Importance of the Allergy Friendly Landscape

Most of us think summer sneezing just ‘comes with the territory’ but did you know that you can alleviate some of it with an allergy friendly landscape!  As landscape professionals, the concept of an allergy friendly landscape is a crucial one. Regardless of the scale of a project our understanding of high pollen generating plants is critical to making some changes for the better in our cultivated landscapes.

Wind blown pollen

Wind blown pine tree pollen. Makes me sneeze just looking at it!

Background

Most of us suffer from just a little sneezing and sniffling from seasonal allergies but the implications of high pollen rates can be far more serious. “Deaths from asthma continue to climb each year at alarming epidemic rates”.1 While the causes of these increases can be debated it is clear that high pollen rates play a role in many health related issues, especially in the young, old and those with compromised respiratory and circulatory systems.

Studies have shown death rates among high-risk populations increase on days with high pollen and high pollution. Similar to the association of very hot or very cold weather to higher death rates, one cannot attribute it directly to the weather condition but rather see a correlation in high-risk populations.2 Impacts like thunder death outbreaks also bring home shocking impacts of high pollen in urban settings.3

So, how did we arrive at the increases in allergies and asthma? We all know the issue relates to high pollen counts, but what is pollen and has atmospheric pollen been on the rise in recent years? Pollen is the microscopic grain carrying the male gamete of a plant that will pollinate (via transport by insects, birds, wind, etc.) the female ovule of a plant. This microscopic grain is both an irritant and a nasal allergen in humans (and other animals; yup, dogs get allergies). Anemophilous plants generally cause the most allergies because they pollinate primarily by wind. The pollen grains of those plants are light and small, in order to be easily dispersed by the wind (and therefore tend to stay airborne and easily breathed in by humans). The role of female plants in an allergy friendly landscape is critical because they are attractive (for sure 🙂 )! The pistil of female plants is STICKY in order to capture the pollen grain. In an allergy friendly landscape female plants (and flowers) are important because they both do NOT produce pollen, AND they pull pollen out of the air with sticky attractiveness! Two other important aspects of pollen creation are important to understand as well – pollen production is increased dramatically with additional CO2 in the atmosphere (urban settings) and changes to the timing of pollen generation is being sparked by increased climatic temperatures.

Microscopic Helianthus Pollen

Microscopic Helianthus Pollen – it sure looks like it would irritate anybody’s nose!

So what does this have to do with the cultivated landscape and an allergy friendly landscape? This is where the concept of botanical sexism comes into our vocabulary. “Arborists often claim that all-male plants are ‘litter-free’ because they shed no messy seeds, fruits or pods. In the 1949 USDA Yearbook of Agriculture, which focused on trees and forests, this advice was given to readers: ‘When used for street plantings, only male trees should be selected, to avoid the nuisance from the seed.’ In the years following, the USDA produced and released into the market almost 100 new red maple and hybrid-maple-named clones (cultivars), and every single one of them was male.”4 At The Plantium, we believe male cultivars have an important place in the landscape, but it is important to understand that the use of male (and only male) cultivars and overall plant selection play the most important role in developing an allergy friendly landscape.

Scope and Scale

When and where it is important to think about an allergy friendly landscape? There are many projects where understanding the right plants for a low allergy and allergy friendly landscape are important. Being conscious of pollen generation on all your projects can help address the growing issue of high pollen in the cultivated landscape. Our responsibility as landscape professionals should be taken seriously! Consider your client when embarking on a residential design. Just asking the question about any allergy or asthma sufferers in the household (and then designing an allergy friendly landscape) can help make a successful landscape and a happy client. Allergy friendly landscape plant selection is most important around high risk populations, including playgrounds and senior living projects. Finally, projects in urban centers should be addressed carefully as the greatest population of allergy and asthma sufferers per capita reside in cities.

Amaryllis Stamen

Up close and personal on the Amaryllis stamen. The sticky pistil of an amaryllis flower gathers up all this pollen for fertilization!

Making Great Plant Choices

All of this background begs the question… what do we do now? Here are a few thoughts.

  1. Understand and educate yourself on the benefits of the allergy friendly landscape.
  2. Familiarize yourself with the OPALS rating system. Thomas Ogren created the first and only known rating system that ranks the allergy potential of plants.
  3. Discuss the need for an allergy friendly landscape with your client.
  4. Educate yourself on types of plants that might fit in an allergy friendly landscape and follow a few best practices such as:
  • Gender balance the landscape.
  • Use fewer wind pollinated species.
  • Encourage sterile cultivars and showy flowers (most plants with big colorful flowers are insect pollinated! Bees welcome?!).
  • Avoid high pollinators: male only willows, poplars, aspens, ash, (fruitless) mulberry, cypress, junipers, yews, myrtles, currants, etc., olive trees, Bermuda grass. Fruit trees are good but nut trees tend to be allergenic.
  • Develop maintenance manuals for your clients that encourages trimming of existing high pollinators and good maintenance of installed plants (e.g. trimming privet before it flowers). The Healthy Schoolyards Initiative5 has a great start at a list of maintenance measures that can be undertaken on existing landscapes.

