Vinegar: A Garden Miracle!

I’ve been working with homemade garden remedies in one context or another for about 10 years now.  As someone who has spent days searching for odd cures to garden problems I consider myself qualified to say that, of all of the remedies I’ve seen, vinegar seems to be the product with the most (supposed) uses.  You can kill weeds with it, as well as plant diseases and insects.  You can also use it as a fertilizer or even to acidify your soil.  It’s amazing!  But which of these uses are real and which are just someone flapping their jaws?

Vinegar as an herbicide:  White vinegar which is about 5% acetic acid and does a nice job of burning the tops of plants, but not their roots – so a larger weed will live right through a spray even though it will look bad right after the spray.  You can buy 20% acetic acid.  It works faster, but it has essentially the same problem killing larger weeds that that 5% acetic acid does.  Besides efficacy issues there are safety issues also.  I’ve used 20% acetic acid and I think that this stuff is too dangerous for the average person.  A little in the eyes could cause permanent injury.  Just a little whiff of it is enough to make the nose start running (in other words it’s not good for mucous membranes).

Vinegar as a disease control:  What a great idea!  Spray something that kills plants onto your prized petunias to control disease!  OK, when you use vinegar as a plant disease control you do use a lower concentration which shouldn’t hurt the plant.  But vinegar has never proven to be particularly effective at controlling plant diseases.

Vinegar as a fertilizer: Nope, doesn’t work.  Acetic acid only contains carbon hydrogen and oxygen – stuff the plant can get from the air.  The other things that may be in vinegar could be good for a plant – but it seems an expensive method of applying an unknown amount of nutrition.

Vinegar as a soil acidifier:  This is one that I’ve seen a lot – and so I tried it.  In a nutshell, it just doesn’t work that well.  It takes a lot of vinegar and the pH change is brief at best.  Use something like sulfur instead.

So to summarize, despite a lot of recommendations, the only thing that vinegar has really proven to be good at is killing weeds – and then only if the weeds are young.

Grass, sedge, or weapon?

What is it?

Why, that’s a “Mace Sedge” – thus a medieval weapon AND a sedge. Actually…not very menacing.  But very cute. Carex grayi is a wonderful clumping sedge, native to Eastern North America.   Mine is situated at the edge of a home-made bog, and is at least 2.5′ tall with an upright habit.

More common in the trade are the cascading Asian sedges such as Carex dlichostachy ‘Kaga Nishiki’, C. oshimensis ‘Evergold’, and C. morrowii ‘Variagta’, all fabulous plants for the part-shade garden.  My hair has been likened to New Zealand native C. buchananii, the coppery leatherleaf sedge (I took this as a compliment).

The genus is chock full of garden-worthy species, of which the North American natives are finally getting some attention. Folks like grass guru Rick Darke and meadow man John Greenlee have been promoting the heck out of native sedges for both the east and west coasts, respectively. I can’t even remember where I put my mitts on this one, but have been enjoying the heck out of it for the past two years.

Does colored glass help root cuttings?

I get a lot of questions about a lot of different products and practices.  New topics send me to the scientific data bases and that’s where I went for today’s posting.  One of my garden writing colleagues asked me about colored glass rooters – glass containers in different colors that can be filled with water and a plant cutting.  The conventional internet wisdom, according to my colleague, is that green and blue glass rooters are the best.

The first mention I could find of such a practice is from an 1801 publication called The Cottage Gardener.  In it, we’re informed that for rooting cuttings “such coloured glass is useless; it has no influence over the production of roots.” Nevertheless, 200 years later web postings like “I have found that cuttings placed in colored blue or green glass root faster than clear glass” are taken as solid evidence that blue or green glass containers are best for rooting cuttings.

There is science behind different colors of light and rooting, but it’s a little more complicated.  Chlorophyll absorbs red and blue light best, so plants whose leaves are exposed to red and blue light grow well and tend to produce a healthy flush of roots.  On the other hand, plants whose roots are exposed to blue light have decreased root growth compared to those under white light conditions.  In this case, the photoreceptor called cryptochrome might be responsible for inhibition, as it is a blue light absorber.  Similarly, plant roots exposed to green light do not grow as well as those exposed to white light.

