June 28th, 2006
Retama Jerusalem Thorn

photo: Retama
2006-06-28. A roadside planting of retama forms an airy hedge along a path in Sunset Valley, TX.

Retama (Parkinsonia aculeata) forms a small, airy, lime green tree that appears as fresh as spring on even the most droughty summer days. You can use it as a specimen plant or to create a vicious hedge. The smooth green trunks and branches are covered with serious spiny thorns hinted at by one of its common names, Jerusalem thorn. Retama can photosynthesize through its green bark; its Spanish name is palo verde (green bark). From a distance retama looks like it’s covered in stringy green streamers which cast a filtered shade. Having such very small leaves it loses little moisture to transpiration making it extremly drought and heat tolerant. Overall, it has a delicate, feathery appearance. Flowers are bright yellow.

Latin names are a bit confusing as the Parkinsonia clan used to be called Cercidium. The common names are worse as nurseries in Austin usually sell this as retama but it’s not the same as weeping white broom, Retama raetam. The City of Austin Grow Green site hedges its bet and calls it Retama Jerusalem Thorn.

Perhaps, as one reader suggested, it is overused in Phoenix. I imagine that when people first brought it under cultivation in those desert towns they were thinking, “Green! Green! Green!” And it’s such a carefree plant that it’s perfect for those median plantings along highways and outside of subdivisions. However, in Australia it’s an introduced invasive weed.

In addition to being spiny, retama has a reputation for being a messy tree. Mine is too small to make much of a mess. If you have small children, or a small yard, you might prefer to admire retama from the comfortable distance of your car. I’ve neither, so I’ve taken a chance with it. Give me another five years or so and I’ll tell you whether I think it’s a curse or a blessing.

Zanthan Gardens History

Friday October 24, 2003
Planted a 1 gallon retama that I bought on sale from Barton Springs Nursery for $3.99.

First flower of the season and ever on this plant which is about 5 feet tall. I have several plants half the size that I received started from seeds from Larvalbug.

This is a terrible weedy tree. Do not grow it in your garden. It’s great for highway planting but in your garden you’ll have nothing but thorns and woe. It seeds like crazy and even the small seedlings are painful to pluck. Once you let it in your garden, you will have a difficult time getting rid of it.

by M Sinclair Stevens

6 Responses to post “Retama Jerusalem Thorn”

  1. From M2 (Austin):

    I have always wondered about that plant / tree / bush. I pass several driving to work. It’s a really lovely desert plant, catching breezes and such a lovely green. Plus I’m thrilled to know the name “Palo Verde.”

  2. From r sorrell (Austin):

    So THAT’s what a Retama tree is. I had no idea. There are a couple in my neighborhood, but I see lots of them west of the fault line. I recall seeing a picture of these little trees with red roses as an understory planting. It was a really nice combination.

  3. From Judith:

    I always find it fascinating that what is invasive in one place is not in another. The Retama Jerusalem Thorn looks light & airy, quite lovely. I am intrigued with your notes, per usual, “Friday October 24, 2003–Planted a 1 gallon retama that I bought on sale from Barton Springs Nursery for $3.99..

  4. From luvsPhoenix:

    There are other trees also referred to as Palo Verde that are native and not invasive. The Foothill Palo Verde and Blue Palo Verde are the state trees of Phoenix. They are a welcome sight during the bloom periods. They also have a longer life span.

    Once again Latin proves slightly more useful in distinguishing between common names. The palo verdes to which you refer are Parkinsonia florida nee Cercidium floridum (blue palo verde) and Cercidium microphyllum (foothill palo verde). The master gardeners of the University of Pima County Cooperative Extension warn that the related Parkinsonia aculeata naturalizes aggressively and is considered a noxious weed. They give it the common name “Mexican palo verde” although it is actually native to Argentina where the Parkinsonia seed beetle keeps it in check. In Australia, Parkinsonia aculeata is an introduced weed of national significance and regarded as one of the worst weeds on the continent. In 1998 it was declared a noxious weed under the Rural Lands Protection Act. Hmmm. Maybe I shouldn’t have planted it in my meadow. — mss

  5. From George McNamara:

    I have a thorn that was given to my late wife,and she was told that it was a Jerusalem thorn it is about two feet tall, it has rather long heart shape leaves, the blossoms are a red to orange in color and are about a half inch in diameter. it’s very hardy and can go a long time without water. This plant dose not seem to match any of what is described as a Jerusalem thorn.(Help)

  6. From Katey Renz:

    I am not an expert, but could your plant be “Crown OF Thorns”. Type it in on the internet they have great pictures. Sorry about the loss of your wife.