roots die when they touch leca!

[kkdcalgary]

dear all
i recently repotted a few of my plants into straight hydroton/leca and they are doing fine in terms of growth, one is in spike, but when they grow new roots, at first they are plump healthy roots but as soon as they touch the hydroton, it seems, they stop growing and the green tips turn white!

Did i not wash the hydroton enough? bad batch? help!

[nutgirl]

A few questions:

Are they being grown hydroponically or are they just potted in leca?

How long have they been in leca?

What kind of orchids are doing this?

What are your growing conditions?


Maureen

[kkdcalgary]

I'm growing them in leca only, semi hydro.
plants include:
- den aggregatum - very happy pseudobulb, but new roots have shrivelled
- hwr. lava burst 'puanani'
- epy. serena o'neill - new pbulb growing nicely but again, green root tips shrivelled
- onc. twinkle star - acting like it's dormant. new root tips dead.

[nutgirl]

I grow most of mine in leca but not necessarily using the semi-hydro method. Most orchids seem to like it. I have a Den aggregatum that is very happy.

Your surface layer of leca may be too dry and the roots stop growing when they start to grow into it.

I am in a dry climate and find that keeping the top layer of leca damp is sometimes difficult. I try to keep it moist when the roots are growing into it with a light layer of sphag moss or frequent spraying.

The timing of transition to semi-hydro is important too. You want your plants to be putting out a real burst of new root growth when you change over since most existing roots will not adapt to the new method.

Maureen

[Ray]

I can think of two possibilities:

1) You didn't clean the stuff well enough.
2) Your atmosphere is dry, so the topmost part of the column of LECA in the pot is literally "sucking" water from the roots.

If the top looks dry, there are a number of things you can try: 1) water more often, to keep it moist, 2) mist it periodically, 3) loosely cover the top of the pot around the plant with plastic wrap or foil, to slow the evaporation rate, 4) put a layer of sphagnum on top.

Once the roots penetrate the LECA and grow downward, it should be no issue.

[camille1585]

I had that issue with a Miltionopsis I transfered to S/H in the fall. It could be a coincidence, but seems that low humidity was the issue (the leca at the top is always quite dry) because once I put a damp layer of sphag on the surface, the roots seem to have grown down into it fine. I removed the sphag a fez months later. Strangely enough I'm not having that problem with a Howeara Lava Burst I recented transferred, the roots are growing in the Leca just fine!

How much / how often are you fertilizing? That could be an issue as well.

[Magnus A]

There is one more thing to invesitgate. If the plant is not firmly secured and stable it will move slightly. When the root just hit the substrate it is hit by movement and the growth can be interupted just at the surface of the substrate.

[nutgirl]

Originally Posted by Magnus A

There is one more thing to invesitgate. If the plant is not firmly secured and stable it will move slightly. When the root just hit the substrate it is hit by movement and the growth can be interupted just at the surface of the substrate.

Good Point! That could definitely have a bearing on it.
Some orchid types seem more sensitive to this than others.

Maureen

[Bud]

if you read the S/H method...in the first few weeks you will lose established healthy roots and also a couple of lower level healthy leaves, because the plant is not used yet to the clay...when the plant is established to the S/H method then and only then you will see the plant grow more roots and grow more leaves...the first few weeks are critical to the adjustment period...
but some plants just dont do this...some of them adjust easily ...like the Vandas...they just love the wet LECA

[Lana]

Could this be because of the salt build up? If the pot isn't flushed regularly?