The winter seems unrelenting this year. Our snow banks are now 5-6 feet high! As such, I have become inspired to write about some additional winter protection tools, some related to soil amendments/fertilizers and other more mechanical in nature.
1. An Even Heavier Frost Blanket
I wrote in my last post about winter protection about the importance of tarping or otherwise covering marginally hardy bamboos. I wrote about Dewitt, a company that produces a 3.0 oz frost blanket, they call their "Ultimate" line, that claims to provide as much as a 10F benefit vs. the ambient temperature. Well, if 3.0 oz is "Ultimate", then 4.0 oz must be "Super-Ultimate" and 6.0 oz must be "Ultra-Ultimate". GinTec Shade Technologies offers just those. They seem to be a wholesale/commercial distributor, but they may still sell to an individual. Obviously, the benefit of a heavier blanket is not linear (6 oz is not twice as good as 3 oz), but even a gain of two or three degrees could make a difference to sensitive plants.
2. Seaweed/Kelp Applications to Roots and Foliage (experimental)
The verdict is still out on the use of seaweed/kelp on bamboo. Seaweed/kelp has been show in a number of well-controlled studies as well as anecdotal accounts to improve frost tolerance, among other things. It is commonly applied as a foliar spray but it is also likely beneficial as a soil amendment given its micronutrient profile. Often, people will point out that seaweed/kelp is high in sodium given that is comes from the ocean. Maybe, but let's run through the math.
The liquid kelp that I have begun using is from The Organic Gardner's Pantry, a retailer on the West Coast that will readily ship across Canada. Included on the website is a chemical analysis of their product, which lists a sodium concentration of 2070mg/L. Now, let's assume one gets a "salty" batch such that we will use 3000mg/L for our math.
Let's also assume that a sodium concentration of 40mg/L, an upper limit commonly used in many municipalities for tap water, is the upper
tolerable limit for bamboo. This is totally unscientific, but we are
basically assuming that tap water in these municipalities does no harm to bamboo even when it is at its upper limit for sodium. Note that in Oakville and many other municipalities, mean sodium concentrations in tap water are actually closer to 15-25mg/L.
At a recommended concentration of 1:250, the "salty batch" of liquid kelp would add about 12mg/L to one's kelp/water dilution, which in most cases would still keep the mixture below 40mg/L.
Still concerned? Switch or supplement with distilled water or rainwater (assuming you are not seaside). You could also decrease the kelp concentration by 25%-50%. Any of these measures would help keep your kelp/water mixture at a sodium concentration at or well-below the typical concentrations found in regular tap water.
I can't yet speak to the efficacy of liquid kelp, but, though this is totally unscientific, it does seem to have given a boost to my very sickly P. Kwangsiensis. It also seems to have benefited my P. Viviax, my P. Edulis Moso seedling, and my Semiarundinaria Fastuosa.
3. Low Nitrogen / High Potassium Fertilizer
Ample research [eg. here, here, and here] suggests that low nitrogen / high potassium fertilizer, applied late in the growing season improves cold tolerance among various grasses. I have not found any research specific to bamboo, but since bamboo is in the grass family, we "might" be able to apply these finding to bamboo.
4. Planting location
This is a simple but important and effective winter protection method that I failed to mention in my last post. There are often different micro-climates around a typical property. For us in suburbia, we typically have several areas around the property that are fairly sheltered from cold, desiccating winds, and some areas that may actually stay slightly warmer than the ambient outside temperature, such as near a foundation or a furnace exhaust (but remember to keep a reasonable perimeter clear around your exhaust!).
Planting with a view to a particular exposure is debatable. Southern exposure gets more sun/heat during the day but also results in greater temperature swings, which is not great for any plant. If you have thoroughly insulated the ground and the plant, thereby moderating the temperature swings, southern exposure might be a good option for enhancing the winter protection of a marginally-hardy bamboo.
So there you have it. I have no more tricks in my winter protection bag (yet).
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