Plants dying right after mulch laid... nitrogen robbing or?

turquoisegardenia(6a Toronto)July 12, 2012

Hi everyone,

I would love some input on a problem I'm having. About a month ago, I planted some new purchases from the garden centre (namely astilbe, bleeding heart, impatiens and miniature hostas) in average to somewhat poor soil in a garden that is mostly shaded. Before planting, I amended the soil with a pretty respectable, but not excessive, amount of compost. Aside from what I planted, the garden already contained large hostas, Canadian anenome, and snow-on-the-mountain. I left these plants be, other than the occasional watering, and they flourished.

A couple weeks ago, I covered the ground around my new plantings with cedar mulch. Now, literally all of the new plantings, as well as one large hosta in particular and a good bit of the snow-on-the-mountain, in suffering dramatically. A couple astilbe are completely dead, having shriveled up and turned brown; the bleeding hearts are yellow and pathetic-looking, as are my hostas on the leaf edges; even the impatiens (we all know how indestructible they usually are) are suffering.

I did a search in this forum and it seems most of you are of the view that nitrogen robbing by mulch is a myth. But I just can't think of anything else that could be causing this! Another reason that I suspect nitrogen robbing is that the yellowing is starting at the oldest leaves.

To try to fix the issue, I have raked back the mulch for the time being, scuffled a small amount of blood meal with additional compost into the first inch or so of soil, and done two foliar feedings, first with kelp emulsion and then with vermicompost tea, as well as a vermicompost tea soil drench.

I'm scared to apply the bone meal at the regular application rate- or do anything else for that matter- before I am sure I've correctly identified the issue, as I find overfertilizing in times of stress worsens the problem.

What should I do, guys? Lime? Leave well enough alone? This house is being put on the market within the week and I'm really hoping to work some miracles here...

Appreciate any and all feedback!


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tropical_thought(San Francisco)

What was in the compost? Did they get enough water? There are too many reasons to tell if it was nitrogen damage, but one sign would be the plants look yellow. Shriveling up and dying could be something else. Newly planted plants are vulnerable. Maybe redwood mulch is better then ceder. Cedar has oils. Maybe they the water is not going into the roots of the plants, but just sitting on the mulch? Maybe they had a diseases that was not apparent when you purchased them at the nursery, but became active when they were stressed.

    Bookmark   July 12, 2012 at 10:28AM
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toxcrusadr(Zone 6a - MO)

It doesn't sound like it's the compost, if it affected established plants nearby that were only mulched. So it seems to be the mulch.

I have heard more of these mulch stories this year than ever before, and I don't know what's causing it. A co-worker said that both he and a friend put wood mulch on their potted tomatoes this spring, and they looked horrible. When they removed it, the plants recovered in a week or two. Perhaps it's fresh wood and something is leaching out of it while it's fresh that affects plants.

Pull that mulch off, keep them evenly watered, and wait. I don't think liming or fertilizing is a good idea unless you have a specific reason to do it. It could do more harm than good.

    Bookmark   July 12, 2012 at 10:44AM
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tropical_thought(San Francisco)

You could compost that mulch. Adding starbucks coffee grounds that are free from starbucks, after composting it should be ok. I don't think you have to discard it, since you paid for it. Compost makes a nice mulch also.

    Bookmark   July 12, 2012 at 11:01AM
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mytime(3/4 Alaska)

Although the majority of plants need plenty of water their first season, I find those selections to be even thirstier. Without adequate water the foliage dies quickly. Although mulch helps keep moisture in the soil, it takes more water to get the soil damp in the first place. I suspect it's a simple case of not enough water for new plants.

    Bookmark   July 12, 2012 at 11:08AM
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I had a couple hundred saskatoon seedlings die after mulching with fairly fresh christmas tree chips. Have no idea what the cause was but the chips had something to do with it.

More of the story here.


    Bookmark   July 12, 2012 at 11:10AM
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methinks you have a red herring.

how is your soil holding moisture this summer? you are describing plants that don't have adequate water. a situation that is, for you, limited to those newly planted things. which would not have a root system estadlished to deal with a dry year.

you are not describing nitrogen defiency. which can occur, does occur. it's just something to be aware of...but the situation where it does occur is high moisture, not dry. and the benefits of mulching for outweigh the benefits of not.

    Bookmark   July 12, 2012 at 1:40PM
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turquoisegardenia(6a Toronto)

It's entirely possible it's a moisture issue. I have been watering, but it's been at least two weeks since it rained and we all know hand watering only gets the topsoil. I'm going to try a slow drip today. Thanks guys!

