Self-Guided Tree Walk: Baylands

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The Tree Walk begins at Environmental Volunteers’ EcoCenter, 2560 Embarcadero, Palo Alto.

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1.Narrow-leaved Gimlet, Swamp Mallee(Eucalyptus spathulata)

Planted as part of a historic introduction of various Eucalyptus species in the Bay Area in the 20th Century by Max Watson and Woody Metcalf. Unfortunately, this history is nearly lost to the City of Palo Alto except to Dave Dockter in the Urban Forestry who has some of the records. Equally unfortunately this tree, Narrow -leaved gimlet or swamp mallee, is not being widely grown in the nursery trade despite its apparent success at this site. We will see more than one here today. From these specimens, it would seem to prefer growing as a multitrunk and would probably not make a good street tree. SelecTree says height of 20-40 feet and spread of 20 feet, so you would need some space, but it would make a good specimen for an Australian dry garden if that’s an aesthetic you prefer. May be grown at select specialty nurseries.

2.Narrow-leaved Paperbark(Melaleuca alternifolia)

Melaleuca alternifolia is the “tea tree” plant. Tea tree oil has medicinal value for a variety of uses: antiseptic, antifungal, reducing inflammation and treatment of coughs and colds. Melaleucas are known in Australia commonly as “paperbarks” due to their whitish, layered bark. The cream-colored, fluffy flowers are also a trait of melaleucas. Melaleucas grow in seasonal swamps in Australia which explains why they do well in our dry/wet climate.

3.Myoporum(Myoporum laetum)

Native to New Zealand. Easy to ID - picking a leaf and holding up to light, you see yellow dots. Shiny leaves and purple fruits. Formerly a popularly planted tree for coastal CA, now nearly decimated by Myoporum thrips. This insect is hard to control because they get inside the leaves and distort them so pesticides are difficult to reach, although there are some spray programs available. ‘Clean and Green’ is a resistant cultivar according to Sunset. Avoiding drought stress seems to help with thrips resistance as well.

4. Canary Island Date Palm (Phoenix canariensis)

Planted in this area to give a tropical feel around the pond which was originally buillt for swimming. There are now more trees than originally planted because the tree can reseed prolifically when fruit falls somewhere conditions are favorable. Dates are not the edible dates that we buy, that is a related species, but these fruits are edible if not as tasty. Eaten mainly by non-native birds, has some nesting value for wildlife. Susceptible to Fusarium wilt which can be spread by pruning (dead fronds are typically removed in an urban setting).

5.Dead tree(unknown species)

Although we aren’t sure of the species, this tree serves as a testament to the difficult growing conditions here - coastal winds, salty water table, periodic flooding. Only a select few species can tolerate these conditions and many of them are from Australia, which has similar seasonal coastal swamps. However, roots need oxygen as well as water and a tree with permanently waterlogged roots will die. Too much salt in the water has its own hazards. Just as we cannot drink salt water and quench our thirst, salt draws water away from plant tissues, dehydrating the plant.

6.Mountain She-Oak, Drooping She-Oak, Coast Beefwood(Casuarina stricta)

These Casuarinas also appear to be casualties of the harsh conditions. We will see other Casuarinas later on that were successful. The goofy common names of this plant tells a revealing story about how immigrants from other parts of the world view trees. Europeans coming to Australia were all familiar with oaks, but Casuarinas must have thrown them for a loop. Still, they chose to name the tree after a familiar tree from home. It is surprising that immigrants to Australia did not call Casuarinas some kind of “Pine” since their leaves much more resemble pine needles. And indeed Aussies do refer to all conifers generically as “pines.” More about Casuarinas later.

7. Valley Oak (Quercus lobata)

Finally an “oak” that is actually an oak, and not only that, native to California! Valley oak is native to interior valleys, Sierra foothills and the Coast Ranges of California so it seems a bit out of its range here. However, it is immune to Sudden Oak Death so someone probably thought it was worth a try here. There’s plenty of space here for trees to reach their genetic potential of 70 feet or more, although wind may keep them smaller. Trees are deciduous and with age produce twisted, drooping branches on a wide-spreading canopy.

8.Coyote Brush(Baccharus pilularis)

An important native plant for wildlife, in the aster family. If you are planting a native garden at home, get plants that are grown from seed from a native plant nursery that also sells to habitat restorers, because the named cultivars sold in commercial nurseries are male clones. Plants grown from seed will produce seed and will also have better genetic diversity. Typically the smaller native plant nurseries will be able to provide you with the seed source of their plants so you know that not only is it not a clone, but if the plants come from your region or elsewhere in the state.

9.Horsetail tree, River She-Oak(Casuarina equisetifolia a.k.a. Casuarina cunninghamiana)

What looks like needles are actually branches - the true leaves are inconspicuous. These trees are supposed to do well in coastal areas and tolerate drought and salinity (although clearly even they have their limits) Sunset says they can be planted in desert areas.

