Category Archives: composting

Sheet Mulching Re-visited

Last week’s blog included a link back to our October 2016 blog on experimenting with sheet mulching (also known by some as “lasagne gardening”) http://wp.me/p5JEJY-YZ so I thought we ought to re-visit and see how that worked. Sheet mulching is the layering of different kinds of compostable garden waste (sometimes with old newspapers or cardboard as well) on the surface of poor garden soil. The aim is to quickly add organic matter to the existing soil, improving drainage, water retention and fertility.

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I had several questions in my mind last fall when this experiment was carried out:

1. Will the cardboard decompose?
2. Is the “green” and “brown” balance right?
3. Will the raccoons and skunks churn it all up?
4. Will there be a crop of new weeds from the imported materials?
5. Will the cold Colorado winter simply stop any decomposition from taking place?
6. Will there just be a smelly slimy heap to remove next spring?
7. OR, will we have achieved that elixir of gardening – fertile, well-drained, moisture-retentive soil???

The experiment has been going on for some eight months now and these are the answers, so far:

1. YES. Some digging about at the base of the layers revealed no sign of cardboard except for a few stray bits of plastic tape that didn’t get removed when I broke down the cardboard boxes.
2. Probably YES. Though close inspection revealed that in some parts the grass clippings were laid too thick and would have done better if they’d been mixed in more with the dried leaves.
3. NO. Apart from a few little exploratory digs by some critters, the layers remained intact.
4. NO. Initially there was some germination from seeds (unidentified grass/cereal) which were in the chicken coop material I used, but these were easily pulled in the first couple of weeks. Since then not a single weed has appeared.
5. NO. Digging into the layers revealed pretty well composted good, brown material though not everywhere. Lots of worms too. Straw seems to have been the hardest to break down and is still recognizable in some places.
6. NO. See 5.
7. Well, MAYBE ….

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The native grey clay soil is still there beneath the sheet mulch

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Well on the way to being compost

There is no doubt that we now have deep layers of composted garden waste on our borders. The layers have not been totally absorbed into the soil below. They have shrunk in depth by a couple of inches which is probably mainly due to gravity and the reduction of air pockets. I accept that these borders may remain as “raised” borders for some time.

So, what happens next? I expect these sheet mulched borders to continue to decompose over the summer and, perhaps, by next spring will no longer be “raised”.

But I can’t wait until then to get new plants in.  Already, I have a planted a Japanese maple and some hellebores in one of the beds (both should benefit from the rich compost.  I dug holes in the compost layers, put in some native soil from elsewhere in the garden and planted and watered.

I was concerned that the compost itself would not hold the plant roots securely which is why I mixed in garden soil from elsewhere to give weight. It will also provide mineral nutrients that may not be present in the compost/mulch. Now, some six weeks later, the new plants are all well rooted and looking good.

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Japanese maple and hellebores just planted

So, is it worth doing? I’m giving the experiment a qualified “yes” at this stage.

I think it works for areas that have been neglected or are being cultivated for the first time. There is an initial effort in gathering the materials and building the sheet mulch layers, but then you just sit back and wait.

Does one big “hit” of compostable material work better than cumulative additions over the years? I don’t know. Time will tell as I compare these borders with others in the garden. Certainly, I got a lot more compost onto the borders than I could generate annually from my compost bins. (You don’t get a lot of kitchen waste from two people; and a modest-sized, young garden doesn’t produce much waste either.)

It might have been less work to simply go out and buy bags of compost from the garden center or big box store. That would have been expensive (my materials were all free). There are no regulations on what goes into bagged compost for retail sales.  At least I knew exactly what was in mine.

Aside from these thoughts, there has definitely been a great sense of satisfaction in doing the experiment.  It was interesting.  It was good exercise.  It was free.  I turned what other people thought was just rubbish messing up their yards into useful, re-vitalizing material for our garden and plants.

Anne Hughes/A Denver County Master Gardener

Fall: The Science of Color and Options for Clean-up

In Colorado and many other states in the US, we enjoy fabulous fall color in our gardens, parks and wilder landscapes.  We notice it most on trees, but many shrubs and other plants change color in the fall too.  Have you ever wondered where all that color comes from?  Why do the leaves drop off the trees?  And what use are all those huge drifts of dead leaves to us?

