Let's debunk some gardening myths

I've heard and read so many times that nothing grows well under a black walnut tree. It secretes a substance called juglone, which allegedly causes the stunting, wilting, and death of most plants growing within a certain distance from the trunk or even growing under the tree's branches. Most of the articles about the toxicity of a black walnut tree specifically warn that pear trees will die if they are planted near a black walnut tree.

I have a large black walnut tree in my garden. It's bigger than large. It's a huge mammoth of a tree. It came with the house when I bought it 25 years ago, so I don't know how old it is. A pear tree, which also was in the garden when I bought the house, is growing directly under the branches of the black walnut, no more than 15 feet from the trunk, and it's still very much alive.

My tree is so big that its branches cover about one-fourth of the garden behind my house. The space below it is densely planted with almost every variety of plant -- from azaleas and rhododendrons to roses and hibiscus. It has never killed anything. The nuts from the tree fall into nine flower beds and are regularly shoveled underground when I dig holes for new plants. They have never killed anything either.

Japanese irises do not require bog like conditions. An extra sprinkle of water is beneficial and acid soil is required but I have had JI's growing in dry shade and they bloom beautifully.

Great! I want to mention two of them.

The Epsom salts I referred to before.

And compost tea.

I think I'll get yelled at for both but especially the compost tea so I'll be as judicious as I can.....



This message was edited Feb 13, 2009 8:13 PM

Pirl, that's great to know about the Japanese irises because I'm running out of room in my bog garden and I want to grow a lot more of those lovelies.

David, please expand on the epsom salts and compost tea.

Apropos of the black walnut, I did some research last night and was amazed to see the lists of plants that supposedly cannot be grown under this kind of tree. The references to azaleas, rhododendrons, and peonies particularly amazed me because all of my azaleas, rhodies, and peonies -- dozens of each -- are growing right under the tree and close to the trunk.

There was something else, though. All of the articles said that the toxic properties of juglone are reduced dramatically by soil with good drainage, and as I've said before, in this forum and others, I have great soil with ideal drainage, so maybe that's the reason my black walnut has never had an adverse effect on any plant.

I trying to figure out what is true about fertilizers. If you use non organic fertilizers are you really destroying all the microbes in the soil. Ive been using both since I started growing. Non organic in the spring when its cool, then I try to go more organic in the summer. Am I destroying my soil? hmmm

Zuzu i think you could grow anything under a black walnut tree, oh wait you already do lol.


David I am most curious as well please go on. I spend way to much money on epsom salts.

I want to believe in Epsom Salts and organic fertilizers but simple compost works best for all my plants.

This year I'm trying vitamins.

steph...I had my soiled tested at UConn the last 2 years and to my surprise I have an excess amount of magnesium in the soil. Among other things, that can hinder the uptake of calcium.

Adding Epsom Salts, magnesium sulfate, would be counterproductive.

What I'm trying is adding gypsum--calcium sulfate. The theory is the magnesium already in the soil will replace the calcium in the gypsum, forming magnesium sulfate (Epsom Salts) and wash out leaving the calcium (of which, the soil test shows, I have a barely optimum level).

Because of the magnesium levels here, dolomotic limestone is also contraindicated. I use calcitic limestone instead.

Its not easy to find in CT. Asked for and explained why I needed it at Ballek's Garden Center in East Haddem. A clerk was very interested and said I had to come back and talk to their horticulturalist. She had mentioned excess magnesium in soils in this area and the need to carry an alternative liming agent. But the public is so convinced "dolomitic limestone" is the best thing it is difficult for vendors to stock anything else.

I've written to the Epsom Salt Industry Council asking why it recommends using Epsom Salts on a regular basis without concern over if the soil needs it or not.

No reply.

Linda Chalker-Scott, at Washington State University, has information on how effective Epsom Salts are here:

http://www.puyallup.wsu.edu/~Linda%20Chalker-Scott/Horticultural%20Myths_files/Myths/magazine%20pdfs/EpsomSalts.pdf

Bottom line from what I've read: If your soil needs magnesium, Epsom Salt will help but a less soluable magnesium compound is better. Most soils are not deficient in magnesium. If you have adquate levels of magnesium, Epsom Salts are a waste of money and may actually harm plants (plus the run off is problematic)

I can't remember what brand but its the one the garden center sells, has a recommended by the master gardeners sticker on it. I realized I was most likely over doing it when I saw one of the fertilizers I was using also contain the salts. There are some interesting articles on that site.

what about adding things like John and Bobs soil conditioner?

