IronWood Needles?

[Menehune]

We bought a lot that is mostly “ironwood” trees - long needles have covered and mulched the whole lot - very little else has grown; except, some magnificent philodendrons which we love. What an experience - a rain-shower and being sheltered by their big leaves growing into the canopy.
We plan on selective clearing the lot to preserve as much as possible - the lava - the plants.
A few questions:
Are the “ironwood” needles something to save and run through a grinder/mulcher or just rake up and discard?
What do the needles do to the soil - make it acidic?
Under the needle mulch are several inches of rich looking humus - is it as good as it looks?
I read a little about “making soil” - what’s best to use cinder, gravel, sand?

Mahalo nui loa

Joey "O"

[Les C]

I can't help much here, except to say that Ironwood Casuarina equisetifolia shades out most vegetation under it. The needles may make the soil under it acidic, but there may be a way to mix stuff with it to neutralize that. Try asking one of the informed people at Garden Exchange, for starters. You can find out more about them at the HEAR website:
http://www.hear.org/alienspeciesinhawaii...index.html

Having grown up in the Islands going to beaches filled with ironwoods, it is nice how the wind sounds blowing through the needles. The branches and bark are favorite hiding places for centipedes and scorpions.

[Mitzi M]

Aloha Joey,

Ironwoods are considered a serious invasive coastal pest in Hawai'i. There is a chemical in their needles that is reportedly toxic to other plants and will prevent anything else from sprouting. When the layer of needles gets thick enough the ground underneath it becomes a "biological desert". I wouldn't use the needles for mulch at all.
In fact, you might consider coming up with a plan to slowly replace then with a more diverse and interesting canopy of coastal trees. I say "slowly replace" because they do provide welcome shade in areas where they have displaced the native trees and other vegetation. If you are close to the ocean, some fast growing native trees to try are kamani, milo, kou, hau and hala (for areas away from walkways). Just as an experiment try and remove some of the needles revealing the soil underneath and see if anything comes up in there. If it does, then you can use the soil, but if not (as is my guess) you may need to add pockets of soil to plant anything else. In my opinion, the best soil mix is 1/3 cinder, 1/3 soil (could be sand or hamakua sugar "soil" and 1/3 organic compost. Mac nut husk compost is good for that if you can get it. "Cinder soil" is most of the time about 1/2-3/4 cinders mixed with some organic material (usually mac nut husks). There is also "dump mulch" which is basically all kind of trees that are chipped at the dump in an un-decomposed state. You can use it as mulch but I wouldn't mix it into soil. It's also full of weed seeds and bugs when fresh.

Aloha,
Mitzi

Uluhe Design
Native Landscape Design
uluhedesign@yahoo.com

Edited by - Mitzi M on 10/23/2007 22:26:29

[Kapohocat]

Puna Rock has a mixture called S4C - 4 soils to 1 cinder - can that be used? (We have been but I wanted to check now readign these posts.)

[Mitzi M]

Hmmm...Is the soil part of S4C like a coarser, tan colored version of Hamakua or Pepekeo sugar soil? If so, I think that's probably what settled in a different layer of the sugar wash tank, and may be what is used now like a base course(?) The thing I'd look at is the soil texture. Does it drain readily and is there enough organic material to make it hold some moisture - not soggy? That sugar soil is a good "filler" that can add some substance, but very little nutrients. The organic part of your soil is key for building good soil structure. I haven't found a perfect mix out there so far, so I recommend mixing your own - well, basically doctoring up what you can get. I'd start with a load of thoroughly composted mac nut husks, add then completely composted manure and home compost. Our native "soils" are already nitrogen poor and if you add anything that is still decomposing, you'll keep even more nitrogen from your plants. It's a dilemma here because most of what you can have delivered is not truly composted. If you have the space, time and patience, you can finish it off yourself. You'll need to tarp or otherwise cover the piles and turn them periodically as well. Black cinder is the one to add for drainage. Red is reportedly somewhat toxic to plants, but I've seen stuff growing in it too. As for your soil, the proof's in the pudding - if stuff grows well, then I'd go with what you have and mix in compost when you can.

Mitzi

[wjbillock]

quote:

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There is a chemical in their needles that is reportedly toxic to other plants and will prevent anything else from sprouting.

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Are the needles toxic to Coqui frogs?

"What? Me Worry?" - Alfred E. Nueman

[Mitzi M]

Yes!!! But only if you have a teeny leetle blowgun and can manage to hit them square on.
(Hee hee!)Good thought though - we certainly have a big enough supply!

[missydog1]

LOL at the blowgun Mitzi ...

Menehune, in addition to all the other bad things about ironwoods, they are hard to kill. Or so I hear from others who have tried, that they will sucker and return unless you get serious (as in stump poison).

Please do not preserve them; they are a nuisance and your neighbors with blocked views will love you for getting rid of them ... in fact, there are those who would gladly do guerilla extermination of the oceanfront ironwoods.

[Tolleys]

Our ocean front lot was covered in ironwoods for many years. We recently cleared the land of the trees and chipped much of it. We now have a few piles of black compost. We have yet to plant with this compost.
Also, there is much soil where the original trees were located especially where there were low spots in the pahoehoe. Some pockets of soil are over 12 inches deep. We have not added any amendments. There are lots of native plants and grasses (weeds too of course) which seem to be thriving in this soil, perhaps because they get sun with the tree canopy gone. So, I am not sure of the toxicity issue. I will be trying other non-native salt tolerant plants in this soil soon. Will let you know the results.


Susan

[missydog1]

one book I have says that casuarina is a nitrogen fixer, so that would explain the fertility of the soil I think.