The Garden Professors™ – Page 115 – Advancing the science of gardening and other stuff since 2009

Tomato takedown

Well, Dr. Rohwer was right – he thought you’d get this more easily than I did! Ray and Jon were spot on – this is classic juglone toxicity from those walnut trees (Juglans spp.) you see in the background. Many of these leaves ended up on the roof, leaching into the rain barrels (good sleuthing Ray and KennyG!), the water in which was used in irrigating the vegetable garden. In fact, Dr. Rohwer divulged that the rain barrel water was quite brown from the walnut leaves. Thus, the tomatoes met an unhappy end, because tomatoes definitely do not love walnuts.

Juglone toxicity, an example of allelopathy, is an interesting phenomenon – it does not affect all plants equally. In fact, this clue was given in the puzzle, when Dr. Rohwer mentioned the "garlic and carrots, amongst young beets, onions, kohlrabi, and bolting radishes and spinach" also in the garden. Many of these vegetables are known to tolerate juglone, as are various landscape plants. (There is an excellent publication from Purdue on juglone toxicity with lists of tolerant and sensitive species.)

Juglone is most prevalent in the nuts, roots and leaves of walnut trees. This makes sense: germinating walnut seeds and expanding root systems are both able to kill their competitors, retaining more resources for themselves.

Juglone tends to be less of a problem for established trees and shrubs, as their root systems are more extensive; seedlings would be the most sensitive stage. And walnut wood used as part of a wood chip mulch has not, as far as I know, been shown to cause juglone toxicity in landscape plants.

When criticism becomes libelous

Dr. Cregg is on vacation for a few weeks so I thought I’d post something today by trolling the web for discussion of my horticultural myth columns. And when you go fishing, you know you might catch something you didn’t really want. In this case, personal and professional attacks.

Like the rest of the GPs, I relish vigorous debates on different horticultural practices and products. Ideally, these debates are based on science, so that we’re all friends afterwards and could go out for beer if we all lived in the same community. But when criticisms become personal, malicious, and in some cases out-and-out untruths, what should one do?

I have a relatively thick skin and ignore most of the nasty comments, but when my integrity as a scientist is challenged, I really have a problem. For instance, one blogger states “The fact that some – not all – of her articles have very little basis in reality and are widely disputed and even denounced in horticultural circles should be pointed out before anyone takes them immediately to heart.” Another blogger remarks “What little I’ve read about this Chalker-Smith person leads me to believe she is an “opinion for hire” much like some “expert witnesses” one sees in courtrooms.” How about this? “She tried to prove compost tea is bad by PURPOSELY using E.Coli infested compost (without telling anyone about it) and proclaimed it as unsafe product to use.” And so on.

I can guarantee you that if I didn’t base my publications in reality, or if I were an “opinion for hire” I would be in serious trouble with the university. The truth is I research the science behind topics and then have at least one colleague review them. (Sometimes that colleague is my husband, also a PhD in horticulture and one of my most honest critics.) The compost tea diatribe is so outlandish it took my breath away.

So onto my question: what should one do when one’s professional reputation is libeled? Do I continue to ignore it? Do I wade into these debates, thus giving credibility to the libeller? These people hide behind their anonymity – none have the courage to simply email me and voice their criticisms.

I’ll be curious to hear from my GP collaborators as well as non-academics.

(Hurry back, Bert. This was a painful experience.)

A quiz – from our visiting professor

We’re glad to have Dr. Rohwer back for another visit! Here’s his Friday quiz – see if you can figure out what happened to his tomatoes.

"Exhibit A is a tomato in our garden. We had 2 tomatoes last year a couple feet away from this one, they met the same fate. Wilting at about flowering time, and water did not resolve the wilting. Previous to last year, the area was turfgrass for who knows how long. There was no vascular discoloration or oozing."

Charlie also included more evidence: "Exhibit B – arrow points to former location of the wilted tomato behind the garlic and carrots, amongst young beets, onions, kohlrabi, and bolting radishes and spinach. Exhibit C – arrow shows the former location of the tomato. In the far background you can see our roof. We have 2 rain barrels collecting most roof runoff." This water is used in their vegetable garden.

And here’s a bit of diagnostic information: "Plants sensitive to this condition exhibit symptoms such as chlorosis (foliar yellowing), wilting, and eventual death."

Can you figure out what happened? Answer on Monday!

Propagating in the air

Most gardeners that I know have tried to produce roots on stem cuttings from plants that they like. Sometimes this turns out well for them, particularly if they are working with what we call an easy-to-root species, and sometimes it turns out poorly. OK, in all honesty, it often turns out poorly. The problem is that plants like very particular conditions when they’re growing roots and the typical gardener is going to have a tough time providing these conditions. So here’s an option. There is a method of propagation called air-layering which works on many plants that stem cuttings won’t work on and which doesn’t need all of the specialized equipment either. It’s not a sure-fire technique, but it’s more likely that the average gardener will get this technique to work than any other (with the exception of seeds).

Here’s how it works. Select a small branch from the plant you want to propagate. Find a point on the branch about 6 to 12 inches from its apex and then cut out a ring of bark around the circumference of the tree. This will allow water and nutrients to flow into the branch (assuming you didn’t cut too deep), but it won’t allow the carbohydrates produced in the branch to flow down the stem — instead they’ll be stuck where you made your cut and be used by the plant to produce new roots.

Around the cut you may apply a rooting hormone. This will help the root production to some degree. To keep the wound moist apply a heaping helping of moist peat and keep it in place with plastic wrap — or a cut up sandwich bag. Wire ties, elastic bands or string will hold these in place. Now you just sit back and wait.

