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Southwest Yard and Garden

This column comes through the Grant County Extension Service out of New Mexico State University.

snowmeltTwo cups of snow scooped up from the front yard at the NMSU Agricultural Science Center at Los Lunas on January 3rd melted down to a little over 1/3 cup of water, but this isn’t always true because temperature has a big impact on snow density. Photo credit M. Thompson.

Question: We got 4 inches of snow just before the New Year that’s still melting a week later. I’m glad the established trees and shrubs are getting some water but is it enough to hold off on watering manually this month?

Joe S., Belen, NM 

Answer: There’s a rule of thumb that 10 inches of snow equals 1 inch of water, but it really depends on how wet the snow is, and that depends on temperature. Drier snow can be expected at lower temperatures and vice versa. I found some fun calculations and snowmelt discussions online. (Just like snow weight, fun is relative.) “In general, colder temperatures make snow fall less densely and lower the rain-to-snow ratio, resulting in more inches of snow per inch of rain… If 3 inches of rain are expected but the temperature drops suddenly to 5 degrees Fahrenheit, 120 inches of snow will fall” (Richard Graham, www.sciencing.com). That’s compared to 30 inches of snow required to get 3 inches of water when temperatures are close to freezing.

Until this past monsoon, I’d have said we’ll never expect 3 inches of rain on a single day in New Mexico. And I would have been wrong. On August 16, some areas of Doña Ana County got over 2.5 inches of rain. On July 24, more than 3.5 inches of rain was recorded in Santa Fe and Colfax Counties. Dr. Curtis Smith and I drove back down from Raton in that wild rainstorm. And some reported almost 4 inches of rain on August 24 in Grant County! When I searched back in previous years, there were lots of times when some lucky part of New Mexico got that much rain on a given day.

Question: I have a large monarch butterfly garden, and I gathered zinnia seed heads to plant next spring. Zinnia seeds appear to have two distinct morphologies. The ray flower seed is shield-shaped and the disk flower seed is smaller and flatter. Which of the seeds is viable? I have researched and found some who say only the ray seed, some say only the disk seed, and some say both. Please let me know which zinnia seed is most viable and why.

Tim P., New Mexico

swyg01Zinnia showing off both disk and ray flowers at the NMSU Agricultural Science Center in Los Lunas. Photo credit M. ThompsonAnswer: I know exactly what you mean. I’ve had this question before myself. Zinnias were one of my first garden successes when I moved to Las Cruces in 2009. I too gathered the seed heads and I too wondered which part was the true seed that should be saved. That year I just saved the whole shebang. In the late spring I crunched up the entire dried flowers and sprinkled them around the garden. It worked, so I kept that routine right up to today.

Question: I love the poinsettias I bought this year, but one is already starting to droop pretty badly. How do I keep them looking good through the season?

Elizabeth S., Santa Fe

Answer: Did you know you can purchase locally-grown poinsettias at plant nurseries across the state?

poinsetta1Poinsettias were already showing off their color potential at the end of October. (Photo by M. Thompson)I interviewed poinsettia growers in Albuquerque, Santa Fe, Las Cruces, Radium Springs, and Estancia to find out more about poinsettia production in New Mexico, how to get my hands on one (or a few) this season, and how to take care of them at home.

The City of Albuquerque Parks and Recreation Department grows its own poinsettias for holiday displays at the Albuquerque International Sunport and various City Hall buildings. I remember being struck by the vibrancy of the gorgeous Sunport poinsettia planters last December. This year, I got to visit the city’s greenhouses twice to check on the growing process. When I first visited in late August, each plant was looking puny, but promising. By the time I made it back by to check on their progress just two months later, they’d grown by leaps and bounds.

by Dr. Marisa Thompson

chollaCholla infested with cochineal scale. (Photo by S. Moran)

cholla2Waxy white clumps produced by cochineal scale on cholla. (Photo by S. Moran)Question: What’s the white cottony stuff growing on my cholla cactus? And should I do anything about it?

Albuquerque resident via Bernalillo County Extension Horticulture Agent, Sara Moran

Answer: Although it looks like cotton fibers, that stuff is actually a fine wax produced by adult cochineal scale insects, and little black specks may be their nymphs. It’s common around these parts on cholla (Cylindropuntia spp.) and prickly pear (Opuntia spp.) cacti. The similar-looking white beards on other cacti, like the Peruvian old man (Espostoa lanata) and Peruvian old lady (Espostoa melanostele), are normal, healthy modified tissues, not an insect product. The white waxy coating made by cochineal scale on landscape chollas and prickly pears helps protect these true bugs from predators—and insecticides.


cottonwood color comparisonThe same vista, 20 days apart, showing the bright colors all turning dark brown down in the bosque at River Park in Los Lunas. (Photo by Marisa Thompson)Question: Why are some cottonwood trees turning brown rather than yellow this fall? Sometimes a portion of the tree (often the lower portion) turns brown while the crown does turn yellow. I think I have seen this in other years, but this fall it seems more pronounced. Is it weather related? Moisture?

Wes B., Albuquerque, NM

Answer: Explanations for why leaves change color the way they do can be related to the species or cultivar, temperature fluctuations, seasonal day length changes, and potentially the soil moisture levels too. A general rule is that while temperature tends to affect the intensity of leaf color, it’s the shorter days and longer nights that trigger overall color change.

Chlorophyll is the green pigment that starts the process of photosynthesis by helping convert sunlight, carbon dioxide, and water into sugars that travel through the plant to other branches or roots where the plant uses them as food. Normally, chlorophyll breaks down and is remade continually throughout the season, but in the fall when the days get shorter, veins that carry water and nutrients to the leaves start to close off, so less chlorophyll is made and more and more chlorophyll breaks down. As the green color fades, other pigments that were there all along, like yellow and sometimes orange, can be seen.

Southwest Yard & Garden by Dr. Marisa Thompson

swyardgarden1Tree growth is slowing as temperatures fall (photo credit M. Thompson).

Question: I’ve seen conflicting advice online on whether or not to fertilize trees now to promote healthy root growth.

Camille R., Albuquerque

Answer: Don’t fertilize anything in fall because we want growth to slow with dormancy, and the salts in fertilizer will either just sit there and be unhealthy for soil/roots or actively damage roots. When carefully selected and applied, fertilizers can help boost a plant that’s already putting on a flush of top growth, like in the spring and early summer. In our areas, applying fertilizer now may extend late-season growth, and that new tender growth is particularly susceptible to cold injury.

cherries in bloom sept 30 2018 stacia jacobi garcia 2Ranier cherry blossoms in Albuquerque at the end of September. Photo credit Stacia G.

Question: Do you know why my Ranier cherry tree is blooming now (September 30)? It doesn’t look so good, but earlier this year it produced a decent amount of cherries. - Stacia G., Albuquerque, NM

img 0033It’s too late to deadhead zinnias now and get new blooms, but cutting flowers earlier in the season can really increase flowering time and number of new blooms. Photo credit M. Thompson.