The Senna species; to plant or not

The Texas Mountains Laurel is a very slow growing large shrub or small tree. The purple flower clusters appear in early spring, and smell like grape bubble gum. The pods produce a hard, orangey-red bean, which is purported to be poisonous. This plant is notoriously slow, but starts blooming when it is only 2 feet tall.The Turpentine Bush is an Arizona native, and is a great choice for a medium size low water used shrub. The Turpentine Bush reaches about 4 feet tall and wide, and is covered with yellow flowers in the fall. The leaves are bright green, giving it a lush appearance despite its drought tolerance. It looks almost exactly like Chrysactinia, only larger. View the list »
The Texas Ranger species comes in a variety of flower colors from deep violet to rosy purple. There is one species, the Texas Ranger ‘Green Cloud’ that has white flowers. The Texas Ranger also varies considerably in height and width. Remember that some plants can reach over 6 feet tall and wide. 

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When looking for an evergreen drought tolerant shrub species for the desert areas around Tucson and Green Valley, you might be wondering about the Senna species, as when it is doing well and in full bloom it can be quite attractive.

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The problem with Sennas is they freeze hard below twenty degrees, despite what many reference books may tell you. This leaves you with either a totally brown plant until late spring, and of course no flowers since they bloom in late winter and early spring, or in some cases as in the hard freeze of 2010, a dead plant.

The Senna is also not very attractive after blooming, as brown seed pods persist after blooming, requiring either shearing or hand picking off to improve the appearance.

If you want to skip the high maintenance plant, try low maintenance shrubs such as the Texas Ranger, Texas Mountain Laurel, or the yellow flowered Turpentine Bush. With the Texas Ranger, make sure you are selecting a species that won’t grow out of its space.

View the list
  • The Texas Ranger species comes in a variety of flower colors from deep violet to rosy purple. There is one species, the Texas Ranger ‘Green Cloud’ that has white flowers. The Texas Ranger also varies considerably in height and width. Remember that some plants can reach over 6 feet tall and wide. 
  • The Turpentine Bush is an Arizona native, and is a great choice for a medium size low water used shrub. The Turpentine Bush reaches about 4 feet tall and wide, and is covered with yellow flowers in the fall. The leaves are bright green, giving it a lush appearance despite its drought tolerance. It looks almost exactly like Chrysactinia, only larger. 
  • The Texas Mountains Laurel is a very slow growing large shrub or small tree. The purple flower clusters appear in early spring, and smell like grape bubble gum. The pods produce a hard, orangey-red bean, which is purported to be poisonous. This plant is notoriously slow, but starts blooming when it is only 2 feet tall.
View the list

, Tucson Gardening Examiner

This author has lived in Arizona since 1972 and has been gardening for more than 28 years. A landscape architect and certified arborist, Linda teaches classes for everyone in desert plant care for Green Valley Recreation, and provides services in landscape design. Contact her at Linda...

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