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.

Three part plant quiz

I’m out of town this week, and taking lots of plant pictures.  Here’s an interesting tree, quite common in the city where I’m staying:

Question 1:  What kind of tree is this?  (Genus is good enough – species might be hard to tell.)

Question 2:  In what geographical region might I be staying?  (The tree is native as far as I know.)

Question 3:  What are these woody structures called, and what function do they play?

Answers next week!

Answers to blue flower quiz

Paul, Joseph, Kandi and Derek are all, apparently, Puya fanciers.  But!  It’s not P. alpestris, but P. berteroana – a species whose flowers are more turquoise than sapphire:

Yeah, Kandi, check out those spines!  Even taking pictures is deadly!

And Paul and Joseph were correct – the long green structures are sterile (they bear no flowers) and serve as bird perches.  The nectar almost runs out of these flowers, and as the birds get a sugar fix their heads are covered in pollen.

Thanks to Paul Licht, Berkeley Botanical Garden Director, for my short but fabulous tour that included these beauties.

Our visiting GP takes on fertilizers

Like many readers of this blog, I’m like a kid in a candy store where plants are sold.  I try to justify the extra cost of a large annual pot instead of a scrawny 4-pack, or I imagine I’ll find room for that lime green Heuchera and my wife will learn to love it.  But unless I keep my blinders on and stick to the shopping list, I’ll probably leave with a fertilizer.  This year, I’ve purchased 12-0-0, 5-6-6, sulfur, and some 5-1-1 liquid.  Those go with my 6-9-0, 11-2-2, 9-0-5, 2-3-1, and 4-6-4.  I can explain why I ‘need’ each one.  I have a decent idea what my soil is like because I’ve had it tested (though I’m due for another test). But I’ve always questioned how those bags of fertilizer can know exactly what my garden needs.  The rates listed on the bag imply they’re universal under all circumstances and will give great results if the directions are followed.   Is that true?   And at what cost?

For example, 2 of the bags are listed as ‘lawn’ fertilizers (the veggie garden doesn’t care about that though).  But if I apply these to my lawn at the rate listed and 4 times per year, I’m adding 3-4 pounds of nitrogen per 1000 ft2.  That’s a reasonable rate if I irrigate and bag my clippings, but I don’t do either.  Therefore, I only need ~1 pound of nitrogen, not 3 or 4 (see this publication for more info). I just saved myself some money by disobeying the bag. That extra nitrogen isn’t useful for making MY lawn healthy.

One of my fertilizers is labeled ‘tomato’.  If I do exactly as the bag tells me for tomatoes, I would be applying the equivalent of 400 pounds of nitrogen and almost 500 pounds of phosphate per acre.  So what?  Well if I look at a guide for how to grow tomatoes commercially, I’d notice that the recommended nitrogen rate is 100 to 120 pounds per acre, and phosphate is 0 to 240 pounds per acre.  Yes, those are commercial guidelines, but they shouldn’t be too far off from garden recommendations. And of course, recommendations should always be based on soil tests.  But 4 times the N and 2 to infinitely more times the amount of phosphate than is required? That’s likely a waste of money at least. And yes, those recommended guidelines are real: you CAN grow food without adding phosphate or potassium-containing fertilizers.  If the plants you’re growing don’t need much and your soil has plenty, you don’t need to add any.

Say I’ve got an acre of onions (Fig. 1; not quite an acre). One of the bags of fertilizers, were I to follow its instructions for fertilizing ‘vegetables’, tells me that I should add 100 pounds of nitrogen and 120 pounds of phosphate and potash at planting (per acre), followed by half that partway through the season (next to the row). The commercial production guidelines tell me that the nitrogen rate is similar to what the bag of ‘vegetable’ fertilizer says, but I actually need about 7 times less phosphate and potash (based on my soil test results; I have quite a bit of P and K already in my clay-loam soil). I don’t want to add stuff my soil doesn’t need, so I use my shelf full of bags, a scale for weighing pounds of fertilizer per cup, and some math to come up with a custom fertilizer regime that suits my soil and the onion’s needs (see Table 1, and remember that the numbers are for MY soil, not necessarily yours).

One problem with using extra fertilizer may be in the extra cost (wasting nutrient the plant won’t use), but that depends on what fertilizer it is and how much it costs. Another problem may not be immediately apparent, and that is nutrient deficiencies. Too much phosphorus can cause zinc deficiencies, for example. Excesses of some nutrients can create greater chances for pest and disease problems. One big problem with using too much is the potential for these extra nutrients to go where they shouldn’t be, like in groundwater, rivers, lakes, and streams. And as Jeff has mentioned, phosphorus fertilizers won’t be around (cheaply) forever.

