Tuesday, December 11, 2012

On Second Thought - Why I'm Ripping Out my English Marigolds

A December cold front with overnight lows in the 20s has blasted these English Marigold (Calendula officinalis) blooms, but the real peril here are the leafhoppers that are far too small to see in this picture.
Yes, dear reader, it was only 8 days ago that I was singing the praises of English Marigolds (Calendula officinalis) for their colorful early winter blooms and their potential as a sort of cover crop for flower beds.

And then, as they say in the U.K., it all went pear-shaped.

(Love the expression, but more prosaically, let's just say that I felt the experiment had run its course and was not a roaring success.)

What went wrong?

In a word: Leafhoppers!

In two words: Leafhoppers, argh!

I tend not to spray pesticides in the garden. Mostly I adhere to a survival of the fittest rule and if a plant can't take care of itself, I'm not going to coddle it along.

Well, I had forgotten just how susceptible the English marigolds are to leafhoppers. These insects are not terribly obvious until you brush against a plant and a little cloud of light green insects goes hopping off onto neighboring plants, only to quickly jump back to the Marigolds when your back is turned.

Leafhoppers suck the sap of vascular plants. In other words, they'll gradually weaken and then kill the host plant as their numbers increase. According to the Illinois Natural History Survey (INHS), leafhoppers do have many natural predators, but those predators do not seem able to keep the leafhoppers under control in my garden on this particular English Marigold crop. In fact, I now remember how I had to pull most of the English Marigold crop in mid-summer due to a leafhopper infestation (plus the fact that the Marigolds were baking in the heat and humidity of July and August).

I believe that English Marigolds must be particularly susceptible to leafhopper infestations, because I cannot recall having problems with them on any other plants this past year, except for the zinnias, which only became infested as they were already declining and reaching the end of their life cycle.

Now part of me, wanting to be a super eco-friendly gardener, supposes that it might be best to leave the English Marigolds. After all, the Marigolds do attract some bees and presumably the predatory wasps, spiders and birds that INHS says feed on leafhoppers would prefer to have a robust prey population.

Well, that may be the case, but I've never seen any birds browsing the marigolds for leafhoppers. Perhaps there are different birds that eat different leafhoppers elsewhere, since INHS says there are an estimated 100,000 species of leafhoppers around the world.

And besides, one major problem is that I don't want to provide an environment for the leafhoppers to breed and flourish. While my gardenia or my camellias for instance may not naturally support loads of leafhoppers, when the Marigolds foster massive populations, I think some of the little critters hop onto other nearby plants and do some damage there.

In any case, once the leafhopper population builds sufficiently on the Marigolds, many of the younger Calendula plants are overwhelmed early in their lifecycle, staying stunted and small, growing yellow and dying before they can flower, which sort of defeats the purpose of growing them as a cover crop.

So, gardening is a learning process and I'm certainly not above admitting my mistakes. (Mea culpa!) Even this late in 2012 I'm still learning and still making mistakes! And that's why at this point, I disavow the post I made just a week ago singing the praises of English Marigolds and revert to my earlier position that English Marigolds are more trouble than they are worth.

Now French Marigolds on the other hand, I endorse without reservations! :)  (But obviously I've been wrong before and may some day have to eat my words on this recommendation too!)

PS - What would you have done? Would you have sprayed? Pulled the plants like I did? Let events run their natural course?

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  1. I would definitely not have sprayed. I might have just waited to see how bad the damage got, or if the leafhoppers declined over time. Pulling the plants seems reasonable. I always feel that putting something in the soil implies no long-term commitment - get rid of it if it's not working for you.

  2. I usually just take a wait and see attitude. I always hope that something will come along to take care of the bad bugs. Of course, sometimes my hopes don't pan out. But by then, the plant is so bad off I don't mind pulling it out. Oh, the decisions we gardeners have to make!!!!

  3. Thanks for the moral support, Jason and Holley. :)

  4. I published a comment the other day but don't see it. Maybe I did something wrong, so I'll try again. I'm not familiar with these leaf hoppers you describe. Maybe I have them, and just don't notice them because of all the white flies I have to contend with. I have grown Calendula off and on for years. I would never consider it a crop cover because, as I recall, they do die back (I think), but they were more of a "place holder" and returned in the spring, along with new ones from reseeding. I would have left them and let the winter take care of the bugs. One thing you might want to try is planting the more common Mexican marigolds (Taygetes) somewhere in the vicinity of your Calendula (an anything else) because they work wonders in keeping certain pests at bay. I knew there had to be a reason for their "distinctive" odor.

    1. Thanks for the comment, Dottie. (Sorry to hear you had problems commenting before. Blogger, like most blogging platforms, has bugs of its own!)

      Calendula certainly does return from reseeding! I have no doubt I'll have more next year, although I think I'll probably pluck out the seedlings in favor of other crops. Although I like calendula blooms, I'm not a huge fan of the foliage or all the prominent dead flowerheads/seedheads.

      As for the Mexican marigolds (Tagetes patula), I love them!! Didn't have any pest problems with them, and I liked both the foliage and flowers better than the Calendula.

      There are two other marigold types that I hope to grow someday:

      - Tagetes lucida, Mexican Marigold. The leaves can supposedly be used to make a tea that produces a slightly euphoric feeling. And who couldn't use a little more euphoria in their life? Oh and the flower petals are reportedly edible as well.

      - Tagetes tenuifolia "Lemon Gem", which supposedly has edible flower petals that taste of citrus

      (As always, these medicinal and edible qualities just refer to what I've read elsewhere online. I'm not an expert on these, at least not yet!) ;)

    2. PS - Dottie, I usually use the Google Chrome browser for general web surfing, but have found that Chrome does not play well with Blogger. For instance, any attempts I make to leave comments on blogger blogs while using the Chrome browser are deleted. It's ironic because Google makes both Chrome and Blogger. The Firefox browser (and other Mozilla-type browsers) seem to have far fewer Blogger problems.


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