BYGL Weekly News for May 28, 2018
The following articles were compiled during the last 7 days by members of the Extension, Nursery, Landscape, Turf (ENLT) team to benefit those who are managing a commercial nursery, garden center, or landscape business or someone who just wants to keep their yard looking good all summer. Access the BYGL website for additional information on other seasonal topics at: http://bygl.osu.edu
For more pictures and information, click on the article titles.
|White Flower Day
Date Published: May 24, 2018
Whaaat. That first picture got your attention, did it not. Pawpaw flowers are not white! But they are beautiful, and now past. To further digress, Michael Dirr wonderfully terms pawpaw flowers “lurid purple” in color, and purple is a color made up of red and blue, and after all, white light is made up of red, green, and blue, so a perfect lead-in to…
…This past weekend, when I took a walk through my yard, starting with a side area where there is a patch of lily-of-the-valley (Convallaria majalis). I took a sniff of the perfumey flowers (smell but do not eat – all parts are poisonous), then noticed that the patch was not as large as I suspected. In fact, at least half of the patch was wild lily-if-the valley (Maianthemum canadense).
I have seen this in woodlands often, but have ignored it probably for years in my yard, supposing it was Convallaria. And spreading among these as well was sweet woodruff (Galium odoratum, the May wine herb), intruding on this scene. Three white flowers taking up the ground amidst lilac, striped maple, weeping katsura, kousa dogwood, and other ornamentals.
It got me thinking of what other white flowers were in the yard. And they were legion, including a dwarf Aronia, daisy fleabane volunteers, flowering dogwood, white violets, a spreading white azalea, may-apples, volunteer shrubby honeysuckles, raspberries about to bloom white from their buds, kousa dogwood which bloomed like crazy last year but gets an honorable mention here even though it is taking a year off, a volunteer euonymus, spring beauty wildflowers, and a Korean mountainash Rich Larson of Dawes Arboretum gave me over three decades ago.
And that is just to start. There were highbush blueberries, tiny, creamy bell-like flowers which have great fall color as an ornamental and three of which provide about a gallon of blueberries each year, or rather a half gallon one year and a gallon and a half the next. Fortunately we have good, acid soil.
There was the delightful fragrance and feathery flowers of white fringetree, a tree in the back of our two acres that I ridiculously thought was a small persimmon for a few years after planting. Emerald ash borer affects this Chionanthus virgincus, a member of the Oleaceae, closely related genetically to its fellow family member, the genus Fraxinus (ashes). The emerald menace has not affected our fringetree, at least not yet, despite three large mega-infested ashes in our yard we had removed two summers ago.
There are diminutive wild strawberry (Fragaria vesca) plants flowering now. They are more than matched by the beautiful fields of garden strawberries (Fragaria x ananassa) for market just past the western edge of our property, courtesy of the ever-bountiful Rittman Orchard. Come June we shall Go Forth Young Man and Woman, to the U-Pick portion of their business as that most wonderful part of the year begins – the Berry Season.
Back to the woody plants: Bloom on our various crabapples was coming to an end then lo these four day ago, but even the spent blossoms of the Molten Lava crabapple demonstrated the elegance of these lovely flowering trees. Flowering dogwood (Cornus florida) was at the end of its reign in our front yard, but a somewhat wild forgotten area in our northern side-yard yielded a surprise. I had almost forgotten and had to relearn the beauty of the creamy butter yellow buds opening to white four-bracted inflorescences of Cornus alternifolia. Wow.
A lowly “weed” disqualified itself as such, at least for the purpose of this bygl-alert, for I want it for the length of time it takes us to see what this tiny white flower represents. It shows us below its plant family credentials. Common chickweeds (Stellaria media) is in the Caryophyllaceae, which commonly has the characteristic of cleft petals, as seen below, with its five petals superficially looking like ten. Other members of this family include, carnation, gypsophila, and many “pinks”.
Note: If you want to see a wonderful YouTube of identifying the lawn weeds, common chickweed and mouse-eared chickweed, and the larger woodland wildflower, star chickweed, check out: https://www.youtube.com/watch?v=GJnp-lqdofM
Two of my wife’s favorite woody plants are the double-file viburnum amidst our crabapple grove and the ‘White Tigress’ striped maple overarching our picnic table. The flowers of this infinitely interesting maple (bark, stipules, leaves and leaf venation, form, fall color) are what caught my eye this time. I had not looked carefully at the chain of flowers about to become winged fruits. They have what I predsume to be two prominent exerted styles, the tips of which contain the stigmas receptive to pollen grains and the base being the ovaries which when ovules are fertilized will ripen around the developing seeds and become the fruits.
