Is anyone aware of oak leaves containing chemicals that inhibit the growth of other plants?
I'm particularly interested in Quercus garryana the Garry Oak.
-
opabinia51
- Super Green Thumb
- Posts: 4659
- Joined: Thu Oct 21, 2004 5:58 pm
- Location: Victoria, BC
-
opabinia51
- Super Green Thumb
- Posts: 4659
- Joined: Thu Oct 21, 2004 5:58 pm
- Location: Victoria, BC
-
grandpasrose
- Greener Thumb
- Posts: 1651
- Joined: Tue Jun 28, 2005 12:21 pm
- Location: Quesnel, BC, Canada - Zone 4a
Hey Opa! There are many plants that fall under the category of Allelopathic, and yes, Quercus Garryana, is one of them. However, being allelopathic does not mean that they are dangerous to all other plants, but only a few specific ones. Quercus Garryana does contain coumarins that effect various species of herbs and grasses.
Another example is Black Walnut - it isn't bad for all plants either. Forsythia, beans and carrots, to name a few grow quite well near Black Walnut trees.
Even many cover crops such as winter rye are allelopathic to other plants.
So Opa, I guess it depends on where you plan to use your leaf mould in the future, and whether there will be any plants put there that will be affected by the coumarins in the oak leaves!!
Doesn't help much does it? Sorry but there doesn't seem to be a straight answer
VAL
Another example is Black Walnut - it isn't bad for all plants either. Forsythia, beans and carrots, to name a few grow quite well near Black Walnut trees.
Even many cover crops such as winter rye are allelopathic to other plants.
So Opa, I guess it depends on where you plan to use your leaf mould in the future, and whether there will be any plants put there that will be affected by the coumarins in the oak leaves!!
Doesn't help much does it? Sorry but there doesn't seem to be a straight answer
VAL
-
The Helpful Gardener
- Mod
- Posts: 7491
- Joined: Mon Feb 09, 2004 9:17 pm
- Location: Colchester, CT
-
grandpasrose
- Greener Thumb
- Posts: 1651
- Joined: Tue Jun 28, 2005 12:21 pm
- Location: Quesnel, BC, Canada - Zone 4a
-
The Helpful Gardener
- Mod
- Posts: 7491
- Joined: Mon Feb 09, 2004 9:17 pm
- Location: Colchester, CT
-
grandpasrose
- Greener Thumb
- Posts: 1651
- Joined: Tue Jun 28, 2005 12:21 pm
- Location: Quesnel, BC, Canada - Zone 4a
I have copied a couple of sections from my books regarding this. From these statements, I would think that as long as you didn't have too many leaves in your compost, things should be okay. And yes, Scott, it appears that in high quantities, they are pre-emergent, as well as killing existing plants.
I guess it's your own judgement call on which way you want to go! Hope it helps.
VAL
"Volatilization. Allelopathic trees release a chemical in a gas form through small openings in their leaves. Other plants absorb the toxic chemical and die.
Leaching. All plants lose leaves. Some plants store protective chemicals in the leaves they drop. When the leaves fall to the ground, they decompose and give off chemicals that protect the plant. Fall foliage tends to release more potent allelochemicals than fresh, spring foliage. Water-soluble phytotoxins may be leached from roots or aboveground plant parts or they may be actively exuded from living roots."
"It appears that there may be an allelopathic effect on some seedlings when grown in undiluted eucalyptus, black walnut or live oak composts. With increased dilutions, the effects become less severe, suggesting that under natural conditions- where the dilution factor would be far greater than 25 percent-there would be little or no damage from these
leaves. "
I guess it's your own judgement call on which way you want to go! Hope it helps.
VAL
"Volatilization. Allelopathic trees release a chemical in a gas form through small openings in their leaves. Other plants absorb the toxic chemical and die.
Leaching. All plants lose leaves. Some plants store protective chemicals in the leaves they drop. When the leaves fall to the ground, they decompose and give off chemicals that protect the plant. Fall foliage tends to release more potent allelochemicals than fresh, spring foliage. Water-soluble phytotoxins may be leached from roots or aboveground plant parts or they may be actively exuded from living roots."
"It appears that there may be an allelopathic effect on some seedlings when grown in undiluted eucalyptus, black walnut or live oak composts. With increased dilutions, the effects become less severe, suggesting that under natural conditions- where the dilution factor would be far greater than 25 percent-there would be little or no damage from these
leaves. "
-
opabinia51
- Super Green Thumb
- Posts: 4659
- Joined: Thu Oct 21, 2004 5:58 pm
- Location: Victoria, BC
You know, I used oak leaves for years as mulch in my decorative beds. They were the little live oak leaves. Nothing ever died, and every year I'd pile them on 6" thick. I STILL got some weeds, even through all that.
Now for a hypothetical: which is worse to use as mulch: oak leaves or that decorative red bark they sell in stores?
Now for a hypothetical: which is worse to use as mulch: oak leaves or that decorative red bark they sell in stores?
-
grandpasrose
- Greener Thumb
- Posts: 1651
- Joined: Tue Jun 28, 2005 12:21 pm
- Location: Quesnel, BC, Canada - Zone 4a
-
The Helpful Gardener
- Mod
- Posts: 7491
- Joined: Mon Feb 09, 2004 9:17 pm
- Location: Colchester, CT
-
opabinia51
- Super Green Thumb
- Posts: 4659
- Joined: Thu Oct 21, 2004 5:58 pm
- Location: Victoria, BC
Oh my goodness, don't even start on the red bark again.
Yes, given that I do tend to grow some herbs in the garden as companion plants, I think that I won't use the oak leaves. At least, not that many of them.
It's interesting that Coumarin has negative effects on the growth of grasses because in local Garry Oak Meadows, that is what is there: Garry Oaks and Grasses (and the associated wild flowers). I guess that grasses that have evolved to grow in the meadows are somehow immune to Coumarin.
Yes, given that I do tend to grow some herbs in the garden as companion plants, I think that I won't use the oak leaves. At least, not that many of them.
It's interesting that Coumarin has negative effects on the growth of grasses because in local Garry Oak Meadows, that is what is there: Garry Oaks and Grasses (and the associated wild flowers). I guess that grasses that have evolved to grow in the meadows are somehow immune to Coumarin.