Self-Guided Tree Walk: Old Palo Alto

Tree Selection by Kevin Raftery, ISA Certified Arborist; Don Ellis, Horticulturist at the Elizabeth F. Gamble Garden Center; and John H. McClenahan, fourth generation arborist with S.P. McClenahan Co., Inc.
Updated by Jana Dilley and Marty Deggeller, summer 2003
Additional information gathered from Sunset Western Garden Book; Plants That Merit Attention-Trees; Oaks of California; AHS Encyclopedia; Trees of North America and The Urban Tree Book and Saratoga Horticultural Research Foundation.

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The Old Palo Alto Tree Walk begins at Gamble Garden Center, Churchill Street parking entrance.

1. Tupelo Tree (Nyssa sylvatica)
~ Row of street trees, north side of Churchill Street
This outstanding tree has vibrant fall color, grows well in any soil, tolerates poor drainage, and has olive-shaped bluish-black fruit that birds find attractive.

2. Red Maple (Acer rubrum)
~ 474 Churchill Street, front yard
Native to the Eastern United States where it receives year-round rainfall. During the hot, dry summers these trees should be watered. Related to the syrup-producing maples of New England. Check the angle between the three main lobes of the leaves; this tree forms a “V”, whereas the sugar maple forms a “U.”

3. Valley Oak (Quercus lobata)
~ 508 Churchill Street, backyard, visible from Cowper
Considered the monarch of California oaks by virtue of its size, age, and beauty. Valley oaks appear in the diaries of many early visitors to California. Describing the open groves of the Santa Clara Valley in 1796, English explorer George Vancouver wrote: “For about twenty miles, it could only be compared to a park which had originally been closely planted with the true old English oak.”

4. Coast Live Oak (Quercus agrifolia)
~ 509 Coleridge Avenue, front yard
Native mainly to California’s coastal ranges, it is classified as a riparian tree. Commonly grows along creeks typically dry in the summer. Native oaks do not do well in lawn areas. This species produces its mature fruit within one growing season, not two. Coast live oak acorns ripen 6 to 8 months after the flowers are pollinated. From August to October damaged acorns are dropped from the tree. Robust acorns begin dropping with the winter rains. With the last acorns dropping as late as May it has a second season to sow offspring.

5. Arbutus ‘Marina’
~ 1631 Cowper Street, south end of front house
This tree grows at a moderate rate. The largest known specimen was planted in a San Francisco garden in 1942 and has reached a height and equivalent spread of 40 feet. It requires full sun. More adaptable than the native madrone, it will tolerate typical gardening conditions and regular watering as long as the soil is well-drained. This highly ornamental evergreen tree has all virtues of the madrone combined with the tolerances of the European strawberry trees. It has a wide range of uses in the garden or landscape.

6a. Copper Beech (Fagus sylvatica ‘Atropunicea’)
~ 505 Lowell Avenue, far left side on Cowper Street
The Latin (and scientific) name for the beech genus, Fagus, comes from a Greek work for eating. The oil-rich, peanut-sized nuts found inside the woody prickled fruit case have been favored as a treat since the Stone Age.

6b. Dawn Redwood (Metasequoia glyptostroboides)
~ 505 Lowell Avenue, front yard along Cowper Street
One of the few deciduous conifers, this tree can reach 80 to 90 feet and grows fast when young. Although this tree tolerates moist soil, it may also be susceptible to root rot diseases such as oak root rot (Armillaria mellea). Exercise caution with summer irrigation.

7. Bradford Pear (Pyrus calleryana ‘Bradford’)
~ 468 Lowell Avenue, 2 street trees
White-flowering ornamental pear, usually grows to about 40 feet. This species is somewhat resistant to fire blight (Erwinia amylovora). Prone towards poor structure and limb breakage.

8. London Plane (Platanus acerifolia)
~ 426 Lowell Avenue, street tree
This fast-growing tree is used as a street tree in Palo Alto. The ‘Columbia’ variety is resistant to anthracnose and reasonably resistant to powdery mildew. The ‘Yarwood’ variety is also resistant to powdery mildew. Both diseases can cause foliage to look unhealthy and cause leaf drop.

9. Coast Redwood (Sequoia sempervirens)
~ 415 Lowell Avenue, middle of driveway
When you plant this tree, remember it is one of the tallest tree species in the world. Count on branch spread at the base (tip to tip) of 14 to 30 feet. Centuries old natives surpass 350 feet in height, but 70 to 90 feet seems to be what to expect in 25 years. Reasonably pest free if not drought-stressed. Notice here, the tree doesn’t stop growing if a little concrete gets in the way.

10. Water gum (Tristaniopsis laurina)
~ 1820 Cowper Street, front of house
Related to the Eucalyptus, it is slow-growing and can take the form of a small tree or shrubby bush. This is an excellent tall screen or boundary tree.

11. Incense Cedar (Calocedrus decurrens)
~ 327 Tennyson Avenue, next to sidewalk
Common to the Yosemite Valley floor, this evergreen conifer is sometimes confused with the redwood because of its reddish brown bark. Initially slow growing, when established it can grow 2 feet per year and will reach 75 to 90 feet.

