Honeydew Drizzles and Cherry Pit Tips

July 31, 2021


by Dr. Curtis Smith with additional observations by Dr. Marisa Thompson

Partial reprints from July 14, 2001 SWYG Archives, written by Dr. Curtis Smith.

Question:

I have a willow tree that seems to be "raining" down what feels like moisture in hot weather. Is this common? What is the tree doing? If you look at the tree with the sun behind it, you can see the droplets falling.

Answer:

This is a common occurrence in the summer. The most likely cause is an infestation of aphids feeding on liquids in the leaves of the tree. This "sap" is high in sugar and low in protein, so a large quantity of sap must be consumed. Surplus water and sugar (in the form of a syrupy substance called honeydew) are excreted by the aphids. This is the material "raining" down. The windshield of a car parked under the tree will soon be covered with little sticky drops of honeydew. Some people complain of damage to the paint on cars as a result of this.

Image of a plum tree
Prairie Red plums ripening at the NMSU Agricultural Science Center at Los Lunas on July 29, 2021. Photo credit Marisa Thompson

Aphids may do relatively little damage to an ornamental shade tree, so they are more of a nuisance than a danger. If the tree is small enough, you may be able to manage the infestation by spraying a strong jet of water into the tree. This washes the aphids from the leaves of the tree, stopping them from feeding until some of them find their way back into the tree's leaves (many will die, but many will return). When they are not feeding on the leaves, the raining of honeydew will also cease.

Additional observations by Dr. Thompson: I remember walking near UNM when I first moved to New Mexico and being “rained” on by a fine, cooling mist falling from desert willow trees. At the time, it was yet another example of how wild and different desert life could be. It wasn’t until I took the Extension Master Gardener training courses that I learned the truth about honeydew and the source of that “mist.” Since then, I’ve noticed a few other clues that aphids are munching overhead: lower leaves shining with dried honeydew, outdoor furniture that appears to be newly varnished, and sticky sidewalks that pull your flip-flops clean off.

One management tactic is to back off on fertilizer applications. Over-fertilized landscape plants can produce flushes of new growth that attract aphids and encourage late-season breeding of new generations that might otherwise be avoided. This is particularly common in roses.


Question:

Can I grow a tree from planting cherry and peach pits? How can it be done?

Answer:

The cherry, like all temperate fruit trees, requires a "chilling" period or winter to prepare the seed for growth. The hard shell of the pit does not need to be removed, but the seed should be placed in moist vermiculite or other seed-starting material that drains well and stored in the refrigerator for six to eight weeks before planting. Do not let the seed dry before beginning this treatment.

Once the seed has been treated by chilling, it may be planted—outside if the weather is already cool, or in a pot in a window or greenhouse. If planted outside, it will experience further chilling and begin growing in the spring. If planted in a pot, it will begin growing in a few weeks.

Plant several seeds because it is possible that only a few will grow. In about seven to ten years, you may begin eating cherries from your tree. If you graft a part of your seedling onto a mature tree, you can cut several years from the wait. The fruit from your seedling may be tasty, or it may be bitter. Like apples and peaches, this is a plant that will not produce a seedling exactly like the parent.

Additional observations by Dr. Thompson: I was excited to reprint this column because I happened to have a plum pit with big aspirations in my pocket. It’s from a ‘Prairie Red’ plum shrub growing here at the NMSU Agricultural Science Center at Los Lunas. I remember loving these small, rosy fruit in the first weeks after starting my new position and looking forward to harvesting them each year. However, that was August 2017, and, sadly, frosts nipped them in the bud each subsequent spring—until this year. We harvested a few of the ripest plums this morning, and they’re better than I remembered.

Until today, I thought that all stone fruits (nectarine, peach, plum, cherry, etc.) “grow true from seed.” So I was surprised to read Dr. Smith’s closing comments about the possibility of bitter offspring. We have six plum varieties growing in close vicinity at the research farm, and as I read more about plum tree cross-pollination, my heart sank. Is the pit in my pocket doomed to become a pit in my stomach? There’s still hope because the ‘Prairie Red’ plum happens to be a self-fertile variety! I’ll give it a whirl and report back in a few years. Stay tuned.

Caution: Most nursery-bought fruit trees are grafted onto rootstock that’s selected for disease resistance, environmental conditions, and size. Dwarf rootstock is highly recommended for backyard growers. The seed you save from a grafted tree will not possess characteristics from the rootstock. You may be better off collecting cuttings from the desired tree and grafting them onto an existing tree in your yard (of the same genus) or purchasing a grafted tree.


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.

Links:

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 desertblooms@nmsu.edu, or at the Desert Blooms Facebook page.

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