Paraserianthes lophantha lophantha - Plume Albizia

I rarely see Plume albizia used intentionally as a landscape plant. Most of the specimens I see are along the highway as escaped specimens growing with Acacia. These are small trees growing to 15' with a slightly narrower spread, with greenish yellow flowers. Most commonly seen on Highway 1 heading south between Larkin Valley Rd and Buena Vista Rd in the medium. This name is new to me. I was taught the old name, Albizia distachya.

Leaves are deciduous to partly evergreen, alternate, bipinnately compound, 6-12" long, containing 7-14 pairs of compound leaflets, each leaflet with up to 40 or so tiny 3/8" long, linear to oblong leaflets with entire margins, and a small pointed tip. There is a gland on the petiole. Leaves usually glabrous, but occasionally with some small hairs.

Leaflets are about 3/8" long.

Flowers early winter to mid winter around SC. Numerous greenish yellow flowers are grouped in 4-6" long elongated clusters.  Most of the show are the stamens.

Fruit is a pod, 3-4" long, flat, drying reddish brown. Shiny black flattened seeds.

Stems slightly hairy.

Synonyms
Albizia distachya
Albizia lophantha

Misidentification:
Albiza julibrissin is similar in foliage but the flower color and arrangement of the flowers is very different.

Location:
Aptos
Highway 1 heading south between Larkin Valley Rd and Buena Vista Rd in the medium.

Santa Cruz
802 Fair St on the Handley St. side of the house.

Ulmus pumila - SIberian Elm

The Siberian Elm is a very common elm in many parts of the country, and pretty common here. They are exceptionally hardy, weedy, brittle, usually with some dead wood, but easy to grow. They are medium to large deciduous trees with a fast growth rate to 50-60' forming a broad upright habit with several strong primary lateral branches.

Leaves are deciduous, simple, alternately arranged, 2-3" long (hence the pumila = small) elliptical to oblong or ovate shaped, with singly serrated margins, medium green upper surface, lighter below. Unlike many elms the leaf base is more or less symmetrical. Fall color usually yellow, but may see a little red here and there. Often no fall color at all.

Terminal stems are thin, resulting in a slightly weeping habit of the fine branching.

These are flower buds, rounded, while the vegetative buds are tiny. Small red flowers in the spring.

Fruit is a flatten samara, about the size of a dime, thin papery with the seed more or less in the middle.

Bark is rough, platy, gray and dark gray to black.

An ever so common sight on these elms is the constant leaking for ooze from wounds or natural cracks. Bacterial wetwood.

Fall color up in the PNW.

Misidentification:
Ulmus parvifolia is commonly confused with this, though several distinct difference are quite obvious. The bark for one, flowering season - this one blooms in spring, and the growth habit - this one is larger, and not as layered as U. parvifolia.

Location:
Aptos
309 and 311 Spreckels Dr.

Santa Cruz
Nice one at the Cemetery on Ocean Street Extension is in the first picture.

Ailanthus altissima - Tree of Heaven

The tree of heaven, what a funny name and I suspect that most horticulturalist think it might be from that other area. Very fast growing, 50+ feet in cultivation. Can actually look pretty nice but often it's lopsided. Weak wooded and weedy to boot. This is the tree that grew in NY city, in the sidewalk cracks. 

Leaves are deciduous, pinnately compound, 1-2' long, with 11-25+ ovate to lanceolate 1-2" long leaflets have entire margins except for a couple of teeth at the base and a distinct gland on one of the teeth. Leaves are dark green with a whitish underside. 

Distinct gland on the one side of the leaf base.

Trees are dioecious, male and female trees. Small yellowish green flowers in the spring. Male flowers smell bad when open. 

Bark is smooth when younger but developing shallow fissures. Stems are thick, reddish colored and have heart shaped leaf scars. 

The fruit found on females only is a samara, about 1" long and is twisted so it spins when it drops to the ground. The female trees look their best when covered with red fruit.

Misidentification:
Perhaps Koelreuteria, either can have similar looking foliage.
A reader suggested Rhus typhina as well. I agree, we don't see them here but in colder climates for sure. Rhus typhina has very hairy stems and more deeply dissected leaf margins. Attractive plant in the fall. 

Location:
Aptos
Soquel Dr at Capitola Rd Empty lot

Santa Cruz
Some on Chestnut heading up the hill toward Mission, no address, just in the wild area there.

Watsonville
121 Carey Rd. (corner of Carey and GreenValley Rd)