In my opinion, this is another example of aesthetics trumping science.  Of course colored glass rooters are more attractive that plain old glass jars.  And that’s a perfectly valid reason to use them as part of one’s home decor.  But it’s not science, nor is it necessarily the best way to encourage rooting.

What seems to be most important in rooting cuttings in water is to use indirect lighting (north-facing windows in the northern hemisphere, for example) so that the water doesn’t get too hot.  And keep in mind that not all species root well from cuttings.

Getting to the root of the problem

After getting off to a cool and soggy start, summer has come with a vengeance to Michigan, with heat indices expected to push 100 degrees by Wednesday.  Along with warmer temperatures, summer also means our research season is getting into full swing as well.  One of our biggest efforts these days involves our project to look at pre-plant storage and handling on shade tree liners.

 

As many GP blog readers are aware, emerald ash borer (EAB) has dominated the conversation regarding shade trees in the Midwest for the past 6-8 years.  Ashes made up 20 to 30% of the shade tree cover in many urban and community forests, so their loss has been devastating.  A major thrust of our extension programming during this time is to promote a wide range of ash alternative to increase species diversity.  One of the challenges we find in making this pitch is that many of the species we recommend (oaks, hackberry, baldcypress) are trees that nurseries often find difficult to grow from standard bare-root liners.

 

My graduate student, Dana Ellison, is in the second year of a project to look at some of the practices that growers use on the difficult to transplant species and some of the underlying causes of poor transplanting.  Dana is looking at a variety of attributes including plant water relations and carbohydrate status, but the order of business these days is roots.  Specifically we’re evaluating root growth potential of oak, baldcypress, and hackberry.  We’ve also included white ash, which transplant easily, as a positive control.

Graduate research assistants Dana Ellison (right) and Brent Crain (left) and undergraduate assistant Arriana Wilcox (center) pot up shade trees for root growth potential testing.

Root growth potential (RGP) is a common parameter in evaluating quality of reforestation seedlings but is measured less often on larger liner material.  The logic is pretty straightforward; a plant’s ability to initiate root growth after plating and re-establish root-soil contact is one of the biggest determinants of its ability to survive and grow.  A variety of systems have been used to evaluate RGP for seedlings – most involve growing seedlings for a set time (3 weeks is standard) in an aeroponic system and then counting or measuring new root growth.

Growing the trees in pea gravel makes it easy to get a look at new roots.

For Dana’s shade tree liners (5’-6’ whips) we’ve adapted a system based on the Missouri gravel bed system (which I first got to see in person at Jeff’s research nursery in Minnesota – thanks Jeff!).  Dana and her helpers pot the trees up in pea gravel in 25-gallon containers.  The trees are grown on for three weeks in a greenhouse while the roots are kept moist with spray stakes operated by a mist system timer.  After three weeks, we dump out the gravel, wash the root systems, and carefully count the number of new, white root tips.

Dana washing roots.

So what have we learned?  Well, the work is still on-going but some trends have emerged.  Baldcypress may experience some transplant issues but they don’t appear to be related to producing roots.  We had several baldcypress trees that produced 400 or more new roots during the RGP test – and, yes, we counted them all!  Red oak and northern pin oak, on the other hand, are very slow to put out new roots.  For hackberry trees, our other measurements suggest their transplanting issues may be related to their inability to re-hydrate after lifting, storage and transport.  These insights should help us provide some guidelines to growers to help them produce a wide pallet of trees for the landscape market and increase species diversity in the wake of EAB.

Counting roots.  Almost as much fun as it sounds…


The defending champion baldcypress: 614 new roots.

Mystery pits revealed

I’d turned Friday’s picture on end to try to fool you…but to no avail.  Deirdre and Gail both guessed woodpeckers, and yes, this is sapsucker damage:

Though some woodpeckers look for insects under the bark, sapsuckers drill neat lines of wells that fill with sap.  The birds can then move down the line of wells, lapping up sugar water.  (Kind of the avian version of lining up tequilla shots on the bar.)  Healthy trees are generally not at risk of dying from drilling injury, though if the tree is completely girdled that would be a problem.  Trees stressed by other factors could be also be killed by this final straw.

(Deb and @s both thought the photo might be a cactus skeleton, and it certainly looks like one!  Hadn’t thought of that myself.)

