Yellow wallflower

I have a friend who asked me about yellow wallflowers. He wants to know how long they last and if he should separate them to keep them healthy.

I find information on mauve wallflowers but not on yellow. I guess they are the natives. I haven't been able to find anyone who knows about these.

Elizabeth G.

There are several species of "yellow" wallflowers. The native one is Erysimum capitatum and grows throughout the West in arid conditions. I have seen it flowering at the top of the Sandia Mountains in October after the first freezing nights. (Their primary blossom time should be spring.) The Siberian Wallflower Cheiranthus allionii (this genus seems to have been reclassified to be included within the genus Erysimum) and Erysimum asperum are also yellow. There are also other yellow and orange species.

In books and on the Internet, this group of plants (related to mustards) is described as annuals, biennials, and perennials. Some are short-lived perennials, but others are biennials and annuals. It may depend on the variety grown. Even within the species Erysimum capitata, there are descriptions of some as annuals and biennials, but one variety is called var. perenne to indicate that it is a perennial. Some gardeners describe the annuals and biennials as perennials because they reseed prolifically.

The Western wallflowers are native to much of the U.S. They are missing as natives in only the Southeastern states of the U.S. Some are called dune wallflowers because they grow in the sand dunes on the Southern California Pacific Coast and Texas Gulf Coast. Their colorful and sometimes fragrant flowers make them good candidates for growing in our New Mexico gardens. Improved varieties are being introduced from nurseries in many countries of the world. Some of these improvements may be increased flower size and different colors, but if these plants are from wetter regions, the low water characteristics may be lost. Test them under your conditions to determine water efficiency.

Since they are short-lived perennials or biennials (or annuals) I would not recommend dividing the plants. That is based on the above evidence. Some gardeners may choose to divide the perennials. If this results in increased life span, I would like to hear of it.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

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