Natural events: orchard edition, August 2017

Featured this month:

  • Harvesting in August
  • August weather
  • Orchard mulch
  • Nitrogen fixers in the orchard
  • Parasitic plants in the orchard
  • Japanese Beetle larvae
  • Solar eclipse and response by plants

Harvesting in August: In spite of the late spring frost, raccoons, woodpeckers, ants, unidentified insect pests, and other challenges, we managed to eat a semi-steady trickle of tree fruit in August. The pear on the left is a Hosui Asian Pear: a really delicious, crisp, and sweet piece of fruit. Our total harvest of these was maybe a couple dozen pears; it should have been much more had we not been hammered by untimely spring frosts that destroyed many blossoms. Harvest timing was late August; we pulled the last pears off the tree on August 23, and some were pushing overripe at that point. We don’t have long-term records on fruit ripening dates, but this does seem early; a local apple grower we talked to said that apples were ripening about a week and a half earlier than normal this year.

We also had some apples, particularly from the Initial, Enterprise, and Liberty trees. Some of these were salvages that we pulled off due to other damage, but some were properly ripened, really nice pieces of fruit. The Initial tree gave us some of our nicest apples. Around the middle of the month, we also finished harvesting the grapes from the Bluebell vine that we had started to nibble on in July; we learned that the ones we ate earlier weren’t as ripe and sweet as they could have been. With patience, they got even sweeter, and remarkably the birds didn’t even go for them. Annual fruit crops of melons did particularly well, too, and we were inundated with Kansas Musk Melons and Crimson Sweet Watermelons.

August temperature: August was remarkably pleasant. The maximum high temperature for August was 91 ºF, and the high temperature equaled or exceeded 90 ºF on only four days of the month. The low temperature for the month was 52 ºF. No records were broken. It was a month that was reasonably near average; maybe that’s why it felt so abnormal?

August precipitation: When I learned several years ago that a total solar eclipse was coming our way, my reaction was, “Well, we can count on it to rain that day.” And, sure enough, we received our biggest rainfall of the month (a glorious and much-needed 1.67″) in the 24-hour period that began the morning of August 21. We record precipitation first-thing every morning, tracking back to the previous calendar day, so each date’s record includes the early morning hours of the following day. Thus, technically, most of that rain fell in the early morning hours of August 22. We had a good view of totality (more on that later), but watching the weather forecast in the days leading up to the eclipse was maddening. In any case, we started the month on the dry side and ended the month with below average precipitation. As of this writing, two weeks into September, we still haven’t received a drop.

Orchard mulch: We have two strategies for dealing with dry conditions in the orchard, one short term and one long term. The short term strategy is to use irrigation when conditions get dry; the black tubes in the upper left photo are irrigation lines. The long term strategy is to add chipped hardwood mulch to the ground near the trees each winter. The mulch adds organic matter to the soil, which over the long term should improve both the drainage and water-holding capacity of the soil. In addition, it acts as a home for fungi, which can access nutrients from the mulch, make them available to the fruit trees, and do various other wonderful things for the health of the orchard. Fungal mycelium colonize the mulch and knit it together, explaining why it’s possible to pick up a chunk for mulch composed of many individual wood chips (upper right photo). A closer look shows the mycelium between the wood chips (lower photo). Conventional wisdom says that wood chips tie up nitrogen, but this idea seems to be more myth than reality, and we also pasture the chickens in this area at times to add some nitrogen.

Nitrogen-fixing plants in the orchard: A healthy, fungal-dominated soil should provide a good supply of nitrogen to the fruit plantings, but it doesn’t hurt to have a population of nitrogen-fixing plants around as well. Most plants in the legume family (Fabaceae) are nitrogen fixing, and a number of these grow wild in the orchard. Some native representatives of the legume family include: Downy Milk Pea (Galactia regularis), tick trefoil (Desmodium sp.), Sensitive Brier (Mimosa quadrivalvis), Slender Bush Clover (Lespedeza virginica), and Partridge Pea (Chamaecrista fasciculata). We’ve introduced a few Fabaceae species. Red Clover (Trifolium pratense) and Alfalfa (Medicago sativa) are more palatable to livestock than some of the native legumes, and the seed is more readily available, so we’ve scattered seed for these in various parts of the farm with degraded soils.

