Killing with Kindness

With the advent of Spring comes a myriad of calls on distressed plants from homeowners, nurseries and landscapers.  One of our better tree service companies (I’ll call the owner/operator ‘Mark’ to protect his clients’ identities) in southeastern Michigan called with a series of problems this spring so I decided to take drive over and get a first hand look. We looked at several problems on plants ranging from trees to ground covers but there soon emerged an consistent thread: overwatering.  Plant problems related to overwatering and poor soil drainage are among the most common landscape issues I see year in and year out.  The stops I made with Mark last week were typical. Mark works in several very affluent suburbs around Detroit (I know readers around the country don’t associate Detroit and affluence, given our recent press, but there is still some serious money in the area).  Some of Mark’s clients spend up to $20,000 per year just to maintain the trees and shrubs on their property – that’s not including lawn maintenance.  Needless to say, these folks want everything perfect.  In their effort to have their landscape look more perfect than the neighbors, the homeowners and their gardeners often go overboard – especially with irrigation.  One of the things that caught my attention during our site inspection was recurring issues with Norway spruce.  For the most part, we regard Norways as a cast iron plant and one of the last trees with which we’d expect to have problems.  Yet we saw several instances were established specimens were suffering needle die-back and declining.  


In each case the trees were irrigated in situations where they would likely grow well without supplemental watering.  But the trees were surrounded by ground covers or annual beds with heavy soils that were heavily irrigated.  Problems usually increased on down-slope positions.  


The solution?  Back off the irrigation.  Everyone knows trees need water, but roots their roots also need oxygen.  At one site we visited, the homeowner already had his gardener running the irrigation system – in April!  This is truly killing with kindness.  Most established landscape trees, shrubs and perennials  in this part of the world need little, if any, irrigation.  Newly planted trees and shrubs need an occasional (weekly to bi-weekly) drink in the first year and some follow-up the second year.  After that they can manage most years on our rainfall. In the end, a lot comes down to design.  Establish thirsty annual beds where they can be irrigated without drowning hardier trees and shrubs.

Friday puzzle untangled

A few of you bravely hazarded guesses about this plant, and while it is a contorted specimen, it’s actually Ulmus glabra ‘Camperdownii’, otherwise known as Camperdown elm.  Here’s a photo of a lovely example at Marymoor Park near Seattle:

As plant geeks already know, this odd tree was propagated from a mutant branch discovered on the Earl of Camperdown’s estate in Scotland in the 1800s.  All Camperdown elms are grown from cuttings originating from this single tree grafted onto a Ulmus spp. rootstock which supplies the straight trunk.

Though these trees don’t get terribly tall, they can become quite broad and need space for their tiers of foliage.  Like other contorted trees, the branches of old Camperdown elms can meet and fuse, as you can see in the photo from Friday.  And while the tree produces scads of seeds (that’s what you see in the photo above – not leaves!), they are sterile. 

A Dangerous Game

Every once in awhile I become infatuated with some idea and can’t stop for looking for information on it.  It usually starts when I want to find a good quote for a particular article or column that I’m writing and then ends up swallowing two or three days.  Well, it happened to me again yesterday and spilled over into today.  I’m currently finishing up a project with an old friend of mine from college who happens to be a political science professor at the University of North Carolina Charlotte.  We’re looking at certain environmental issues and the stances taken on them by both the left and the right.  Anyway, I wanted to make a point about biotechnology — that point being that when we graft two plants together we often get different chemicals in the plant which we grafted onto the rootstock than we would get if the plant were growing on its own roots.  This is because many chemicals can be translocated from the roots to the leaves or even the fruit.  Anyway, I quickly found a number of nice scientific articles to back up my statement, but I also found some other fascinating information about, of all things, tomatoes.  There are many plants related to tomatoes that tomatoes can be grafted onto.  For example, every spring our plant propagation class grafts potato roots to a tomato top.  Tomatoes can also be grafted onto eggplant (which is actually very useful because eggplant roots are very resistant to flooding unlike tomato roots).

While the above examples are interesting, they’re also relatively common knowledge among horticulturists.  Here’s the part that’s not common knowledge (or perhaps I should say here’s the part that I didn’t know about — I’ve been known to be ignorant of things that other people consider common knowledge before).  Tomatoes can be grafted onto tobacco, and, if they are, they will have nicotine translocated to their fruit — not a lot mind you.  Most of the nicotine ends up in the leaves and stems of the tomato plant, but still, why couldn’t a nicotine-laden tomato be developed which could help smokers kick the habit — in a semi-healthy kind of way?

I also found that tomatoes could be grafted onto jimson weed.  Big mistake there.  Jimson weed develops some pretty nasty alkaloids, and they end up in the tomato fruit.  So, if you eat the fruit, your done for.  In fact, I found an instance where 5 people were killed because they ate tomatoes grafted onto jimson roots.  I am now curious about what happens if you graft tomato onto deadly nightshade — but not curious enough to actually try it.