Another myth is that mushrooms growing around trees, or on nearby lawn means your soild is deficient. A lot of fungi lives in the soil, and it's just sprouting like any plant. Some fungi help trees take in nutrients.

And how about that watering plants during the day burns them. Not true. It might not be as effective as sone of the water evaporates, but think of all the big businesses that can't cover their plants during a rainstorm, and then the sun comes out right after.

The mushroom one is funny. I have heard that before too. I wonder how that got started?

Speaking of rainstorms, what about the myth that overhead watering is bad for roses? Where are these gardens with low-lying horizontal rain? How can overhead watering be avoided? And why should it be?

I only water roses from overhead. It knocks aphids and other bugs off them, not to mention dust and other things that invariably land on the petals and foliage, and it guards against powdery mildew, which can't grow in a wet medium. The only roses that have ever suffered from powdery mildew in my garden are the huge monsters that can't be watered from overhead without a helicopter.

I don't have a lot of roses, but due to the size of my gardens, I need to use towers to water. I have never had a problem because of it. Actually even my lilacs have been quite mildew free.

How about the pruning of roses at just the right spot on each cane with an outward facing leaf bud. This year the big ones are getting a buzz cut grabbing a bunch of canes and whacking off a third. The little ones are getting no haircut.

Yes, Louise, that's the latest word from the experts. Buzz cuts are just as good as all that pussyfooting around with diagonal cuts exactly one-fourth of an inch above the leaf bud.

I must admit I haven't resorted to a buzz cut yet. I don't want to have little black stumps of dieback on every branch, so I'm still doing those close-to-the-bud cuts. I am saving hours and hours of pruning time, though, by ignoring the now disputed rule of opening up the middle of each rose bush. Apparently, instead of providing space for air currents and deterring black spot, this actually stimulates the canes to fill up the middle twice as thick as before and compounds the black spot problem.

pollyk...my dad was a builder. He always looked for mushrooms when evaluating a lot. An inordinate number of mushrooms often meant someone evened out land not with good topsoil but brush, logs and other debris with enough dirt to make it look nice.

For a while. Long enough to sell it.

over head watering seems like the normal way.

Hmm interesting theory on pruning. I pruned everything really well this year. It all just was ginormous by the end of the summer. I know that is not a word but all the kids I work with are using it lol.

A lot of fungi does live on dead roots and old buried timber and lumber David Paul. And actually that really enhances the earth after quite some time, but many more fungi live in harmony with trees and shrubs assisting in water uptake and nutrient uptake. And I bet your Dad knew his shrooms!

So yes that is a garden fact, but a lot of myth around places that have never had the soil disturbed and have fungi growing. People think it needs lime, or fertilizer, but in actuality it's nature doing it's thing.

When we used to use fresh wood chips, from the guys who cut down trees around here, we'd get mushrooms the following year. The decomposing wood was the reason but I loved the smell of them and the natural look to the garden. Columbine spreads seeds best in wood chips.

I'm with you for the netueral look in the garden.
Cant understand why people use the red stuff.
Years ago we used to get cocoa shells.The back yard smelld great for months.

My neighbor from long ago, Mrs. Loeffler, used to use the cocoa shell mulch in one large area right next to our living room window. I'd always keep those windows open to get the smell. Yummy!

Put me down as another red mulch hater.

It seems to blend in-in Hawiian gardens

Myth: hostas need shade.

Many don't. Many just want cool roots. I'd never shy away from planting one that supposedly wants only shade if I wanted it in a sunnier spot. It's worked for us beautifully in the past and I wouldn't hesitate to do it again. We've had ten giant Plantagineas out in full sun for years and they thrived. All were planted with a lot of compost.

The ones that really insist on shade will look so awful that we can just give them the conditions they demand.

Add me to the red/ orange mulch hater. Nothing less natural looking.

