Landscape - Horticultural Ecosystems X

This is the last of the series on horticultural ecosystems in sustainable landscaping. Slides are from a presentation that I give on the subject.

Pest problems in the landscape result from a horticultural ecosystem that is out of balance. This often is due to lack of diversity in a landscape that leads to pest buildup. Use of plants that have noted pest problems should be reduced. Practice those methods that encourage the buildup of competitors or natural controls of pests. If pest control is necessary, practice integrated pest management and consider all options before using a pesticide.

Encouraging beneficial or benign organisms in the landscape can go a long way to reduce or eliminate pest problems. Strive for a balanced ecosystem. Understand those practices that can encourage these "good" organisms above ground and below ground.

It is critical to use native plant species as much as possible. These are well adapted plants that are important for wildlife and will help to develop a horticultural ecosystem that will function well in our area.

In the end, consider whether you want to fight natural forces or learn to take advantage of them. Highly managed horticultural systems with limited diversity and high maintenance species are costly and often do not succeed in the long term. Think of how your short term actions will end up in long term consequences. In landscape design make sure your vision includes the creation of a successful and healthy horticultural ecosystem. Strive to understand the interactions that occur in the landscape to help you make better decisions.

I hope this series has been helpful with those of you interested in sustainable landscaping.

Gordon Johnson, Extension Horticultural Agent, UD, Kent County

Landscape - Horticultural Ecosystems IX

This is a continuation of the series taken from a presentation that I give on sustainable landscapes as horticultural ecosystems.

In a balanced horticultural ecosystem, plants will for the most part be healthy. However, undue stress from abiotic (environmental) factors and biotic stressors (such as pests) can upset the balance. The goal in any horticultural ecosystem is to create and maintain a healthy environment. Landscape maintenance activities should be designed to maintain plant health.

Abiotic or environmental stress factors include drought/water stress, flooding, high temperatures, low temperatures, wind dessication, physical damage, salt injury, and nutrient deficiencies. Plant health can be negatively affected if these stress factors are excessive. However, moderate stress is normal and a healthy landscape can tolerate many stresses and actually will benefit in some ways. Understanding when you should intervene to reduce stress (such as with water during a drought) is key. Other stresses can be avoided by prudent landscape maintenance activities (no damage to landscape plants for example).

Biotic stress factors in the horticultural ecosystem include the common pests - insects, mites, slugs, weeds, diseases (fungi, bacteria, nematodes), rodents, and other animal pests. Many times our pests become an issue because of a lack of diversity in landscape, improper plant selection or use of poorly adapted plants, having excess environmental stress that predisposes plants to pests, or improper landscape maintenance activities that favor pests.

As stated before, the goal is to reduce plant stress. Use of organic amendments can go a long way to reducing water and nutrient stress. Proper pruning and thinning can reduce diseases by lowering humidity around plants. Providing proper drainage can reduce the incidence of root rots. It is important when considering methods to reduce stress not to upset the balance in the horticultural ecosystem. For example, excess nitrogen fertilizer can push plants to produce too much growth. This excess growth is often more susceptible to plant diseases.

To be continued.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape - Horticultural Ecosystems VIII

This is a continuation of the series on managing landscapes as horticultural ecosystems for sustainable landscaping. Slides are from a presentation I give on the subject.

Consider what effects structural components will have on the horticultural ecosystems and design to minimize negative effects. Limit root restrictions or design with rooting in mind (structural soils under walkways for example). Consider where water runoff will go and design to manage that runoff (rain gardens for example). Consider how structural components may increase radiation load, change light conditions, or limit plant space.

Consider how the landscape will be used by people and how this will effect the horticultural ecosystem. The goal is to blend man as part of the landscape.

Your management activities in the horticultural ecosystem can have major effects. Consider how you will manage the root environment. Plant nutrients and water can be limiting factors in a landscape; however, overuse of these inputs can have negative effects. Consider how your management affects light conditions, temperature, wind, humidity, and other microclimate effects.

Consider what the effects of the above management decisions would be on the horticultural ecosystem.

To be continued...

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape - Horticultural Ecosystems VII

This is a continuation of the series on viewing the landscape as a horticultural ecosystem. Slides are from a presentation that I give on the subject.