Do the work of figuring out what kind of soil you have and what’s in it, what your fruits and veggies need, and what kinds of fertilizers can do the job for you.  Heck, you can even organize your fertilizers based on “cost per pound of nitrogen” to see where the best bang for your nitrogen buck will be.  But none of us are THAT obsessed about our fertilizers, right?…. [$ per bag / (pounds per bag * (% nitrogen/100))].

As a reminder, the numbers on your fertilizers are percent nitrogen, phosphorous (as ‘phosphate’, P2O5), and potassium (as ‘potash’, K2O).  One cup is 16 tablespoons, and an acre is has length of one furlong (660 feet) and width of one chain (66 feet), or 43,560 square feet.  Side rant: metric rocks.

Safety first?

I was driving around town recently and saw a tree service crew clearing up some storm damaged trees. Because of my line of work I usually do a little rubber-necking and try to assess why type of tree came down and what issues may have preceded it’s demise. In this case, however, I was struck not by the trees but by the tree crew. What I saw left me speechless. Well, here, see for yourself…


No eye protection.  No hearing protection.  No sign of a hardhat, face-shield, or chaps by the chainsaw.  No personal protective equipment anywhere as near as I could tell.  Of course the photo illustrates a lot of what’s wrong with the landscape and tree service industry.   Economists tell us that this industry has a ‘low barrier to entry’; in other words any one with a chain saw and a pickup truck can put an ad in the classifieds and call themselves a tree service.   As a consumer, you may not care if the employer makes their employees where personal protective equipment (PPE).  But if they don’t care about their employees’ safety, what else don’t they care about?


Periodically I’ll write an article for a newspaper or other media on selecting an arborist.  I always make the point that you get what you pay for and urge consumers to compare bids and companies carefully.  Truly professional tree services have to cover the cost of hiring and retaining quality employees, worker training, proper equipment (including PPE), and insurance.  If you skip over those things, like Fly-by-night tree service here, it’s probably not too hard to come out with the low bid.

Bt in the Bloodstream!

Over at my favorite blog (besides this one of course!) Garden Rant, Amy Stewart posted about exploding watermelons — which Linda blogged about below — and about how Bt from genetically engineered food had found its way into our blood stream (and the bloodstream of unborn children).  Sounds pretty scary doesn’t it?  I’m not going to tell you it isn’t a little troubling, because it is, and I absolutely do not think this finding should be disregarded.  But the truth is that I’m not too worried about Bt in the bloodstream for the following reasons:

1.  The world’s ending on Saturday anyway, right?

2.  It’s impossible to tell from this study where the Bt toxin came from — I do think it probably came from transformed crops — HOWEVER, as scientists we can’t make that assumption.  We eat Bt all the time EVEN IF WE EAT NO TRANSGENIC CROPS because this bacteria is found all over the place.  I would have liked to have seen testing between people who eat transgenic food and people who eat no transgenic food.

3.  The Bt toxin is extremely specific in terms of what it affects in an insects gut.  It’s unlikely (but not impossible) that it would react with anything in our bloodstream (or an unborn child’s bloodstream).

4.  There are arguments over whether transgenic crops are sprayed more or less than than non-transgenic crops — but for insect control transgenic crops are generally sprayed less — and non-transgenic crops are sprayed with some seriously nasty stuff including nerve toxins.  If I get to pick my poison I’ll go with Bt any day.

5.  As a rule you should NEVER worry until a second study confirms the findings.  This paper is important enough that you can be sure that within a year someone else will try something similar.  If the findings hold my concerns will increase somewhat.

6.  Finally, the dose makes the poison.  Bt has been fed to various mammals for years to determine the effects that it has on them — and it generally has little effect, even over long periods of time.  These animals, obviously, had the toxin in their blood (just because it wasn’t tested doesn’t mean it wasn’t there).

It should be no surprise that when we eat something with a toxin in it, that toxin gets into our blood.  When you eat garlic — toxins from the garlic get into your blood.  When you eat hot peppers — capsaicin (an insecticide) gets in your blood.  When you drink alcohol — you get the picture.  Is it bad for things to be in the blood?  It depends entirely upon the thing and the concentration.  This article talked about fetal issues so lets use a fetal example — Aspirin is considered a bad idea during pregnancy — it can get into the unborn child’s bloodstream.  However, low doses of aspirin can reduce risks of pre-eclampsia.  By the way, a chemical very similar to aspirin is also known as a fungicide….(actigard).

So, there are my reasons for not being too worried.  Could I change my mind — YES.  Could I be wrong — YES.  BUT as a scientist who reads a lot of what I’ll call “reactionary/radical articles” I have my doubts when I read about the next thing that’s going to kill us all.  If we responded to every troubling article we’d never leave our houses.  BUT there’s always that one important article that warns us about something real — and we need to be on the lookout for it.  My reaction to the Bt threat — this isn’t it — but time will tell whether I’m right or wrong.