Color

Most plants have green leaves.  This is because chlorophyll in the leaves absorbs the red and blue parts of the light spectrum but reflects green light-waves so we see “green”.  Chlorophyll is used in photosynthesis.  This is the chemical process by which plants convert light, carbon dioxide and water into oxygen and carbohydrates – i.e. food for the plant. Chlorophyll is an unstable compound and the plant continuously replenishes it throughout summer when good sunlight and high temperatures prevail.

When temperatures cool and nights lengthen, chlorophyll production stops and so does photosynthesis (the plant’s food production system). As the green-reflecting chlorophyll disappears, other colors “appear.”  In fact, these colors were always present in the leaves but now they are no longer masked by the green light-waves reflecting from the chlorophyll.

Carotenoids absorb blue-green and blue light and reflect yellow light waves.  This is perceived by the human eye as yellow or greenish-yellow.  This is why the fall color of birches and aspens is yellow.

Anthocyanins absorb blue-green, blue and green light and reflect red light-waves.  This is perceived by the human eye as red through to purple.  This is why the fall color of red oaks, sumacs and some maples is red.

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Acer tartaricum ‘Hot Wings’ still green

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Acer tartaricum ‘Hot Wings’ turning red

 

 

 

 

 

 

 

The depth and shades of fall color depend not only on the presence (or absence) of these pigments, but also the temperature and sunlight available.  Low temperatures and bright sunlight destroy chlorophyll.  So, falls with dry, sunny days and dry, cool nights tend to produce the best fall color.

In severely dry falls, the lack of moisture available to the plant may mean that leaves simply die without producing their usual fall colors of yellow, red or purple.  The leaves lose so much moisture that the normal chemical processes cannot continue and the leaves dry, turn brown and drop early.

The ‘Fall’

Once the spectacular show of fall color is over, deciduous (i.e. leaf-losing) trees and shrubs drop their leaves.  Cooling temperatures and lengthening nights trigger plants into sealing off the point on their stems where leaves are attached so that no more exchanges of moisture and nutrients between the leaves and the rest of the plants are possible.  This is called the “abscission layer”.  When this layer is complete, the leaves drop (or “fall”).

What use are those dead leaves?

Think about how nature deals with this “problem”.  Leaves fall from trees to the ground of the woodland, forest, mountainside, meadow – wherever they are situated.  Rain, frost, snow, the trampling of animal feet all help to break the leaves down into smaller and smaller pieces.  A huge drift of fallen leaves decreases significantly in size as air spaces between the leaves diminish.  An army of creatures from the soil surface, and from beneath it, break down the leaves further through eating and excreting them (think: earthworms, beetles) or chemically decomposing them (think: fungi, bacteria).   In this way, the dead leaves are decomposed into the tiny elements that create soil.  It’s a mixture of humus and minerals.  The humus is the last vestiges of the leaves that are hard to break down like cellulose and the minerals are the chemical components of the leaf tissue, e.g. nitrogen and carbon.

The humus and minerals help to form new soil structure in which new plants can seed, germinate, develop and continue the cycle.  The new fertile or replenished soil provides the moisture and nutrients that the now-leafless trees will need to survive winter and re-start photosynthesis and growth in spring.

How to deal with those huge piles of leaves

We’ve seen above that the dead leaves have an important part to play in the garden’s eco-system.  So, what can you do?

  • Just let the leaves remain where they drop on garden beds. They provide great mulch to maintain soil temperatures and protect plant roots and will rot down over winter, improving your soil as they go.
  • Leave a thin layer of leaves on lawns. Rake or blow them off (if you must) but a thin layer of leaves (especially if you run over them once or twice with the lawnmower) will break down quickly and help re-vitalize your lawn.
  • Rake or blow leaves off walkways, drives and sidewalks on to adjacent garden beds, so that these hard landscape areas are visible and don’t become slippery. Do not sweep or blow leaves into the street, as they can cause serious blockages in street drainage systems.
  • For a neater look, you can blow the front edge of borders clear, letting the leaves accumulate at the backs of borders and behind and below larger plants.
  • Put layers of leaves in your compost bin (even better if you can run the lawnmower over them first) between your layers of green garden/kitchen waste.
  • Save the leaves in plastic trash sacks (stored in an unobtrusive part of the yard) and let them rot down over winter, to be returned to the garden when they have decomposed. This leaf mold (the lovely dark brown material you get from decomposed leaves) is like “gold-dust” to the soil.
  • Save the leaves in an open cage made of upright posts and chicken wire to decompose – more “gold-dust”. If you have room, let your neighbors drop their leaves in the cage too.
  • BUT if leaves come from a diseased plant e.g. one with powdery mildew, black spot (roses), apple scab, anthracnose, they should be collected up and disposed of as garbage to help prevent re-infection in the next year.
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Leaf cage made from old timber and chicken wire

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Fallen leaves make great mulch (and are warm and cosy for the dog!)

