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Monday - September 20, 2010

From: Houston, TX
Region: Southwest
Topic: Wildflowers
Title: Fertilizing hayfield with wildflowers in Brenham TX
Answered by: Barbara Medford

QUESTION:

I have property near Brenham, TX that produces wild bluebonnets, Indian paintbrush and other wildflowers each year. I would like to fertilize the pastures to help with hay production (the grass is harvested after the wildflowers have gone to seed). Is it okay to fertilize the pastures in the spring before the bluebonnets bloom or will it harm the wildflowers? Thanks, Ken Wright

ANSWER:

We used to live in Brenham, for a few years, and still drive through it frequently. We were always so impressed by the beautiful fields of wildflowers in Spring. You are to be congratulated for mowing sensibly for the seeding of those flowers. This is not a subject that has come up for us before, but it is bound to be an issue. We'll see how much information we can pass on to help you make your decision.

Our first thought is that fertilizing the field when the rosettes of the bluebonnets are up (usually early in January or even before Christmas) is that nitrogen-rich fertilizer might cut down on the blooming of the flowers. Since you are planting grasses for hay, obviously, the nitrogen-rich fertilizer is what you want for grasses, but it might retard the blooming on the wildflowers. The bluebonnet itself is a nitrogen-fixing crop, and it could be that the hay and the wildflowers will both benefit from this nitrogen, saving you from fertilizing, or at least not as much. With fewer blossoms, there will be fewer seeds, and then perhaps a more sparse bloom display. Once the seeds are set, and blooming is over, very little can hurt those hard-shelled bluebonnet seeds. Although Nature plants them naturally when the seed pods mature in May to June, the experts say that if you are planting the seeds yourself in a garden, you should do so in November.

From this Iowa State Extension website Fertilizing Pasture we extracted the following information about legumes (bluebonnets) and grasses in the same fields:

"Legume-grass pastures normally do not need nitrogen. Legumes fix nitrogen from the air for their own use and for grass growing with the legume. If the forage stand is one-third or more legume, do not apply nitrogen fertilizer. If the legume portion is less than one-third, the grass in the mixture is likely to respond to nitrogen fertilizer. Legume or legume-grass pastures have a higher requirement for phosphorus and potassium than do grass pastures. These two nutrients not only increase legume yields but also enhance disease resistance, winter hardiness, and longer stand life."

It doesn't sound like you need instructions for seeding, your wildflowers seem to be taking care of themselves. However, please read this How-To Article on How To Grow Bluebonnets, to give you some more understanding of the life cycle of the bluebonnets.  Castilleja indivisa (Entireleaf indian paintbrush) which you mentioned grew in the same fields, is hemi-parasitic, meaning it will extend its roots into the roots of other plants, drawing nutrients from them. That is why it is so frequently seen with the bluebonnet, because of all the nitrogen the bluebonnet is injecting into the soil. Because these plants are native to Central Texas, they should not need fertilizing. Does your grass? As you will note from the information above on fertilizing pastures, the legume-grass pasture may have a higher requirement for phosphorus and potassium, and the two nutrients will increase legume yields, as well as the grasses.

So, it would seem that fertilizing the grass should not hurt the wildflowers, depending on when you fertilize, as well as the composition of the fertilizer. As we mentioned before, a high-nitrogen fertilizer on the developing plants in late Winter can suppress blooming, while encouraging greenery. But, if you can use a lower-nitrogen and higher-phosphorus and potassium mixture, that should not be an issue. You probably already know that the bluebonnet seeds ripen about 6 to 8 weeks after the blooms, and the field can then be mowed, scattering the seeds for next year. Hopefully, we have given you enough information about the bluebonnet that you can determine when you want to fertilize, since we don't know much about grass fertilization.

Since we are aware that people in the know in Brenham consider both the bluebonnets and the hay-making as important, we are going to suggest you double-check this with the AgriLIFE Extension Office for Washington County.

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