Tuesday, May 28, 2013

Sith-Cada, Return of the Broodii

Just when you thought it was safe to start gardening again, Mother Nature has a surprise in store for us.  If the wild temperature swings we've seen this year wasn't enough, the ground is beginning to rumble to life.  The earthquake I'm talking about comes from a swarm of biblical proportions as Brood II makes it appearance from deep within our soil after its 17 year slumber.

Cicada's are nothing new to Virginians.  Every year annual cicadas appear, making themselves known as they sit in our trees producing a whirling call to attract a mate.  If surprised, the clumsy bugs take flight, buzzing loudly as they motor off to safety.  However, this 17 year Cicada, or technically called 'Magicicada' species is different because of the sheer amount that emerge from our ground in the next few weeks.  Some put the number around 30 billion, but a researcher at the Smithsonian Institute puts that number close to 1 trillion over its entire range.

Brood Emergence Timeline
When I first moved to Virginia, I got to experience Brood X (the biggest swarm) first hand.  Although many expected the damage to be immense, the trees still had leaves on branches and gardens remained the same as the brood retreated.  Of course, the sound of these horny critters searching for their soul mates drove you nuts, the next worst thing was smell of the deceased bugs as they littered the ground.  Birds had a good time snacking on these protein rich flying bug bars, after a while they even seemed to of had enough of a one sided diet.

So what can a gardener expect?  Fortunately, Cicada's have no functioning mouth parts capable of chewing a plant to pieces it does feed like an aphid on a plants sap. We don't need to think of them as a swarm of locust that will blot out the sun and lay crops to waste. These clumsy flying machines are only concerned with finding a mate, having sex and laying eggs. The last stage of laying eggs is where we can expect the most damage as the female splits the bark of small branches and lays anywhere from 600 to 800 eggs in the wound before she dies. Once the eggs mature, the nymphs hatch and fall back to the ground, disappearing for another 17 years. Although trees with significant damage from the egg laying process will invariably loose tips from branches, one shouldn't despair as trees quickly recover. It's nothing more than the Cicada's Barbers shop for trees, just taking a little off the back and sides.

So what benefit can come from all these Cicada's waking at the same time?  After all, events like this don't happen in nature without some kind of reason.  As it turns out, a researcher who studied the 2004 Brood X emergence found some positive repercussion following that outbreak.

It was discovered in the years following the 2004 outbreak, that there was an increase in plant growth stimulated from damage that had occurred by the Cicada's.  Also, as the larvae tunneled through the soil, it helped aerate the soil around the plants roots.  This tunneling reduced compaction of the soil and allowed moisture from rain or sprinklers to penetrated deeper into the soil.  Lastly,  the dying bodies of Cicada's actually became a great source of fertilizer.  As their bodies decay, it provided a valuable source of nitrogen and other nutrients that plants re-absorb.    

Scientist refer to this occurrence as a 'Resource Pulse'.  It is a term given to a large magnitude, but short interval and infrequent event where an resource availability was increased.  The study showed that plants given a diet of decaying Cicada's produced seed 9% larger than non-insect fed plants.  It's possible that a single acre of forest can yield up to 1 1/2 tons of nutrient rich dead bug carcass.  Those nutrients end up pouring back down the millions of finger sized holes in the ground from where they emerged.  In someways they return back to where they came from.

The whole ordeal is only expected to last 4 to 6 weeks before they all die after finding there one true love.  Its very Shakespearean to see a bunch of bugs sacrifice themselves so their species can keep on existing.  But one thing the press has failed to mention is when a species population explodes, so do the things that feed on them.  Ever heard of Cicada Killers?  Now there's a swarm of apocalyptic proportions!

Cicada Killer in action - Dendroica cerulea

Tuesday, May 21, 2013

Damn Good Plants - Aesculus pavia, Red Buckeye

One of my favorite trees growing up in England was the Horse-chestnut tree, Aesculus hippocastanum.  It made a large stately tree, often reaching heights of 100 ft, and very spring it puts on a show of upright panicle white flowers with blotches of red and yellow at the base of each flower.  But, as a boy I didn't care much for the flowers or even the size of the tree, it was the conkers I treasured the most.