Doublefile viburnum blooms
Finally two usual suspects, except from a certain perspective. Dent-de lions, the French name chanelling the toothed leaves or lion’s teeth, or dandelions, are certainly beautiful in their blowball stage, though unpopular in this seed-spreading mode. And tiny, cream-white flowers of Rhamnus, also in that wild northern area of the ChatScape. But wait, it is diseased. Alas, not in a killing way: A rust fungus (you will have to wait to see it) that has infected this invasive woody plant. Whither will this fungus go next? Stay tuned soon for some springtime rust alerts, as we segue from white to orange.
|Asian Chestnut Gall Wasp
Date Published: May 22, 2018
The Asian Chestnut Gall Wasp was introduced to North America in 1974 on imported chestnut cuttings. To date it has be identified in Georgia, Alabama, North Carolina, Virginia, Maryland, Pennsylvania, Kentucky, Tennessee and Ohio.
This pest can be distributed throughout the United States by transporting infested seedlings to new areas and by the exchange of infested scion wood used in grafting new trees.
The insect lays its eggs in the buds of chestnut shoots then galls develop on the shoot tips, leaves and catkins. Nut production and shoot growth are greatly affected by the galls. Once the adult insect emerges from the gall the dried spent galls become woody and can remain on older limbs for several years. If the infestation is severe enough it can hurt the overall vigor of the tree and can even cause death.
The adult female wasp is about an eighth of an inch long and they lay a cluster of three to five eggs in the chestnut buds during early summer. Several adults can oviposit in a bud which could add up to as many as 25 eggs per bud. Eggs hatch in 40 days with the larvae remaining dormant until the following spring. When the bud starts to grow the larvae induce gall formation on developing plant tissues. Before the larvae pupate they feed on the inner gall tissue for 20-30 days. The adult wasp emerges from the gall in late May to early June.
Management of the pest is very difficult and insecticides are ineffective in suppressing the gall populations. There are natural enemies that attack and parasitize newly developing galls. If you have Asian Chestnut Gall you can prune and burn the infested plant material this may slow further movement of this pest.
|Soil Temps Determine Planting Time
Date Published: May 21, 2018
One of the most often asked vegetable questions during this early season is “How soon can I plant my tomatoes and peppers in the garden?” There are two reasons that the northeast Ohio gardener’s rule of thumb is “wait for Memorial Day” before planting out the tender annuals like tomatoes, peppers and green beans. The first reason is the possibility of a frost is almost eliminated by waiting until Memorial Day. Those tender annual plants like squash, tomatoes, green beans and peppers, cannot tolerate a frost event or even lower temperatures at all!
The other reason to wait is that the soil temperatures need to warm up. Regardless of what daily highs the ambient air temperatures reach, the key limiting factor for early season plant growth is soil temperatures. The simplest and best way to know when it is time to plant those “prize winning” tomatoes is to buy a soil thermometer and test the soil temperature at about 3-4 inches deep.
Brilliant sunshine, snow showers or cold rains, partly cloudy or completely overcast skies, all serve to impact our soil temperature coming out of the winter season. It is all about sunshine heating the dark soils, followed by the mostly topical heat layer being gradually moved deeper through the soil profile via conduction. This is the reason that soils covered with a mulch, are slower to warm up in the spring. This is due to the mulch acting as a barrier or insulator that prevents the sunlight from directly striking the soil to heat it.
Research studies have provided insight for us to know that tomatoes seem to have problems uptaking phosphorus when soil temperatures, are around or below 50°F. This lack of phosphorus in young, tomato transplants shows up as a purpling of the underside of the leaves of the plant. Germination of vegetable seeds is also contingent upon soil temperatures. This is why peas, radishes, broccoli and other veggies we call “cool-season crops”, have no problem germinating and thriving early in the spring with cooler temperatures.
Put squash, pumpkin, green bean or corn seeds in the ground under those same cool soil conditions and little to nothing happens! Germination is very slow in these cold, spring soils and the seeds are often overwhelmed by the soil microbes and other decomposers, becoming their source of energy or food. This is one of the reasons why they are referred to as “warm-season crops”. The threshold or minimal soil temperatures appears to be about 60°F or higher, which will provide the necessary soil environmental conditions needed by warm-season vegetable crops to grow.
