Issue: October 26th, 1998

Skinny Pampas Grass revisited


My neighbor has a pampas grass that has big, fat plumes and the neighbor up the street also has a pampas grass but the plumes are small and skinny. Why?


Last year I received a similar question. In the answer I suggested that changes in lighting due to growth of surrounding trees or changes in other cultural conditions may be the cause. Albuquerque Master Gardener, Ruth Bronson, did a little research for me and pointed out that the Pampas Grass has male and female plants. The prettiest plumes are on the female plants.

So this year, while culture may also be a problem, if the plants once had pretty plumes and now don't, I will suggest that your plants with skinny, less attractive plumes are male plants. Buying the plants when they are in bloom helps avoid the problem. By the way, if there is a male plant in the clump with the female which has nice plumes when you buy it, the male might take over and predominate after a few years and a pretty female plant may seem to change to the male.

What to do with left-over pesticides


I was told that I couldn't dump leftover insecticide when I finish spraying. I was also told that I should not save the insecticide from one week to the next to use again. Which is right?


Both are correct. Dumping leftover pesticides, insecticides, fungicides, herbicides, or any other material, is not good practice. This creates what is called a point source of contamination, a place where the contaminants are highly concentrated and more likely to leach into the ground water. Here in New Mexico that is especially critical in sandy soils or in areas where the aquifer is in fractured rock. In the fractured rock situation, there is a thin layer of soil over rock with cracks leading to the water. It takes relatively little moisture to leach the chemical into the aquifer in that situation. However, regardless of the situation, don't dump leftover pesticides on a single spot.

Many insecticides and some other pesticides lose potency or undergo chemical reactions if allowed to sit in diluted form for a time, even a few hours in some cases. It is best to use the pesticide immediately after mixing. If it will take a few hours to use it, use a buffering solution in the water into which the pesticide is mixed.

So, what do you do with any leftover pesticide? Don't have it. Mix only what you need. It is better to mix too little and need to mix more than to mix too much. If there is a little left, rather than dumping, spray it out over an area or crop allowed by the label. That is, if the product is for lawns, spray it out over the lawn. If the product is for vegetable gardens, spray it out over the vegetable garden. The same holds true for the rinse water produced as you clean your sprayer. Don't dump it; spray it out over an appropriate area or crop.

It is important to use pesticides correctly. Even "organic pesticides" should be used in the manner described above. Misuse of pesticides, any pesticide, is a problem which must be remedied. Remember that when used properly, pesticides can enhance our landscapes and gardens, but used improperly, they can be hazardous.

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:, 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.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!