We also introduced a single specimen of the Siberian Peashrub (Caragana arborescens) on the advice that it can be a good companion plant in orchards, both fixing nitrogen and producing biomass. There are places where this plant is invasive, and we did our homework to be pretty sure it wouldn’t have that problem here. The plant has barely survived in our location and it has never flowered, suggesting it is not likely to be invasive, but also suggesting that it is not likely to be very useful either.

The lower right photo shows one plant that is invasive, Autumn Olive (Elaeagnus umbellata). This isn’t a  legume, but it is a nitrogen fixer, and it is one that was well established before we arrived here. Getting rid of Autumn Olive entirely is difficult, so we’ve come to accept that its presence is inevitable, and as a consolation prize we’ll accept the idea that cutting or mowing it should release nitrogen to the soil. We’re also experimenting by introducing other natives, including Indigo Bush (Amorpha fruticosa) and Purple Prairie Clover (Dalea purpurea), in part on the advice of this blog post from Eric Toensmeier on the relative nitrogen-fixing effectiveness of plants.

Parasitic plants in the orchard: In general, we like to have botanical diversity in the orchard, but there are a couple of species that have the potential to be directly detrimental to plants that we’re trying to grow. On the left is a specimen of dodder (Cuscuta sp.) that I found in the weedy edge biodiverse border of the orchard. We’re not sure of the species ID, so we’re not sure whether this particular specimen is a threat to any of the plants that we’re trying to grow in the orchard. Each species of dodder has some degree of host specificity, but some species do attack woody as well as herbaceous species. For example, according to the book Flora of Missouri, the list of potential hosts for Common Dodder (Cuscuta gronovii) includes Rubus (brambles such as blackberries and raspberries). The plant on the right is Big-flowered Gerardia (Aureolaria grandiflora); this specimen has already flowered and is setting seeds. According to Flora of Missouri: “Species of Aureolaria have been documented to parasitize the roots of a number of woody species, including both pines and hardwoods, but have been documented most commonly on the roots of oaks….” (Yatskievych, Volume 3, p. 566). We don’t know whether fruit trees could be parasitized by this plant, but we do know we have this plant growing in places not particularly close to oaks, suggesting that they are flexible in their host choice. It seems a sensible precaution to strongly discourage this plant in the general vicinity of our fruit trees.

Japanese Beetle larvae: Though we are not accomplished at identifying beetle grubs to species, common sense tells us that the large numbers of grubs we started to encounter in the soil in late August are Japanese Beetles, given the very large number of Japanese Beetle adults present in June and July. We found most of these with our annual crops, particularly in areas that had been irrigated during June and July. When the soil was moist, they were quite easy to find near the annual crops, particularly as we were working in the soil to harvest potatoes, hill leeks, and do general weeding. We’re not as certain about the population in the orchard soil, in part because we try to disturb that as little as possible. Japanese Beetle larvae reportedly feed heavily on grass roots, but do they go for the roots of other plants as well? The adults have clear preferences for some species over others; do the larvae like the roots of those same plants or different ones? Now that we’re pretty sure we have significant numbers of Japanese Beetle larvae in a known location, one option for management is Milky Spore, a bacterial control for the grubs. Perhaps we’ll write more about that later….

Solar eclipse and response by plants: Chert Hollow was in the path of totality, giving us a once-in-a-lifetime opportunity to watch how plants and animals responded to a solar eclipse right here. During the days leading up to the eclipse, we paid special attention to the bloom times of a few plants that have daily cycles of opening and closing. The Four-O-Clocks (upper right) typically open during the late afternoon (thus the name) and stay open in the evening but closed in the morning. Morning Glories (lower left) open in the morning. We noticed Bottle Gourd flowers (lower right) in the evening. On eclipse day, all of the flowers were closed during the midday eclipse: no flowers opened with the fading light or in response to the returning sun. So we thought, oh well, so much for that. Then, two days later, I noticed the Four-O-Clocks were open at 10 a.m. (the approximate time of the photo upper right). I watched it closely for a couple of days, and it was open in the morning, closed in the afternoon, then opened again late in the day. Even now, into September, the plant routinely has flowers open in the morning; it seems rather confused. The Bottle Gourds also seemed to get a bit confused, and we saw flowers open in the morning for a while following the eclipse, something we had not noticed before; the Morning Glory photo was taken post-eclipse, and one Bottle Gourd flower is visible upper center. The Morning Glories continued to bloom normally, only in the morning.

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