Scientific: Poincianella mexicana (formerly Caesalpinia mexicana)
Common: There are many common names for this plant. They are Mexican poincianella, Mexican Caesalpinia, Mexican Poinciana, Mexican bird-of-paradise, or yellow bird. All of this is confusing and demonstrates why use of scientific names to properly identify landscape plant material is important.
Family: Fabaceae (Leguminosae)
Origin: northern Mexico into south Texas

Pronounciation: Poin-ci-a-NEL-la mex-ee-KAA-na

Hardiness zones
Sunset
12-16, 18-23
USDA 9-11

Landscape Use: Large seasonal accent, quick background though canopy is too sparse to make a screen, small multiple-trunk or standard tree, a good plant for transition areas in oasis landscape design themes.

Form & Character: Upright, sparse and open, arborescent character with age and training, festive, warm, and attracting, brittle.

Growth Habit: An evergreen, woody perennial. This fast-growing shrub is strongly upright and sprawling to 10 to 20 feet or more with less than equal spread. The 'Mexican bird' or 'yellow bird' has INCREDIBLY BRITTLE wood that one could actually smash up into a mulch material with bare hands.

Foliage/texture: Leaves twice pinnately compound, leaflets to 3/4 inch and less, light green, stems without spines but with well-defined, light grayish white lenticels; medium fine texture.

Flowers & fruits: Lemon yellow flowers on terminal racemes, fruit are green pods in terminal clusters turning to brown pods in early summer, indehiscent. Pods are heavy and weigh down branches. When pods are dry and brown, the seeds will "crackle and pop" out of their pods if splashed with water.

Seasonal color: Festive yellow color in early spring and late fall

Temperature: Heat loving, more cold hardy than Caesalpinia pulcherrima, damaged by cold when temperatures fall below 25oF.

Light: Full sun

Soil: Tolerant. Regular fertilization will increase foliar canopy density which is otherwise typically sparse to open.

Watering: Needs summer water

Pruning: Because of its strong upright habit, training Mexican or yellow bird is difficult. I rather choose to elevate the canopy base in order to train this shrub into a small multi-trunk landscape tree. In stark contrast, horticultural clods stubbornly do the only thing they know how to do and repeatedly shear this shrub throughout the year into Oblivion. If one really desires a small size, then I prescribe that it's better to extensively prune Mexican bird shrubs to near ground level in late winter and then manage the regrowth by making selective heading and thinning cuts with hand-held pruners in late May/early June so as to remove ugly clusters of terminal brown fruit pods.

Propagation: Seed

Disease and pests: Sometimes white flies in late summer.

Additional comments: So here's my official story line....Mexican or yellow bird of paradise (or whatever common name you call it) in Phoenix is a servicable, LARGE accent shrub with an open canopy that can attain small tree stature with age and training. The wood is amazingly brittle with distinct lenticles. The beautiful yellow spring flowers attract hummingbirds. The seed pods however are visually distracting and make this shrub look bad to almost goofy during late April and May.

But now here's my unofficial storyline about Mexican or yellow bird of paradise.....This large shrub/small tree grows into the most awkward size for today's cartoon desert landscapes. It's too small for horticultural clods to say, "Hey man, this is a tree so let's limb it up like a mesquite". And it's too large for these same horticultural clods to say, "Hey man, this is a bush so let's get out the gas-powered hedgers and trim this guy up like we do to every other 'bush' in Phoenix". It's because of this awkward "too large, but too small" size that I recommend that Mexican or yellow bird of paradise NEVER be planted where professional landscape gardeners (cough, cough) are employed to "mow, blow, and go".

Exception to the rule: One exception to the above narratives is the patented hybrid cultivar from Mountain States Nursery in Glendale, AZ. This hybrid cultivar, Caesalpinia x 'Sierra Sun' (using the former genus name), is simply beautiful. It is a quite symmetrical and rather dense free-flowering large shrub or small tree that'll grow to a height of 15 feet with near equal spread. It is so nice that 'hort clods' need to be banned from coming close to this gem. It just does not need to be pruned...cough, cough...sheared, like ever.