care as the tree budgets shrank overthe decades. By the 1980’s many of the elms had lived over acentury and were nearing the end of their lives. An Elm TreeReforestation Program was initiated by the City of Sacramentoto replace the overmature elms with similar large canopyspecies such as valley oak, European Beech, and ginkgo.
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An English elm tree in front of Sacramento’s Memorial Auditorium.
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IONThe elms faced their greatest threat from Dutch elm disease
(DED) which was first detected in Sacramento in 1990. Thecommunity’s love of their trees came to the surface as hundredsof volunteers came together to monitor their trees for earlydetection of the disease and to prevent it’s spread in a campaigncalled Save the Elms Program (STEP). This grassrootsorganization was formed in response to the federal and statewithdrawal from DED control in 1993. This group ofconcerned citizens working in partnership with the City TreeServices has remained committed to the goal of safeguardingelms and keeping removals at a minimum. But the threat isstill real and the aged giants are slowly falling to disease androot problems.
Our Save the Elms Program and its alliance of partners haveconcluded that one of the best ways to ensure that Sacramento’selms will be safeguarded from DED is to teach neighborhoodsto monitor their own trees. Concerned neighborhood residentsare continually being trained to be those eyes which examinetrees not just once or twice a year, but regularly throughout theDED season, getting to know their own trees and beingresponsive to sudden changes.
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To tell if a tree is an elm, first look at the silhouette for anumbrella like form with a vase like branching from the trunk.Then look at the leaves – they have ragged edges and anuneven base. The bark is rough, with different patternsdepending on the species. Elm trees originated in central Asiaand have naturalized over most parts of North America,Europe, and Asia. We will discuss and identify the five majorspecies of elms growing in Sacramento. The chart that follows is aguide to help you identify each individual species for monitoring .
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I D E N T I F I C A T I O N
American Elm 60-80’Ulmus americana 40-70’
Spread out in a vase like shape
English Elm 80-120’Ulmus procera 40-70’
Crown of nearly upright spreading branches
Chinese Elm 30-70’Ulmus parvifolia 30-70’
Somewhat weeping and delicate, lattice like
Siberian Elm 40-65’Ulmus pumila 35-60’
Open reaching, with large ascending branches
Leaf Type
Doubly serrated, tough and thick,no hairs
Broad and rounded, uneven at base, hairs above and below
Lanceolate, even at leaf base,glossy and leathery
Eliptical to lanceolate, smooth green above, lighter below
Ovate to lanceolate, serrations are rounded with pointed tips
Zelkova 50-90’Zelkova spp 50-90’
Dense and broadly rounded
Common and Average HeightBotanical name Average Spread
Average Canopy
Ash gray bark with basket weave fissures
Rectangular, light gray fissured and plate like
Light brown to gray, often sheds in puzzle like pieces
Rough dark brown/ gray bark, deeply fissured, often showing orange inner bark
Gray to brown, young bark is smooth with horizontal, dicontinuous ridges
Bark Patterns
SURVEYING ELM TREES FORDUTCH ELM DISEASEDutch Elm Disease (DED) is a fungus that clogs the elm’swater conducting system. It is passed from tree to tree by barkbeetles or through tree roots, and can kill an elm tree in eightto twelve weeks. There is no cure. Only careful management,monitoring, detection, and prompt removal of diseased treescan control the spread of DED. A tree infected with DED willfirst show sudden wilting or drooping of green leaves on one ormore of the major branches in the canopy of the tree.
The second stage of the disease is termed “flagging”, andbecomes apparent as the wilted leaves first turn yellow, thenbrown, and eventually shrivel on the limb. As the diseaseprogresses, the infected branch or branches die and take on theappearance of autumn. Most of the infected leaves will fall, butsome will persist on the tree into winter. Surveying elmsinvolves monitoring the trees for symptoms of DED, as well asnoting any other health problems you may observe. Whenviewing an elm tree, view from all sides if possible, look at thetree from a distance so you can get the entire tree in view; alsolook at the tree from the base upward, inspecting all areas ofthe tree. If you observe signs of DED while monitoring,contact the STEP Program so that we can inspect the tree.
SYMPTOMS RESEMBLINGDUTCH ELM DISEASEAt times, other factors can cause symptoms on elms thatresemble Dutch Elm Disease. Below is a partial list ofDED look-alikes:
Squirrel Damage
As squirrels feed on the branches, they often chew off the bark ina circular fashion around the branch. This causes the death of thebranch and the look is similar to flagging. Look for squirrel nestsor large bundles of branches high up in the crown of the tree.
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“Flagging” on an elm is a symptom of DED.
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Drought Stress
Prolonged drought will cause burns on the older leaves. As thedrought progresses in severe cases the scorch will be greater,often progressing beyond the older leaves to the younger leavesand at times causing entire branches to flag.
Chemical Damage
Chemical treatments can burn a tree. Chemical burns willoften produce gnarled growth, molten leaves or dieback.Chemical damage may appear on the tip growth or furtherdown in the tree, depending on the type of chemical applied.
Compaction
Compacted soils have poor air space so oxygen and waterpenetration is poor. In time this condition can cause diebackin the tree.
Root Damage
Root damage from construction work such as trenching cancause a tree to be impacted and go into shock. When thisoccurs, it is common to see branch dieback and general treedecline. If you suspect root damage, look for signs of construction.
Power Line Burn
High power lines can burn limbs. This can happen during astorm when limbs may arc with power lines. Examine the branchclosely, looking for burn marks on any part of the branch.
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UESVolunteers training for the Save the Elms Program.
OTHER FACTORS AFFECTING ELM HEALTHMonitoring elm health and keeping the elms healthy in the urbanforest is an important element in keeping DED to a minimum. Belowis a list of some common health problems associated with elms.