12. Australian Tea Tree (Leptospermum laevigatum)
~ 320 Tennyson Avenue, west side of front yard
Leptospermum scoparium and L. laevigatum are both called tea tree because on his trip to New Zealand and Australia, Captain Cook had their leaves brewed into a tea to prevent scurvy. It may have had medicinal uses, but it doesn’t taste very good.

13. Giant Sequoia (Sequoiadendron giganteum)
~ 310 Tennyson Avenue, front yard
It looks like an incense cedar, but is closely related to the coast redwood. It has the distinction of having the most massive trunk in the world; at higher altitudes trunk diameter can reach 30 feet. Native to the western slopes of the Sierra Nevada.

14. Mayten (Maytenus boaria)
~ 1750 Bryant Street, right of front door
Its beautiful weeping form makes the mayten a good substitute for the weeping willow; it has a similar appearance without the problems. Without deep root watering. it will root near the surface and invade planting beds. Resistant to Oak Root Fungus.

15. Western Redbud (Cercis occidentalis)
~ 300 Lowell Avenue, right of driveway
Predominantly native to the California foothills below the 4,000 foot level. As a shrub or small tree it reaches 10 to 18 feet high and wide. In spring it has a stunning three-week display of magenta flowers.

16. Chinese Pistache (Pistacia chinensis)
~ 290 Lowell Avenue, front courtyard
Fall foliage colors are stunning; scarlet, crimson, orange and yellow. The fruit on female trees is initially bright red, turning a dark blue. The seeds yield an oil used in cooking, and the Chinese have been known to boil the leaf buds and eat them.

17. Carob (Ceratonia siliqua)
~ 280 Lowell Avenue, right of front gate
The pods are often used as a chocolate substitute. This tree is resistant to oak root fungus and is extremely drought tolerant. The female trees can be messy. It has long leaflets and is quite attractive.

18. Deodar Cedar (Cedrus deodara)
~ 250 Lowell Avenue, right front yard
Native to the Himalayas and commonly planted throughout Europe and North America. Usually sheds pollen in early November. It is susceptible to oak root fungus. Avoid frequent summer irrigation around the roots. Some deodar cedars drop limbs in late summer or early fall.

19. Black Locust (Robinia pseudoacacia)
~ 200 Coleridge Avenue, right corner of front yard
This is fast growing to about 75 feet. Flowers are white and branchlets typically have thorns. Because emigrants brought seeds with them from the eastern U.S., black locust is now common everywhere in the West. In California’s Gold Country it has naturalized. With pruning and training in its early years, it is a handsome flowering tree.

20. Chinese Photinia (Photinia serrulata)
~ 232 Coleridge Avenue, left of driveway
Nice ornamental tree, grows to 35 feet. Look for insect damage from thrips; this species is also susceptible to mildew. The tree is reasonably drought tolerant when established.

21. Siberian Elm (Ulmus pumila)
~ 1570 Bryant Street, street tree
Extremely hardy and tough, enduring cold, heat, aridity, and poor soil. It has brittle wood, weak crotches, and also tends to produce suckers. Common pests include elm leaf beetle, elm bark beetle and Dutch elm disease (Ceratocystis ulmi.) Palo Alto is planting new elms resistant to Dutch elm disease as street trees.

22. Fern Pine (Afrocarpus elongatus)
~ 345 Coleridge Avenue, street tree
Native to Eastern Africa but well-adapted to California. Depending on the type of pruning this plant receives, it can be used as a street or lawn tree, a hedge, large shrub, container plant, or as an espalier. Despite its common name, it is not a member of the pine family.

23a. Turkey Oak (Quercus cerris)
~ 1651 Waverley Street, front yard near driveway
Named for its country of origin, this deciduous oak is fast-growing; it can reach 40 feet in 20 years.

23b. Crape Myrtle (Lagerstroemia hybrid)
~ 1651 Waverley Street, in yard flanking gate on left
In addition to their stunning bark and bright summer flowers, crape myrtles provide beautiful fall color. To guarantee a tree resistant to powdery mildew, chose one of the ‘Indian Tribe’ cultivars. Good for small gardens and drought tolerant.

24. Cork Oak (Quercus suber)
~ 1617 Waverley Street, corner of Coleridge Avenue
Thank this tree for the cork in your wine bottle. The trunk and principal limbs are covered with a thick, corky bark that is commercially cultivated in the Mediterranean. The correct amount of cork must be removed each harvest to leave the inner layer of the tree intact. If the inner layer is damaged regrowth will not occur.

25. Southern Magnolia (Magnolia grandiflora)
~ 435 Coleridge Avenue, street trees
Often used as a street tree in Palo Alto and Menlo Park; however roots can cause sidewalks to lift. This tree is native to the southern states but seems to adapt to areas with adjacent lawns which are heavily watered. Grows 25 to 80 feet tall, usually pyramidal or decurrent in form. Notice the large douglas fir (Pseudotsuga menziesii) in front of the house.

26. Coast Live Oak (Quercus agrifolia)
~ Corner of Waverley Street and Churchill Avenue, street tree
This is a good example of a bad tree environment, and a tree fighting to survive. Notice how the root crown is impacted by the sidewalk and asphalt. This environment is not conductive to root development. The soil compaction creates anaerobic conditions in the soil, favorable to root rot organisms. Hardscape removal would improve the tree’s environment.

This publication was funded by the California ReLeaf 2003 Capacity-Building Grant Program and the California Department of Forestry and Fire Protection.