Roots, Shoots, Fruits & Flowers: Macadamia Nut Tree, Gigantic Grubs, Pink Lichens, and Small Shade Trees


A cluster of macadamia nuts. Photo: University of Florida.

Macadamia Nut Tree

In August, a gentleman brought a couple of unusual green “fruits” to the AgCenter for identification. He said he bought his home about a year earlier, and his tree bore these strange “fruits” this summer.

At first, AHA had no clue until cutting one of these green “fruits” in half and discovered a hard shell forming inside. Then AHA searched for “exotic nuts” online and found an image resembling these green “fruits”. This homeowner has a macadamia nut tree at his home.

Macadamia nuts originally came from Australia and named after Dr. John Macadam, a noted scientist and secretary of the Philosophical Institute of Australia in 1857. Hawaii leads the United States in production while Florida also has some macadamia orchards as an alternative crop. In California, macadamia trees have ornamental value. According to Aggie Horticulture, “Although tropical trees, macadamias tolerate mild freezing (28-32 F), and do not tolerate excessive heat.” Macadamia trees are like citrus and fig trees in that they require some protection during the winter.

The Agricultural Marketing Resource Center (AMRC) at Iowa State University reports that macadamia nut trees have disease issues in the trunk and flowers. These trees “prefer deep, well-drained soils that have a pH of 5.0 to 6.5 and require 60 to 120 inches of rainfall per year.” In short, this tree is high maintenance because of its need for fungicides and irrigation but can grow here.

Finally, AMRC shares this benefit from this nut tree, “In addition to providing the nuts for harvest, macadamia trees can also help to generate honey production for nearby beehives.”


These large grubs will become rhinoceros beetles. Photo: Cynthia Dowers, Ragley, LA.

Gigantic Grubs

Cynthia sent this image of these large white grubs for identification after hurricane Laura.

An insect specialist identified these giants grubs as juvenile forms of rhinoceros beetles. Another name for this insect is eastern Hercules beetles. The grubs feed on rotten logs, stumps, and leaves, and they are regarded as beneficial because they help with decomposition. Despite the fierce appearance of the adult beetle, these insects are harmless and not considered a pest.


Pink lichens growing underneath a large oak branch. Photo: Tricia Heyl.

Pink Lichens

Tricia observed an unusual growth on her oak tree, “[I] saw what looked like pink fungus on this oak tree on our property in Central [Louisiana]. It was only on one side. Just curious what you thought about it. Thank you!”

Tricia has pink lichens on her tree, and they are harmless. Dr. Raj Singh, the AgCenter’s “Plant Doctor” writes, “Dr. Raj Singh writes, “They are composed of two different organisms – a fungal partner and a photosynthetic partner living in a [beneficial] relationship. The photosynthetic partner is either a green alga or a blue-green bacterium. Lichens get their nutrients from the food prepared by the photosynthetic partner, and the fungal partner provides the body and shape.”

918_fig_4_Native_Tree_Growing_Guide_for_LouisianajpgFront cover of Native Tree Growing Guide for Louisiana. Image: LSU AgCenter.

Small Shade Trees

Lillie made this request, “Recommend trees for our area that provide some shade that are not extremely tall to plant near houses.” The AgCenter has a 16-pages, free, downloadable publication entitled “Native Tree Growing Guide for Louisiana”, and it has a list of small flowering trees on the last page. This publication also shares information on the selection, planting, and care of trees in landscapes.

If you want to contact Roots, Shoots, Fruits and Flowers, please send your questions and pictures to Keith Hawkins, Area Horticulture Agent (AHA), 337-463-7006 or Also, you can be on the “green thumbs” email list by emailing your request to the address above.

“Before you buy or use an insecticide product, first read the label, and strictly follow label recommendations. Mention of trade names or commercial products in this article is for informational purposes only and does not constitute endorsement by Louisiana State University AgCenter.”

“This work has been supported, in part, by the USDA National Institute of Food and Agriculture, Renewable Resources Extension Act Award, Accession Number 1011417.”

9/17/2020 7:36:47 PM
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