“Dirty Dozen” is one of those short, alliterative phrases that’s easy to remember and fun to use. In today’s post, I’m applying it to garden products whose production or use can be damaging to the health of ecosystems, environments, and even humans. How many of these products are in your garden shed, or appear in ingredient lists of other products? Each short description below has one or more links to additional information. After you count them up, see how you rank on the Charlotte Scott Meme-O-MeterTM
Product manufacture damages ecosystems
A protected peat bog in British Columbia
Peat moss. Peat moss bogs are slow-growing ecosystems that store vast amounts of carbon. Removing peat moss destroys these ecosystems (which can take centuries to regrow) and releases C02 into the atmosphere. Do a little experimentation with sustainably sourced or locally available crop residues and see if you can find a more environmentally friendly substitute.
Kelp forest at low tide. Image courtesy of NOAA Photo Library
Kelp. Kelp, or macroalgae, are the basis of intertidal and subtidal food webs. Removal of these plants creates underwater deserts where little life can be found. Restoration can be done, but it’s a slow and expensive process. Ask yourself why you think you need kelp and compare this to the facts.
There are lots of sources of manure on the internet…
Bat guano. Seems like a reasonable use of a waste product, right? Nope – and Dr. Jeff Gillman explained why in a post more than a decade ago. If you want a sustainably produced, manure-based fertilizer, you can find many options at garden centers.
Products whose use damages garden and landscape soils
Rubber mulch. Look closely and you can see bits of metal from steel-belted tires.
Plastic mulch. There is nothing worse (see chart in this link) you can put on a living soil unless your intention is to kill everything under it. You may see it used in agricultural production, but that doesn’t make it a good choice for your gardens and landscapes. Again, there it a much better alternative to this and all other sheet mulches.
Lots of claims about Epsom salt…but does your soil need magnesium?
Products whose use damages plants and plant-associated microbes
Always check that NPK value before you buy anything
Phosphate fertilizer. The most overused nutrient in home gardens and landscapes, and one that can cause iron deficiency in plants. The only time you should add anything containing phosphate – including compost or other rich organic material – is if you have a soil test indicating a deficiency.
Wound dressings. Unfortunately, many gardeners don’t understand that plants and people respond differently to injury. While antibiotic dressing and bandages are good for healing our nicks and cuts, trees have a completely different response. Slathering black goo or paint over tree wounds is the last thing trees need to seal damage naturally.
You score 1-3: Maybe you’ve been a part of this community for a while or maybe you’re just acutely aware of sustainable products and practices. Either way, the Garden Professors thank you!
You score 4-6: So maybe you recently broke up with your local garden center and are reevaluating some of the products they recommend. Stay strong!
You score 7-9: Oh, bless your heart. Let’s talk.
You score 10-12: So you take the phrase “scorched Earth” pretty seriously, huh?
All jokes aside, sustainability and gardening require constant adjustment and learning. You came here, you read through this list, and you are thinking critically about your practices.
For many gardeners around the US (and the northern hemisphere) the weather is warming up for spring planting season and many are itching to get out in the garden. But when is the right time to plant those veggies and flowers and not gamble on their success? Just like Kenny Roger’s character in The Gambler, knowing when to do something is important (this is where I’ll end the cheesy comparison – you’ve just got to come up with a catchy title sometimes).
I’ve spoken previously on this blog about understanding frost dates, which is important for planting warm-season crops like tomatoes, peppers, and cucumbers that won’t survive a frost. (You can read that article here.) But another temperature factor we must consider, especially for cool season plants that we plant BEFORE last frost is the soil temperature.
Soil temperature is especially important for direct sowing seeds in the garden, but it can also affect the success of transplants planted in the garden. For transplants, having an appropriate soil temperature supports root growth and development and helps plants get established faster.
Many warm season plants, especially plants like peppers, won’t establish easily or thrive unless soil temperatures are sufficient for root growth.
Why soil temperature mattersfor seeds
For direct sowing of seeds, soil temperature has a major effect on the speed of germination, which also affect the success rate of germination. Each different seed has a different optimum temperature for germination. If the soil temperature is below, or above, that level then germination can be slowed down. Slow germination can decrease germination rates through a few different avenues:
Germinating seeds are vulnerable to infection or decomposition by fungi and bacteria in this soil. When starting seeds indoors, this can be limited by using a sterile seed starting mix. But when direct sowing outdoors, there are any number of fungi and bacteria in the soil that will decompose a struggling seed/seedling. Some seeds sold for large-scale production will have a coating of fungicide on them that will provide a few weeks worth of protection. You won’t likely find this on home garden seeds, but it might appear if you buy seeds from a farm supply store or a catalogue that caters to farm-scale producers.
Seeds have a finite amount of stored energy. Once germination begins, the respiration rate of the embryo in the seed radically increases. If germination is slow, the embryo can expend the stored energy before the seed leaves emerge and start producing energy to support the developing seedling. (This also occurs if you plant the seed too deeply).
