Let’s Talk about Mulch

It is no secret that mulch is great for the landscape.  There are so many benefits when you add mulch around your plants.  Mulch is a great insulator, because it modifies the soil temperature.  It reduces erosion, prevent weeds from germinating, retains soil moisture, provides a buffer between equipment and the trunks and stems, and increases the aesthetics of the overall landscape. As you add mulch to your garden, here are some things to know:

How much mulch is enough?

Mulching is not an exact science, but as a general rule, we try to apply 2-3 inches of mulch consistently throughout the landscape.  This depth of mulch will control weeds by decreasing sunlight exposure, which prohibits seeds in the soil from to germinating.  More than three inches of mulch seals off the soil and suffocates your plants.  It is extremely important that the plants are able to get the oxygen they need.  Spread the mulch evenly and don’t build a mulch volcano around the base of the tree.  Since mulch decomposes slowly, it is good to periodically check the depth and add some as needed.

Mulch volcano at base of tree. A big no no!

Nicely mulched new planting

What is the best way to mulch?

We start by laying out a garden hose, which allows you to visualize the curves and width of a bed.  You can either spray the area inside the hose or dig up the vegetation and let it slowly die.  When the area is cleaned up, we begin applying the mulch and leveling it to the desired depth.  Keep in mind that too much mulch will encourage growth of the roots into the mulch, where it will be susceptible to freeze damage.  The ideal 2 to 3 inch depth of mulch will keep the roots in the soil.

When is the best time to mulch?

We are mulching throughout the year, but direct most of our efforts in the spring or fall.  As we clean up our display beds in the spring, it is always a good time to freshen up the mulch, too.  At this time of year, soil temperatures are beginning to warm and a new layer of mulch will slow down the warming process.  A new layer of mulch will also cover seeds that may have landed in the mulch and covering them now will prevent germination.  We mulch anytime a new tree or shrub is planted.  This practice will keep the soil cooler, help retain moisture longer and insulate new roots from the cold weather. Some thicker mulch areas may benefit from being fluffed from time to time.  Simply take a rake and loosen up the top few inches of the mulch.

What type of mulch is best?

We use whatever is available to us.  Mulch is not cheap, so we use chippings from the tree trimming service.  We have used semi loads of hardwood mulch, which is expensive. It is not as important what you use, but how much you use.  Even free mulch can look attractive and function just like the most expensive mulch.  For sloped areas, the larger and heavier mulch works the best.  It is not as susceptible to runoff or wind displacement.  Smaller or finer mulch decomposes quicker too.  The bottom line is use what is available to you.

Our mulch pile of chipped up trees

River rock as mulch with blackeyed susan and prairie dropseed

Can I use plants as mulch?

In the book Planting in a Post-Wild World: Designing Plant Communities for Resilient Landscapes, Thomas Rainer and Claudia West develop the ideas of layering plants.  There are usually at least three distinct layers of plants: the upper layer filled with taller structural plants used to frame and punctuate the landscape, the middle layer filled with ornamental flowering plants and the ground level that weaves the other layers together and shades the soil, which controls weeds.  These layers mimic natural plant communities and each layer is important for the health of the plants.  A collection of plants living in community can be extremely drought tolerant and water-thrifty.

Lenora Larson’s Garden with dense plants that smother weeds

A few final thoughts:

Purchase a heavy duty mulching fork and stiff garden rake for leveling.

Essential mulching tools: Silage fork and stiff leaf rake

Insects can be a problem in mulch, so keep it away from the foundation of your house and base of the plants.  Termites generally like larger pieces of wood but can even live in the finer mulch, especially if it is too thick.

Landscape fabric under mulch is something we avoid.  It only keeps weeds out for the first few years and then the decomposing mulch turns into compost, which is ideal seed bed for weeds.  It is also hard to transplant into it and often suffocates the soil.  We have purged the Arboretum of just about all landscape fabric.  Save your money and buy more plants.

You can use rock as a mulch, but don’t buy the recycled rubber mulch.  The rubber mulch may last forever but it does nothing great for the soil or the plants around it.  In fact, the compounds and residues that leach over time may do more harm than good.

Happy Mulching!

Cicada Killers

“Hunting, warring, patrolling, tunneling, they do more in two months–the length of their adult lives–than periodical cicadas do in 17 years.” ~Tim Heffernan, The Atlantic

The insect world never ceases to amaze me. I had a new experience with insects in my yard a few evenings ago. A cicada making a ruckus landed on the ground right next to me in my garden. I quickly realized that it was in a tussle with a large wasp. I had heard about cicada killers before, and it didn’t take long to deduce that I was seeing my first one take down its prey. The cicada struggle didn’t last long as the sting and subsequent paralysis happened in seconds. The cicada killer shortly flew and when checking back later, I noticed that the cicada was gone too.

A cicada killer taking down a cicada.

A friend recently posted a great article about cicada killers. Do yourself a favor and read Tim Heffernan’s 2013 brief article on cicada killers in The Atlantic. This article explains the cicada killer’s interesting adult 2-month life, soil-burrowing nest habits, process for taking down cicadas, hatching of their larvae in a cicada’s live but paralyzed state, and the flies that can also parasitize the cicada killers themselves.

