Ragweed

Great ragweedThere are two ragweeds found throughout North America: Common ragweed (Ambrosia artemisiifolia) and Great ragweed (Ambrosia trifida).  Let’s start with Great ragweed (pictured above) and study its parts and life cycle . . .

Great ragweed

Great ragweed (Ambrosia trifida)

The lower leaves of Great ragweed have three — sometimes five — lobes (the trifida species name) while the upper leaves of a mature plant are elliptical:

Great ragweed

Great ragweed

As the plant begins its reproductive phase, it starts with growing its staminate (male) flower spikes:

Great ragweed

Great ragweed

Initially, the staminate flower spikes look fuzzy:

Great ragweed

Great ragweed

Here’s a closer view of the developing staminate flower spike. . .

Great ragweed

Great ragweed

. . . and a closer view. . .

Great ragweed

Great ragweed

. . . and an even closer view — with the staminate flowers open, spread along the spike, and producing pollen:

Great ragweed

Great ragweed

Let’s pull back and look at the top of a Great ragweed plant:

Great ragweed

Great ragweed

All those staminate flower spikes have elongated and look thin and “weedy” now.  At the base of the staminate flower spike, and from various points where leaves are attached to the plant’s stalk, the pistillate (female) flowers have grown.  They are well-positioned to receive the wind-borne pollen from the staminate flowers:

Great ragweed

Great ragweed

After the flowers are pollinated, the Great ragweed plant looks like this:

Great ragweed

Great ragweed

You can see the clusters of pistillate flowers — now developing the seeds — and the flower spikes stripped of their dead staminate flowers:

Great ragweed

Great ragweed

Here’s a closer view of the pistillate flower cluster (for scale, note the ant along the stem) . . .

Great ragweed

Great ragweed

. . . and a final very close shot of the pistillate flower as the seeds are developing:

Great ragweed

Great ragweed

Now, let’s turn to Common ragweed (Ambrosia artemisiifolia).  As you look at these photos you can see the similarities between these two ragweeds.  Common ragweed is in the foreground and some leaves from Great ragweed are in the background (in the photo below).  This gives a sense of the relative difference in size between the two ragweeds.

Common ragweed

Common ragweed

Common ragweed has deeply cut lobes on all its leaves:

Common ragweed

Common ragweed

Here are its developing staminate flower spikes:

Common ragweed

Common ragweed

Just as with Great ragweed, the Common ragweed’s flower spikes elongate . . .

Common ragweed

Common ragweed

. . . and the flower heads spread along the length of the spike:

Common ragweed

Common ragweed

The pistillate flowers, again, are primarily at the base of the staminate flower stalk:

Common ragweed

Common ragweed

This final photo is a close-up view of the clustered pistillate flowers on a Common ragweed plant.  The dead stalk to the left is the staminate flower spike.  We are looking down into the pistillate flower clusters.

Common ragweed

Common ragweed

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6 Responses to Ragweed

  1. Pingback: Is this mugwort? Or something else? | Identify that Plant

  2. carlos says:

    I LOVE RAGWEED>

  3. Cath says:

    How can anyone like ragweed and why would you ever SMELL it!
    It is one of the worst allergens and is the cause of much misery from August until the first frost. I pray for frost to kill it And where we live it doesn’t freeze sometimes until December or January !
    The FDA has taken all the good medications to fight this terrible weed off the market!

    Don’t smell I if you suffer from allergies or asthma!!!
    I would die because I have both!

  4. James Welch says:

    I couldnt find the ant anywhere in that picture haha

  5. Crystal R says:

    Cath, ragweed is its own remedy. Tincture the flowing tops in 100 proof vodka for 6 weeks and you have a wonderful allergy remedy! Susun Weed has very helpful YouTube videos on the subject.

  6. Heath says:

    @Cath You know, if you actually tried crushing and smelling the leaves (before the pollen production begins in late summer, as you observed) you’d find it quite harmless. Hyperbole like yours makes charming entertainment ;-) I, for one, usually “lean in” to anything challenging, which requires a commitment to growth. Research and try out Crystal R’s suggestion and you may outgrow anything, even something as identity-linked as an allergy. I did it with gluten intolerance twenty-five years ago…

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