Elm leaf beetle
Elm leaf beetle has been a persistent pest to Sacramento’s elm trees fordecades. It is not the same problem as the fatal DED, but it is aserious nuisance just the same. The elm leaf beetles thrive in barkcrevices, litter, woodpiles, or in buildings. They fly to the canopy ofelm trees in the spring and feed on them, chewing through the leaves.After a few weeks, they lay eggs on the underside of the elm leaves.The eggs hatch and small black larvae emerge. Mature larvae are dullyellow or greenish color. After several weeks of chewing on elm leavesand leaving them with “lacy” skeletonized appearance, the larvae crawldown the trunk and form bright yellow pupae in the soil under thetree. After about ten days, adult beetles emerge from pupae and fly tothe canopy to feed and lay eggs again. Elm leaf beetles do not kill elmtrees, but the defoliation eliminates summer shade, reduces treeaesthetic value, and causes annoying leaf drop, which can resembleautumn throughout the summer in downtown Sacramento. Extendedelm leaf beetle damage can contribute to deadwood accumulationand, if left unchecked, would have serious consequences for longterm elm health.
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Elm leaf beetle (inset) and the resulting damage
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SAphids
Aphids are small sucking insects that seldom cause serious problems.Although these pests are normally not serious on elms, in largenumbers, they can excrete copious amounts of honeydew (sugar waterextracted from the tree) which can drip on cars, people, and thepavement below. Aphids are most common on American Elms.
Scale
The damaging stage of this insect is non-mobile. The crawler stagehatches from eggs and moves around the tree. At maturity, the insectssettle to feed by inserting their mouth parts into inner bark or leaftissues. At this time, the crawler loses its legs and becomes a scale.Scales occur normally on American elms and can often occur in largeclusters on a branch. Scales are also a sucking insect and can produceheavy amounts of honeydew. Sometimes, a fungus called sooty moldwill feed off the honeydew. Sooty mold appears as black mold on topof the honeydew but does not damage the elm.
Ivy at the base of an elm
Ivy around the base of an elm can cause crown rot. Crown rot is a fungusthat survives in a damp environment. Removal of ivy around the base of atree helps it dry out, thereby greatly reducing the threat of crown rot.
Dieback/Broodwood
Broodwood is dead wood used as a breeding site for bark beetles.When dead wood is left in an elm it can increase the population ofbark beetles and may contribute to the spread of DED.
Elm Wetwood
Wetwood is a bacterial disease seen in virtually all elms, but morecommon in English and Siberian elms. Liquid from the point ofinfection often seeps out of the crack or wound giving the wood a watersoaked appearance. Often you will see dark streaking going down theelm from the point of infection. Wetwood does not decay the wood andis normally not of concern unless there are enough infection sites tocompromise the structure of the tree. There are no known controls.
CARING FOR YOUR ELMIf you have an elm tree in your yard there are a few simple things youcan do to help prevent DED and keep it healthy. The most importantis deep watering during the summer months. Place a hose at a trickleat various locations near the drip line of your tree or use a soaker hose.Elm trees do not normally need fertilizer, but mulch over any barepatches of ground will help improve soil conditions. Be careful not tobury the crown of the tree with mulch because this may encouragecrown rot. Most street elms are maintained by City Tree Services,therefore you should not prune them yourself. Avoid pruning elmsduring the spring and summer because the elm bark beetle is activeduring that time and is attracted to fresh pruning wounds.
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HOPE FOR NEW ELMSBecause the elm is such a valuable urban tree, extensive researchhas been conducted to find elms that are resistant to DutchElm Disease and suitable for urban areas. After years ofresearch, several purebred American Elms have emerged and areavailable for planting. This new generation of elms comes fromparent trees that have survived many years in situations withsevere DED and bark beetle pressure with minimal damage.These survivor trees have been propagated and the youngseedlings inoculated with the DED fungus to assure resistance.The new cultivars have the classic American elm shape andpollution tolerance characteristics. They go by names such as‘Liberty,’ ‘Valley Forge,’ ‘New Harmony,’ and ‘Princeton’ todisplay their rich heritage.
The American elm has been selected by City of SacramentoTree Services for replanting in the city and many new elms aregrowing in park locations such as Land Park and Cesar ChavezPlaza. The Sacramento Tree Foundation is also propagating‘Valley Forge’ elms to increase the local supply and retain thebeauty and history of elms along Sacramento’s streets forhundreds of years to come. Help keep the American elm alivein Sacramento by joining with the Tree Foundation and CityTree Services in this effort to renew our City of Trees.
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A DED resistant American elm planted in Cesar Chavez Plaza as the“Millenium Tree”
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LIST OF CONTACTS
City of Sacramento Tree Services433-6345www.cityofsacramento.org/parks/trees
Sacramento Tree Foundation STEP Program924-8733 x [email protected]
County of Sacramento Tree Coordinator8 7 4 - 7 9 1 1
Additional information for elm tree links, events, andprogram information is located on the Sacramento TreeFoundation Website -
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SPlanting the Millenium Tree which celebrates one million treesplanted in Sacramento between 1990 and 2000.
The mission of the Sacramento Tree Foundation is to
promote the importance of trees and community
action in improving the quality of life and enhancing
the unique character of the Sacramento region.
Our vision is to work with the community to create a
legacy of trees for future generations.
OUR PROGRAMS INCLUDE:
• COMMUNITY SHADE
• MISTLETOE MANAGEMENT
• NEIGHBORWOODS
• NATURE
• SACRAMENTO NORTHERN RR PARKWAY
• SAVE THE ELMS (STEP)
• SEED TO SEEDLING
• REGIONAL URBAN FOREST STRATEGY
• COOL COMMUNITIES
• SHADE TREE PROGRAM
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