Lunar control? Or lunacy?

Yesterday one of my dear skeptical colleagues sent me a link to a new article on lunar influences on plants (you can find it here).  Briefly, the authors argue that scientific evidence supports the concept of a lunar cycle influence on plants.  Interspersed within the discussion are references to seasonal and daily plant cycles, along with legitimate references to these verifiable phenomena.  (Had these references to circadian and diurnal rhythms been left out, the literature citations would have been rather paltry.)  Plants depend on these daily and seasonal cues for a variety of physiological and behavioral activities; lunar cycles have little obvious relevance to plants.  Nevertheless, “planting by the moon” is a belief system that has existed since ancient times.

This article is a great example of how pseudoscience insinuates itself with legitimate science.  Many of the references used as evidence for lunar effects on plants are of nebulous quality as they haven’t been reviewed by the scientific community; these include self-published books or lectures.  Furthermore, for every article that claims a lunar effect, I can find another discounting it entirely.  That being said, there are some legitimate papers indirectly linking lunar cycles with plant biochemistry.  Coincidentally, the lead author of one of these articles is a close friend and colleague whose research credentials are impeccable.

Here’s where the fascinating and complex nature of species interactions helps explain conflicting data.  Lunar cycles do affect certain species, including some herbivorous insects which are dependent on moonlight for feeding.  During the full moon, such insects feed more heavily and affected plant populations retaliate by altering the digestibility of their tissues. It’s likely that these biochemical changes have been erroneously attributed to direct lunar influence rather than herbivore defense.

To demonstrate direct lunar influence, one would need to study plants in an herbivore-free, controlled environment so that the only variable under consideration was lunar cycle.  Under such controlled conditions, would the same changes be noted over time if plants weren’t eaten by moon-managed insects?  Would you see changes if you modified the lunar cycle to make it longer or shorter (again without insects)?  Positive and repeated results would be necessary to establishing a role for lunar control.

As with so many other mystical explanations of natural phenomena, the real story is infinitely richer and more satisfying.

UPDATE: A peer-reviewed literature review on this topic has just been published. It’s well worth reading.

Do These Come In Control Top?

For those color-conscious gardeners who can’t bear to have visible tomato ties (or panty lines):

Only $2.99 for eight pieces?  Whatta deal!

Do you know how many tomato ties you can get from a pair of hose? Especially if you are a “long”? About fifty. Of course they’ll be nude or black, unless you bought into that purple trend last season.

Yeesh.

ps:   I do like Lusterleaf’s (company responsible for the above) can o’ twine with the handy cutter-top, though. $4 and it has lasted through several seasons.

Selling dawn redwood

As with last week, this past week and weekend were largely occupied by my role as a faculty advisor for the MSU Horticulture club.  This weekend was our annual Spring Show and Plant Sale.  Each year our undergraduates commandeer the Horticulture department’s conservatory, bring in a boatload of plants, pavers, turf and mulch and design and install a landscape.  It’s actually quite a process to watch.  http://www.youtube.com/watch?v=4NTPzB6YVSk
In addition to the Spring Show the Hort Club puts on a plant sale, which is the group’s principle fund-raiser for the year.  My duty station for this year’s plant sale was working outside in the tree sales yard.  For the record, retail is not my thing but, hey, it’s for a good cause. The star of our tree sale this year was a container-grown 14’ dawn redwood (Metasequoia glyptostraboides).

For those not familiar with this tree, dawn redwood is an incredible tree.  It’s a deciduous conifer, similar in many respects to bald cypress (Taxodium distichum) but with a finer, more refined character.  Metasequoia is considered by some to be a ‘Living fossil’, similar to Gingko biloba.  The genus Metasequoia was originally described in 1941 from Chinese fossils from the Mesozoic era.  Although local people in China knew the tree and used it as an ornamental, living trees were not formally described by botanists until 1948.

Dawn redwood is well adapted to wetter sites

Seed collected by Arnold Arboretum in the late 1940’s were distributed to universities and arboreta and this attractive, fast-growing tree found its way into the nursery trade.  Ironically, millions of Metasequioa have been planted as ornamental trees but the species is considered critically endangered due to loss of its native habitat in China.  Dawn redwood is extremely fast growing and some trees planted in the U.S. from the original collections in the 1940’s are reportedly 3’ in diameter.


Dawn redwoods on MSU campus

So, how did I fare in nursery sales for a day?  Put it this way, I better hang on to my day job; retail is still not quite my thing – though I did move the dawn redwood and got to spend a good bit of my weekend talking about this awesome tree.