Below is a graphic I made for Nebraska featuring the best soil temperature range for major vegetable crops (notice how it also lines up with last frost dates). Just ignore the info on frost dates for Nebraska, unless you live in Nebraska.
Most of the resources you’ll find on soil temperature and germination are for vegetable crops. If you are trying to start seeds of ornamentals, you’ll likely have to find the information yourself. The seed packet will give you some indications of when to sow (before/after frost, or maybe in the fall for overwintering to break dormancy) and you can search online for guidance for specific plants. For info on starting seeds indoors, check out this previous article I wrote on the subject.
How to measure soil temperature
Of course, the tried-and-true old fashioned way is to use a thermometer. You can find a soil thermometer at many garden centers and retailers. You’ll want a soil thermometer because the ones for your kitchen likely don’t have the right temperature range – we’re measuring well below the temperature of a roasted chicken here. Instert the thermometer two to three inches into the soil and wait several minutes for the temperature arm to adjust before reading. Also keep in mind that temperatures fluctuate with the weather and throughout the day depending on temperature and the amount of direct sunlight hitting the soil surface – so you want to measure a few times to make sure the temperature is staying within the right range.
Now, the new technological way is to find a soil temperature monitoring station online. Soil temperature monitoring is a common feature of many weather stations these days and data is more available than ever. Many university extension services or ag research centers compile soil temperature maps for use by farmers and this data is also often accessible through NOAAA or weather.gov. In Nebraska, we have an extension program called CropWatch that provides average daily and weekly soil temperatures year round. We also have a weather station with soil temperature probes at our extension office (perks of having a meteorologist as a master gardener volunteer) and we (and our master gardeners) use it when providing information to clients. It can be hard to find a resource that provides soil temperatures nation-wide to share in the patchwork of private and public stations (and the National Weather Service site can be notoriously hard to navigate). There are a few online resources from the ag industry that provide a country-wide system, like this one.
And now its time for me to walk away, time for me to run
Unlike The Gambler you don’t want to wait until after the plantings done to count your money, er, check the temperature. Remember that knowing the soil temperature, whichever method you use, will help your plants succeed in the garden. If you do, your garden could pay out bountiful winnings all through the season.
By knowing the soil temperature, your seeds will turn into a sure bet. Source: Wikimedia Commons
I know what you’re
thinking: “No Mow May? But it’s March!” Although spring currently seems like a
distant wonder for us here in Montana, many of our warmer states are seeing the
signs of spring that get you thinking about, among other things, your lawns
(and if you’re a bee enthusiast like myself, you’re also thinking about the
early season pollinators that are beginning to emerge in these landscapes).
What is ‘No
Mow May’?
No Mow May (or April, or March- depending on where you are) is a movement that was originally made popular through an organization based out of the United Kingdom called Plantlife. The intention behind the campaign is to eliminate mowing your lawn for the month of May, with the goal of creating habitat and floral resources for early-season pollinators. This initiative has since become more and more popular in the United States in addition to other countries, where we see the classic image of a turf lawn speckled with bright yellow dandelions along with signage that says ‘No Mow May’.
No Mow May sign (from beecityusa.org)
Lawns are a staple of American landscaping and one can hardly imagine urban and suburban areas without the iconic image of the green turfgrass yard associated with many homes. We have about 40 million acres of lawn, which accounts for 2% of all the land in the continental US, making lawns the number 1 irrigated crop in the country! The ideal vision of a good lawn has long been a weed-free, monocultural, uniform green space and people spend a lot of time, effort, and money to maintain them in this way. The image of overgrown, non-uniform, unconventional, and weedy lawns have been historically considered to be unattractive, unkempt, and poorly managed. Although more and more people seem to be changing their opinions and preferences for these conventional turfgrass lawns (and we likely need to rethink some of these expectations anyways), most people still have those underlying perceptions.
The idea behind No Mow May is that flowering lawn weeds, if left unmown, would provide food sources for early season pollinators such as newly emerging native bees (with the added benefit of less work in terms of lawn maintenance). The primary targets of this initiative are generally more urban and suburban areas where food sources and habitat for pollinators can be harder to find and spaces where weedy lawns are less tolerated.
Although the intention behind this campaign is a good one, providing food for pollinators, there are some aspects of this initiative that seem to miss the mark.
So let’s get
into some of the science!
Is ‘No Mow
May’ good for pollinators?
The answer to
this question is: yes and no.
