Natural events: orchard edition, March 2017

Featured this month:

  • Cold spell effects
  • March temperatures
  • Asian pears blooming
  • March precipitation
  • Cedar-quince Rust
  • Our “favorite” cedar tree
  • How many cedars?
  • Asian pear blooms
  • Uneven leaf-out of apples

Cold spell effects: March had one notable cold spell. The early stages brought a little snow (upper left), which we hoped would stick around as an insulating layer, but it did not. Damage showed up on crops and plants that are usually quite resilient. Daffodil flowers flopped, the tips of Garlic Chives (upper center) got burned, and even native plants such as Fragarant Sumac (upper right) had damage on their flowers. The cold wiped out any hope of having our own peaches in 2017. A few blossoms tried to open (lower left), but they were clearly damaged and deformed. Others peach buds just shriveled (lower center), and the darkened buds fell off at the lightest touch (lower right).

March temperatures: So how cold was it? The coldest night read 14ºF at the Columbia airport. (It got colder here, but we’re not sure by how much because we are skeptical of the readings from our thermometer.) Those temperatures are not at all unusual at this time of year, but the unusually warm January and February meant that biological spring was far ahead of calendar spring, and resulting in damage to plants. Most of the rest of March tended towards warm, but at least not in a record-smashing way.

Asian pears blooming: We lost the peaches to the freeze, but we’re cautiously optimistic that other buds in the orchard made it through with the potential to still bear fruit this year. At the time of the freeze, the Asian pear blossoms showed a range of developmental phases from bud scales separating to tight cluster. (Photos of these stages are included in this excellent Michigan State publication of critical spring temperatures for tree fruit bud development stages.) The upper left photo from March 11 was pre-freeze. The upper right photo shows the same buds on March 26. The lower photos, also from March 26, show a range of outcomes. Some bud clusters shriveled (not shown), some blossoms are deformed with black spots (lower left), while others proceeded to open with a more-or-less normal appearance (lower right). The early blossoms didn’t seem to attract much in the way of pollinators, even on warm days. Pollinator activity has since picked up, and we wonder if that’s an indicator of damage to the earlier blooms? We also saw different levels of resilience between the Asian pear varieties: the Hosui and Shinko trees seem to have made it through without too much loss, while Olympic lost almost all of its blossoms. This is a classic argument for diversity in agriculture.

March precipitation: Here in central Missouri we’d reached a classification of Moderate Drought after a very dry winter, but those concerns have, for the moment, been quenched. Conditions remained on the dry side through March 23, then each of the next seven days delivered rain for a total of 3.36 inches in a week. We were ecstatic about the first inch or so, but it took little more than that to create conditions for runoff and excessive sogginess in this pre-leaf-out phase of spring (when evapotranspiration isn’t yet pushing trees to draw up large quantities of water). The prolonged wet spell has continued into early April; it is raining as I write this on April 5, as it has on each day of the month so far, meaning 12 of the last 13 days have brought measurable precipitation.

Cedar-quince Rust: Prolonged wet spells can provide opportunities for colonization of fruit trees by disease fungi. One example of a potentially problematic species for our orchard is this neon-orange specimen growing on the trunk of a living Eastern Red Cedar tree. We don’t remember observing this fungus before, but we looked it up and discovered that it’s Cedar-quince Rust. As with Cedar-apple Rust, it needs two hosts to complete its life cycle, cedar and something else. Alternate hosts include several important members of our orchard: apple, pear, and serviceberry (according to this informative page from the Missouri Botanical Garden).

There are various strategies to help fruit trees ward off fungal infection, and that’s an area in which we have limited experience, but we know one method that won’t work. When the topic of cedar-rust diseases come up in the presence of knowledgeable orchardists from other regions, a common tidbit of advice that they cheerfully share with their struggling Missouri counterparts is to remove cedar trees from around the orchard. Often the proper eradication radius is quoted as two miles. Others, feeling that their advice ought to be realistic, will restrain themselves to advising cedar removal in just a half mile radius. A New England orchardist, at a workshop here in Columbia, recently delivered the advice that, “You might want to cut down that favorite cedar tree next to your orchard.”

Our “favorite” cedar tree: Since then, we’ve been jokingly referring to a beastly cedar tree right next to our orchard as our “favorite”. It has stayed put because its thick double trunk that splits ten feet off the ground was too dangerous to take down with our logging skills. Years ago, we made the intentional decision to let it be and live with it (after all, cedar is ubiquitous in the central Missouri landscape). Then, on March 6, some severe storms rolled through the area. For a brief period after nightfall, we hunkered in the basement in response to a tornado warning. The next morning, we made the delightful discovery that this severe storm did us a big favor. The bulk of our “favorite” cedar came down, doing a domino effect and taking out two others, all in a direction away from the fence. Whew.

All of which raises the question, now that our “favorite” cedar is gone, how many more would we have to take out to mitigate the cedar-rust disease problem via tree removal? How many cedars? Let’s look around. A view to the west from within the orchard (upper photo) shows we’re not yet done with cedars. A view to the north from the orchard (lower right) reiterates that conclusion. Easterly and southerly views also contain cedars. And a wander around the property shows a variety of other cedars (lower left). Then there are the cedars that we have no control over, such as the ones on our neighbors’ properties, not to mention the ones in the state park within the 2 mile radius. But just how many are there?

I decided I wanted an estimate, so I walked around and counted some cedars to roughly assess cedar density per unit area for sample patches of cedar monoculture and mixed cedar/hardwood.Then I pulled up our farm GIS and roughly digitized areas that match those descriptions. In the map above, the reddish oval shows a zone that is a quarter-mile buffer around the orchard proper; this extends well beyond our property boundaries. The dark green polygons are dense cedar monocultures, while the light green polygons are mixed forests with a lot of cedars. There’s some slush in all of this (for example, do baby cedars count?), but my conservative estimate suggest that there are at least 5,000 cedars in this area, and 10,000 wouldn’t surprise me.

Removing all the cedars in a 2 mile radius, in a half-mile radius, in a quarter-mile radius, or even just on our property is completely out of the question.

The good news? Some fruit varieties are resistant to rust diseases. To find out what varieties work, we’ll take the advice of regional growers to the extent we can, but we recognize that trial and error is a part of the process, too. In the meantime, we will continue to laugh and cringe at out-of-state orchardists who advise cedar removal.

Uneven leaf-out of apples: Most of our apple trees appear to be leafing out in a rather non-uniform way. This photo shows one fairly advanced bud cluster leafing out nicely, while other buds on the same tree are still virtually closed. We’ve read that insufficient winter chilling can lead to uneven flowering and leaf-out, and we’re wondering whether that’s what we’re observing here. But we’re open to thoughts from readers regarding what else could cause this. Ideas?

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