Table of Contents
Adam’s notes from the garden
Winter is setting in, and things are not following the same pattern as last year. Interestingly, things that displayed fall color in late January or February 2016 are currently at their peak. John Fairey’s collection of bigtooth maples (Acer grandidentatum) from the San Carlos Mountains in Tamaulipas is showing nice yellow colors here in late December. My photos verify the trees were a clean orange color in early February. The Taiwanese maple Acer oliverianum var. formosanum was also a nice consistent scarlet color in late January, but currently, has rather “dirty” red color as the leaves unfortunately, got blemished by superficial leaf spot pathogens originating from the moist late spring we had. Another Taiwanese native,
Liquidambar formosana, glowed a brilliant orangey-red in late January earlier this year but was rather weak and brief this past week. Acer discolor was the last to color up with sherbet orange last February, but it is on its way to peaking here the last week of December.
On schedule are native eastern US natives Quercus shumardii, Q. michauxii as well as Acer barbatum. The Taxodium disticum along the creek colored up nicely with their rusty orange canopy that soon became deposited in a striking monotony on the ground below following a breezy frontal boundary.
The blue-grays of the neighboring Serenoa repens, Yucca rostrata and Agaves really popped sharply against this rufous backdrop, moderated by the clean yellows of Tilia americana leaves and orange blush of Fagus grandifolia.
Bordering the cypresses, and appearing to stay on their mid-winter color transition schedule, are the Mexican sugar maples (Acer skutchii) which are still not quite feeling the chill and remain a dark green for now. A surprise to me were the two species of Sinojackia trees that had decent clean-yellow leaves retained for some time, longer than their related native Halesia grandifolia.
Asian spicebushes (Lindera sp.) always have fascinated me with their year-round interest as small understory trees. First to color up were Lindera cheinii and another unknown Lindera sp., both a pale, clean yellow color.
Next were the several Lindera angustifolia and L. glauca that John has planted around the garden, the latter with a brief orange color, and the former with school bus yellow. Both soon transitioned to a coppery tan color, that when focused on out of context, simply looks like dead leaves. To more perceptive observers, who take the landscape in as a whole, the leaves, which are retained through the winter, catch the light that filters down through the woodland garden canopy just right, glowing with a translucent copper richness that blends so warmly with the adjacent evergreens and flowering camellias.
Our first significant freeze killed back the foliage on a few hardy tropicals like the various gingers, Hamelia patens, Calliandra species, and a number of random perennials. Still, the garden is quite unfazed by the cold, being mostly composed of hardy plants. Some of the early flowering Mexican Mahonia species are already in bloom, including M. chochoca as well as a new, soon-to-be-named species flowering for its second time in cultivation. Soon to follow are the Asian Mahonia species and hybrids, which are budded up nicely, along with the remaining Mexican species which will provide a succession of canary-yellow flower spikes through early March. Our first deciduous magnolia cultivar is flowering, but most of the others still have developing buds. I continue to be impressed by Scutellaria wrightii in the rockery near the offices, as there has not been a day since late spring when it didn’t bear at least some purple/blue flowers.
It’s Not the Borer’s Fault! The Fascinating, Inbred, Misunderstood Beetles That Didn’t Kill Your Trees
By Adam Black
As I was strolling the gardens a few weeks ago, I noticed sawdust accumulating around the base of a hardy cinnamon tree, Cinnamomum chekiangense, north of the creek. Having a background managing the forest entomology lab at the University of Florida, which is at the forefront of research dealing with ambrosia and bark beetles, I carved a few of these “borers” out, all smaller than a sesame seed. I found two species – the abundant, pill-shaped granulated ambrosia beetle, Xylosandrus crassiusculus, and the more elongated pinhole borer, Euplatypus compositus. The latter is native, but the former was introduced from Asia and has been one of the most successful of insect invaders worldwide. Regardless of whether they are native or introduced, “borers” are often blamed for the decline and death of a prized ornamental tree based solely on their conspicuous presence, yet unjustly so. That’s right, the borers didn’t kill your tree, and in some cases, you wasted money fruitlessly treating with chemicals only to have the tree still die.
How can this be? The tree was healthy, and all of a sudden there was clear borer activity on the trunk, extruding compacted spaghetti-like masses of sawdust from their boring activities as the tree quickly died. Of course, it must have been the borers’ fault. Wrong! Though your landscaper or arborist will happily take your money in order to drench the root zone with chemicals, administer trunk injections and other pricey witchery, treating for the beetles is pointless. By the time you notice the beetle activity, it is almost always too late. And again, it is not the beetle’s fault. Why? Because the beetles are attracted to the chemical cues given off by an already-stressed and dying tree. Yes, the tree looked fine before the borers colonized the trunk, but what you didn’t see what the fungal infection slowly rotting the interior of the tree. The beetles sensed it and came in to serve as the secondary, opportunistic undertakers.