As you add plants to a landscape you will alter the horticultural ecosystem. Light conditions will change over time with trees and large shrubs. These larger plants will also modify exposures to wind and reduce heat loads. Microclimates around plants are determined by the plants selected and their growth patterns. Plants will also provide food for the microbial community and for wildlife. In the end, the horticultural ecosystem will develop specific complimentary microbial communities in the soil and canopy and certain complimentary animal components from earthworms in the soil to birds in the landscape.

Horticultural ecosystems will be impacted by changes in terrain, changes in light, soil disturbance, soil modification, exposures (wind and temperature), movement of water (drainage), microclimate effects (humidity for example), and interactions with microbes and animals.

On the slide above, take time to consider what the effect will be by the actions listed. For example, the addition of compost to a soil will modify the soil conditions greatly and will positively impact plant growth. In contrast, adding a paved driveway will raise temperatures nearby and negatively impact plant growth.

I will continue with this series in future posts.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape - Horticultural Ecosystems VI

This is the sixth in a series on viewing the landscape as a horticultural ecosystem as a part of a sustainable approach to landscaping. Slides are from a presentation that I give on the topic.

Once you have your landscape in place, the landscape maintenance company will manage the horticultural ecosystem. You can introduce new species and replace current plants. Interplant competition is a major factor that needs to be managed to favor one plant over another or to allow plants in close proximity to coexist. Growth modification will alter the horticultural ecosystem so pruning and thinning must be done with that in mind. Remember that the plants themselves will modify the landscape environment. You must also manage spread of plants and control invasives. Another point to consider is that natural succession is a strong force and plants from surrounding natural areas may come into a landscape without your assistance.

When you introduce or remove a species consider the effects on the horticultural ecosystem. Is the new plant compatible with the system? How will the removal of a plant alter the landscape?

Invasive species can be a challenge in some landscapes. Take time to understand why these species are invading your horticultural ecosystem and use appropriate control measures that do not harm the landscape.

I will have more on these topics in future posts.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape - Horticultural Ecosystems V

I often recommend that the landscape should be viewed as a horticultural ecosystem where the landscaper's influence is critical and the decisions they make can affect the balance. By understanding the horticultural ecosystem, landscapers can often make better decisions. The goal is to create a sustainable landscape system. This is the fifth in a series of slides on the subject from a presentation I give.


Diversity should be a major goal of any landscape. The diversity in a horticultural ecosystem is selected by you as the landscaper or landscape designer. Large expanses of lawn are not diverse systems. Neither are single species screens or windbreaks. Most of our landscapes have limited diversity with only a handful of mainly non-native species. This can lead to many problems such as increased pest problems, reduced habitat for desired wildlife such as birds, high maintenance requirements, and reduced longevity of plantings.

A common suburban landscape. Diversity is limited to a monoculture of grasses, a few shade trees, and a few foundation plants.

In horticultural ecosystems with limited plant diversity, the diversity of other organisms is also limited from soil microbes to desired wildlife. Food sources for native animals are limited thus limiting their numbers in communities that have low diversity of plants and many non-native plants. Pests are often more of a problem and reduced plant vigor often results. There is a reduction in the benefits from plant synergism. Landscapes can also be very monotonous and of low aesthetic value in these low diversity systems.

Create more horticultural ecosystem diversity by selecting a wide range of plants from many different plant families and using a majority of native plants. You can add diversity to any landscape by replacing existing plants with different species and by converting parts of lawn areas to landscaped areas. When adding plants or designing systems, consider how plants are placed and what effects they will have on each other. Design for complimentary effects. Alter soils to favor the species that you install. Eliminate those plants that have high maintenance requirements from a pest management perspective or that are pest prone.

I will continue these thoughts in additional posts.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County.

Landscape - Horticultural Ecosystems IV

This post is a continuation of the series on understanding horticultural ecosystems as a part of sustainable landscaping practices. Slides are from a presentation that I give on the subject.

After a site is disturbed, a new ecosystem must be established. The function of this new horticultural ecosystem is dependent upon the choices you make as a landscaper. It is important to consider plant interactions with the specific environment. Planning should take into consideration ecological factors, what is the desired ecosystem, what do you need to take into account in the site environment to arrive at the desired horticultural ecosystem, expected interactions in the new landscape, how the landscape will be used, and of course aesthetics. Consider more naturalized areas if possible and use native plants as much as possible.

This landscape has achieved a balance between having areas that function for the needs of the homeowner (a lawn area for children to play) and landscaped areas that build a sustainable horticultural ecosystem. One negative would be that not enough native plants are used.

