Repotting Cattleyas

This page is dedicated to Conrad Thomas (May 31, 1931 - June 23, 2015)

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Many members have visited Conrad's greenhouse over the years, participating in his New Members Workshop.  We found the visit very informative the first year we joined the Society.  The enthusiasm of Conrad is contagious.

Conrad was one of the founding members of the CVIOS, wrote the Society's constitution, has been President and mentor of many.

I revisited with Conrad recently and here are some of his comments.

Conrad's most important point for the new member to consider when choosing a new orchid is;

"Where are you going to grow it?"  Think about where a particular orchid grew in nature and can you provide a suitable environment.  If all your other orchids are cool growers; adding a Vanda which wants a warmer environment is going to be a battle and vice versa.  

Conrad's favourite orchids are Cattleya's (as long as they are species).  We were looking at the pictures  of the April Show Table and he commented when we looked at this one 

"Here you can see why Cattleya's are my favourite, how can one not love an orchid like this"

Catts in Conrad's opinion are also easy to grow.

The orchids on the ends of the spectrum are the problem-children.  The really cool growers and the hot growers.  

Planning a Greenhouse

If you are planning a greenhouse Conrad suggests including:

1     the highest height possible.  A higher height gives you;

        a)     more air volume so the temperature will not fluctuate as wildly in a short time period

        b)    height to hang plants

        c)    different temperature ranges, so you might put sun and heat lovers higher up and intermediate lovers below.

 2    a concrete floor.  A concrete floor is easier to clean (use a bleach wash as required); provides a heat sink to slow down temperature fluctuations and can be hosed down to generate humidity.

3    use tempered glass for the roof (or polycarbonate) in case a tree branch falls on it (or in the case of one member, an air-conditioner.  Who would have thought falling air-conditioners were a risk).

4    Make sure you have lots of ventilation.  That  does not mean gale force winds but a steady breeze.  Conrad uses an ex-furnace squirrel-cage fan; several oscillating fans and an exhaust fan.

5     Orient the greenhouse if possible for best use of the sun.  The north wall of Conrad's greenhouse is solid and fully insulated.  There is very little light to be gained from a north wall and it can be a major heat loss if the winter winds come from the north.

6    Do NOT use a wood burning heat source.  Splitting wood may be good exercise but one can have too much of a good thing.

Fertilizer and Water

Conrad is a convert to liquid fertilizers from the hydroponic store.  He mixes Nutrilite A; B and C all together (100 ml. of each in a 8 gal garbage can, then uses a sump pump) and fertilizes once a week in summer with a three month break in winter.

Note that the plants should slightly dry out between watering.

Conrad has rigged up a hot-water heater to warm the water for watering.  (Using cold water can cause damage to hot leaves.)  He took out the normal heating coil from an old water heater and replaced it with a lower wattage heater coil.  The water should be 60 - 70 degrees.  It should be comfortable on your hand.  Not too hot and not too cold.

Misting in the summer is done three to four times a day finishing by 1:00 to 2:30 to give the plants a chance to dry out before night.  During the winter he will only wet the floor.  Only water with no fertilizer is used for misting.

Temperature / Humidity / Lights

Summer should not go above 90 F.  Winter he will try for 80 F and not go below 58 F at night.

Day time humidity should be 70% and less at night.

Conrad does have two 400 watt HPS lights.  The idea is that while this is not enough to fully light a greenhouse of Conrad's size, it will provide supplemental light, particularly in the winter, for a selection of the more light needy plants.  Remember, light is like fertilizer, an ingredient for growth.

Zero Tolerance Pollination policy

Flowers are to be admired not pollinated (unless by the boss).  If a bee or similar pollinator  infiltrates the greenhouse all-out-war is declared.  The problem being, if the pollinator is successful in its mission, the flower having done its job, will quickly fade.  Conrad has had good success with Malathion.  (Note: Malathion is a strong chemical.  Read the label and use caution.)  


Repotting a Division

To the question of how often should one repot, the obvious answer was, "when it needs it".  The second obvious answer was "when you have time".

We found a Catt.  that needed repotting (possibly needed it a while ago).

This was a good time to repot (early May) as you can see that both branches of the plant are putting out new growths and new roots.   If the plant is dormant it might be set-back by a division.  If the plant is vigorous and in growth mode, it should grow into its new space with less stress.

There was the obvious two branches to split with at least three pseudo-bulbs each side.  Upon inspection it appears that one of the back bulbs has an enlarged "eye" which might sprout if the back -bulbs are split off.  If there were no "eye" that looked promising it might be better to only divide into two to provide more backup energy for the division.  The decision in this case was that the plant was healthy enough and the "eye" looked promising to divide into three divisions. 

Always sterilize cutting tools between plants.  Conrad uses a propane torch.

Now the "fun" part,  remember orchid growers must be patient.  You need a little patience and persistence to clean as much of the old medium off the roots, while doing the least amount of damage to the roots.    Conrad's delicate touch paid off as he worked the old medium out, as there were plenty of new roots in the middle of the root mass, which a more impatient grower might have damaged, figuring the roots in the middle would have died off.  This plant has lots of roots

Now for the surgery.  Conrad dresses the cut with a paste of Benomyl to ward off any infection.  He uses a small amount of Benomyl powder mixed with a small amount of water in a tablespoon (like the measuring spoons that come with your fertilizer).  Note: Benomyl is a strong chemical.  Read the label and use caution.

Part of the cleanup of the plant should be to remove the old sheaths.  That is a handy place for bugs and livestock to hide.  

After making the divisions the roots are washed to remove more of any old medium.

Here we have Conrad in the middle of his jungle with three plants where there used to be one.  The bane of a good grower,... where is he going to fit in those new pots?

Conrad uses clay pots.   They let the roots dry out between watering.  Make sure you bleach-wash pots between usage.  Conrad collects his used pots and after getting the old medium out, submerges the pots in a garbage can filled with a bleach solution.

He has been an advocator of the benefits of coconut fiber for some time.  This provides good drainage, resists decay better than bark and retains moisture well.

Put in enough fiber so the rhizome will be at the finished surface, hold the plant at the right level and then gently fill in around the root ball.  There is no need to push and compact the medium.  The objective is to provide a good amount of air to the roots and compacting the medium will crush the roots.  Manipulate the fiber amongst the roots as best as can be done and if the plant is a little wobbly (as one that is top heavy like this is), stake it and/or use a rhizome clip.  The plant should be steady in the pot so the delicate new roots do not get jostled and scarred or broken.        

When finished, water the pot well.

Pat down the medium after the watering.

You can see that the older part of the rhizome is placed at the edge of the pot to allow the new growth room to grow.  The size of the new pot should allow for 2 years growth.  The roots that had grown outside of the old pot are now in medium.

As roots grow to the edge of a pot, wedge a little coconut chip between the root and the edge of the pot to force the root to grow down.

Division of plants should not be intimidating to the beginner.  

Thanks Conrad for sharing your techniques and advice.

Now the hard part,  where are those new pots going to go?