Have some fun in your garden and buy a soil thermometer and track the temperature of your garden soils throughout the growing season. I think that you‘ll be astounded, amazed and fascinated by what you discover about the temperature trends of your garden soils!
|Apples Don’t Fall Far from the Oak Tree
Date Published: May 21, 2018
Several types of “oak-apple” galls are now obvious on the leaves of their namesake oak hosts in Ohio. These unusual plant growths range in size at maturity from 1/2 – 2″ in diameter and are named for their resemblance to apples.
Oak-apples are constructed of leaf buds that have been hijacked by a gall-wasp (Family Cynipidae) to surround a single gall-wasp larva located within a seed-like structure positioned at the center of the gall. The gall structure provides both a protective home and a food source for the developing gall-wasp larva.
Cutting the gall open will reveal the gall’s internal structure. In general, there are two groups of oak-apple galls: those with internal tissue composed of a mass of white fibers radiating from the central larval capsule, and those with tissue that strongly resembles the flesh of an apple; it is spongy and juicy.
The so-called Large Empty Oak-Apple Gall is produced by the gall-wasp, Amphibolips quercusinanis (syn. A. inanis). Galls measures up to 2″ in diameter and arise from leaf buds on scarlet and red oaks. The gall surface is light green and covered with purplish-red bumps.
The internal structure of this gall is composed of white fibers radiating from the central seed-like gall chamber. Wasp larvae have chewing mouthparts; so what do the gall-wasp larvae eat? The inside of the gall chamber is lined with specialized cells called nutritive tissue which is constantly being replaced as it is consumed by the gall-wasp larva. Imagine lounging in a room with pizzas constantly emerging from the walls.
As with all plant galls, oak-apple galls change their appearance once they reach “maturity;” the point where a mature gall-wasp emerges. In fact, oak-apples are racing towards completing their appointed task this season in the southern part of the state. They will soon dramatically change color from Granny Smith apple-green to caramel brown. The mature, brittle galls are called “empty” because the filaments eventually disintegrate leaving an empty gall husk.
There are over 50 species of gall-wasps that are known to produce oak-apple galls in North America and there are probably at least 10-15 distinct species of oak-apple gall-wasps found in Ohio. Each type of oak-apple is produced by a different species of gall-wasp and their individual handiwork is so unique the galls alone can be used to identify the gall-wasp to species with actually seeing the wasp.
For example, the Small Oak-Apple Gall is produced by the gall-wasp, Cynips clivorum. This gall forms on the underside of leaf blades as you can see in the images below. The gall surface is free of any spots or other markings; however, the internal structure is very similar to the Large Empty Oak-Apple Gall.
As with the vast majority of plant galls, oak-apple galls cause no discernable harm to the overall health of their oak hosts. I believe they actually add ornamental value to their oak hosts, but I may be biased.
The Gall Backstory
Gall formation by wasps and other gall-making insects and mites is a complex and fascinating process that is not yet fully understood. Thus far, no researcher has ever produced a plant gall without the aid of a gall-maker.
Part of the reason the gall-making process is so complex is because gall-makers produce chemicals that turn plant genes on and off at just the right time to direct gall growth. The resulting galls provide both a protective home and nourishment for the next generation of gall-maker.
The chemicals exuded by gall-makers can only act upon “undifferentiated” meristematic plant cells. Under the influence of these chemicals, the meristematic cells that were originally destined to become flowers, stems, or leaves in the case of oak-apples, begin marching to a different drummer.
Once the errant cells fall under the chemical spell of a gall-maker, there is no turning back; they will become gall tissue. Conversely, this also means that gall formation cannot occur once meristematic cells are committed to becoming “normal” plant tissue. Once leaves are produced, the leaf cells can’t become gall cells. It’s one reason the leaf-gall season begins in the spring!
The vast majority of galls found on trees cause no appreciable harm to the overall health of their tree hosts. Keep in mind that the galls are an outward result of a complicated physiological and chemical dance between the gall-maker and the plant host.
No human has managed to duplicate the work so handily done be a group of organisms that are often viewed with disdain. If not viewed with a sense of wonder and fascination, at least insect and mite gall-makers should garner begrudging respect. Imagine the plant secrets that would be unlocked if we could unlock the gall-maker’s secrets?