Category Archives: Lawn care

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

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Lawn Care: Core vs. Liquid Aeration

Core lawn aeration, completed in the spring or fall (or both, especially if revitalizing a stressed or sadly neglected lawn) is considered one of the best practices for maintaining healthy lawns as it promotes strong turf by reducing soil compaction and thatch. The practice of removing plugs of lawn (which are approximately 2.5+ inches long, .75 inches in diameter and spaced 2 inches apart) is done by a company using specialized equipment. It’s a simple, non-chemical, relatively inexpensive process which promotes healthy growth throughout the lawn.

The removal of plugs creates better air circulation below the soil line, reduces approximately 10% untitledof the thatch layer and allows moisture and other nutrients to reach the root system more efficiently. These healthy roots create a thicker lawn, which is less susceptible to weeds and more heat tolerant. When the plugs are left on the lawn to disintegrate in a week or so, they redistribute nutrients into the turf. However, raking up the plugs for aesthetics is a personal preference and perfectly OK.

Judging by the number of flyers left on my porch, there are a proliferation of companies offering an alternative to core aeration called liquid aeration. According to two reputable companies I contacted, this product is popular because it does not deposit plugs and provides 100% coverage. Both companies indicated they use proprietary formulations, applied with a truck-mounted hose. The liquid solution breaks up compaction and thatch through the use of non-toxic ingredients, such as thatch eating microbes and surfactants which are wetting agents that increase the absorption of water to the roots. Treatment prices vary and can be more than the cost of core aeration.

Liquid aeration treatments are receiving anecdotal praise by homeowners and appear to be gaining in popularity. Colorado State University researchers note that application of wetting agents at the correct rate may  improve moisture absorption. However, liquid aeration’s impact on soil compaction or overall lawn health has not been scientifically researched. Without evidence to support or negate liquid aeration’s effectiveness, CSU continues to recommend the practice of traditional core aeration.   

 

Photo courtesy of Jodi Torpey

Written by Linda McDonnell, a Denver County Master Gardener

 

 

 

 

 

 

 

Take a Soil Test to Start the Gardening Season

soil sampleWhen it comes to growing a garden, if a little fertilizer is good, a lot is better. Right?

Not really. Fertilizer applications should match the needs of the soil and plants. Too much fertilizer, especially applied to smaller areas, can create more problems. One proven way to avoid overfertilizing is to invest in a simple soil test. It’s a tool that gives the most accurate method to tell the fertility of a garden, lawn, field or pasture.

“It’s important to get a soil test to know how your garden will grow over the season,” says Tegan Deeney, a lab tech with CSU’s Soil, Water and Plant Testing Lab in Fort Collins.

“I tested my soil when my pumpkin plants started dying when they were only two inches tall. My soil test showed there wasn’t enough nitrogen nitrate in the soil, and there was a simple fix.” She says a lot of pumpkins grew that year after she amended the soil with the recommended nutrients.

“The earlier you test, the better. You won’t run into the issues of trying to amend the soil around plants,” she adds.

Instead of guessing what your soil needs, a routine garden and landscape soil test will give you the specifics. For the $35 fee per sample, you’ll get results on soil pH, EC (Electrical Conductivity measures the available nutrients in the soil), organic matter, nitrate, phosphorous, potassium, zinc, iron, copper, manganese, boron, lime, and texture estimates.

In 2015 CSU’s Soil Testing Lab evaluated 2700 soil samples from horticulture alone. That total doesn’t include research soils or soil samples from farmers.

A soil test uses samples collected from the yard, garden or field. Soil sample collection kits are available from CSU Extension offices or some garden centers. CSU’s Soil Lab website has soil collection forms, instructions and a list of participating garden centers. For more information contact the lab at 970-491-5061.

A typical sample uses only two cups of soil that’s a combination of 5 to 15 samples (depending on the size of the area). Here are the basic steps for collecting a sample:

1. Use a clean, rust-free trowel or spade.
2. Collect samples at a depth of 6 inches; dig straight down, not at an angle.
3. Take at least 5 samples of soil from the area and combine in a clean plastic container.
4. Remove about two cups of soil and allow to air dry.
5. Place the sample in a CSU soil container or a sandwich-size plastic bag.
6. Seal and label with name, address and location of the sample.
7. Send the sample to the testing lab.

The turnaround time for results is about two weeks. Results will be mailed to you or include an email address for a faster reply. The lab results will tell you which nutrients your garden needs or if there’s an overabundance of nutrients.

With all the time, money and effort it requires for successful planting and growing, it makes sense to invest in a simple soil test. Consider it a gardening investment, almost like buying a plant insurance policy.

By Jodi Torpey
Denver Master Gardener

How to Celebrate Lawn Care Month in April

green lawn with chairs

It takes a little work to whip a lawn into shape each spring.

After a long winter, it’s time to step outside and take a long look at the lawn. Most gardeners won’t like what they see.

While some lawns will look thick and green, thanks to that routine fall fertilizing, other lawns will need some help. To get the turf back on track means raking, aerating, weeding, reseeding, fertilizing, and watering. Fortunately it doesn’t all have to be done on the same warm spring day.

1. Grab a rake. Remove dead grass, fallen leaves and other debris from the lawn. If your lawn shows signs of thatch, like brown spots and general thinning, it may be time to use a power rake to lightly go over the lawn. The rake will remove the layer of built-up organic matter that sits between the leaf zone and the soil, usually caused by compacted soil.

2. Aerate the soil. Invigorate the lawn by aerating, also called core cultivation. Aerating reduces soil compaction, improves water infiltration, encourages root growth, and helps with seed germination. Rent a machine or hire a lawn crew to pull plugs of grass at regular intervals over the lawn surface. Be sure to leave the plugs on the lawn to decompose and help fertilize the lawn.

3. Manage weeds. It’s best to tackle grassy weeds, like crabgrass, with a pre-emergent herbicide in spring after the soil has warmed. With proper timing, one application will eliminate these troublesome weeds all summer long. It’s better to apply pre-emergent herbicides sooner rather than later. Apply either before or after aeration and water in well.

Because most pre-emergent herbicides can also kill germinating grass seed, delay adding grass seed to the lawn until late summer or early fall.

4. Add grass seed. The best way to keep the lawn healthy and weed free is to encourage thick growth. Apply a good quality, compatible grass seed after the lawn is aerated to give maximum seed-to-soil contact and to improve seed germination. Keep the seed moist, but avoid saturating the grass. It will take about 10-14 days for seeds to sprout.

5. Fertilize. Fertilizers add the nutrients your blue-grass lawn needs. Nitrogen is especially important if you want a thick green lawn. Use a balanced fertilizer that has nitrogen, phosphorus, potassium, iron and sulfur. April is a good time to fertilize, especially if no fertilizing was done in fall.

For all the top turf tips, including how to handle dog spots in the lawn, visit CSU’s Turf Program website.

Now, what tips do you have for celebrating National Lawn Care Month?