It was a constant struggle at our lab to convince clients that borers weren’t the primary cause of death for their rare, or highly valued tree. Fungal infections can be slowly eating away at a tree internally for months before it displays any visual signs of distress. The beetles are able to sense the stressed tree and home in on it. In fact, when trapping these beetles for research, one of the best lures is ethanol, produced in a plant’s decomposition process. The beetles’ affinity for alcohol is also clear on some humid summer night when you are outside drinking beer…if you pay attention, that little hard thing you felt go down your throat quicker than you could spit it out was often a tipsy Xyleborinus saxesenii that ended up in your bottle! One larger introduced species, Cnestus mutilatus, so named as its blunt abdomen looks as if it was chopped off, is such a glutton for ethanol that it has been known to eat through plastic fuel containers that bear gasoline containing ethanol.
Ambrosia beetles (boring into the wood) and bark beetles (living just under the bark) have evolved where they carry a little bit of fungus with them from tree to tree. Different species have their own types of fungus they specialize in, while others can carry several species, or are generalists. Some have special pockets inside their mouths that get stuffed with fungi, others carry it under their wing covers, in a pocket under the top of their back, and a few even have dense tufts of orange hairs on their head that bear the fungi. When they find a stressed tree, ambrosia beetles chew a tunnel, known as a gallery, deep within the tree, while bark beetles hollow out tunnels directly under the bark. The sawdust generated is pushed out the hole in a compacted tubular mass that can get quite long on a calm day. These are affectionately called sawdust “noodles” among bark beetle researchers and are usually the first visual sign of an infestation. Once the galleries are dug, the beetle will transfer the fungus it brought with it into the tunnels, where it soon grows on the gallery walls. The beetles tend to this crop, which they and their eventual larvae will consume. There is evidence preserved in fossil amber that beetles have been doing this for millions of years, since the time of the dinosaurs, and therefore may be one of the earliest farmers on earth.
The fungi they carry can serve various purposes. Some species are “saprophytes,” helping to decompose dead wood, while others can act as mild or even severe tree pathogens. Wait a minute, didn’t I just say that the beetles (or the fungi they carry) were not killing trees, only finishing them off?
There are a few rare, but significant instances where a certain species of beetle will colonize a perfectly healthy tree, introduce its fungus, which then kills the tree. There are very few species in this category, five or so species in the U.S. that when introduced into a new environment, shift from being attracted to stressed trees as they behave in their native range to making themselves at home in healthy, unstressed trees. One of the most noteworthy invasions following this pattern in recent years is the redbay ambrosia beetle, Xyleborus glabratus which arrived from Asia. A single beetle was introduced into the U.S. via Port Wentworth (Savannah, Ga.), likely hitchhiking among wood pallets or other untreated wood crating materials, back in 2002.
It is most fascinating that one tiny individual beetle and its fungal accomplice could initiate one of the most significant impacts on native U.S. tree species in recorded history known as laurel wilt disease. These beetles are among the most successful colonizers of new territory due to their unique modes of reproduction. One female was liberated from her foreign shipping materials at a sea port, easily found a redbay tree, Persea borbonia in the nearby maritime forest, dug her gallery and introduced the laurel wilt fungus she brought with her in specialized pockets inside her mouth. Possessing a unique reproductive strategy, she has the ability to lay fertile eggs without being fertilized by a male. The initial eggs all hatch as males, which mate back with their mother. Her second round of eggs will include females, sparking a new exotic introduction to the country and reproducing exponentially. Originating from one female, all the millions of current redbay ambrosia beetles that have spread from North Carolina south to the tip of Florida and west to east Texas are all one clone, bearing identical genetics. Furthermore, the fungus that is now killing back millions of trees in the southeast is also a single clone. Quite an interesting story.
The introduction of the redbay ambrosia beetle was highly unique in that this was a case where there was a significant shift from normally being attracted to stressed trees in Asian forests to attacking perfectly healthy, unstressed trees upon introduction into the US. Other southeastern US natives laurels are also fair game, including swamp bay, sassafras, spicebush, along with the cultivated avocados and bay leaf. This is one of the few cases where you can blame the beetle for a tree’s death, assuming the tree is a host plant for this particular beetle. Still, nearly all beetle infestations among cultivated trees take place in trees dying from other environmental or cultural stress.
