Question
QUESTION: I have been growing marigolds from seed for a number of years. 3 or 4 years in a row I saved the seeds and replanted the next year and they did great. But then last year they came up fine and produced large green plants but few blooms and late in the season. This year I started with fresh seeds and many are still producing large plants but many have no blooms. I planted them inside in mid April, transplanted in late May and still no blooms. Any suggestions.

ANSWER: There are a bloom-less summer landscapes in many parts of the country, all collateral damage arising from blistering heat and intense radiation.  Baby, it's hot outside.

How hot is it?

Stephanie, it's SO hot, even heat-tolerant plants are melting.

Hard to believe, but that is almost certainly what's wrong with this year's Marigold crops.  Blame it on the weather.

Yes, Marigolds are supposed to be plants you can count on for color through every heatstroke.  And usually, you can.  It's just that you can't BOIL them, you can't FRY them, you can't make them walk on red hot coals and expect them to flower like nothing was wrong.  They won't die.  They just can't perform.  The hotter it gets, the longer they'll ignore you.

Don't take my word for it. Michigan State U's Cooperative Extensioners back me up on this. Read their word, particularly Item XIE 'Flower Initiation':

archive.lib.msu.edu/DMC/Ag.%20Ext.%202007-Chelsie/PDF/e1443-1980-print1.pdf

and I quote:  'Temperatures above 85 degrees F will inhibit flower bud initiation.'

Over in India, where Marigolds are fed to chickens so they'll lay eggs with bright yellow yolks, they take gardeners seriously.  One research center discovered the perfect growing medium for this undemanding plant: Vermicompost plus Poultry Manure plus biofertilizer Azospirillum.  Maybe you'd like to try that cocktail.

Commercial growers often find that their Tagetes (Marigold) crops become less and less vigorous as the Nitrogen in the soil is depleted; consistent replenishment of soil nutrients reverses this.  Bear in mind that organic 'fertilizing' maintains nutrient levels without burning roots, since it is the Soil bacteria that flock there for dinner and yield so many high quality nutrients.

Marigolds, like everyone else, have optimal temperature ranges, peaking around 85 degrees F.  That's usually enough to produce a bumper crop of flowers all summer long.

But put it thru the 'thermal death threshhold' and you're asking for trouble.

As I told someone else recently, photosynthesis ends when the thermometer registers 90 degrees.  The chlorophyll doesn't work when it gets this hot.

So... What can you do about this?

First, let's agree that this egg-frying weather is going to end.  While we're waiting for this Act of God, water your Marigolds every day, nice and deep.  DO NOT FERTILIZE -- there's nowhere for those fertilizer salts to go except into the Marigolds, and that's not good for anyone on a hot summer afternoon.  Plus, Marigolds make leaves instead of flowers when you feed them too well.

Topdress with something Marigold-friendly, like the aforementioned Vermicompost or some Humus-rich layer.  Mulch with dead leaves to retain water and keep roots cool.  Remove spent flowers (when you finally get some).

Now I'm going to have breakfast. I think I'll go fry an egg on my sidewalk.  Thanks for writing,

THE LONG ISLAND GARDENER

---------- FOLLOW-UP ----------

QUESTION: Thanks for the information about the marigold problem. I actually am living in Eastern Europe and we are not having the heat problem as the States have. However, the hint about nitrogen depletion may be a clue. Actually I have 3 different beds of the marigolds and one is blooming well, but the other two have tall green plants but no blooms as of yet.

So I have another question: What natural product (not bought from Home Depot or a garden shop) can I put into my beds for next year to replenish the nitrogen? Like I said, I live in Eastern Europe basically in a 3rd world country. So I have to use natural products.

Answer
Eastern Europe... A foreign soil I am not, unfortunately, familiar with.  But I love a challenge.  Let's get started.

First, you don't narrow down your location much - at least we have corrected the Continent.  You don't have to give me your zipcode, or your GPS coordinates, but I would be able to reference the soil structure of your region if you could narrow it down just a little more.  For the sake of accuracy.

Also, speaking of accuracy, 'Marigold' is a common name for several species, each with its own peccidilloes.  Do you know if you have seeds of Tagetes erecta, T patula (preferred by the French), T minuta or something else?

Now for a little scientific methodology.

You've probably read about mycorrhizae, those underground food factories also known as beneficial fungi.  Mycorrhizae build better Marigolds, it turns out, according to research you can access on the internet.  One study (done in Egypt, by the way) figured out that the Marigolds grown with mycorrhizae have bigger, better flowers due to the power of those friendly fungi to pour Phosphorus into the plant, EVEN WHEN THE SOIL IS CRAP!

Here's the link to that study, which you will have no trouble comprehending judging from the articulateness level of your question:

www.insipub.com/ajbas/2008/234-242.pdf

If you have access to their mycorrhizal strains in Hanover, Germany, please send some over.  They used strains of Clomus intraradiaces.

In Croatia, researchers in 2008 noted that 'mycorrhizal fungi influence[s] better development of the root, and consequently more exuberant plant development and earlier flowering.'

In Canada, evaluators examined 9 different mycorrhizae and grew them with Marigolds (T patula):

'Nine different AM strains were produced in pot cultures with marygold plants (Tagetes patula L.)... Under greenhouse conditions a strain of Glomus intraradices showed the highest levels of colonization.'

Here's a tidy little website that lists those Glomus fungi and what they can do for you:

home.comcast.net/~pholowko/OnLineShows/Soil/MicroBio/BioCertianFungiDescription.html

Eastern Europe may not be much of a market for mycorrhizae, but for the North American gardener, here is one stop shopping for all your mycorrhizal needs:

www.fungi.com/mycogrow/index.html

That said, let's assume you have a few billion Glomus spores floating around in your soil.  These things have been around since the dinosaurs.  All you have to do to activate them is provide moisture, plant seeds, and leave them alone.  It's the 'leave them alone' where we tend most to destroy mycorrhizae; every time you slice into the soil with a shovel, you sever the slender, invisible hyphae that grow under foot, meandering through particles of silt and organic matter.

As with Earthworms, friendly fungi are destroyed, irrevocably, when soil is dusturbed.  Best thing is to sow your seeds and let them penetrate the soil.

Keep soil from becoming parched and lifeless, especially in heat waves and periods of drought.  And never, never use fungicides of any sort, which will wipe out all your friendly fungi and certainly miss some pathogens; if you're concerned about disease, fight it biologically.  That works better, anyway.

A rich top dressing over a bed of healthy Earthworms will give your soil a new lease on life.

That can be done with mulches as well as the aforementioned Vermicompost products, compost tea, home made compost, humus, and all kinds of manure (we can go into manure another day in a separate question - I could talk about manure all day).  Rabbit manure and chicken manure are splendid amendments.

Eastern Europe?  Cool.
THE LONG ISLAND GARDENER