Self-Guided Tree Walk: Southgate

The Southgate Tree Walk begins near the Palo Alto High School parking lot on Churchill Avenue at Castilleja Avenue.

1. Blue Atlas Cedar (Cedrus atlantica ‘Glauca’)

~ 50 Churchill Avenue, 2 trees on the left and right sides

These trees are magnificent examples of the silvery-blue variety of Atlas Cedar. Slow-growing conifers, they are open and angular when young and become denser with age. Because of their massive size, Atlas Cedars are recommended only for the largest landscapes.

2. Southern Magnolia (Magnolia grandiflora)

~ 339 Manzanita Avenue, street tree

Southern Magnolias are lovely in summer and early fall. Their giant creamy white flowers stand out against the dark green foliage. They line many of Palo Alto’s older streets, but are no longer planted as street trees due to large surface roots. Magnolias grow well in deeply watered lawns.

3. Little-leaf Linden (Tilia cordata)

~ 323 Manzanita Avenue, 2 street trees

Little-leaf Lindens are medium-sized trees that have unusual greenish summertime flowers consisting of papery bracts. The bract floats the seed clusters in the wind for short distances, distributing the seeds away from the parent tree. They grow 30–50’ high and 15–30’ wide and have yellowish fall color. In our area Little-leaf Linden consistently suffers from aphids, which drip sticky sap beneath. A better choice for a lawn or street tree is Silver Linden (Tilia tomentosa).

4. Silk Tree (Albizia julibrissin)

~ 1512-1514 Madrono Avenue, street tree on the corner

An excellent patio or yard tree that grows broadly in an umbrella form. Showy pink, puff-like flowers cover the tree in late spring to mid-summer. Responding to low light, the Silk Trees’ leaves fold up at night. Native to Iran, China, and Japan.

5. Black Locust (Robinia pseudoacacia)

~ 1524 Madrono Avenue, tall airy street tree closest to the corner

The fast-growing Black Locust sports white, sweet-smelling, pea-like flowers in 8–10” clusters beginning in June. The Black Locust originates from the Appalachian Mountains and is a weedy invasive here in California.

6. Coast Redwood (Sequoia sempervirens)

~ 1509 Portola Avenue, front yard

As the state’s official tree, the Coast Redwood symbolizes California’s unique and varied landscape. It grows best in foggy coastal mountains. In 1995, this tree was measured at 114’. It was most likely planted in 1924, when the house was built.

7. Canary Island Date Palm (Phoenix canariensis)

~ 1523 Portola Avenue, right front corner

This stout-trunked palm is one of the most recognizable feather palms and was often planted in Victorian times to line boulevards and estate entrances. Stanford University’s Palm Drive was named after these graceful trees. It is related to commercial date palms.

8. Monterey Pine (Pinus radiata)

~ 1550 Portola Avenue, left of the garage

Monterey Pines are easy to distinguish from other pines by their asymmetrical cones, which can remain on the trees for years. Pitch pine canker and associated pests have devastated most Monterey Pines, reducing their native habitat to only small areas on the California coast and one island. Despite the stresses of urban landscapes, this tree appears remarkably healthy.

9. Camphor (Cinnamomum camphora)

~ 1602 Portola Avenue, 2 street trees

The elegant and massive Camphor tree was once a popular Palo Alto street tree, but has lost favor because of its tendency to lift pavement. New foliage emerges in pinks and bronzes during early spring and becomes light green in summer. The inconspicuous spring flowers are extremely fragrant, as are the crushed leaves. Native to China and Japan, the bark and leaves are distilled to obtain camphor oil and gum, which are used by the pharmaceutical industry.

10. Scarlet Oak (Quercus coccinea)

~ 1610 Portola Avenue, right of the driveway

This is a lovely example of this deciduous oak from the eastern U.S. The Scarlet Oak grows deep roots and is planted as a street tree in a few areas of Palo Alto. Fall color ranges from yellow to shades of orange and scarlet red. This species tends to hold its brown dormant leaves well into winter. Grows quickly to 60–80’ high and 40–60’ wide.

11. Cork Oak (Quercus suber)

~ 1630 Portola Avenue, street tree on the right

Notice the thick, fissured, light-colored bark on this tree. The source of commercial cork, the bark is used for wine bottles and, more recently, as sustainable flooring material. Native to the western Mediterranean, the Cork Oak is well suited to our own summer-dry Mediterranean climate.

12. Japanese Persimmon (Diospyros kaki ‘Hachiya’)

~ 1651 Portola Avenue, right of the house behind the corner of the fence wall

Japanese Persimmons have huge glossy bright green leaves and brilliant fall colors ranging from deep yellow to electric orange and red. The fruit ripen to deep orange after the leaves drop and persist on bare branches well into winter (if squirrels don’t get them first). Selective pruning of the sculptural branches makes Japanese Persimmons a great choice as an ornamental tree as well as a fruit tree.

13. Chinese Sweetgum (Liquidambar formosana)

~ 306 Sequoia Avenue, 2 street trees

At first glance, these trees look like the familiar American Sweetgum (Liquidambar styraciflua), but look closer. Chinese Sweetgums have denser leaves, a more free-form shape, and softer seed capsules. Fossil records indicate that prehistoric Liquidambar was once distributed worldwide, gradually evolving into today’s three distinct species: American Sweetgum in the eastern U.S., Chinese Sweetgum in southeast Asia, and Oriental Sweetgum in Turkey.