Harmless to People

“With bodies up to two inches in length, huge jaws, and glossy black paint jobs streaked with yellow, they are unmistakable, and more than a little intimidating.” ~Tim Heffernan, The Atlantic

Cicada killers are fascinating insects, and you should add them to the list of insects around you that make you say “oooooh”, rather than “ewwwwww!” They may look ominous, but they really are harmless to people.

In addition to taking in the fascinating information in Tim Heffernan’s article, I want you to take away that this insect holds minimal danger for people. Their large size relative to other wasps is due to the fact that they need to wrestle a large cicada to their nest. The warning coloration is probably some form of mimicry that they have evolved to look fearsome like their yellow jacket and hornet relatives. My hope would be that folks could minimize the knee-jerk reaction of reaching for the can of wasp killer whenever they see any wasp, but especially a non-threatening cicada killer. Don’t fall into the societal stigma that causes many people to recoil when they see an insect, and especially a wasp.

The Hymenoptera Order of insects (wasps, bees, and ants) has long been maligned in our society. A quick search for “movies about killer insects” shows that we love to be terrified of insects.

I’d like to encourage a respectful and non-aggressive approach to all insects in general. So, to finish on a calming note, I’ll leave you with an image of a cuddly monarch butterfly caterpillar that I took right outside the Arboretum Visitor Center door this week munching away on common milkweed.

But be careful, it is filled with poisonous cardiac glycosides and if you were only 2 inches tall and you ate it, it could kill you. Aaaaaggghhh!

A deadly monarch caterpillar.

Five Water Saving Practices for your Landscape

Last week the Arboretum staff visited a flower farm near Lawrence.  It was interesting to see how they were growing their flowers to be used in arrangements and displays for special occasions. They focused on native plants, but also had some annuals, bulbs and shrubs, too.  During our tour, the topic of irrigation and water use were explored, because they are under severe drought conditions.  It made me think about our irrigation practices and ways to create a water-wise landscape.  Here are five water saving practices for you to implement in your garden.

Choose plants adapted to your site

One of the biggest mistakes I have made when establishing a new garden is choosing plants that I like rather than plants that like the area in which I am trying to establish them.  There is a big difference. It is critical to match plants to the site. The closer they are adapted to your landscape the less water they will need to survive.  Native plants are always a good choice, because they are already adapted to our climate.  Evaluate your landscape’s soil, sun exposure, and moisture content.  By understanding these aspects of your landscape, you will be able to make informed plant choices.  There is a palette of plants that will almost effortlessly grow in your garden.  Grouping plants with similar water needs that match your landscape conditions will ensure success.

 

Space Plantings Tightly

In their book Planting in a Post-Wild World: Designing Plant Communities for Resilient Landscapes, Thomas Rainer and Claudia West develop the ideas of layering plants.  There are usually at least three distinct layers of plants: the upper layer filled with taller structural plants used to frame and punctuate the landscape, the middle layer filled with ornamental flowering plants and the ground level that weaves the other layers together and shades the soil which controls weeds.  These layers mimic natural plant communities and each layer is important for the health of the plants.  A collection of plants living in community can be extremely drought tolerant and water-thrifty.

Use mulch around trees and shrubs

Mulches can be a blessing and a curse depending your mulching practices. We typically apply a two to three inch layer of mulch around a tree by simply mulching a tree a few inches away from the root flare and extending out to its drip line. Shrubs get the same treatment.  It is vital to keep mulch several inches away from the trunk or stem. Please, no mulch volcanoes!  Mulches prevent weeds, eliminate erosion, retain soil moisture, help moderate soil temperatures, provide a buffer between equipment and the trunks and stems and increase the aesthetics of the overall landscape.  Too much mulch (over four inches) starves roots of oxygen by sealing off the ground suffocating the plants. Old mulch can matte up and restrict water infiltration, too.

Viburnum prunifolium in bloom

Irrigate efficiently

During times of prolonged drought, irrigation may be necessary.  Plants naturally go dormant, but in a display bed you can add supplemental water to keep them more vibrant and healthy.  We use pressure compensating drip irrigation tubing with emitters spaced 12 inch apart.  Drip irrigation puts water where it is needed for optimum efficiency in the root zone rather than on the leaves. If you irrigate with overhead sprinklers, start sprinklers early in the morning or later in the evening.  Avoid watering during the hottest part of the day to reduce evaporation and loss from wind.  You can also recycle rainfall and create a rain garden.

Pressure compensating 1/2 inch soaker hose

 

Reduce your lawn

Cool season grass lawns with roots that are maybe six to twelve inches deep are one of the most watered landscape plants. If you think strategically and replace part of a water-guzzling lawn with deep rooted wildflowers, grasses, shrubs and trees or even with native buffalograss, you will save water and increase wildlife diversity in your landscape.  You may like open spaces with lawn for play or leisure, but you can scale back the size of your lawn and still have the aesthetics you appreciate.  Mow your lawn at the highest height and water only as needed.  Turfgrass has its place in the landscape, but maybe not the most prominent place it currently does.

We don’t think often enough about the water we use. It is a precious commodity. Remember the 2011 and 2012 drought in Kansas? We were using tremendous quantities of water to keep our landscapes alive. It made us evaluate each plant according to its response to these extreme conditions.  Obviously, some plants did better than others and we lost some plants those years. It made us think critically about our plant choices and irrigation practices. A beautiful and resilient landscape that uses little if any supplemental water is an achievable result.  A few changes can make a big difference.