Friday geography answer

As several of our astute readers knew, the photo from Friday was taken on the west coast of the Salton Sea in California.  Specifically, it’s at Salton Sea Beach, a nearly deserted region that I managed to make more picturesque through careful photography.  Here’s another picture of the same beach:

There were few plants at Salton Sea Beach – a palm tree here and there – and only a few waterfowl like these pelicans:

The Salton Sea is really the Salton Sink – it’s a low area that has occasionally and naturally filled with water.  Given the high rate of evaporation in the region, the lakebed became highly saline over the centuries.

So what does this all have to do with a gardening website?  Well, the reason the Sea exists today is because of natural flooding combined with agricultural development.  Initially the Sea was seen as a boon to tourism, so spots like Salton Sea Beach and Salton City (near curiously named Squeaky Springs) became tourist destinations.  But as agricultural runoff began to change the nature of the Sea, fish populations failed and so did the tourism industry.

You can see the algal bloom where runoff meets the sea (check out this Google map here).  These desert valleys have been used for conventional agricultural production for many decades, and the results are seen in a sea full of fertilizers and pesticides.

In any case, a visit to the Salton Sea is both fascinating and depressing.  It’s well worth the effort.

Friday geography quiz!

Like last week’s, today’s quiz is a little different.  (I haven’t forgotten about last week’s question – just haven’t gotten a good answer yet!  Never fear!)  In any case, you know I spent some time in Palm Desert CA last week.  On one of our day trips, I took the following picture (we are looking east):

So here’s the question:  where are we?  (It was a day trip, so not terribly far from Palm Desert.)  You can ask questions that I may or may not answer.  Monday’s answer will tell you lots more about this “accidental” landscape!

Dandelions and clover

It was fun to read all of your comments last week about your opinions on lawn care.  To follow up on it I’m going to talk a little bit about why I’m not fond of companies which apply herbicides multiple times throughout the year.  But first I think I’ll mention why I apply herbicides at all — aesthetics.  That’s it — the whole reason. Could I go the no-lawn route?  Yes, but I like having a yard to run in.  Not a huge yard, but a little yard to play tag with the kids.

What I long for though is the yard from the house that I grew up in.  Our house in southeastern PA (About an hour west of Philly and an hour east of Lancaster) was set back about 800 feet from the road and was on old agricultural land.  The area around the house was planted in grass in the mid 70s and then it was left alone.  Fertilized once the first year I think, but that’s it.  Dandelions invaded quickly as did clover.  Over the years the clover began to dominate the grass, but not to the point that the grass disappeared, and the lawn actually appeared relatively homogeneous.  Dandelions never left, but their numbers declined.  The clover grew low and the grass never shot up like it does in a heavily fertilized lawn and so mowings only happened once every two weeks or so (well, OK, sometimes more often depending on the weather and where on the lawn you were — the spot over the septic tank needed mowing every 48 hours or so).  The grass did go dormant most summers, but 800 feet from the road there wasn’t anyone to complain, and besides, the clover kept the lawn from appearing completely scorched.  The lawn looked good for well over 30 years (until my parents remodeled the house and the yard was torn up).

The typical suburbanite might not have liked this lawn, but to me this lawn looked great, and, besides, it was low maintenance.  The reason I’m bothering to tell you about this lawn though is because it illustrates so well what lawn care companies make impossible.  They say (and by “they” I mean professors like myself) that pesticides beget pesticides and fertilizers beget fertilizers, and nowhere is that as true as in a well manicured lawn.  The herbicide of choice is 2,4 D (though there are many others that are used) which lawn care companies apply multiple times over the the course of a year.  This pesticide does a great job of killing dandelions, but it also kills clover.  It rarely hurts grass unless it’s grossly over-applied.  The problem with killing clover is that this clover is the stuff that fed the grass in the house where I grew up.  Clover takes nitrogen out of the air and makes it available to grass every time the lawn is mowed (the clipped off pieces of clover degrade and the nitrogen in them feeds whatever plants are around).  Without the clover you need to add fertilizers.  So, because the lawn care company is keeping the lawn free of weeds they also need to fertilize because they’re killing all of the natural fertilizer.  Here’s the thing, the weed that most people in the suburbs like least, dandelions, is actually very sensitive to low potassium.  The lower the potassium in the soil the worse it does.  In fact, dandelions can easily be out-competed by grass and clover if potassium is low — just as happened in the yard of the house where I grew up.  But do lawn care companies pay attention to this (by using high nitrogen, low potassium fertilizers?)  What do you think?

My guess is that many of you thought that I’d cite all kinds of scary side effects of the pesticides used on lawns.  Nope.  In general I think that, if used properly, they’re pretty safe for humans (with a few notable exceptions).  I’ve spent a lot of time reviewing epidemiological and toxicology studies and I can think of many worse things.  I am somewhat fearful of what 2,4 D may do to dogs in particular — they can’t excrete this poison like we can.  Don’t think for a minute that I’m calling these poisons perfectly safe — I just think there are plenty of other better established reasons to avoid lawn care company pesticide schedules.