Milkweeds Sacrifice; Monarchs Take Flight

As we were walking the propagation beds a few weeks back, Pandra and I approached a patch of about 8-10 milkweed plants (Asclepias tuberosa) and she said “Oh no!”  Only one was still green, and all that remained of the others were brown dried out stems with a few dead leaves still clinging to the ends.  It looked a little like this:

We started to discuss what could have caused all these plants to die off and whether or not it was the same beetles that took out nearly all of our Coreopsis last spring.  I said that I’d seen a Monarch butterfly caterpillar feeding on one of those plants the week before, and maybe they were the cause?  We took a look at another patch of milkweed plants and saw essentially the same thing, dead crowns on all the plants except one.  The one remaining green plant in this patch had three monarch caterpillars feasting on the leaves.  I didn’t get a picture, but they had obviously come from the plants with the dead crowns, as this last green plant was the farthest down the line.  We both said “well, that’s why we grow milkweed” and hoped that the crowns would re-sprout in the spring.

Fast forward two weeks and I’m out at the front beds again checking to see if seeds had ripened on some of the sunflowers.  A Monarch butterfly floated by on the breeze.  Then another one caught my eye flying down to the other end of the bed.  Fortunately I had my camera.

This is a newly hatched Monarch feeding on the nectar of a Georgia Aster flower.  This is also a good example of why you need butterfly host plants AND flowering nectar plants to support a healthy population of butterflies in your garden.  If this butterfly had hatched and there was no food in the area she might have perished, but there were multiple species of plants flowering within 30 yards of the milkweed so she had plenty to eat.  Hopefully it provided a good first meal for the incredible journey to Mexico or South Florida that this lady is about to embark upon. 

    That’s fine and well for the butterflies, but what about our poor milkweed plants?  I went to check on their roots and to my surprise I found this:

Already sprouting new growth!  All of the plants with dead crowns were putting up some form of new growth, and most of it looked larger and greener than the growth that the monarchs devoured.  The milkweeds abandoned their crowns as a result of the siege, and then after the caterpillars left and pupated they simply sprouted new stems.  Host plant/insect relationships are so complex and fascinating.  Almost as fascinating as how successive generations of butterflies know how and when to migrate thousands of miles to a place they’ve never been, but that’s another post.  Until then……

Happy Trails!


Hugelkultur: Using Woody Debris in the Garden

 

           Atlanta and the surrounding metro area are blessed with an abundance of trees compared to other cities of similar size.  It’s unusual for a yard to not have at least a couple of trees shading part of it, which leads to the most frequently asked question at plant sales, “What grows well in shade?”  While most people are thankful for the shade that these trees provide from the summer sun, the thankfulness turns to irritation in the fall because the trees drop their leaves and dead branches.  Seasonal pruning of shrubs also creates piles of ‘yard waste’ that most people bag up and set on the curb.  There is another option for disposal of this material that will enhance your garden beds and return the nutrients that the trees and shrubs have removed from the soil back to square one, thus completing the nutrient cycle.

            Hugelkultur translates roughly from German as “mound culture” (so I’ve been told…) and was a common practice in Europe centuries ago.  It is a technique that is regaining popularity with permaculturists and gardeners because it mimics the nutrient cycling that naturally occurs in forests.  It also helps the soil to better retain moisture which reduces the need for supplemental watering of plants and helps them to survive prolonged periods of drought.  Trees and other woody plants naturally accumulate and concentrate minerals from the soil as they grow, so by incorporating woody materials back into the soil these minerals are released and made available to plant roots as the materials are broken down by soil microorganisms.  All-natural fertilizer, less watering, and healthy plants. Sounds like a win-win situation.

         A  hugelkultur bed can be started on the existing ground surface or can be partially buried depending on the desired final height.  The photos in my example are from a vegetable garden bed that I constructed in my back yard using 1) Branches from pruning back shrubs, 2) Fallen leaves and small branches from oak trees, 3) Partially composted kitchen scraps and 4) The topsoil that I dug out of the bed area prior to starting.  You will need some soil to cover the top of the pile, so if you want to start on the existing ground surface and end up with a raised bed you can either remove the top 2” of soil or find another area to borrow some topsoil.  The latter option is a necessity if you start on eroded or clayey soils that lack a good topsoil layer.  Once the necessary materials are gathered and the site chosen it’s time to get started.

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          I made my bed outline 3 x 8’ because that’s how big my other raised beds are, but your bed can be any shape or size.  Rectangles are kind of boring, so don’t be afraid to get creative.

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I saved the dirt I removed on a tarp so it would be easier to replace it once I finished.

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          Once I started hitting clay I stopped digging.  I’m fortunate that my garden area has had 50 years or so to build up a nice layer of topsoil since the house was built, so I was able to go pretty deep.  Soil transition layers vary widely, but once you hit clay or mineral soil you should probably stop.

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          Chopped up twigs, sticks, pruned branches, etc. go in the bottom of the trench.  This was my first attempt at building one of these beds and subsequent reading has made me wish I had put some larger diameter branches/logs on the very bottom. The larger branches have more biomass, will take longer to break down, and have the ability to hold more moisture than the small stuff I used.  C’est la vie. Next time.  Water down the woody materials well before proceeding to the next step.

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          Partially composted kitchen scraps went on the wet branches.  This is what I had available, but anything with a high nitrogen content, such as fresh manure, alfalfa, green grass clippings, or coffee grounds will work. The fresher and greener the better.  My material was partially composted, so had lost some of that valuable nitrogen, but it was what I had on hand, so it was what went in. I drink enough coffee that it was probably 1/4 coffee grounds anyway, so I wasn’t too worried. The reason that high nitrogen material is needed is that the woody material is high in carbon, which is slowly broken down by fungi and microorganisms in the soil.  These decomposers need the easy to digest simple sugars and nitrogen in the green material to build their bodies and secrete the enzymes that allow them to break down the more complex carbon compounds in the wood. 

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          Soil goes back on top.  That’s about 6-8” of soil, but as little as 1-2” would suffice.  Just enough good soil so that plants can have a healthy root zone to start growing in until they are able to tap into the bounty below.

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            This is the bed as it is today with some pepper plants growing in it.  I surrounded the bed with several large sections of an oak branch that came down during a storm a few weeks after I built the bed.  It helped define the bed and prevent soil erosion during heavy rains.  The soil has settled considerably as the woody materials have broken down.

           My anecdotal evidence for improved moisture retention is that the pepper plants in this bed showed less leaf wilting than their counterparts in my other beds that are just straight soil on many hot summer afternoons.  We also utilize woody debris (often tree trunks) in the propagation beds at the farm and our plants there are doing great.  I see fungal mycelium strands running through those beds every time I weed or plant something new.  Fungi break down the wood, and in the process create vast networks of mycelia (think of them as ‘roots’ for fungus) that transfer nutrients and water throughout the area.  Most plants can “barter” with the fungi for nutrients in exchange for some of the sugars they exude from their roots.  Search for “soil food web” if you’d like to learn more about this fascinating process.       

           So, there you have it: hugelkultur.  Hard to spell, relatively easy to do.  A little internet searching will help you to find people and sites more knowledgeable on this subject than I am, but I hope this was a good introduction and has gotten you to think about reusing the woody debris that property maintenance inevitably produces.