NDSU Extension - Griggs County


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Feb 26

The Extension Connection Column by Jeff Stachler

Crown of Thorns

Good day! 

Pick up your crop pest guides at the Extension office.

Here are some meetings to keep in mind.  NDSU will be offering the Livestock Drought Planning Webinar Series.  Register for this series of meetings at the following website:  https://www.ag.ndsu.edu/drought .   Griggs County Pesticide Recertification will take place on March 18, 2021 starting at 9:00 AM.  To register for this pesticide recertification meeting go to https://tinyurl.com/GriggsPrivate .  If you have questions about registering for any of these meetings feel free to contact the extension office at 701-797-3312 or e-mail Jeff Stachler at jeff.stachler@ndsu.edu.

For those of you interested in horticulture, an in person virtual meeting series will take place at the County Courthouse on March 22, 29, and April 5 and 12, 2021 from 6:30 to 8:30 PM.  Please preregister by calling the extension office at 701-797-3312 or e-mailing at jeff.stachler@ndsu.edu. 

Crown of Thorns, Euphorbia milii, has thorny stems with long spoon-shaped leaves at the stem ends along with clusters of tiny flowers.  Crown of thorn flowers are very small and surrounded by colorful bracts in red, salmon, and yellow.  There are many cultivars varying in flower size and color. Crown of thorns is native to Madagascar.

In the 1970’s, breeding programs produced a wide range of plant forms and flower colors.  California hybrids were developed for their stout stems and larger colorful flower bracts often referred to as “giant crown-of-thorns” series.   German growers made selections of natural crosses producing thicker leaves and thinner stems with flower colors ranging from cream to various shades of pink and red.   Short and Sweet™ is a compact dwarf cultivar with soft spines and small bright red bracts.

In the early 1990’s new hybrids with larger flowers were developed in Thailand.  These Thai Poysean hybrids were likely the result of a mutation and spurred the production of hundreds of cultivars.  These new cultivars produced a huge range in flower colors and plant sizes.  Bract (flower) colors include pastel shades and blends of different colors.  Unfortunately many of these cultivars were lost in the Southeast Asian economic crash in the late 1990’s and the lack of successful introductions into the U.S.  There are some specialty nurseries in the U.S. that produce cultivars such as ‘Jingle Bells’ having soft pink bracts tinged in red and green to ‘New Year’ having buttery yellow bracts that change to cherry red as they age.

Crown of thorns is a very hardy plant tolerating a range of conditions.  Crown of thorns prefers full, direct sunlight and average temperatures.  They will grow in part shade, but flowering tends to be reduced.  Crown of thorns do best when the soil is allowed to dry between deep waterings.  Some hybrids prefer more frequent watering.  Fertilize lightly in spring and summer with a balanced fertilizer.  Over fertilizing will produce soft and vigorous vegetative growth with few flowers.  Use fertilizers with little to no micronutrients as crown of thorns are sensitive to these nutrients.  Some varieties like to be grown in small pots while others prefer large pots.  Plant crown of thorns in rich (high organic matter) well drained planting medium.  Plants can be pruned to keep their shape and size although most hybrids need little pruning.  Cut stems back to axillary buds to increase branching.  When stems are cut copious amounts of sticky, milky sap is exuded.  This milky sap may cause dermatitis for some people, temporary blindness if enough gets in the eyes, and is poisonous if ingested. 

Crown of thorns is easily propagated, but the cut end needs to be dipped in cold water or powdered horticulture charcoal to prevent the milky sap from running.  Allow cuttings to dry for two to three days before placing stems in well-drained planting media.  Water carefully as too little and too much will reduce successful rooting.  Seeds will not be produced unless flowers are hand pollinated with different plants.

There are few serious pests of crown of thorns.  Excessive watering is the most likely way to kill a plant.

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