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Extrafloral Nectaries on Luffa Leaves

Did you recognize the big yellow flower from the Wordless Wednesday post with the carpenter bee? This might give you a hint:

It was from a luffa or sponge gourd, Luffa aegyptiaca (previously named L. cylindrica.)

Why were the ants on the underside of the flower in the last photograph of that post? It turns out that the luffa plant has been crawling with rover ants, even before it started to flower.

For a clue, let's look at the underside of the luffa leaves. What are those green bumps on the leaf surface between the veins?

You might wonder if they are the leaf openings called stomata, but the stomata are the smaller dots.

Close up the bumps look like tiny green volcanoes.

Those are extrafloral nectaries, or EFNs. Extrafloral nectaries are nectar-producing glands found in areas of the plant outside of the flowers. Extrafloral nectaries occur in at least 66 different plant species and vary in size, shape and placement. The type of found in luffa are called "button-shaped."

Like the nectar produced in the floral nectaries, extrafloral nectar is a liquid solution of sugar in water, with trace amounts of amino acids. The nectar attracts many different kinds of insects, but ants are often the most common visitors. The ants often chase away or capture plant-feeding insects, thus protecting the plant.

This means we can add luffas to the list of plants that might be useful for gardening for ants.

For more information, see:

Vivek Mohan Agarwal and Neelkamal Rastogi. 2010. Ants as dominant insect visitors of the extrafloral nectaries of sponge gourd plant, Luffa cylindrica (L.) (Cucurbitaceae). Asian Myrmecology, 3, 45–54. (free .pdf available at the "Read full PDF" link after the abstract.)

Have you seen the journal Asian Myrmecology? Currently the articles are offered for free online at the website.

6 thoughts on “Extrafloral Nectaries on Luffa Leaves

  1. Charles Laird

    This was a great article to let me know why the ants are coming - being attracted to the Luffa. But the ants are also eating off the plant where they are trying to create flowers. There are one or two ants at nearly every single joint (where the leaf comes in). First it was the little black ants (name unknown), but the ant trap I laid out did the charm. Now however, there is a larger black and red ant that has come in their place. Still, not one flower, because they are chowing down all throughout the day and night. I'm open for suggestions to remove this ant, but not necessarily kill them. I know neem oil doesn't work - I spray on my plants as preventative every couple month, because of huge pest problems I have had in years past. I may just be resolved to remove the plants or just watch them grow with no fruit all season long. LOL . This is an aquaponics system and I refuse to use poisons. Deterrents - let's go. bT however is not going into my garden!

  2. Roberta

    Are you absolutely sure?

    Other than leafcutter ants, there aren't many kinds of ants that chow on plants. Instead, they eat the caterpillars and other bugs that attack plants. Ants get a bad rap because caterpillars and slugs -- the true culprits that are eating the plant -- often hide during the day.

  3. Stephanie Salyer

    I am having the same issue. Over 3 months of beautiful plants with no flowers while my other squash have already been producing fruit. Little black ants are all over the joints where the flowers and new growth are coming from. Am going to try some diatomaceous earth to see that helps.

  4. Roberta

    Ants are probably not the issue, but if you want to make sure, putting a band of something sticky, like double-sided tape or Tanglefoot (https://www.tanglefoot.com/), around the base of the plant will likely keep the ants off it.

  5. Zach

    I've planted luffa plants and small soon gourd plants this year (planted at the same time, in the same vicinity). The small spoon plants have yielded gourds out the wazoo, while no luffa plants have even started to flower. I'm not too worried yet, I know they have different expected harvest durations.
    The spoon plants, along with my zucchini and yellow squash plants, have been nearly wiped out by a squash bug infestation. Interestingly, the squash bugs haven't touched the luffa plants. I'm curious if the medium-size black and crawling all over my luffas have protected them from the squash bugs, or if the squash bugs are not generally interested in luffa plants (or both?). Maybe they're not interested in the luffas because they haven't started flowering yet?
    Anyway, as long as the ants aren't doing any harm I'm going to keep them around.

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