I can't stand the stuff, either. It seems like every other house up here uses it, and it is right up there with those icicle lights at Christmas. Everyone has them and for no good reason. I will duck now, waiting for the slings and arrows!

Supposedly, it's a myth that clematis need their roots shaded. "Roots in the shade, heads in the sun." ...not!

Myth 2: You need to use pruning paint on large cuts on trees and shrubs. (NO covering is best and allows for quicker healing)

Myth 3: You need to stake newly planted trees. (Stake minimally only if there is danger of an evergreen or top-heavy tree blowing over. Otherwise, not staking makes the tree develop stronger roots.)

This message was edited Feb 15, 2009 10:38 AM

mamasita: It's safe to come out now ! LOL No airborne daggers coming your way.

As far as Clematis go, I stopped with the "pussyfooting" pruning methods and I've never had better results. (Leave it to Zuzu to use the word " pussyfooting " LOL ) All I can say is that if it works for you, do it.

It always cracks me up how non-gardeners will leave dried up flower stalks on plants to "give them another chance"...(i.e. agapanthus...)
They leave them on the plant for years and they look ridiculous.

Another chance to do what?

Bloom again, from those dried up sticks. I'm serious !

There's a wealth of information here. Staking things and painting cuts are such tedious chores. Your post, HoosierGreen, is going to save me a lot of time and effort -- time which would be better spent by sitting down and having a margarita.

Which you can do, Zuzu, since it should be your birthday by now.
Happy Birthday!

You're right. It is my birthday even in California now. Let the celebration begin. I've just armed myself with a mudslide.

We bought this 20 yearold house two years ago..
There is a line of spruces between us and the neighbors .
Trees must have been in since the house was built bexause (roumor hasit) the contracter did all the landscaping and mad rules about what could be planted.
We noticed one of the trees was dying and on further inspection ,saw a green hose wrapped around the trunk just above the second set of branches.
When the tree cutters were here last fall ,they said someone had tried to stake and straighten the tree and never removed the wire supports,they grew into the trunk and killed the tree.
No matter- - - - Now I have a full sun part of my shade garden.

And now you know how to get some more sun.

As a matter of interest for anyone using Cocoa mulches ~ http://davesgarden.com/community/forums/t/949607/

JD - here I thought our neighbor, Anne the Dumb, invented that one with not deadheading her daylilies to "give them another chance". Someone beat her to it I guess.

Here's a thread for Zuzu's birthday: http://davesgarden.com/community/forums/t/953035/

I'd like to put in a cautionary word here about black walnuts, they do kill other plants. Zuzu, you must have a particularly blessed soil. We have heavy clay loam and the black walnuts that were here when we moved in have killed lots of things, some among the recommended to grow under black walnuts.

The important thing about adding anything to your soil is to first have it tested. We test the soils on our farm regularly and adjust any lime or fertilizer to the new tests. Just adding things willy nilly is a waste of money and, as David said, can be harmful. There is probably a lot of over-fertilization going on. Generally speaking, I don't fertilize my flower beds at all, instead letting the mulches (bark and wood chips, straw and old hay) do that as they break down.

Around here, the mushrooms grow best in the pastures regularly inhabited and pooped upon by cows. Good sign of a fairly rich soil, in my opinion.

Happy birthday, Zuzu.

Thanks for the birthday greeting, Kathleen, and I'm sure you're right. Drainage is the key.

As for overfertilization, I agree completely, especially in the case of roses. An old local gardener once told me that overfertilization was almost always the problem when people called him because their roses weren't doing well.

You know that is something that really needs to be talked about more. I remember when I first started growing roses that I went gung ho on fertilizer.


ok myth or not to much nitrogen in roses causes vegitative centers?

A lady at our last rose society meeting said there was a study were this is proven false I need to track down the info it was pretty interesting.

I'm not sure about the nitrogen, Steph. I've only had blooms with vegetative centers twice. One rose had them shortly after I bought it at a nursery and brought it home, so it could have been from a nitrogen overload in the nursery's fertilizer, but the other rose had blooms with vegetative centers only once in the last 20 years, and nothing had changed in the soil, so it couldn't have had anything to do with nitrogen. I had heard it's sometimes caused by drastic temperature changes.