"Should I change all my plants over to LECA?"
"What the heck is LECA, anyway?"
"What's that stuff that looks like Cocoa Puffs people grow orchids in?"
...these are common questions from visitors to our nursery, so we thought we'd take a little time and space here, to explain the pros and cons of a potting medium that's more than a century old, yet unfamiliar to many people until quite recently.
To start with, "LECA" is an acronym for Lightweight Expanded Clay Aggregate, which is often known in Europe as "Exclay" (short for "Expanded Clay." And it's a lot older than most folks' experience with it (including our own, initially) would suggest. It was actually developed in the United States back around 1917-1918, as part of an experiment to produce a lightweight, durable material that would eventually be used (at least for a short time) as a component of seafaring ships! It also found application in certain types of commercial concrete construction, combining strength with light weight. It turns out that when the proper type of clay is heated to around 2,000 degrees Fahrenheit, gases trapped within the clay vaporize, expanding the clay and creating a very useful material. This is done in a commercial high-temperature rotary kiln, and the rotation of the kiln vessel creates the round or nearly-round shape of the final product. LECA is produced in a variety of sizes, and while it was originally an experimental building material, it soon found popularity with horticulturists seeking new and better media for hydroponic gardening. LECA's primary benefits as a plant medium include:
-Light Weight (which reduces transport costs and weight of potted plants.)
-Resistance to chemical reaction with most common fertilizers, pesticides, etc.
LECA is also very near pH-neutral, which is an advantage for growing plants.
-Porosity (the air spaces created by gas expansion allow the pebbles to absorb and hold water very well.)
-Durability (LECA is tough, and can be cleaned and reused almost infinitely, which
makes it cost-effective versus soil, which wears out and eventually has to be
renewed through composting.)
-Appearance (although it's a subjective thing, some folks really like the look of plants growing in a LECA substrate, especially in clear glass containers.)
-Health & Pest Control: A lot of common houseplant pests breed in soil, including thrips and scale insects (like Mealybugs), fungus gnats, nematode worms, etc. With plants rooted in LECA in an aquatic solution, we remove the breeding
ground for many of these pests, as well as making it easy to keep an eye on roots
for any signs of rot or disease.
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On the flip-side, LECA can have a few disadvantages, too, including:
-Lack of nutrients: LECA is essentially inert, meaning that any nutrition plants grown in it receive has to be added by the grower. Also, plants grown in LECA require special fertilizer considerations, usually with a liquid mix designed for
hydroponics.
-Expense: LECA is pricey compared to most other potting mixes, at least on the front
end. This is offset by its ability to be cleaned and re-used almost infinitely, so
long as you're willing to take the effort to ensure that it's sanitized between
uses.
-Availability (LECA isn't something you can easily find in bulk at most garden centers.
Typically, it's offered in small one-pound packages, and if you're potting a
number of plants with it, you'll either have to pay-up for lots of these, or else
order from a reliable online source and incur shipping charges.)
-Need for Plans to Adapt to LECA: This is the "deal-breaker" for some gardeners,
because moving plants from soil to LECA isn't just a matter of normal repotting.
Plants have to be scrupulously cleaned of all remnants of soil before putting them
into LECA, and there's a period of transition that can be quite rocky, as the plants
grow new roots that are adapted for underwater respiration. These "water roots"
take time to form, and in the meantime, your prized Monstera may experience
things like leaf-drop, yellowing, and other symptoms--though these are usually \ temporary.
If you want to try LECA, here are a few helpful tips:
-Identify the size and quantity of LECA you'll need. You'll find LECA offered in various
grades (diameters, usually identified in millimeters) and package sizes. Plants with finer
roots (like Begonias) typically will benefit from a finer-grade medium, while plants with
large, thick roots (like Moth Orchids or many Aroids) will do fine with larger balls of
LECA. Of course, check reviews and make sure you're purchasing from a reliable
source.
-Rinse the LECA thoroughly. A sieve or colander works great for this. You'll want to
run lots of fresh, clean water over the LECA pebbles to get rid of dust and any other
trash from the medium.
-Soak the LECA pebbles. Before use, LECA needs to be hydrated, and the cleaning
rinse isn't enough. You'll want to put the LECA into a container of clean, fresh tepid
water and leave it to soak at least a few hours, preferably overnight, before using them.
-Add your plant. (See our recommendations below for your first effort!)
-Allow time for your plant to adapt. Plants grown in water develop roots that are
structurally different from the roots they'd use to thrive in soil. There going to be some
transition, and you're likely to lose a few leaves, and quite possibly some existing roots.
Assuming your plant is able to adapt well, it will soon replace these. In the meantime, any dead or dying leaves or any soft, mushy roots should be trimmed away, back to
healthy tissue. We recommend checking your plant at least weekly for signs of such
stress-related adaptation, so they don't rot and cause damage.
-Once your first plant is doing well and you've gained a little confidence, feel free to
branch-out! Remember that some plants adapt better to hydroponic culture than
others. Even within the same family, we find that some Aroids like LECA better than
their close cousins. It has a lot to do with how the plants grow in nature. Some plants
aren't suitable for LECA culture at all (think succulents, some Gesneriads, etc. that just
don't tolerate wet roots.). Do your research online, call or email us for advice, or maybe
check an internet group or local plant club for someone who's been down this road
ahead of you.
-Don't fear, but manage your risk: Work up from plants you can afford to part with, to
the rarer specimens in your collection. As in all things gardening, be humble enough
to ask others when you need help. And above all, enjoy the experiment!
Here's our bottom-line assessment:
If you want to try LECA for plants, we recommend you not start out with the $600 "dream list" reverse-variegated glow-in-the-dark one-of-a-kind Anthurium you've mortgaged your firstborn child to purchase. "Get you feet wet" with something commonplace, preferable a plant that's readily available, or maybe one you have a duplicate of. Carefully clean all soil from the roots and put the plant into pre-rinsed and soaked LECA, fertilize appropriately, and see how it goes. Once you've had success for a few months with your inaugural effort, you can venture into deeper waters...but we advise you to go slowly, always remembering that there are no guarantees in horticulture, much less in life.
Best of luck & Happy Growing!
-Steve, Kristi, Sawyer & Cooper
The Specialty Tropicals Team
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