Not a monarchist myself. So a Shakespearean quote like: “Uneasy lies the head that wears a crown” doesn’t do much but set me off to scratching mine. But there is another sort of crown that I can get my head around. This would be the crown of a plant. And now that we stand in the midst of winter, the crowns of winter cereals are top of mind.
On our early morning walk, the dog and I head to a field beyond the last house on the road. Yesterday as we entered the field one could feel the crunch of frozen plants under foot. There being no snow cover at the moment this is a tough situation for these plants. Will these plants survive until the spring thaw? It will depend upon several factors.
Winter hardiness is a plant characteristic that pretty much describes itself. Surviving the winter is what it’s all about. But like almost anything else in plant biology, the simplicity is deceiving. Frost is one thing, freezing is another. And temperature is only one factor in the mix. The winter of 2014-2015 was particularly difficult and Robert Klein, a Nebraska Crop Specialist wrote up a pretty nice Extension piece describing what happened that winter and how several factors affect winter wheat’s ability to survive in the face of nature’s brutality. [available here]
Winter survival also can be affected by a number of factors besides variety tolerance to winterkills. This week we saw examples where the same variety would rate excellent in one field but poor or fair in other fields. Several factors contribute to winter injury or winter kill, including lack of rain, lack of snow and snow cover, fluctuating high-low temperatures, loose seed beds, crop residue, seeding date, hoe or disk drill, seeding depth, soil type and quality, fallow practices, terraces, field edges, field exposure or silt blown into a field due to high winds. (In one case, wheat 100-120 feet in from the road was killed due to silt blown in during the October 18, 2012 wind storm.)
With the harsher winter conditions, the effects of practices such as seeding date and seedbed preparation are more evident. Early-seeded winter wheat used soil water last fall, leaving little moisture in the soil profile in some areas. Dry soil heats up and cools down six times faster than moist soil, increasing winter injury and winterkill.
Where Robert talks about heating up and cooling down faster (due to dryness) there are couple issues for the plant to deal with. First is heaving, where frost heaving lifts the plant and then when it warms the soil settles back and leaves the seedling pushed up (frequently breaking roots off – ouch!). More on heaving from the Missouri Botanical Garden here. Secondly, frequent cycling between warm and cold can desiccate plant tissues which causes a drought type symptom. Also ouch.
Plant breeding to develop varieties that better tolerate inclement winter conditions has been going on for ages. Robert Klein’s coauthor for the UNL Extension piece mentioned above is Dr. Stephen Baenziger who is the UNL wheat and barley breeder.
Our winter cereal plants – at least the ones that survive the winter – green up in the spring and grow on toward maturity by making a head or spike that bears the grain. Perhaps this could be the head which Shakespeare refers to – “Uneasy lies the head that depends upon a winter hardy crown” …
In putting this post together I did a search for “wheat crown” in order to get an image to share. Much to my surprise more than a dozen images of wheat being woven into a headdress popped up before the plant drawing used above. More evidence that our society cares less for the nature of agriculture and more for concerns of personal adornment. Reminds me of thoughts shared earlier on a rural vs. urban societal divide.
Sources of the images in this post: