New roots and water absorption

[kelbel2185]

Ok,

So, I have just broken the ice (yesterday) and I have my first question.

Perhaps, like most, I went about orchid growing the wrong way. Starting to buy orchids last October and buying what I loved without truly knowing what and how orchids grow! But, being a biologist now I want to KNOW EVERYTHING....

So here it goes. When a new root starts emerging from new growth or established growth how long does it take before the root starts absorbing water? So, I ultimately want to water my orchid when I see roots because I know its looking for water. My fear is I'm doing my plant no good because the roots aren't 'turning green' when the water touches the root and therefore I tend to over water because I'm not seeing the absorption I expect to see when I water.

Sorry if this question has been discussed but, I've been dying to know the answer and I hope it helps more than just me to know the answer. Please help me out

[Bud]

its the warmer growing months so you must not get scared to overwater especially if plants are outdoors....if you are using the correct media mix, it will dry out evenly....if not it will retain stagnant water and rot your roots.
if I see new roots appearing, I water liberally because I know my plants are in growth mode. it also means the rest period is over so I continue the regular regimen of fertilizer and watering.
The longer bigger thick roots absorbs better than the baby little ones....they have experience and well established.

[Dendy83]

I would actually like to know too. I have a phal with 2 lovely aerial roots with green tips, however the rest of it is gray and does not turn green like the others when I water. I wonder if a good soaking would help?

Edit: Hah! Bud posted as I was typing this. Thanks!

[tucker85]

That's an interesting question. Even though I've never paid a lot of attention to this subject, it seems to me that once a root gets to be 3"-4" long it will start turning green when watered. I don't know if short roots that don't turn green are absorbing water or not. I do often mist aerial roots even if they aren't very long and I've never seen it harm them. This time of year new roots grow pretty rapidly so my opinion would be that misting the new roots won't harm them and it won't be long before they are functioning roots if they aren't already.

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[kelbel2185]

Thanks so far for the responses!

I often get criticized my the grower I buy from for being 'too technical' So I'm hoping someone has an answer to ease my mind for the time being

The reason I am persistent about knowing is several of the plants I purchased at Redlands came bare root and now that they are starting to grow and establish I'm worried about 'over watering' since no roots really exist (but pseudobulbs are not shriveling) but the 'new' roots. But they have to be getting water from somewhere!!

[Bud]

you are in lowland sea level Florida area where there is abundant humidity in your atmosphere....that is where the roots get water.... morning dew also helps water the plants....if you are in the high altitude dry atmosphere area=that can be quite tricky for the plants.
yet there are Vanda growers in your area who still water everyday.

[Aki_James]

This is a great question. I do not know technically but from experience I would say young roots seem to be inefficient at utilizing direct water, so I would believe they get moisture mostly via the air(this is why I believe humidity is so important in root development). After a period of time the rest of the velamen (spongy water absorbing outer layer of the root) becomes active. At this time there also seems to be an increase in growth rate.

This may not be accurate as this is just my personal observation.

Hope it helps

I should add orchids also take in water through the leaves, so it is important when an orchid has no roots that humidity is maximized while maintaining air flow to prevent fungi,bacteria and other such infections.

[james mickelso]

This is a very good question and there is no simple answer. But here goes.....roots of orchids are covered with a spongy material called velamen which when mature, soaks up water immediately if not sooner. It is a sponge. But immature velamen hasn't opened up yet and doesn't absorb water readily. Here are a few quick pics. You can see the older velamen has soaked up the water (nearly instantaneously) I poured onto it and the younger velamen hasn't soaked up any at all. The intermediate aged velamen has started to soak up some water (it has turned mottled color) It takes awhile for velamen to age and open up it's structure. The new growth doesn't need to hasten the velamens growth because monopodial orchids have fleshy leaves and thick roots which have already differentiated and grown spongy while the newer hasn't. But it has enough mature roots to accomplish what it needs. Orchids that have pseudobulbs ( I forgot the name which isn't multipodial) grow from older pbulbs and the new growth gets moisture and food from the older pbulbs until their own roots grow mature enough to absorb water and food. So when we buy young orchids with new roots, they usually have older pbulbs or enough leaves if mono's the keep them going. When a root matures under the surface of the media it has always been exposed to moisture and matures faster because it has always been damp. What we call air roots or arial roots get wet and dry, and take longer to mature. The orchid doesn't want those roots to be able to take in much moisture just to lose it again to evaporation so the velamen stays more closed. But eventually the velamen matures and absorbs water and nutrients just like those under media. Hope this helps.

[King_of_orchid_growing:)]

Sympodial - multiple growths along a rhizome. (Example: Cattleyas)

Monopodial - a singular growth. (Examples: Phalaenopsis and Vandas)

---------- Post added at 05:17 PM ---------- Previous post was at 05:10 PM ----------

To answer the original question...

I have a Galeottia negrensis, (It is a Maxillaria relative with a sympodial growth habit and pseudobulbs), that had short roots that were emerging from the new growths. The roots started to absorb water as soon as the separation between the green root tip and the velamin was apparent. And they were no longer than .75 cm - 1 cm in length.

Velamin is an inefficient water absorbent. It is hypothesized to be more effective with preventing water loss, water retention, and catching organic ionic nutrients. This doesn't mean it doesn't absorb any water, because it does. If I'm not mistaken, the velamin tends to be far more efficient at absorbing ambient atmospheric moisture than it is at precipitation or water run-off.

The root tips are far more efficient at water absorption in general.

You will generally notice/observe that an epiphytic orchid root that is growing in wetter conditions tends to generally have a thinner layer of velamin, while those roots that are growing in drier conditions tend to generally have a thicker layer of velamin.

I think this is quite possibly the "simple" answer to your question.

[Bud]

In most orchids, the roots are responsible for taking in water from its surroundings, along with the dissolved nutrients that water contains. These nutrients are not exactly "food" for the plants but they are substances the plant needs to stay healthy so it can manufacture its own food by a process called photosynthesis.
Thick large robust established roots intercept water as it filters down through the media mix, capturing the nutrients the water has picked up as it travels through its path going out to the holes of the pot.
The little newly formed baby roots can barely perform these simple process yet.