Though few people grow members of the laurel family as ornamentals (though they should), the south Florida avocado industry has been impacted. The outlook was grim for the native host plants, but after more than fourteen years with a foothold in the southeastern U.S., it is clear that trees do die back, but most resprout from the roots vigorously and will grow for several years and even produce fruit until they attain a trunk diameter attractive to the beetles again. Furthermore, Dr. Marc Hughes earned his PhD. in our Florida lab with a primary focus on identifying naturally resistant trees in the areas hardest hit by the disease. He found that some of these resistant trees developed disease but were able to shrug it off, while others simply had a genetic profile that didn’t give off the right chemical cues that attracted the beetles. That said, we don’t know if all members of the laurel family will show similar resistance, especially if the disease spreads into the Lauraceae-rich regions of Mexico, Central America and down into South America. It appears we have natural barriers in place in south Texas (consisting of a complete lack of native laurels south of Corpus Christi) to prevent a natural flow of the beetles into Mexico, but this can be circumvented if people move firewood from an infested area to a new area, like the Rio Grande Valley where avocados are grown on a small scale. It has been proven that other significant insect pests have been introduced to new regions through hitchhiking in firewood, so it is always critical to obtain wood close to where you plan to burn it.
So what can you do to combat borers? Plant only trees that are proven adaptable to the soil chemistry and climate of the region. If you are a collector and likely trialing odd species of trees, expect some to not be happy and eventually decline and serve as a home for ambrosia beetles. If you already have an infestation, just say your goodbyes to the tree, and make the best of it by enjoying your newfound appreciation for these complex organisms just trying to make a living. There’s no use treating with expensive chemicals. Try to narrow down any stress-causing factors that lead to the tree’s susceptibility to borers and work towards making changes with remaining and future trees.
The infested hardy cinnamon tree I mentioned was one of several established trees we have had that declined slowly over the summer through fall almost surely due to the flooding earlier this year. Several steps away from the dying cinnamon, I more recently spotted an infestation at the base of a large magnolia, also subjected to the flooded conditions. This tree had another species of exotic ambrosia beetle, Euwallacea interjectus that has become well-established in the southern U.S. DNA studies conducted by Dr. Anthony Cognato and collaborators have shown that the E. interjectus found from Louisiana eastward to Florida are a separate introduction from Asia than the few previously recorded from east Texas, meaning there were two separate invasions of the same species. The eastern beetles are more genetically similar to those that naturally occur in Japan, whereas the Texas introductions match Taiwanese native populations. We can surmise that those in Texas arrived via wood packing crates or pallets at one of the ports in Houston on a freighter from Taiwan. Coincidentally, I had collected this species in Taiwan over a year ago and Dr. Matt Kasson’s lab at West Virginia University found that they carry a distinct species of fungus related to, but quite distinct from the fungus the Japanese E. interjectus carry. I sent his lab some of our presumed Taiwanese-turned-Texan beetles from the magnolia to confirm they have the same fungus as those I collected from the Taiwanese mountains. I find it quite interesting that I have been coincidentally involved with the characterization of the fungal symbiont from the beetles’ Taiwanese range and its new range extension in the U.S.
After being exposed to the complex world of ambrosia and bark beetles with my previous job, I can not shake my appreciation for such amazing creatures that, love ’em or hate ’em, are forever intertwined with our love of gardening. I must continue to stress though, to not automatically feel you should waste money on chemicals thinking you are doing something helpful. Just accept losses in the garden as normal, all the while having a greater appreciation for the complexities of these hard-working invertebrates who are avid gardeners themselves!
December Slideshow[rev_slider alias=”December2016″]
Follow Peckerwood on Instagram or Facebook!
We maintain an active Instagram ““@peckerwoodgarden” and hope you will become one of our followers and join our hosts, Adam Black and Craig Jackson. On Facebook, “peckerwoodgarden” shares images of what the garden is like that week and what is happening soon, hosted by Bethany Jordan and Adam Black. “@PeckerwoodG” on Twitter also updates you on current happenings at Peckerwood Garden and is hosted by Bethany Jordan.