Update on root-rotted Cornus kousa

A little more than a year ago I posted a Friday quiz based on a failing Cornus kousa.The answer explained that our landscape has, in part, a perched water table that effectively rotted most of the roots of this poor tree over several years.  Last spring we moved it to a different section of our landscape where we know the drainage is better, and I’ve been monitoring its recovery since that time.


Cornus kousa leaves in 2007


Cornus kousa leaves in 2011

We were gratified to see that the leaves this year are significantly larger than those of previous years.  This tells us that root function has resumed, providing enough turgor pressure to expand the leaves to normal size.  It was especially helpful that we had one of the rainiest springs on record.

Take home lesson:  if a tree or shrub is failing in its current location, it’s worth digging up to see what’s going on.  Bad soil conditions?  Move it to a better location.  Bad roots?  Time to hone your root pruning skills.  But wait until fall to do this.  Transplanting this time of year is the most difficult for plants because of the increased water demands of warmer temperatures and expanding leaves.

Getting Stung Can Be Fun!

Today I was reading a review of Amy Stewart’s new book Wicked Bugs and noticed the glee with which the reviewer noted that stings of various insects have been rated on a four point scale.  Having read Amy’s book I can wholeheartedly recommend it, but in terms of the stings I thought, what the heck?  Let’s see if I can impart some glee to our readers by taking a look at the pain that stings cause (I think it’s kind of like highbrow slap-stick).  So here is a brief review of sting science over the years.

First of all, scientists have known for some time that the pain of an insect (or spider) sting is not necessarily correlated with the amount of damage which the sting causes, so scales that have been used to assess the pain of insect stings do not necessarily correlate with the amount of damage done by the sting.  The stinging critter is not actually trying to kill the person which it stings (though stings may certainly kill smaller critters), rather, it’s trying to keep them away from itself and its family.

The first person in modern history to actually go to some trouble to figure out how badly a sting could hurt you was William Baerg who, from what I can tell, was dared by a colleague to get himself bitten by a black widow around 1923.  He did so, but since the bite didn’t hurt too badly he had the spider bite him again the next day.  After this second bite he recorded his reactions – including difficulty in breathing and talking.  Apparently a masochist, Baerg continued to allow himself to be stung by scorpions, centipedes, and tarantulas — supposedly in the name of science.  And here I’ve gotta say that, as a scientist, you need to set some limits.  Actually the stings must not have affected Baerg too badly – he lived from 1885 to 1980.

Following in the footsteps of Dr Baerg, another scientist, Justin Schmidt, has been sting by a tremendous variety of venomous insects (I’ve heard that it’s over 100 different species) and has actually developed a scale to sort out which hurts the worst.  The scale runs from 1-4 with a 4 being “debilitating” and 1 being a “spark”.  Apparently he never gets stung on purpose – but dang, you can’t be trying too hard to avoid the stings if you’ve got that many species on your “been there done that” list.

Dr. Schmidt published his first paper on the painfulness of stings in the early 1980s.  His work was soon followed by a paper published by Christopher Starr.  The name of this paper was “A simple pain scale for field comparison of Hymenopteran stings”.  This paper includes a list of insects and the level of pain which they cause with their sting – basically following Schmidt’s work – but Starr makes sure that he has at least two data points before he lists the pain which the insect causes.  He also makes a point of noting when the insect was induced to sting instead of having the sting just happen.  According to his chart he was stung by 34 (if I counted right) different insects, and of those stings only 6 were induced.  Obviously this guy didn’t take his work as seriously as Baerg or Schmidt!

Most of the stings that we’re accustomed to – bees and wasps – are around a 2.  There are a few at a level of 4 – probably the most notable is the bullet ant.

Starr ends the conclusion section of the article by listing 6 important rules for grading stings – I found them fascinating – so here they are:

  1. Reports should only be made by adult observers in good health.
  2. Disregard all stings accompanied by allergic reactions.
  3. Reports should not come from observers who are rarely stung.  This is to avoid mixing pain and novelty.
  4. Reports should be based only on events in which a very small number of stings are received at once.
  5. A ranking should never be based on just one sting.  Although individual social wasps probably sting rarely (I suspect that most never do), so that significant day-to-day variation in venom volume is unlikely, uncompleted or grazing stings are uncommon.  It is not known to what extent the regular use of the stinger by solitary wasps causes variation in venom delivery.
  6. Reports on stings received through free attack by the insect (volunteer stings) are preferable to those deliberately induced by holding her between the fingers or against the skin (induced stings).  We are not always so fortunate, though, to be attacked by those species of special interest……[deleted for brevity]

Upside: I’m Two Pounds Lighter!