One way to view the initial stage of landscaping is as a healing process. You need to understand the soil changes that need to take place to quickly develop the new horticultural ecosystem and add amendments to help that process along. As plants root into the new landscape, a new ecological community starts to develop.

Over time, as the landscape matures, changes take place and the ecosystem evolves. Understanding this process is key to landscape maintenance needs.

Landscaping is in essence a controlled succession of species. Young landscapes will favor certain species and more mature landscapes will favor other species. Trying to force species to grow in this succession out of their natural adaptation will result in failures or excessive maintenance needs.

In your landscape design, one of the most important set of decisions that you have in establishing a new horticultural ecosystem is species selection. Once the selections you make are installed, natural processes will act upon those species. As the horticultural ecosystem evolves, other selections are made naturally including plant invaders (weeds, invasive plants), animal selections (both pests and beneficial animals, for example you can have insect pests and beneficial insects), and microbial selections (again both beneficial such as mycorrhizal associations with roots and detrimental such as plant pathogens).

Your species selection is very critical for the new horticultural ecosystem. Diversity should be sought. Think of short term and long term effects of your selections. Native species offer significant advantages in adaptability and in support of desired wildlife (habitat). Poor selection can result in problems such as invasive plants and pest buildup.

I will have more on this subject in future posts.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County.

Landscape - Horticultural Ecosystems III

This is the third in a series on horticultural ecosystems, a sustainable way of looking at landscapes and landscaping. Slides are from a presentation that I give on the subject.

As a landscape site is developed, you must assess those natural forces that will work upon the landscape. How will biotic factors (living things) act upon the landscape, how have site modifications affected the ability of plants and other organisms to live and thrive, how has water and the hydrologic characteristics of the landscape been affected, how have exposures to wind and sun been altered?

An extremely exposed site prior to landscaping. Plants will be affected by wind and full sun conditions. Water may runoff or may be lost to excessive evaporation. Soil disturbance and compaction will affect rooting conditions.

Clearing woods for a parking area. Surrounding vegetation is severely impacted by increased exposures and root damage.

Making a road through a formerly wooded area. Land disturbance has increased exposures, affected soil conditions, opened up the potential for erosion, and altered the existing ecosystem. You must assess the effects of all these actions before considering how to install the new horticultural ecosystem with landscaping

I will continue on this topic in future postings.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape - Horticultural Ecosystems II

This is the second in a series on viewing the landscape as a horticultural ecosystem. This is a sustainable approach to landscaping. Slides are from a presentation that I give on the subject.

Disturbance plays a key role in horticultural ecosystems. How the landscape is designed, installed, and managed after this initial disturbance will determine how well it will function as a horticultural ecosystem.

This is a an example of what a landscaper has to work with on a newly developed property in DE. It is challenging to get the landscape to establish and even more challenging to develop a healthy horticultural ecosystem.

When the land is disturbed during development, there are many changes that take place that will affect the subsequent success of the landscape. The natural ecosystem is destroyed and it is up to you to help create the new horticultural ecosystem.

Woods clearing alters the ecosystem drastically. The environment is exposed to greater extremes in temperature. Wind now becomes a factor. Soil characteristics change because of the clearing.

Soil movement can destroy soil structure, result in compaction, and expose subsoil with poor chemical characteristics for plant growth.

Topsoil movement off and back onto a site has large impacts on the root environment.

Construction activities can leave a challenging soil environment that needs to be modified before establishing the new landscape.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County.

Landscape - Horticultural Ecosystems I

I often like to teach horticulture from an ecological perspective. By Viewing the landscape as a horticultural ecosystem where your influence as a landscaper is critical and the decisions you make can affect the balance, you can often make better decisions. The goal is to create a sustainable landscape system. This is the first in a series of slides on the subject from a presentation I give.

In a horticultural ecosystem, all the above actions are determined by you as the landscaper or landscape maintenance person. Your decisions will affect the success of the landscape.

In natural landscapes, there is a succession of plants to a climax vegetation that dominates. This does not change until something disturbs the balance such as fire caused by lightning.

The above pictures are examples of a "naturalized" landscape using native plants. Man's actions are still critical here as this meadow environment is not the climax vegetation in our area. Weedy annual and perennial plants can invade. Woody shrubs followed by trees will then come into the area without intervention.

This is a landscape that uses native plants but is more highly managed. The land is disturbed and a new landscape is established. Species are predetermined, planting patterns established, and maintenance practices such as mulching are put into place.

I will continue on this topic in future posts.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County.