The Mother Load! - Rainerschuetz
Conkers I hear you say?  Simply put,  a conker is the large mahogany brown seed encased within the leathery, slightly spiny covering.  This seed was hunted by almost every school boy as they dropped from its tree.  I was no stranger to this harvest, often filling my pockets and school bag with fallen seeds that had broken free from its covering on impact with the ground.  Hours would be giving to select what we believed was the strongest seed to be entered in the school yard tournament of conkers!

Take aim, FIRE!
The game pitted two people, each with a seed (or conker) dangling from a string.  One opponent would swing his conker at the others, which dangled in front of him, in hopes his would crack and destroy it.  Each person would take turns until a champion emerged.  It was a modern day Gladiator battle, flailing a ball on a chain until you conquered your opponent, but this version allowed you to return to classes without blood loss!

The European Horse-chestnut trees of my childhood are rarity in the Mid-atlantic.  Our summers don't favor it delicate complexities too well.  However, North America has a few of its own native Horse-chestnuts, although here they are commonly referred to as Buckeyes (for the chestnut brown eyes of a male deer or 'buck').  Red Buckeyes, Aesculus pavia are by far one of my favorites and takes pride of place in my backyard.  At this time of year it explodes with bright red blooms, that has earn it an alternative common name, the 'Firecracker Plant'.  So vibrant is the color, it draws in Ruby throated Hummingbirds that feed from the flowers after its migration from the warmer southern states.  

Red Buckeyes become handsome flowering trees in the home landscape, typically growing between 10 to 20 ft tall.  They prefer moist sites, but appreciate some shade from the fierce afternoon sun.  Past flowering, Buckeye's present an interesting texture in the landscape.  The dark green palmately compound leaves give an almost tropical feel, but without feeling out of place.

Apart from its obvious attraction in the landscape, it holds other properties worth mentioning.  Early European settlers were rumored to make soap from the roots and the bark was believed to have medicinal properties.  Native Americans were known to also crush the branches to exude sap for use it fishing.  It is said to 'dope' the fish making them much easier to catch.  However, it should not confuse with edible chestnuts, (Castanea sativa), though it does share a name similarity.  Seeds from Buckeyes contain a toxin called 'Saponin', common in many plants.  Fortunately, it is not easily absorbed by us humans, but will make you feel very sorry for yourself.

At the end of the day, it's highly unlikely that I'll ever be making soap or doping fish with my tree, but at least I know where to go if needed.  Instead, my enjoyment comes from watching my daughter discover the joys of finding the dark brown seeds that have fallen from its canopy. To see her hoard the bounty as if it was treasure, reminds me of my youth.  In years to come, I hope my children will experience the same fun I had playing conkers. First though, they'll have to learn my killer swing, often dubbed the 'Woodman Technique'  by those I conquered in the tournament of Conkers!

Sunday, May 12, 2013

Headache Hollies - The Crenata Conundrum!

It can't be denied, one of our most returned plants at the garden center happens to come from a group of Hollies commonly referred to as Japanese Hollies, or Ilex crenata.  The majority of the time we caulk up their death to improper watering, either too much or in most cases too little.  However, my suspicions have lead me to believe that something more sinister may be lurking in our soil leading to the masses of garden deaths being reported yearly.

Dubbed the 'Poor Mans Boxwood' due to the low cost of purchase, Japanese hollies share similar characteristics to their more expensive lookalikes. Small, dark green leaves and compact growing nature give little clues that they are in fact different to Boxwoods. One feature that suggests you have a Japanese Holly is the presence of small reminiscent spines along the leaf edge, barely noticeable unless you run your finger on the sides of the leaf. Many cultivars exist such as Soft touch, Helleri, Compacta, Skypencil and Steeds to name just a few, and are popular with gardeners and landscapers alike. However, Japanese hollies have becoming one of the most disease prone landscape plants around.