The Politics of Allergy Friendly Landscapes

While it appears uncertain that low pollen ordinances are having an impact, landscape professionals should be aware that there are a growing number of urban centers enacting pollen control ordinances, including Pima County, AZ, Clark County, NV, Albuquerque, NM, Phoenix and Tucson, AZ, and El Paso, TX, among others. Other cities such as Louisville are embarking on some truly innovative approaches to understanding and addressing the epidemic.

Conclusion

While we can thank pollen for so many wonderful things like solving murders (it’s a plant’s fingerprint!), determining the age and quality of coal seams, and our delicious fruits and vegetables we now need to be stewards of our own air and address the issue of excessive pollen in our cultivated landscapes!

References:

  1. http://www.academia.edu/4110694/Politics_of_Pollen_Article Copyright 2001, Tom Ogren
  2. http://www.webmd.com/allergies/news/20000427/high-pollen-linked-death#1
  3. http://www.bbc.com/news/world-australia-38121579
  4. https://blogs.scientificamerican.com/guest-blog/botanical-sexism-cultivates-home-grown-allergies/
  5. http://www.healthyschoolyards.org/

Image References

https://commons.wikimedia.org

Designing with Dog Friendly Plants

Ever wonder how we get our yards, parks, and streetscapes to be ‘dog friendly’? As in, how do we design a urine and trample resistance landscape filled with dog friendly plants? Well, let’s start with thinking about some alternative groundcovers that can take a little beating. These are plants that can be used as an alternative to turf. Turf alternatives can save water AND help fight off the brown patches that come with a ‘dog heavy’ landscape. A couple good examples in the attached pdf include Elfin Thyme and Ajuga. These are just two great choices, but you can always use your filter criteria and select low growing plants that can withstand foot traffic. In The Plantium’s filter criteria you’ll find the foot traffic filter under ENVIRONMENT.

The second issue is urine resistance. While this is NOT a filter in The Plantium, the attached pdf has some tried and true choices that can withstand the excessive nitrogen content in dog urine. Again, not an exhaustive list but a good start. Remember to also consider any plants that are TOXIC to pets and avoid those. Sending your little furry friend to the vet would definitely NOT be considered dog friendly plants! For those Plantium users, this is a filter criteria under WILDLIFE. For those of you not yet in The Plantium you can visit the ASPCA site (Plantium’s filter criteria is WAY easier, though!) 🙂

Lastly, and perhaps most obvious would be water. The faster you can wash away any leave behinds from the doggie visitors, the better chance of avoiding the burn spots, so let’s take back those brown patches and get into our dog friendly plants!

Dog Friendly List

https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants

 

Fun Facts: Planting Design ‘at Altitude’

This short article attempts to bring some clarity to the complicated discussion of “designing at altitude.”

Everyone acknowledges that elevation plays a role in plant growth. The most widely known and visible example of this is the phenomenon known as Treeline. (Check out this article for a great explanation). But there is significant confusion among landscape professionals as to how and why elevation affects the plants you can grow in a cultivated setting. In fact, many commonly held beliefs are misconceptions or generalizations applied erroneously to all high elevation areas.

What truly changes as altitude increases, and how do these changes affect plants?

There are four factors that are universally tied to increased elevation:

  • Decreased temperature (generally)
  • Decreased atmospheric pressure
  • Increased exposure to overall solar radiation (on clear days)
  • Increased UV-B Radiation

All of these affect plant growth to varying extents. Decreased atmospheric pressure can translate to increased transpiration rates (the loss of water through plant leaves), however the lower air temperatures at high altitudes often negate this. Increased exposure to solar radiation can result in higher photosynthetic rates. Conversely, increased exposure to UV-B radiation impairs photosynthesis in many species of plants. And while exposure to both types of radiation increases with elevation, this is only on clear days, the number of which varies significantly by location, regardless of altitude.

Of the above elements, decreased temperature is the most universal change, and most likely the one that has the biggest impact on ornamental plant survival. Temperatures decrease by about 3.5 deg. F for every 1,000 feet in elevation gain. These cooler air and soil temperatures can affect many facets of a plant’s growth including seed germination, bud break, photosynthesis rate, flower season, and even pollen formation.

What isn’t a factor of elevation change?

Many other things attributed to increased altitude are not actually direct factors of elevation change, but rather location-specific environmental characteristics, such as:

  • Increased exposure to wind
  • Decreased available moisture
  • Shallow or poor soils

These are often applied generally to all high elevation settings, but in fact are highly dependent on the individual location.

