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LECA and/or Rockwool in outdoor containers?

Posted by cottagegardenlover 9b (My Page) on
Fri, Jun 14, 13 at 1:44

Has anyone used LECA in outdoor containers?

How often do you need to water?

Can you use Foliage Pro or do you have to buy Hydro Nutes?

Would adding RockWool cubes help with water retention, especially in hot Sacramento (sometimes to 110 degrees)?

Could I still handwater (I enjoy it) or would I have to install
a drip system?

What could be put on top as a decorative and more natural looking mulch?


(I'm looking for something more user friendly and long lasting to the gritty mix because I have a disability and have to rely on caregivers for help. ;) )

Follow-Up Postings:

RE: LECA and/or Rockwool in outdoor containers?

  • Posted by nil13 z21 Mt. Washington L (My Page) on
    Fri, Jun 14, 13 at 11:29

You can use LECA outside just fine. Watering frequency is hard to tell you about because it depends on the species and the climate. But you will have to water LECA a lot more often than the same plant grown in say Miracle Grow potting mix.

I wouldn't add rockwool. Rockwool is a non reusable product.

Yes you can handwater, but an irrigation system would provide a good backup in case of vacations or illness.

I don't know about Foliage Pro specifically, but it sounds like it would work just fine. Hopefully someone who has some will answer that. You just need a product that has micronutrients, Calcium, and Magnesium.

You can topdress LECA with gravel.

The only problem with LECA is that it is light and can float. This may or may not be a problem depending on what you are trying to grow. For instance, orchid people growing hydroponically, (I can't bring myself to call it semi-hydro like everyone else because there is nothing semi about it) have problems with floating because they completely fill the container with water and let the excess drain out. However, if you just have a pot full of LECA and just water it like a normal container floating won't matter.

What are you planning on growing? Some things will like more water while others more air. Things that like water will be more happy in something like straight Turface instead of LECA. Whereas stuff that gets root rot easily would like LECA more.

RE: LECA and/or Rockwool in outdoor containers?

Thanks so much for your help! :D

I read that Groban cubes/chunks/wool is reusable, and I'm liking that it is so lightweight. Plus, it really holds water.

I'm not sure how you would root prune the plant though.

The cost would be high at first, but if it's reusable it may pay off in the long run, especially since I have to pay a caregiver or yardworker by the hour to help me.

I grow roses, clematis, boxwood, verbena, lavender, foxgloves and annuals.

The only thing I'm not sure about with the Groban is that many say it will grow algae if you overwater and I'm not sure how to evaluate the proper amount of water.

This video shows them putting the LECA in the bottom of the pot for drainage. I'm not sure if that works because of what Al has taught us about PWT's, but it may be different with rockwool.


Here is a link that might be useful: Patio and Container Gardening with Groban Rockwool

RE: LECA and/or Rockwool in outdoor containers?

  • Posted by nil13 z21 Mt. Washington L (My Page) on
    Fri, Jun 14, 13 at 16:33

That stuff is reusable in the sense that you can tear it off the roots and use some of it over, but it's like working with fiberglass insulation. The LECA bit at the bottom is just the same old silly rocks for drainage bit.

From what you want to grow, I think your best bet would be a 50:50 mix of pumice and turface. It's fairly lightweight and holds a lot of water. It is going to be the most like growing normally. Plus ot won't be a PITA when you want to tear out annuals and such. You would probably want to use a bloom booster fertilizer that's high in Phosphorus in the beginning with your flowering plants though because the Turface has an affinity for Phosphorus and you'll need to load it up a bit to get a good bloom. (yes, this is one situation where bloom boosters are not hogwash.)

RE: LECA and/or Rockwool in outdoor containers?

Heyyyy.....that's some great info!

Thanks so much. It would probably be alot more economical too.

I've been searching all over the internet into the wee hours for information because I managed to make a lovely urban patio garden this year with Fox Farms OF, but am overwhelmed at the long term maintenance of repotting every year or two.

Where is the best place to buy large quantities of Turface and Pumice?


RE: LECA and/or Rockwool in outdoor containers?

Oh, and Nils,

What do you think about that mix in the high temps here in Sacramento in the Summer? It can get to 110.

I'd probably put some colorful pea gravel on top to look nice and maybe a little bark. Would that help it to stay cool?

Also, if I'm understanding this right, all I would have to do each year is pull the plant out, root prune, let it soak in some Super Thrive water for a few hours and replant in the same mix, right?


RE: LECA and/or Rockwool in outdoor containers?

Oh, and I found the pumice and turface locally. They'll deliver too!

Here's the thing:

The MVP turface is approx 1/8"
The pumice is 5/16"

Will they work together all right? I really don't think I can handle screening. :(


RE: LECA and/or Rockwool in outdoor containers?

  • Posted by nil13 z21 Mt. Washington L (My Page) on
    Fri, Jun 14, 13 at 20:50

I'm in LA and we get the same heat. I'm testing that mix for green roofs and so far the yarrow planting in a nursery flat with 1 inch of mix can make it through 90 degree days with a single watering during the day. That's on a roof with full southern exposure. Regular pots should be fine.

It doesn't look half bad, but I would top it with something inert like gravel. That way if some gets mixed in it will never be a problem.

I don't screen them. Just mix them together in equal portions. I don't even bother washing them. Like I said, I'm testing this for green roofs and we can't mess around with all that fussiness. We need to be able to dump bags in a concrete mixer and be done. But if you don't wash them, the pale dust can wind up on the patio.

If you want to root prune like that every year, be my guest. I'm a little lazier. Ideally, you would put the mix in a tub of water to clean it before reuse. The organic matter (roots), still remaining in the mix will float and can be poured off.

RE: LECA and/or Rockwool in outdoor containers?

  • Posted by nil13 z21 Mt. Washington L (My Page) on
    Fri, Jun 14, 13 at 21:43

but don't go switching everything all at once. You may find that you need a little more pumice or a little more turface depending on climate, watering habits, and plant needs.

RE: LECA and/or Rockwool in outdoor containers?

Okay, great...thanks! I will start with a few plants this summer and fall and see how they do before changing them all out in spring.

I have some climbing roses that may need annual pruning, but the others will probably only need every two years.

I think roof gardens are so brilliant! I'm sure they are a resource that will become more commonplace in the near future. Research like yours will be a great contribution to the pool of information, so great work!


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