The pros and cons of growing indoor plants in LECA

Luke Tribe owns a collection of 40 luscious green plants but among them, one was struggling to keep its leaves.

"The leaves would [die] or they'd go yellow, and I'd be like 'are you being overwatered or underwatered?" ABC Everyday's graphic designer says.

"I would put my finger in the soil to [test it] but it always felt the same… It was this confusion of 'Am I making it better or worse?'"

Caring for plants can be confusing, especially when it comes to watering. As Gardening Australia presenter Jane Edmanson points out, symptoms of underwatering and overwatering are very similar.

As Luke began researching for a solution, he came across a semi-hydroponics method, called LECA (lightweight expanded clay aggregate) and decided to give it a try.

What is LECA and how does it work?

LECA are small 'marble-sized' balls made from clay that you can use in place of soil.

Using LECA provides space for oxygen to flow through to the plant's roots, botanist Rosie Yee explains.

"Plants don't have a pump in their body like we do," she says.

"They have to absorb oxygen through their roots [and so] LECA provides pockets of airflow around the roots."

She explains that LECA also provides the perfect balance of hydration, by slowly diffusing water into the roots of a plant.

A LECA set-up typically involves two pots: the first pot will have small holes in the bottom of it and will house the LECA balls and your plant.

The second pot will be slightly larger and will have a small portion of water sitting at the bottom of it.

"The water [in the bottom of the pot] will diffuse into the clay balls and from the LECA balls, the water diffuses into the roots."

How is LECA different from soil?

The other difference between LECA and soil is nutrients.

Because LECA is made from clay it doesn't hold any of the nutrients that a good soil and potting mix provides, which means caring for your plant might need a little more attention, time and money (more on the cost of setting up below).

"You have to put the essential minerals like nitrogen, phosphorus, and potassium that all plants need, to do their basic functions and grow [plus] all the trace elements," Rosie says.

"You also have to use hydroponic nutrients, so they don't have a smell because it's sitting in that body of water and as you can imagine, after a while it'll start to smell a bit funky."

If you struggle with common pests like fungal gnats LECA might be a solution.

"Pests normally breed and lay their eggs in soil, so when you buy a bag of potting mix it might already have pest eggs in it, [whereas] they don't seem to survive in LECA," Rosie explains.

It can make watering easier, but keep an eye out for algae

Unlike plants growing in soil, LECA takes the guess work out of how much water your plant needs because you can see the water levels in your pot, helping to prevent diseases like root rot.

"When the reservoir goes down at the bottom, you just refill it back to where your marker is," Rosie says.

Just remember to replace your pot with fresh water every 1–2 weeks, depending on the climate you live.

If you do use clear pots for your LECA set-up, algae might start to grow, especially if it's exposed to sunlight, so Rosie recommends 'flushing out your pot' every fortnight or once a month.

If you have lots of plants like Luke, it can also create a synchronised watering routine.

"Some of my plants used to need watering every three days, and others once a fortnight," he says.

"Now they're all getting watered once a fortnight… and I only need to refill the bottom third of my containers."

Setting up can be expensive

The other advantage that comes with LECA is it's sustainable and can last a long time, Rosie says.

"You can boil it in water to clean and sterilise the balls and dry them out and put them [away] or reuse them for another plant," she says.

But LECA isn't widely available in Australia which can make your set-up expensive, so Rosie suggests starting small.

"If you have a look online, you can find some for around $10 for 2.5 litres whereas a bag of good quality premium potting mix is around $12 for 25 litres, so it's almost 10 times the price," Rosie says.

"[Anyone can use LECA] but it's for people who are passionate about plants, have time or love to experiment and are looking to try something new, where costs may not be a factor."

Which plants work best with LECA?

If you're looking to make the switch from soil to LECA, Rosie says it works well for plants that would usually grow in an environment where their roots get lots of airflow — like the tropical rainforest plant, Monstera.

"Tropical epiphytic plants like Hoyas, Philodendrons and Monsteras, that have large soft foliage and take to LECA really well because it kind of mimics that [environment]," she says.

"If you're propagating cuttings, I like to use LECA for Hoya cuttings and the speed at which the roots grow, is quite phenomenal."

Before you pop LECA into your pot, make sure you've washed it thoroughly to remove any leftover residue.

The last tip is to test LECA with younger plants, over plants you've had for a while.

"It's probably not a good idea because the root system will be quite substantial, and it'll be difficult to remove all of the soil without damaging it," she says.

"You could risk causing a lot of stress, so it's better to try it with a young plant that still has a small root system."