Other environmental characteristics are actually a combination of latitude and altitude together, such as the perception of a shorter growing season. In central latitudes there is very little difference between the growing season at sea level and the growing season at a higher elevation. However, the closer you get to the poles, the more pronounced the difference becomes.

Sourcing plants from outside your elevation: Does it matter?

It is not a surprise that the same plant grown in a different area may appear different. Distinct temperature ranges, soil types, humidity, etc. will cause a plant to display different characteristics as it adapts to its environment. Species sourced from alternate regions may even have divergent genetics. An example provided by the Larimer County Ag Extension is Redbud (Cercis canadensis). Trees from seeds collected in northern areas (Wisconsin, Minnesota) are much more hardy than seeds collected from warmer climates like Oklahoma or Texas.

Regardless of elevation, it is always a good idea to source your large material from a climate comprable to that of your project. The years the plant has spent adapting to a similar climate will prepare it for successful establishment when you transplant it at your site. Compounding the stress of transplant with the stress of a wholesale change in growing environment will only increase the chance of death or failure to thrive.

The Takeaway:

At its core, successful establishment of ornamental plants depends on day length, season length, high and low temperature tolerance, and moisture/nutrient availability. The environmental factors that your site experiences must be taken into account when creating a design and selecting plant material, but elevation does not need to be added as a mysterious compounding factor.

If you think a plant can withstand your temperatures, moisture level, water, and exposure: give it a try, and let others know what you find out!

References:

http://aob.oxfordjournals.org/content/94/2/199.full

http://northernwoodlands.org/articles/article/why_is_the_treeline_at_a_higher_elevation_in_the_tetons_than_in_the_white_m

https://www.era.lib.ed.ac.uk/bitstream/handle/1842/283/worre3-4.pdf?sequence=2 (Georgraphical variation in Sitka spruce productivity and its dependence on environmental factors)

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.502.5473&rep=rep1&type=pdf

http://www.life.illinois.edu/ib/514/K%F6rner_2007.pdf

http://www.ext.colostate.edu/mg/gardennotes/143.html

Larimer County Ag Extension

Designing with Cactus

What is a Cactus?

Many people, even those who consider themselves familiar with arid plants, get confused when it comes to what really constitutes a cactus. Isn’t it basically anything spikey that grows in dry climates? No! A cactus is, in fact, a very specific thing.

Cacti are members of the family Cactaceae. There are approximately 1,800 species of cactus.

Two specific things set cacti apart from other plants:

  • Not all cacti have spines when they mature, but a great way of distinguishing a spiney cactus from other spikey plants in the field is the presence of “areoles,” little bumps on the plant from which clusters of spines grow. If the spines on the plant are not growing in clusters out of these bumps it’s not a cactus!

Cactus aerole

  • All cacti also have a specific flower structure. Though the flower of each cactus species may be very different, all cactus flowers have many tepals (a term used when the sepals of a flower are indistinguishable from the petals) that are somewhat fused; hundreds of stamens; and many-lobed stigmas.

Yellow prickly pear cactus flower

Designing with Cacti

As a group, cacti are drought tolerant and are a great option for any water-conscious landscape. But xeric gardens aren’t the only ones that can benefit from the use of cactus! Their frequently strong sculptural or geometric forms and punchy colors can add punctuation to any landscape design, as long as the growing conditions are right.

Cacti with upright or twisting forms are popular for use against a striking backdrop such as a richly-colored wall, or for their silhouette against a vista. They can also be grouped together for great large-scale textural effects, or consider pairing their chunky forms with something soft such as Mexican Feather Grass (Nassella tenuissima) for inviting contrast. Barrel cacti are perfect for creating rhythm and reinforcing patterns in design, and the bold textures and colors of pad cacti (Opuntia) provide great backdrops or focal points in the landscape.

Agaves, other succulents, and grasses are great design companions, but cacti can really be added to any composition with complimentary leaf colors, contrasting textures, and similar environmental requirements.

Most cacti are very sensitive to over-watering, so make sure the soil is very well drained, and the other plants in your design have compatible water use requirements. Use The Plantium to easily find great cacti and appropriate design companions for your next project!

Fun Facts about Cacti

  • All cacti are succulent, but not all succulents are cacti!
  • All cacti are native to the Americas, though they have spread around the world post-colonization.
  • Although they are typically slow growers, cacti are very successful in arid climates, so much so that in certain countries like Australia many cacti are considered noxious weeds.
  • Cacti grow in a wide variety of places, though mostly in habitats that experience some drought. People associate cacti with hot climates, but there are many species that are hardy to -30 deg. F and lower!
  • Cacti come in a wild variety of shapes, sizes, and forms, from the stereotypical Saguaro, barrel, and prickly pear, to the Rose Cactus (Pereskia grandifolia) which looks like a tree or shrub at first glance.
  • Most cacti don’t have true leaves, instead performing photosynthesis in their modified stems. However some cacti, like the rose cactus, can be very leafy!