Studies have shown that certain common flowering lawn ‘weeds’ can be an important food source for pollinators, especially in urban and suburban areas where other floral resources can be scarce. A paper from the University of Kentucky found 50 species of pollinators, including 37 species of bees, foraging on white clover and dandelion in lawns (Larson et al., 2014). Although white clover is a nutritious source of nectar and pollen for bees, dandelions on the other hand are not very nutritious (with low protein content in their pollen). That being said, bees and other pollinators will still forage on dandelions especially if other floral resources are unavailable at that time. In the ideal world we would have a plethora of floral resources for pollinators which would incorporate an abundance of diverse flowering plants from early spring all the way through the growing season and into the fall. Unfortunately, most urban and suburban spaces do not meet the specifications of this ideal pollinator-friendly world. Dandelions, on the other hand, are pretty universal in these urban areas (and you have likely seen them in many lawns in your neighborhood). Although they are not a great resource, abundant dandelions can fill the gaps of food sources for bees (especially when the alternative is no food). Other lawn ‘weeds’ and bee lawn plants (as you have seen in last year’s blog post) can also support a diversity of pollinator species and can be a great way to offset the lack of pollinator-friendly resources in a turf-only lawn.
Research from a pilot project of No Mow May in Appleton Wisconsin evaluated the bee species richness and abundance in properties that participated in the initiative and found the species richness was 3 times higher and the abundance was 5 times higher when compared with areas that had been mowed (Del Toro and Ribbons, 2020).
However, if left unmown: your turfgrass will soon outgrow any other flowering lawn weeds which can make them difficult to find for pollinators, and that is if these flowering lawn weeds aren’t smothered by the tall grass altogether. A study conducted in Massachusetts which evaluated the impact of mowing frequency on bee abundance and diversity showed that lawns which were mowed once every 3 weeks had 2.5 times more flowering plants, though lawns which were mowed every 2 weeks had the highest bee abundance, likely due to easier access and visibility of these floral resources in shorter grass (Lerman et al., 2018).
Is ‘No Mow
May’ less work?
The answer to
this question, as you probably could guess, is also: yes and no (but
mostly no).
I am a self-proclaimed ‘lazy gardener’ and am always looking for ways to reduce the amount of effort I need to put into my gardening endeavors. No Mow May claims to be less work for you in the month of May. Although that is true (because the intention is not to mow for a month), it can often result in more long-term effort in trying to reign in your turfgrass in the after-effects. Not to mention the negative impact that this style of management (or lack thereof) can have on your turf itself.
Photo: Iowa State University Extension
In many places, lawns can grow a foot or more during the month of May. An un-mown lawn can set you back on your lawn maintenance and result in more work for you in the long run . Then when you are trying to get your lawn back on track afterwards- remembering the rule that you should only remove 1/3 of your turf in any given mowing, it could take weeks to get back to a good functional height (which varies depending on the type of grass, but for most of our lawns, it ranges between 2.5-4 inches). Furthermore, most mowers don’t have the capacity to handle a lawn with a 12 inch height. This will result in removing too much of the grass leading to unintended consequences like stress and decline of your lawn, which can also make it more susceptible to pest and disease issues. This will also lead to a large amount of grass clippings which, if left on the lawn, could smother sections of it and result in an unpleasant and patchy lawn.
Unhealthy lawns can also struggle to compete with and leave spaces open for other undesirable invasive plants, including noxious weeds. These can then spread to other areas and have significant ecosystem impacts (and make it even more difficult to get your lawn under control). Following weed management needs could also require the use of herbicides that can have unintended consequences on pollinators and other beneficial insects.
Furthermore, as
noted in an article on No Mow May by Iowa State Extension’s Consumer Horticulture
Specialist, Aaron Steil: lawns are not actually a natural space, as most lawns
are constructed out of non-native grasses, usually for functional purposes, and
require quite a bit of maintenance including water and nutrients. Leaving your
lawn unmown will not make your lawn a more natural landscape, and it would not
be a responsible way to manage these non-native landscape plants.
What you can
do instead of No Mow May: Low Mow May!
Based on what we’ve learned so far: lawn weeds can sometimes be an important food source for bees (especially in urbanized areas, where the diversity and availability of floral resources are fewer) and mowing less frequently results in more of these flowering lawn weeds for bees. We also know that slightly higher (though not too high) mowing heights for many lawn turf species make for healthier root systems and make turf more resilient to stress, pests, and disease issues.
If you have flowering lawn weeds and pollinator conservation is your intention, your best bet would be to aim for a sweet spot between the extremes of mowing way too frequently and not mowing at all. Mowing every other week could be a way that you can reduce the amount of time spent mowing and also support urban and suburban pollinators by letting your lawn weeds flower (in addition to maintaining your lawn at the recommended heights for healthy turfgrass).
Even better yet, you can reduce the amount of space in your landscape that is dedicated to a traditional turfgrass lawn and incorporate a flowering groundcover and/or a pollinator garden that hosts an abundant array of diverse floral resources that provide food for bees all season long!
Now that’s
something to be buzzing with excitement about!
Less lawn (speckled with clover), more pollinator plants, and habitat! Photo taken at the home of a colleague and scientist on the Wild Bees of Montana project.