    Bookmark   July 12, 2012 at 2:09PM
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toxcrusadr(Zone 6a - MO)

Report back and let us know how it turns out.

    Bookmark   July 12, 2012 at 3:51PM
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mytime(3/4 Alaska)

My solution for new plants when I don't think I'll water them enough when it doesn't rain enough...
Cut the bottom off of plastic drink bottles. Bury the bottle upside down (with the lid off) at a slant towards the roots of the plant. Everytime you water, fill the bottle...if it drains quickly, I fill it a couple of times. This gets water down to the root zone of the plant (if it's a large plant, I put bottles on opposite sides of the plant). If it's a shrub I planted in the fall, I leave the bottles in through the following summer. Otherwise, I remove the bottles and fill the resulting hole with soil either in the fall or the following spring. I haven't lost a plant since I started this method.

    Bookmark   July 13, 2012 at 12:18AM
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How have you been watering?
How much water have you been delivering?
How moist is the soil these plants are growing in?
Newly transplanted stuff will have a very hard time getting enough moisture from the soil, especially if tghe weather is hot and dry and those newly transplanted things loose moisture faster then the undeveloped root system can supply. Leaf edges that turn brown indicate the plant is suffering from "scorch", when a leaf looses moisture faster then the plants roots can supply it.

    Bookmark   July 13, 2012 at 7:49AM
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How is everything doing now?

    Bookmark   July 17, 2012 at 1:55PM
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For the record, I've had plantings turn sick with cedar mulch. I don't use it anymore and if I use wood chips I only use ones that have been exposed to the elements for a while (or composted). Maybe it's the oils, maybe it's nitrogen robbing. It would certainly be convenient to use fresh wood chips, so if anyone is using them successfully, I'd be interested to hear about it, but so far my experiences have not been good.

    Bookmark   July 20, 2012 at 12:04PM
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tropical_thought(San Francisco)

You do need a layer of compost on the ground underneath the plants, and then you need to be on a feeding schedule with them. Preferable a liquid mild food every two weeks. Then try to move away some of the mulch from the stems and use redwood not ceder. I did my whole yard in redwood microbark and I don't have any problems. Fish emulsion if you want to go organic with the food is fine. Just a souse of nitrogen is needed, but you would do that anyway right?

    Bookmark   July 20, 2012 at 12:38PM
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Fresh wood chip mulch slowly killed off a bunch of my trees and the ones that lived have taken almost 2 years to recover. Leaves, pine needles, kitchen scraps, are good. Wood chips need to sit out at least a year before using.

    Bookmark   August 3, 2012 at 9:05PM
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I placed a thick, 4 to 6 inches, layer of fresh wood chips around some Privets several years ago that were not growing very well and after those fresh wood chips were plunked down those Privets greened up and grew an additional 12 inches. I have also placed aged wood chips around other plantings and have not seen the same results although those other plantings did show improvement when the soil moisture levels improved.
If there is a slow down in growth after wood chips are plunked down, on top of the soil, as a mulch something else is wrong with the soil.

    Bookmark   August 4, 2012 at 6:35AM
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Death due to the fresh wood chips. Dont take a chance, learn from others mistakes.

    Bookmark   August 4, 2012 at 11:49AM
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tropical_thought(San Francisco)

How does sitting for a year change the wood chips? Do you mean a year of just sitting or a year in a compost bin?

    Bookmark   August 4, 2012 at 12:43PM
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girlgroupgirl(8 ATL)

I've got fresh wood chips all over my garden. My very very happy garden! Know what's in the chips - here if you ask for free chips you could get something in them you don't want on the garden like Tree of Heaven, or another allopathic tree species. There is also the odd chance that disease or fungus will be a problem. A friend had a fungus in the dead tree contaminate her garden.

    Bookmark   August 5, 2012 at 6:29PM
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I have also witnessed the mysterious ability of wood chips to cause plants to lose color and slow in growth. They are a great cheap way to slow evaporation, however, so I keep using them and I recommend them - but with some granule 10-10-10 underneath, and with compost. Some compost guides say that bark consumes some nitrogen while breaking down. I use just a little bit of fertilizer, though, and it keeps the plants green despite the 3 inches of bark.

    Bookmark   August 6, 2012 at 12:19AM
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toxcrusadr(Zone 6a - MO)

If you're getting wood chips from a tree crew, you can ask them what rules they have for what goes in. The rural elec co-op that I got chips from says that they won't chip a tree that is already dead when they take it down, so as to avoid spreading tree diseases wherever the chips go.

    Bookmark   August 6, 2012 at 10:51AM
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