Cape San Blas
mullet and bass
cheap sunglass
sand flea and crabgrass
beachy landmass*

Had big, relaxing fun last week in the greater Port St. Joe/Cape San Blas/Apalachicola region of the Florida panhandle (billed as the "Forgotten Coast" or more locally "Florida’s Last Stand").  The bays are filled with fishies, the gulf is turquoise and rimmed with soft white sand. Highly under-developed, it’s truly paradise for anyone who likes to boat, fish, kayak, and run with your hounds on empty, wide, dog-friendly beaches.  I’ve got fodder for a couple of posts, but will postpone the flora/landscape observations until next week. 

The news of the awful outbreak of a particularly virulent and dangerous strain of Escherichia coli in Europe coincided with my own mid-vacation, not-so-pleasant experience. Twenty-four hours of bed-bound, trash-can-gripping, don’t stray far from bathroom non-activity while paying for a beach house and boat rental gave me some time to think deep thoughts about food safety.   Salad, meat, seafood, and cream sauces were all involved. I could have ingested one of any number of sweat-and-barf-inducing microorganisms. Being off food and drink for another couple of days wasn’t ideal either. I didn’t go on vacation intending to detox (rather, "to tox").  But at least I was up and about. Renal failure and death takes the E. coli strain O104 to a whole ‘nother level. 

In digging for a bit more information, the usual safe food handling advice has been trotted out in regards to this vicious beast; wash, peel, cook, etc.  But a microbiologist at a Scottish agricultural research center (The James Hutton Institute) has noted there are strains of E. coli “associated with plants, not animals.”  Dr. Nicola Holden says that the bacteria “are not simply sitting on the surface of the plants and are particularly difficult to remove post-harvest.” She goes on to state that these particular bacteria colonize the root system and then “have the opportunity to move to the edible foliage or fruits.”  Yes, E. coli is a motile organism; that’s one way to get from the soil to your salad, but there is evidence it can invade the tissue and move within the plant; no amount of peeling or washing will help. Dr. Jeff LeJeune’s lab at Ohio State was taking a look at this several years ago, especially how E.coli can enter through points of damage from mechanical injury or plant pathogens.  Haven’t had a chance to dig any deeper, but will be having a chat with a friend from our Food Science and Technology Department to find out more. 

*apologies to the Car Talk guys, but I always wanted to do that.

Quiz answers – more or less

I just got back from a 9 hour overseas flight, just in time to post the answer to last week’s quiz.  So now you know…I wasn’t in the states.  More on that later.

As many of you guessed, this is a fig tree (Ficus spp.) of some sort.  I have horrendous taxonomic abilities anyway, but will cover my ignorance with the excuses that the tree wasn’t in flower, nor were there any signs in any of the little parks identifying the tree.  So we can continue to speculate on what species this is.  I do know it’s quite an old specimen, and that there are some Ficus native to the region, but past that I’m clueless as to whether this really is a native species or not.

And where was this huge tree?  In Alicante, Spain, where I spent a few days visiting my daughter who’s studying there this semester.  (Non-scientific aside:  I would go back there in a heartbeat.  If you are looking for a Mediterranean tourist destination that isn’t overrun with Americans, this is the place to go.)

Finally, these cool wavy woody structures are buttress roots, as Jospeh, Shawn, Rotem and Deb all pointed out.  They have both a structural and storage function: like all woody roots they store carbohydrates, but the over-developed flare helps support the tree in thin soils (like here) or in wet, low-oxygen soils (like those where mangroves grow).  In both cases roots can’t reach far enough below ground to stabilize the trunk, so the buttressing serves that function.

@Rotem also noted that branches can root and support the tree.   While the buttress roots in the original photo arose from root tissue, you can see examples of the rooted branches in the photo above.

And I do love the less-than-serious answers some of you kindly provided for our amusement.  Fred’s "rumble strips for drunks" was particularly apropos, since my last night there was one big street party after Barcelona beat Manchester United in the Champions League soccer match.  My daughter and I ended up in our hotel elevator at 8 am the next morning with a fan with no pants.  We did not ask.