It usually takes anywhere from 4-8 weeks for roots to emerge (you’ll see them when they do because they’ll push up against the plastic wrap). Once the roots are there plant your new tree/shrub/perennial in it’s own container just like you would any new plant, care for it as you would any other plant, and then plant it out if you so choose (I like to keep young plants like this in a container for at least a few months — the landscape is usually a harsher environment than a container, and so the time in the container gives it a chance to get stronger and store needed nutrient reserves.)

Five little lavenders – an update

Long-time readers of our blog might remember my August 12 column (linked here for your convenience). You saw my giant lavender plant devolve into 5 small plants with tiny spiraled root systems that put Marge Simpson’s beehive to shame. In any case, I promised to keep you up-to-date with their progress.

Transplanting in August is a risky proposition, especially when you prune out root defects. Nevertheless, all but one of the five survived the summer and here they are earlier this spring:

The one that didn’t make it was in the upper left corner of this south-facing landscape, where there is a lot of reflected heat from the nearby bricks and concrete. (You can see the empty spot where it was in this photo.)

If you haven’t tried corrective root pruning before, I’d encourage you to try it with an inexpensive shrub. Your best bet will be older containerized plants in the “sale” section of your nursery.

John Bartram Lives!

Yep, there he is. Showed up at our state Master Gardener College, just last week. I even went to dinner with him. The snake-on-a-stick startled the bartender just a bit.

The elder Bartram (his son William was also a great botanist and explorer) was the Royal Botanist to King George III and a member of the Royal Academy of Sciences, Stockholm. As with many of the Great Plant Explorers, his life combined botany with politics,
adventure, and lust [for plants,anyway]. Someone should make a movie…

Probably best know as the discoverer of the soon-to-be-doomed little tree, Franklinia
alatamaha, he also was responsible for the introduction of lots of
other North American native garden staples such as rhododendrons,
Kalmia, and deciduous magnolias. Bartram died in 1777, but has recently been resurrected by Kirk Brown, master thespian and all-around talented guy.

Kirk works with Joanne Kostecky Garden Design in Allentown, PA, and is a director for Garden Writers of America. But his passion for the life and times of fellow Pennsylvanian John Bartram takes the audience far beyond the usual gardening lecture. His presentation "John Bartram: The King’s Gardener" unveils the travels, collections, and psyche of the father of the nursery industry in the original thirteen colonies. I love the review by Stephanie Cohen (The
Perennial Diva!) "Kirk Brown did not imitate John Bartram, he actually
became him…anyone who has an interest in history or horticulture will
be spellbound by this presentation." She’s absolutely correct. For more on John/Kirk, check out www.johnbartramlives.com.

Questions on sustainability

Linda’s recent post on the sustainability of topiaries got me to thinking, is any horticultural practice sustainable? And, does it matter?

Picking up on the topiary theme I thought of the ultimate form of tree manipulation, bonsai. I few years ago I visited the National Arboretum in Washington DC, which includes an incredible bonsai display. Some of the bonsai specimens in the collection originated in Japan and are over 300 years old. Is 300 years long enough to consider this a sustainable practice? Does it matter as long as there are individuals willing to devote the time and effort to tend and prune these awesome and inspiring plants?

More recently I visited the International Rose Garden at Washington Park in Portland. Established over 90 years ago the garden is one of the premier attractions in Washington Park and in Portland. Maintaining the garden, however, requires paid staff and an army of volunteers. Is 90 years long enough to consider this sustainable? Does it matter as long as the city is willing to commit resources and volunteers are willing to line up to dead-head and pull weeds?

Closer to home, I maintain about an acre of my place in lawn and various beds – trees, shrubs, herbaceous perennials and even a few (gasp) annuals. Is this sustainable? Does it matter as along as my family and I enjoy our surroundings and are willing to commit the time and effort to mow, weed, edge, prune and dead-head?

Clematis mystery solved

Friday’s quiz was a tough one. Bernadette and Lisa B. gave it a good shot, guessing that this might be a phosphorus deficiency. While they’re on the right track (it is a nutritional disorder), the mineral of interest is iron, and it’s a toxicity problem, not a deficiency.

Under wet conditions (the affected Clematis is in the part of our landscape with a perched water table – see the March 15 posting), iron is predominantly in the Fe⁺² form (ferrous) rather than the Fe⁺³ form (ferric). The ferrous form is easily taken up by roots, and when leaves accumulate too much iron they turn reddish-brown. This diagnostic characteristic is called bronzing, and it’s different than the reddening caused by anthocyanin accumulation. (As an aside, nonagricultural landscapes rarely have phosphorus deficiencies and are more likely to contain excessive levels of phosphorus.)

Finally, all this talk of iron has reminded me of one of my favorite chemistry puzzles – see if you can figure out what this is:

Give up? It’s a ferrous wheel!

Friday quiz – a tale of two clematis

These two Clematis are the same cultivar growing in my landscape about 15 feet apart. Both are growing on a fence facing north. Compare the leaves of the two:

Normal, happy Clematis

Not-so-happy or -normal Clematis

What do you think is causing the leaf discoloration? Very large hint: this is not a biotic stressor. Another hint: you’ve seen this part of our landscape before…back in March. For full credit, identify both direct and indirect environmental stress (in other words, [1] what is directly causing the discoloration in the leaves, and what is allowing [1] to occur, thereby causing stress indirectly)?

Answers on Monday – have a happy 4th of July.!

An interesting blog for science-loving oenophiles

There’s a new blog already generating a lot of discussion among wine aficionados. The not-so-subtly named “Biodynamics is a hoax” discusses all things related to Rudolph Steiner and his philosophies, including the pseudoscience of biodynamics.