14. Flowering Pear (Pyrus calleryana ‘Aristocrat’)

~ 1665 Madrono Avenue, street tree opposite the front door

Flowering Pears are covered with white blossoms in early spring and have yellow to red fall color. The ‘Aristocrat’ cultivar has upwardly curving branches forming a strongly rounded shape. The very narrow branch angles make older trees prone to breakage. Many newer cultivars are available with wider, stronger branch angles.

15. Atlas Cedar (Cedrus atlantica)

~ 1585 Madrono Avenue, left of the driveway on Miramonte Avenue

As a result of pruning, this tree has a very unusual branching structure. Standing below the tree, look for limbs pointing straight up. Atlas Cedars limbs taper only slightly as they grow. The extra weight at the branch tips can cause branches to break at the trunk. This may have been the motivation for this particular pruning. Compare the blue-green color of this tree to the silvery-blue color of the Blue Atlas Cedar, the first tree on this walk.

16a. Saucer Magnolia (Magnolia soulangeana)

~ 400 Miramonte Avenue, in the front yard near the street corner

Blooming on bare wood in late winter, Saucer Magnolias tell us spring is near. The large tulip-shaped flowers vary in color from pale pink to purplish-red, usually with white inner petals. Often used as a lawn-tolerant tree, this specimen has been effectively used here as an anchor tree at the corner of the house.

16b. Chinese Hackberry (Celtis sinensis)

~ 400 Miramonte Avenue, street tree on Escobita Avenue

The glossy leaves and smooth bark distinguish it from its corky-barked cousin, the Western Hackberry (Celtis occidentalis). Inconspicuous flowers are followed by orange, quarter-inch, berrylike edible and sweet fruit. Leaves turn yellow in the fall. Palo Alto has stopped planting this tree because it is prone to infestation with aphids that produce large amounts of honeydew.

17. Crape Myrtle (Lagerstroemia hybrid)

~ 1619 Escobita Avenue, 2 trees at the left and right front corners

Native to China, Crape Myrtles are strikingly beautiful small specimen trees that grow 14–25’ high and 8–15’ wide. Deciduous trees, they have profuse and showy summer bloom, bold fall color, and extremely attractive winter bark. Naturally multi-trunked, they can also be trained into single trunks like these. This yard has two different cultivars; look for others on this street.

18. Idaho Locust (Robinia x ambigua ‘Idahoensis’)

~ 1623 Escobita Avenue, center of the front yard

In the spring, Idaho Locusts are covered with pendant clusters of lavender flowers. It is a deciduous tree, but its delicate foliage leaves very little litter. Compare the smooth, vertically striated bark to the rough-barked Black Locust earlier in this walk.

19. Southern Magnolia (Magnolia grandiflora)

~ 420 Sequoia Avenue, street tree

This Southern Magnolia has very unusual bark on its trunk and limbs, resembling the cracked mud of a dry lake bed. Compare the bark on this tree to the Southern Magnolia next door at 430 Sequoia Avenue. What could be the cause of this unusual bark?

20. Valley Oak (Quercus lobata)

~ 450 Sequoia Avenue, front yard near the street corner

This Valley Oak is a fantastic specimen of a locally native deciduous oak. It is well over 200 years old. The house was rebuilt in the 1990s and designed to accommodate the canopy of this magnificent tree. Notice the cables and pole that support this giant.

21. California Box Elder (Acer negundo californicum)

~ 1652 Castilleja Avenue, street tree

Box Elders are native to most parts of the U.S. This tree is a locally native subspecies with fuzzy leaves rather than the more common glossy leaves. Box Elders have yellow fall color and interesting winged samara seeds in spring. Elsewhere in the U.S., damage caused by Box Elder Bugs is quite a problem, but locally it is only an occasional nuisance.

22. Coast Live Oak (Quercus agrifolia)

~ 1621 Castilleja Avenue, front yard

Native oaks are superbly adapted to our long summers and dry Mediterranean climate. Ideally, landscapes with native oaks should receive little to no summer irrigation, thus insuring the long-term health of these magnificent trees. Acorns or one-gallon seedlings can grow to 25’ in 10 years and to 50’ in 25 years.

23. Jaquemont Birch (Betula jacquemontii)

~ 1601 Castilleja Avenue, right front corner and numerous other examples, especially on the Miramonte Avenue side

Jaquemont Birch is renowned for its brilliantly white bark. They have strongly vertical main branches and diagonally upright side branches. Their deep green, teardrop-shaped leaves are coarser textured than European White Birch (Betula pendula). They need deep, regular watering during the hot summer months.

24. River She-oak (Casuarina cunninghamiana)

~ 1595 Castilleja Avenue, street tree to the left of the front walkway

While they look like pine trees, the dark green “needles” of this Australian native are actually jointed stems. Using modified stems for photosynthesis helps this tree retain moisture in hot climates. It is also able to grow in nutrient-poor sand and is tolerant of wind and alkalinity.

25. Majestic Beauty Indian Hawthorn (Rhaphiolepis ‘Majestic Beauty’)

~ 1591 Castilleja Avenue, 2 trees inside the corners of the green fence

The evergreen Majestic Beauty Indian Hawthorn is larger than its more shrubby Rhaphiolepis cousins. It grows to 20–25’ high and 8–10’ wide and has glossy, dark green leaves and large clusters of light pink flowers from winter to spring.

26. Willow Pittosporum (Pittosporum phillyreoides)

~ 1565 Castilleja Avenue, left side of the house behind the fence

Naturally a large shrub, this Willow Pittosporum has been trained into a lovely small tree. Weeping branches and narrow leaves create the illusion of a small Weeping Willow. Tiny yellow, very fragrant flowers from late winter to early spring are followed by deep yellow fruit. Pittosporum is drought-tolerant so summer watering should be deep and infrequent.