Though my investigation I have learned that the top issue plaguing Japanese Hollies is a disease called Black Root Rot, Thielaviopsis basicloa. It is a soil borne fungal disease occurring frequently in high soil moisture areas coupled with seasonal low temperatures that attack the plants root systems. First discovered on nursery stock in North Carolina in 1977, this pathogen has made its home in the Mid-Atlantic states. What makes Black Root Rot more troubling is that it can persist in the soil for many years, even without the presents of a host. To the unsuspecting homeowner who plants anyone of these Japanese Hollies, there is no way to detect if this pathogen is lying in wait ready to strike.

Tell-tale signs include stunted terminal growth, yellowing foliage, reduced vigor followed by die-back then death. Infected roots turn black from the tips, progressing further into the remaining root system as it spreads, choking out the ability of the plant to suck up moisture. Diseased plants decline over several months, frequently dying after periods of drought as the compromised roots cannot sustain the demand of the plant any longer.

Providing your hollies with the best possible drainage and practicing good hygiene by cleaning your garden tools will greatly improve your chances of survival and reducing its spread. Also, keeping your plants happy and well watered is just as essential as drainage. Hollies that become stressed from drought can easily contract the disease as there immune system becomes compromised. As yet there is no effective chemical control to help combat this pathogen.

The good news is that there are many plants that have shown some resistance to the pathogen. Nandina's, Chinese Hollies and Boxwoods (though not English Boxwood) will all grow well in areas known to be contaminated. The irony in this Japanese Holly story is that many of us switched from using Boxwoods for the cheaper lookalikes to save a few dollars, only now to spend more in replacing them as they fall to this black death of root rot.

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Sunday, May 5, 2013

Damn Good Plants - Sorbaria sorbifolia 'Sem'

There are so many wonders to be found in Spring, its hard to keep up with what's going on around the garden.  Flowers explode from every corner of the yard and perennials push up from their winter slumber, readying themselves for their moment to shine.  However, one shrub manages to jumps out from the pack with its vivid display of foliage color that rivals any spring flowering display.  This shrub is Sorbaria sorbifolia 'Sem', or otherwise known as the Ural False Spirea.

Originating from the harsh and inhospitable Ural Mountains of Russia into Kazakhstan and other regions further west through Siberia and into Northern Asia, 'Sem's' parents come from tough stock.  The straight species is too large and unruly to be considered garden worthy until the work of a clever Dutchman brought us 'Sem' from two unnamed Sorbaria selections.  It's appearance is much shorter and greatly more compact with new growth showing bronzed highlights that is very common when compared to its parents.  Its cold tolerances, coming from such a harsh region allows us to grow it in locations as low as Zone 2.  In fact, America seem balmy in comparison.

The best way to describe a Sorbaria 'Sem' is to say that it looks like a mix of Spirea, Astilbe and Mountain Ash, but wrapped up in a nice little package.   The delicate fern like foliage unfurls in spring, displaying a brilliant show of bright pinkish-red hues that persists on the shrub for weeks after.  As the seasons progress into summer, the color gradually changes to chartreuse-green with brighter tips that still show hints of red.   Creamy white flowers erupted like the plumes of an Astilbe during midsummer, set off by the now darker green foliage.

Though this shrub is a marked improvement over its parents it still has a wondering habit as it sends up suckering growth from its roots.  If you intend to let it spread and colonize, then this trait wouldn't be a problem but if you intend to shoehorn it into an already crowded boarder then be aware.  However, just like training a puppy, correcting it when it begins to misbehave and spread will lead to a desirable specimen.  Don't be afraid to hack it back in early spring to control its height or attack the suckers with a shovel.  Chopping around the shrub will manage its spread with no ill side effects. - Kerry D Woods
With such a stubborn attitude to grow in the most challenging environment, its amazing not more of us flock to the garden center to buy one.  Still its lack of use in the landscape only increases it exclusivity for the true horticultural connoisseur.