- Sat, Jan 7, 2016, Peckerwood Insider’s Tour, 10 am
- Sat, Jan 14, 2016, Monthly Training, 9 am
- Fri, Jan 20, 2017, Evening at Peckerwood Garden Lecture, 7 pm
- Sat, Jan 28, 2016, Open Day, 10 am – 3 pm
- Sat, Feb 4, 2017, Peckerwood Insider’s Tour, 10 am
- Sat, Feb 11, 2017, Monthly Training, 9 am
- Fri, Feb 17, 2017, Evening at Peckerwood Garden Lecture, 7 pm
- Sat, Feb 25, 2017, Open Day, 10 am – 3 pm
Plant of the month: Ilex x ‘Cherry Bomb’
By Adam Black
In last month’s newsletter, I made note of the hybrid holly from the National Arboretum breeding program initially referred to as NA28255 but then renamed Ilex x ‘Cherry Bomb’. Within minutes after we released the newsletter David Creech at Stephen F. Austin University contacted me with the full story on the plant with some clarifications, credits and additional information on this plant. David wrote:
“This is a J.C. Raulston (North Carolina State University) distributed plant via National Arboretum . . . he wasn’t supposed to propagate or distribute but that wasn’t his style. Margaret Pooler of the National Arboretum announced to the breeding program cooperators that since there was no interest in that particular plant at the time, it should be destroyed. John Ruter of the University of Georgia told her that he thought Creech had the plant and had handed them out, and that Treesearch Farms in Houston was selling it. The nursery’s then-horticulturist Scott Reeves asked me if I liked the name Cherry Bomb . . . I did . . . so, Scott (now at Creekside Nursery) should get the credit for the name and SFA Arboretum should get credit for saving it from the trash heap. I called Margaret after I had visited with Ruter, got everything smoothed out . . . and it was made as a joint release under that name. It is a good plant. Alkalinity tolerant. Proof positive in my mind that plants need to be shared . . . sometimes a failure in one spot sets up a success in another.”
If this one hadn’t made the cut in National Arboretum’s trials, I’d be interested to see what did. I remember first seeing this dense tree loaded with fruit and already bearing the name ‘Cherry Bomb’ at Tony Avent’s Plant Delights Nursery/Juniper Level Botanical Garden years ago. He shared cuttings with me to root in north Florida. I shared with a few folks in Florida and was then surprised to find it in Peckerwood’s collection upon moving here. It soon became apparent it was in many collections out here with the Texas connection. Prior to David’s clarifications, after the newsletter was released, Scott visited Peckerwood and told me about his naming of the tree that had caught my eye years earlier. It’s always great when things come full circle – a good plant earns its well-deserved time in the spotlight through the combined efforts of several good plantsmen, all of whom I have come to know except, regrettably, J.C. Raulston, whose untimely death left a huge void in the horticultural world yet firmly instilled the philosophy of freely sharing good plants, a mission which lives on in so many to this day.
Volunteers in 2016
By Bethany Jordan
This past year has been a time of great change and development for Peckerwood Garden. Our volunteers have been instrumental in aiding our transition into a public garden. Now with open days being held at least once a month, our reliable docents have increased their time with us by leading tours, helping volunteer groups, assisting with open days, helping in the nursery, and participating in monthly classes.
In the office, volunteers have transcribed interviews with John Fairey, prepared membership mailings, researched information, and much more. Working in the garden house, volunteers have cleaned seed, maintained the house for guests and events, prepared for lectures, assisted guests, and compiled large documents.
Volunteers have cleaned large areas of the property around the buildings and have worked with Adam on our mission to develop an aesthetically pleasing entry and reception area.
Volunteers helped reorganize and maintain the nursery and price the plants for sale. From tedious weeding, data entry, tour assistance, class participation and propagation our volunteers have been here with us every step of the way. When setbacks or needs arise, the volunteers are available and present through the whole process and are critical in the positive changes created.
Our Open Days and other increasing events are possible only because our volunteers are here to assist guests in every area from sign-in and parking to tours and nursery sales. Thank you to all of our volunteers for 2016! We look forward to working with you as we continue to advance our garden into a more publically accessible place of enjoyment.
Join us in remembering 2016 at Peckerwood Garden with this slideshow.[rev_slider alias=”2016-remembered”]
Need transportation to Peckerwood from the Houston area?
By Adam Black
Do you want to visit Peckerwood Garden but refuse to fight with the hectic traffic? Are you planning to visit Houston and need a ride from the airport to the gardens and points beyond thereafter? Gardens supporter Albert Howell, an independent contract driver licensed by the city of Houston, has generously agreed to offer his driving services to Houston area residents and visitors to/from the gardens. Even more generous, Albert is offering discounts to our members as one of our newest partner businesses. His late model Chevy Equinox is very fuel-efficient and can seat up to four passengers. Albert is a very friendly plant enthusiast so there will surely be some great botanically-oriented conversation on the way! Please feel free to coordinate directly with Albert for a ride in advance of our open days or other events. His phone number is: (832) 206-1877 and you can also find his contact information on our website.