The debate rages on among the garden crew (Stanford and ‘Bama) at a Cherry Hills installation.
Adversity can be a good thing
No doubt you have read or seen some information on Impatiens Downy Mildew, the newest fungal disease to hit our front range gardens in a substantial way. It’s a new adversity to deal with in our challenging garden environment. Like most pathogens, Impatiens Downy Mildew attacks a specific species, impatiens walleriana, and is characterized by downy growth on the underside of the leaves. This low-growing multifloral annual plant is a workhorse in our shade gardens.
Because the disease requires specific environmental conditions to develop and spread, most experienced horticulturists and nurserymen never thought the disease would arrive in the arid west. However, our unusually cool moist spring coupled with nighttime overhead irrigation helped increase the spread of the spores responsible for the disease.
The disease was first reported in the UK in 2003, and was found in US greenhouse production in 2004. Reports of its spread in the landscape included many eastern and midwestern states in the US, as well as in the provinces of Manitoba and Quebec, Canada.
The disease is not curbed by cold temperatures. Overwintering spores survive to (5F) USDA Zone 5. A trial conducted by Dr. Aaron Palmateer at the University of Florida in 2012 evaluated the effectiveness of fungicide treatments in both nursery production and the landscape. The evidence from the trial showed that impatiens could be successfully grown in the landscape for 8 weeks if a weekly spray program in the nursery was followed by a granular soil application prior to planting, along with a monthly rotation of fungicide sprays. Ann Chase, Ph.D, of Chase Agricultural Consulting also recommended to skip planting impatiens for one year in a bed that was previously infected.
What does this mean for our shade landscapes in the future? While impatiens may be available for purchase in limited quantities, the cost to maintain this plant, because of the recommended fungicide treatments, might exceed its desirability. For now, change is a good thing. Begonias, coleus, and lobelia are great colorful substitutes for shade planting. The New Guinea impatiens, and SunPatiens have been shown to be disease resistant, and are excellent substitutes for impatiens walleriana. It is likely that nursery production of regular impatiens will be reduced next year,and the following years. It’s a great opportunity to shake up your landscape design, and try something new. Plant diversity is a good thing.
Regular water conservation: the new normal
Recently, I was energized to have a conversation with Kristen Fefes, Executive Director of the Associated Landscape Contractors of Colorado (ALCC). The ALCC is the industry trade organization for landscape contractors, who become members of the organization by agreeing to a code of conduct with respect to Best Management Practices. These BMPs relate to commercial and residential landscape installation and maintenance care throughout Colorado.
This year, the number one topic on the industry plate was the watering restrictions imposed by our recent drought. How, as an industry, do we serve our customers as well as make money for our businesses, and families when our fortunes are so dependent on weather issues?
In my comments with Kristen, I advocated that the water utilities, such as Denver Water, and others, take a longer term view of the problem of landscape water scarcity, and regularly (annually) encourage homeowner and landscape conservation efforts through educational and public awareness events.
Teaching homeowners to conserve landscape water as much as possible in any give year, helps the entire community move to a new paradigm. Rather than take draconian measures in one year, and create the wrong emphasis on the problem (I am using less water, and I get to pay more for the privilege!!!??), I would suggest that through regular water conservation practices, we treat each year as an opportunity to find new water savings in our landscapes. While it might take 10 years or so to convert homeowners and their HOAs to a new look, I would advocate that this is the right approach for the long term health of our communities amidst certain future water scarcity issues.
Certainly those who work in the landscape industry have the knowlege to share different water-saving practices with their clients.
Here’s a suggested survey: Look at what outdoor activities actually take place around your home. Define practical turf zones to accommodate the volleyball net, croquet set-up, or just a place to use the summer slip and slide. Move the swingset to a corner of the lot (within view of Mom’s kitchen window) and place the structure on a non-irrigated (and more forgiving) mulch bed. Use hardscape near the backdoor to define an outdoor eating and living area, or deck.
After assessing your individual needs, choose to regularly irrigate only the practical turf areas, and provide less, or no water to those areas in your landscape that don’t require water. Invest in a good irrigation audit. Find, and fix the leaks, address sprinkler coverage issues, (often this just means adjusting, or replacing a head), and be a better outdoor water consumer. Use mulch, and follow other sustainable practices that improve the health of our landscapes.
We (and our plants)struggled through the beginning of the summer on a two-day per week watering schedule. Now that we’ve added a third day to our watering schedules, I’m very impressed with the health of much of our plant material. Even though we have had extended hot weather – another 95 degree day is forecasted for the Front Range – we have learned that deep, infrequent watering works. It is a best practice that we all can embrace.
Let this be a lesson for future summers. It won’t be long before sprinklers are blown out, and the garden put to bed for the winter. Remember the success of this summer,and resist the urge to change your clock next spring.
You’ll be helping your landscape, as well as conserving water!
Better than a paycheck!
A Few Hardy Souls
Mother Nature hasn’t been kind to the Denver Metro Area recently. Heavy snows, and late record cold temperatures followed a winter (and summer and fall!) of drought. It was great to see this display of garden resilience in one of my client’s gardens as I was doing the spring clean-up. What made the difference here?
Mulch. My sustainability tip #1. Mulch, in many forms can provide the following benefits: it retains soil moisture, and reduces soil evaporation, reduces weed growth, and reduces soil temperature fluctuations. The latter can cause heaving of shallowly rooted plants during a freeze/thaw cycle. 3-4″ of mulch is recommended as an organic, sustainable practice of weed control because the depth of mulch helps prevent weed seeds from setting as easily. Less weed seeds means less likelihood of the need for later chemical control. During a drought year, with watering restrictions, retaining soil moisture is the most important benefit of mulch.
Perennial gardens, and other landscape areas look beautiful with a uniform layer of organic mulch. Sourcing the mulch locally, or using a recycled product from an arborist or tree company is an additional way to promote sustainability. As perennial gardens mature, and spreading plant material or groundcover plants fill in the bare areas, less mulch is needed. Vegetable gardeners may choose to use straw, or grass clippings as organic mulches. With the latter, it’s best to let the grass clippings dry before application to prevent matting. Grass clippings from lawns treated with herbicides should not be used as mulch.
When using organic mulch, it’s also a good idea to test for nitrogen deficiency in the soil occasionally. As organic mulches decompose, surface soil nitrogen is used in the decomposition process. If a soils test shows the need, nitrogen can be added to those areas where soil deficiencies occur.
Check back for other sustainable garden maintenance ideas.