If none of these options work for you, you can dispose of the leaves in degradable paper sacks which are usually available from your local hardware store at this time of year.  The sacks can be collected with your normal weekly trash service.  Some towns and cities will have leaf drop-off points where you can take the bags for the city to collect.  The city will then use the leaves to make leaf mold for local parks or otherwise dispose of them.  If you can’t do these things yourself, look for a local lawn service company that can, or hire a local teenager to help.

But, whatever you do, remember that the leaves really belong on the ground.  That’s nature’s way, after all.

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Acer saccharinum (silver maple) turned yellow

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Quercus rubra (young red oak) turned red

Anne Hughes/Denver County Master Gardener

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Worm Composting – It’s Easier Than You Think (and it’s fun)

Are you looking for something to occupy your time after your garden is put to bed and the snow starts falling? How about vermiculture (aka worm composting)? It’s easy. It’s fast. It’s year-round. It reduces kitchen scraps going to the landfill. And it provides rich compost for your garden and houseplants.

Worm box worms are not your average earthworms. The most common worms for vermiculture are Eisenia Fetida, commonly known as red wigglers. Red wigglers love kitchen scraps.  They will eat pretty much anything from your kitchen except meat and dairy products. Avoid meat and dairy because they can attract unwanted pests to your box. Some people say not to feed them citrus fruit and peppers. I have not had a problem giving them citrus or peppers as long as both mixed in with other scraps.

Red wigglers enjoying a meal of kitchen scraps

Red wigglers enjoying a meal of kitchen scraps

Worm composting produces rich, finished compost called worm castings. And it produces them faster than your regular compost bin. And you don’t have to turn it.  And the worm castings are richer in nutrients than regular compost. What’s not to like? The worms do all the work and you get all the rewards. It seems unfair, but the worms don’t seem to mind.

Finished worm castings

Finished worm castings

The first thing you need is a box to hold your worms. Many people make worm boxes out of Rubbermaid containers. I prefer wood boxes because I think a wood box breathes better. Worms need air. If you use Rubbermaid containers, make sure to drill plenty of holes in the container for air and drainage. I know what you are thinking – “Won’t the worms escape through the holes?” They won’t for two reasons.  They need a moist environment to live and they are photophobic (they hate light). Your dark, moist (not wet) box filled with bedding (shredded newspaper) and kitchen scraps is worm heaven for them. They are very happy right where they are.

Red wigglers dwell near the soil surface so the box does not need to be deeper than 12 to 18 inches. One foot wide by two feet long is a good size for a small household. Two feet by three feet works for a bigger household or if you have a lot of kitchen scraps.

Red wigglers like about the same temperature range as us. Not too hot and not too cold. The ideal range is 55-77 degrees Fahrenheit. A basement, laundry room, heated garage, kitchen or living room corner are all great places for a worm box. Some people are reputed to use worm boxes as coffee tables, which I suppose could help with awkward lulls in conversation – “Guess what’s under the hors d’oeuvre plate?” Worm boxes can be kept outside in warmer weather, but be careful that the box does not get too warm or too cold. A well-managed worm box is odorless and unobtrusive.

Now you need worms. One great way to get red wigglers for your box is from someone who already has a worm box. A healthy box produces a lot of worms. Most worm composters are happy to share their surplus worms with people just starting out.  You can find worms on the internet. Years ago I ordered my worms on the internet and they came in the FedEx box with air holes punched in the side with a pencil. The worms did not seem any worse for the wear and their descendants are still going strong many years later. You can also find worms for sale locally (see the link below).

A great place to learn about worm composting is Denver Urban Gardens (DUG). They have a basic worm composting outline on their website.  DUG also holds worm composting workshops in the spring and summer. The website has a link on where to get worms in the Denver area. Check the DUG website to find a class schedule for next year.  Vermiculture at DUG.

Also, check out this great YouTube video on worm composting from CSU Extension and Tagawa Gardens.  It is a good visual primer on starting a worm box.

If you really get the bug to start worm composting, the classic book Worms Eat My Garbage by Mary Appelhof is thorough guide to starting and maintaining a wormbox.

One last word of advice: don’t try to name all of them.

 

Written by Mark Zammuto, a Denver County Master Gardener