10.Purple-flowered Mallee, Coffin Bay Mallee(Eucalyptus albopurpurea)

This is a rarity in California with a limited range even in its native Australia. Yet it seems to have been quietly succeeding here. Flowers range from white, pink, purple, mauve. We usually see Eucalyptus here with flowers that are white or in the red/orange/yellow color families so this is a nice pleasing exception. Unlikely to be grown here but you may be able to order seeds or plants from Australia.

11.Blackwood Acacia(Acacia melanoxylon)

You cannot even find this tree in the newest Sunset, it has fallen so out of favor. However as we know if we try to deny history we will fail to learn from it. Fortunately there is still an entry for it on CalPoly’s SelecTree website. There are many problems with Blackwood Acacia, including invasiveness - it will reseed but the California Invasive Plant Council has classified its invasiveness as limited. However it was once widely planted for its tolerance to coastal conditions, attractive yellow flowers and value as a screening or shade tree.

12. Coast Live Oak (Quercus agrifolia)

Native to the California coast, although not directly in coastal winds or on the shore. Leaves can look very different on the same plant - lower leaves are often spiny to deter browsers while leaves higher up lack spines. “Shade leaves” are larger than “sun leaves.” For this reason it is good practice to collect at least 10 leaves from this tree - and indeed any tree - before trying to identify it, because this kind of variance is normal on all trees. It is just more pronounced on Coast Live Oak. Trees are considered evergreen although they can go through partial defoliations.

13.Swamp Mahogany(Eucalyptus robusta)

Native to southeastern Australia. May flower any time of year and flowers may be maroon, pink or white. Notable for its light brown, thick bark. Potential to grow 60-75 feet high and wide, so requires space to grow. Grown in tropical areas as a lumber crop. From a 1963 US Forest Service report: Eucalyptus robusta wood is excellent for purposes requiring high strength and for finish work where an attractively figured, dark reddish-brown wood is desired.

14.Flaxleaf Paperbark, Snow-in-summer(Melaleuca linarifolia)

The poetic common names describe the leaf and bark, or the appearance of the copious white flowers all over the canopy. Like other melaleucas, it does well in swampy areas and could be a good solution for a poorly drained site that other plants don’t like.

15.River Red Gum(Poss. Eucalyptus camaldulensis)

This tree ID may not be accurate because the flowers and seed capsules are not present. Let’s look on the ground for any seed capsules to help out with ID. Eucalyptus camaldulensis has smooth, peeling bark and lance-shaped, blue-green leaves. Flowers are white or yellow and seed capsules are bell-shaped with a pointed bottom. As the common name suggests this tree can grow in wet areas.

16.Australian Tea Tree(Leptospermum laevigatum)

From the Greek: “Lepto” = thin + “sperma” = seed. “laevigatum” = smooth, likely a reference to the leaves. This plant looks best when it can sprawl irregularly. Attempts to manicure it will be futile and unsightly. White, 5-petalled flowers in spring. Good in cool, coastal conditions. Subject to light brown apple moth.

17.Sydney Golden Wattle(Acacia longifolia)

Resembles Blackwood Acacia but smaller and shrubbier. (10-25 feet tall) Can sprawl and lay down like Leptospermum laevigatum. Good screening plant. Like all acacias, Sydney Golden Wattle (wattle is a common Aussie term for acacia) is in the bean family, Fabacae. This means it has the ability to fix nitrogen - it can convert nitrogen present in the air to usable soil nitrogen thanks to small nodules on its roots. This allows plants in this family to grow in nutrient-poor soils.

18.Flooded Gum(Poss. Eucalyptus rudis)

Eucalpytus rudis has rough-textured bark and ovate blue-green leaves. Flowers are cream-white and seed capsules are bell-shaped (like half an acorn) with a star on the flat bottom. Native to southwestern Australia, As the common name suggests this tree can grow in wet areas. This tree like the other Eucalyptus here was part of a historic planting of rare Eucalyptus species to test what would be successful. Unfortunately the exact planting records were lost.

19.Myoporum(Myoporum laetum)

Why does this Myoporum look so different from the tree we saw earlier? Possible reasons: 1) could be a resistant cultivar. 2) could be more resistant due to better growing conditions, i.e. wetter location, higher water table etc. 3) the smaller shrub form may be easier for water and nutrients to reach the leaves so less stress on the plant over all, leaving it more able to resist the pests. Or a combination of any of these reasons.

20.Italian Buckthorn(Rhamnus alternifolia)

Native to Mediterranean region. Generally planted as a screening plant because the flowers are inconspicuous. Plants are either male or female and the females produce small black fruits, considered to be toxic. Often seen with cloudy yellow leaves and dark green veins which is a sign of iron deficiency.

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Trees protected by the City of Palo Alto tree ordinance

A permit is needed to remove or prune these trees.

Check the City of Palo Alto Tree Regulations.

Trees with low watering needs

These trees are best adapted to our climate and water availability.

Thirsty trees

These trees require frequent summer irrigation and will suffer from the drought cycle in our area.

Do not plant unless you are aware of a water source such as high water table or creek proximity.

Trees not recommended for planting

These trees are either invasive, do not perform well or create infrastructure or other problems.