parkinsonia

( par - kin - SOH - nee - uh )

At-A-Glance Information

This genus of flowering deciduous trees, known under the alternative botanical name Cercidium and under the common name Palo Verde, needs full sun and little to moderate water to perform well. These trees are some of the best desert shade trees, and have beautiful bark and flowers. Blooms are bright yellow, and leaves drop quickly in response to drought and cold. The flowering branches are attractive in cut flower arrangements. Take care when planting these trees in the landscape, as many species have sharp spines that can damage skin and clothing of humans and pets.

Parkinsonia Species and Varietals

the genus Parkinsonia is a member of the plant family Fabaceae and includes 11 species. The genus is named for English botanist John Parkinson. The best growing zones for Parkinsonia vary depending on the species. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Parkinsonia aculeata (Jarusalem Thorn, Mexican Palo Verde, Jelly Bean Tree, Palo de Rayo, Retama)
This species is native to the southwestern United States and Mexico, and grows well in zones 8-24, H1 and H2. It reaches 15-30 feet tall and about as wide, and has yellow-green bark and spiny twigs. Flowers bloom in springtime, and intermittently through the rest of the year. They are followed by seed pods that drop off the tree in summertime, creating a bit of a litter problem. Will reseed freely in desert climates, and can tolerate alkaline soils.

Parkinsonia africana (Green-Hair Tree)
This species is native to Angola, Botswana, Namibia, and South Africa, and forms a bush that reaches between 3 and 10 feet tall when mature. These plants prefer to grow in desert or semi-desert habitats. Flowers are yellow, and are followed by yellow to brown seed pods. Wood is resistant to heat and is used locally to make smoking pipes. 

​Parkinsonia 'Desert Museum'
Best in zones 8-14 and 18-20, this species is a hybrid between Parkinsonia aculeata, Parkinsonia microphyllum, and Parkinsonia floridum. These trees reach 20 feet tall and just as wide in just 3-5 years, and has large blooms that appear most profusely in springtime, and rebloom if possible in summer. Stems and leaves are light green, and this tree has no thorns.

​Parkinsonia florida (Cercidium floridum) (Blue Palo Verde)
This species does well in zones 8-14 and 18-20 and is native to desert areas in southern California, Arizona, and Baja California. Reaches 35 feet tall and 30 feet wide in garden settings. Leaves are blue-green, as are branches, and flowers are bright, pure yellow, blooming in clusters in springtime.

​Parkinsonia microphyllum (Parkinsonia microphylla) (Little-Leaf Palo Verde, Foothills Palo Verde)
Does well in zones 8-14 and 18-20, and are native to southern California, Arizona's Sonoran Desert, and Baja California. Slowly reaches 20 feet tall and just as wide, with yellow-green leaves and bark. Springtime flowers are pale yellow.

Parkinsonia praecox (Palo Brea, Sonoran Palo Verde)
This species grows best in zones 10-14 and 18-20, and is native from the Sonoran Desert down through South America. It has an umbrella-shape when mature, and a moderate growth rate, reaching 20 feet tall and wide. Bark is lime green as are leaves, and springtime flowers are bright yellow.

Parkinsonia texana (Border Palo Verde, Texas Palo Verde, Retama China)
These plants grow as small trees or shrubs that reach about 25 feet tall and spread to 20 feet wide. These trees and shrubs are considered heat and drought-tolerant, and have a preference for alkaline soils. Flowers are commonly yellow, sometimes with red markings and bloom from April through June in their native range.

Caring for and pruning parkinsonia Trees

These beautiful landscape trees do well in full sun. For optimal growth and foliage color, make sure that the tree receives between 6 and 8 hours of direct sun each day. These trees can grow to be quite large, so make sure that the chosen planting site has enough space to allow for the full size of the tree. They can reach widths of 20-25 feet wide and 33 feet tall when mature. These trees prefer moist but well-draining soil that is slightly acidic to neutral with a pH of between 5.5 and 7.0. They can tolerate a wide variety of soil types (including clayey), as long as they are well-draining, but do prefer loamy soil. Apply a thick layer of mulch around the base of trees to suppress weed growth, increase soil moisture retention, and help to regulate soil temperatures. Water new plantings regularly as they develop strong root systems. Water should be applied to young trees about once a week during the summertime and monthly in the wintertime. During extended dry or hot spells, make sure to provide extra deep waterings. Established trees are very drought-tolerant, getting by on deep waterings only during the driest months of the year. Water deeply, allowing soil to dry out between waterings to discourage fungal root rot issues.

These trees do not require heavy feedings and typically do well with a simple application of organic compost to their root zone yearly in springtime. If trees seem to be struggling or foliage is somewhat discolored, trees may benefit from an extra feeding with a balanced, slow-release fertilizer (such as a 10-10-10). Avoid over-fertilizing trees, as this can negatively affect their growth and development over time. Mature, established trees do not need fertilizing. These trees also don't require heavy prunings, and have a natural open canopy shape. Prunings should focus on maintaining this form instead of changing it. In late winter or early springtime, remove dead, broken, or diseased branches and lightly shape the canopy by removing crossing or poorly placed branches. Don't prune off too much foliage at any one time, as this can damage the tree and open it up to attacks from pests and disease.​

Propagation

Parkinsonia can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Parkinsonia, follow the instructions below:

Propagating Parkinsonia by Cutting
  1. Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
  2. In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch semi-hardwood portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
  3. Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
  4. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Parkinsonia by Seed
  1. Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
  2. Harvest your seeds. The seed pods on Parkinsonia plants are pretty easy to spot, they're large and dangle from the branches, left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
  3. Parkinsonia seeds have a hard coating that protects them, but this coating also makes it a little difficult to get them to germinate. We can help the process along by scarifying them with sandpaper (or simply rubbing them against an abrasive surface). Do this with as many seeds as you can; they will probably not all sow, and the ones that do will be of varying characteristics. The more seeds you plant, the more chances you will have to get the resulting shrub you want. Place your seeds in lukewarm water for six hours. Viable seeds will sink to the bottom, and non-viable seeds will float to the top. You can discard any seeds that float.
  4. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
  5. Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.
Palo Verde trees produce seed pods.
Palo Verde seeds.

Problems and Pests

Parkinsonia trees are not typically susceptible to many issues, though they can suffer from time to time from the following:
  • Snow Scale
  • Fungal Die-Back
  • Termintes
  • Root Rot
  • Witches-Broom
  • Palo Verde Root Borer
  • Trunk Blister
For more information on these pests and diseases, consult the following pages:

Gallery

Parkinsonia spp. is the state tree of Arizona.
These trees are perfect for creating shade in desert landscapes.
Parkinsonia trees bloom profusely in springtime.

Videos

All about Blue Palo Verde.
Learn about these water-wise superstars.

Resources

Germinating Palo Verde Seeds
Parkinsonia Growing Guide
How to Grow Parkinsonia - Jarusalem Thorn
Wikipedia: Parkinsonia
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 475, Parkinsonia
If you have any questions, comments, concerns, or photos you’d like to add to the gallery, please let me know by sending me a message using the button below!
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