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Thursday - March 18, 2010

From: Austin, TX
Region: Southwest
Topic: Non-Natives, Trees
Title: Flowering problems with Mexican Plum and Mimosa in Austin, TX
Answered by: Jimmy Mills

QUESTION:

Greetings, My Prunus mexicana (Mexican Plum) did not produce flowers before its leaves. Can you tell me why? I was hoping to have some fruit this year. Also, as of this morning March 13. My Mimosa has not bloomed nor has any leaves. I do see a few green shoots and the branches are pliable. Does it need phosphorus?

ANSWER:

Let me begin by stating that the mission of the Lady Bird Johnson Wildflower Center is to increase the sustainable conservation of native wildflower, plants and landscapes. Mexican plum Prunus mexicana (Mexican plum) is right down our alley. Mimosa, Albizia julibrissin (silk tree), not so much.

The Mexican Plum is a native to North America and occurs in Texas from the northeast southward to the Edwards Plateau and into Mexico. Its showy, fragrant white flowers that are followed by juicy fruit in the summer make it a desirable ornamental plant throughout Central Texas. In the case of your tree, I have a couple of questions.

Did the tree flower last year? If the answer is yes, you need to determine what has changed since then. What about fertilizer? Often times, absence of flowering is a result of a change in the relative amounts of nitrogen and phosphorous (the nitrogen/phosphorous ratio). If the ratio of N/P is high, flowering can be inhibited. The imbalance can occur if the tree is getting too much lawn fertilizer which has higher nitrogen levels. Keep this in mind for next spring. Since the leaves are already out, your tree is not going to flower this spring. If the answer is no, then we need to know the age of the tree. Perhaps it isn't old enough to flower. This link from Zanthan Gardens gives a chronology of a gardener's experience with his Mexican Plum that might prove helpful.

Mimosa is a native of China and was introduced into the United States in 1745 where it has been cultivated extensively as an ornamental. It has become a popular ornamental because of its showy and fragrant flowers. However it has been classified as a Category II invasive by Florida's Exotic Pest Plant Council. The link suggests some plants that might be used as alternatives to Mimosa.

Cercis canadensis (eastern redbud)

Amelanchier arborea (common serviceberry)

Cornus drummondii (roughleaf dogwood)