Avid Gardener Series: Responsible Water Usage for Edible Landscapes

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UPDATE: Sorry to say that this class has been cancelled due to lack of enrollment. We’re going to rework the content into a one day or afternoon class. Watch Root Simple for the announcement and we hope to see you at the Huntington!

Hey gardeners, we’re teaching a three part edible landscaping course April 2, 9, and 16 from 9 a.m.- 12 p.m. at the Huntington Ranch.

Learn creative ways to grow a delicious, drought-conscious garden in this hands-on series. Sessions will take place in The Huntington’s Ranch Garden and will address drip irrigation, greywater systems, plant selection, mulch and soil health, and more. The Huntington Ranch is a beautiful edible gardening demonstration area that is seldom open to the public.  The class will focus on growing food in our increasingly dry and challenging Southern California climate.

Best Practices for Gardening in Contaminated Soil

File this ad under "bad ideas."

File this ad under “bad ideas.”

The benefits of growing food in cities (nutrition, exposure to nature) outweigh the very low risks of lead contamination. This is the conclusion of a recent University of Washington study:

It is highly unlikely that urban agriculture will increase incidences of elevated blood Pb for children in urban areas. This is due to the high likelihood that agriculture will improve soils in urban areas, resulting in reduced bioavailability of soil Pb and reduced fugitive dust. Plant uptake of Pb is also typically very low. The exceptions are low-growing leafy crops where soil-splash particle contamination is more likely and expaneded hypocotyl root vegetalbes (e.g. carrot). However even with higher bioaccumulation factors, it is not clear that the Pb in root vegetables or any other crop will be absorbed after eating.

The paper outlines a set of best practices for dealing with contaminated soils. You should always:

  • Wash fruits and vegetables from your garden. Also wash your hands and don’t wear shoes in the house.
  • Compost, compost, compost! Compost dilutes the overall amount of lead in soil and encourages healthy plant growth which also dilutes the (usually small) amount of lead a plant will uptake. Apply compost annually since it breaks down over time.
  • Plant away from painted surfaces of old (lead paint era) buildings.

Some other things to consider especially if you garden with children under 5 years old:

  • Don’t eat a lot of carrots, radishes, redbeets or turnips grown in contaminated soil. The edible portion of these plants consist of xylem tissue that traps lead (potatoes are OK since they are phloem fed). That said, you’d have to eat a lot of contaminated root vegetables to elevate lead levels in your blood.
  • Adding phosphorus fertilizers will decrease the bioavailability of lead.
  • In general root vegetables uptake the most lead, leafy greens less and fruit almost none.
  • The most conservative approach is to grow in raised beds.

The main concern is for children under 5 years old. If your soil tests high in lead and you have young ones you should consider doing your edible gardening in raised beds and limit their exposure to garden soils to a few times a month. Mulch and ground covers will also decrease lead exposure in the other parts of your yard.

The paper concludes that for older children and adults, “There is little indication that growing or eating food from urban gardens will result in high Pb (lead) exposure.”

Is Lead Poisoning a Risk in Urban Gardens?

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Those of you who have followed our blog over the years know that our yard is contaminated with lead. This is, most likely, due to some combination of lead paint residue and car exhaust. For years we’ve grown vegetables in raised beds because of this issue.

But if the results of a University of Washington study on lead and urban agriculture are to be believed, we might not need to be as concerned. The researchers note that most vegetables don’t take up lead and that improving soil with compost greatly reduces the bioavailability of lead.

You can read a summary of the results of this research paper here.

Thanks to Joanne Poyourow of Environmental Change Makers for tipping me off to this research.

074 Beyond the War on Invasive Species with Tao Orion

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Is there something wrong with the “war” on invasive plants? What are these resilient plants trying to tell us? Is there such a thing as a “natural” landscape? What’s wrong with Glyphosate? These are some of the topics we discuss in our conversation with Tao Orion, author of Beyond the War on Invasive Species: A Permaculture Approach to Ecosystem Restoration. Tao is a permaculture designer, teacher, homesteader, and mother living in the southern Willamette Valley of Oregon. She teaches permaculture design at Oregon State University and at Aprovecho, a 40-acre nonprofit sustainable-living educational organization. Tao consults on holistic farm, forest, and restoration planning through Resilience Permaculture Design, LLC. She holds a degree in agroecology and sustainable agriculture from UC Santa Cruz. Her website is www.resiliencepermaculture.com.

If you want to leave a question for the Root Simple Podcast please call (213) 537-2591 or send an email to [email protected]. You can subscribe to our podcast in the iTunes store and on Stitcher. The theme music is by Dr. Frankenstein. A downloadable version of this podcast is here.

Ill advised grafting projects

Many thanks to Dr. Brew for alerting us to this Simpsons routine about crossing tomatoes with tobacco. I took a look at the research on grafting tomatoes to tobacco root stock (though it seems Homer crossed the seeds) and the technique shows some promise. According to this study,

Tobacco grafting had a positive effect on the tomato plant cultivation performance; the onset of flowering was almost 15 days earlier and the tomato flower and fruit yields increased in both tomato cultivars. Tobacco grafting resulted in 5.0% and 30.1% increase in total fruit weight for cv. Sweet and cv. Elazig, respectively. Because the level of nicotine was within acceptable ranges, tobacco-grafted tomato fruits were considered to be safe for consumption. Self-grafted tomato cultivars also had flowering time onsets almost 11 days earlier. However, self-grafting caused 6.0% and 7.6% less total fruit yield per cv.

It does remind me of the unsuccessful attempt back in the 1970s to graft hops onto cannabis root stock with the goal of creating a legal looking plant containing THC. The grafts take but the “Hopijuana” plants contain no THC. No doubt this is a huge disappointment to the microbreweries of Colorado.