Phalaenopsis gigantea - long term growing project
 

Mr.Fakename and I have started a project of sorts with Phal gigantea, which began by sharing cultural notes about our respective plants, and we thought it could be a nice idea to open this up to other Orchidboard members.

The idea behind this project is that while there’s information on how to easily grow this species in a greenhouse or tropical climate, there seems to be much less on how to grow and bloom this species (and do it well) indoors in temperate regions, and potted instead of mounted.

Anyone growing this species is welcome to join in, and we’d especially like input from members who are growing it in the same sort of conditions as we are. If you don’t have this Phal you are welcome to buy one and join the ride, but I would NOT advise it if you are new to orchids as this is not a particularly beginner friendly species. Please also consider that these plants get very large, and as they are very slow growing most plants for sale are (large) seedlings, still several years away from blooming. Larger plants can be found, with a corresponding price tag.

Show your plants, tell us about your growing techniques/conditions, what you noticed about your gigantea, successes and failures, post progress pics?

In the post below this we've put together a fact sheet about the species, as well as some useful culture information.

Phalaenopsis gigantea was described by J.J. Smith in 1909 (“Bulletin du Département de l'Agriculture aux Indes Néerlandaises”).
It is named after the size of its leaves, reaching 60+cm (2+ feet). It is, to date, the biggest Phalaenopsis.
Closely related species: Phalaenopsis doweryensis, Phalaenopsis kapuasensis.

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Distribution:

• Indonesia (Sumatra, Java, Kalimantan (Timur)), Malaysia, Borneo (Sabah)
• Phalaenopsis gigantea is a low to mid land species. It is found from sea level up to ~400m (1300 feet)
• The shape and color of leaves, as well as shape, colors and patterns of flowers, depend on the origin of mother plants - white/cream/golden background, small red spots/big burgundy patches…
• Gigantea is one of the most poached orchids. It is now believed to be near extinct in the wild.

Culture:

Light - Gigantea inhabits the canopy and forest clearings, where it gets plenty of light.

Some plants can adapt and thrive under a wide range of lighting conditions. This is not the case of gigantea:

• Low light will affect its health, making it more prone to various diseases.
• Insufficient light also inhibits flowering.
• This is the #1 reason for plants sulking, or suddenly rotting.

A well grown gigantea can handle (personal discretion advised) direct sun. Leaves should be light green/yellowish.

Temperatures - - The warmer the better, but a healthy plant will adapt to a wide range of temperatures.

• In their natural habitat, Phal gigantea grow in warm to hot conditions year round (30C/23C [86°F/73°F] day/night) with high humidity (75+%)
  
• Many growers note that it can be grown at lower temperatures than this, as explained by Peter Lin in this article he wrote about Phal gigantea (Big Leaf Orchids - Phalaenopsis gigantea).
  
• However, metabolism will be slowed down in cool environments. Low threshold seems to be around 18°C (64.4°F), under which the plant will stop growing and will be weakened.
• Summer temperature spikes in the 40°C (100+F°) and huge night/day variations seem to promote spiking.
• Adequate ventilation is key; leaves should not be warm to the touch.

Water and fertiliser - - Gigantea is unique amongst Phalaenopsis in its capacity to hold water, with very thick, succulent like leaves.

• There are two schools of thought regarding watering techniques for this species: allowing the roots to go dry between waterings, to force the plant to look for moisture, increasing its root system; or keeping the pot slightly moist at all times. Letting roots dry appears to be in phase with what gigantea sees in nature; this species arguably gets less water from the surrounding moisture than other Phal, and has evolved to stock more resources in its leaves.
  
• Successful growers tend to fertilise this species on the heavier side. 250 ppm N every two weeks, or better 125 N per week, is a good starting point.
  A local orchid enthusiast mentioned he would go up to biweekly feeding of 100 ppm N in the dead of summer, when growth is at its maximum.
  Several reports point that more frequent wet/dry cycles and fertilisation application enhance growth.
  
• Due to the very compact growth with little space between leaves, plants are prone to rotting. It is advised to water early in the day, without wetting the plant. Allowing the plant to grow sideways (as it naturally wants to do) allows for any trapped water to trickle away from the base of the leaves.

Potting - - Choose high quality materials, the less you have to repot, the better.

• As a rule, Phal gigantea does not like to be disturbed so repotting should be limited as much as possible, and when using bark, it’s advised to use a durable type such as Orchiata.
• Something that comes up often in discussions is that once a gigantea reaches adult stage and blooms, it no longer tolerates repotting and condition changes.
• After a repot, leaves are usually smaller/narrower, and they can take several years to grow again. This does not seem to apply to seedlings and young plants.
• Another other common comment is that root bound gigantea bloom better, probably because they feel more anchored and secured.
• A happy gigantea will quickly need a very big pot, which makes watering tricky. For adult plants, very coarse bark or slow decaying material is advisable. Proper gas exchange is extremely important.
• Potting methods to explore:
  Double pot technique => net pot inside, bigger pot to create a mini “greenhouse”.
  Smaller pot inverted inside the main pot. Keeps central area free from water pockets.

Trivia:

• Genetics are very important, choose a reputable strain if you can trace the parents. Some plants are very reliable and will grow easily, some will want to die no matter what. Dud ratio seems high in gigantea.
• Potted/indoor plants are often observed to have fewer leaves than counterparts grown in greenhouses, they will often hang on to no more than 3 leaves at a time.
• For all gigantea (potted and mounted) a large, healthy root system is essential. Because of the huge leaves, the plant needs to move a lot of water and nutrients to keep them happy and healthy. In indoor conditions with typically low humidity, transpiration rates greatly increase and this becomes all the more important.

This is of interest to me. I'm strictly indoors grower and have passed up on phal gigantae for this reason. If its possible, I would love to one day get an Alba version!

I’m gonna tune in to this for sure!

Feel free to share your plant with us DC! You have a great climate for gigantea. How's it doing on that hygrolon mount? (That was you, if I recall correctly)

Mine is doing well. Is hardly say thriving but it is “winter” so it’s cold for that plant

New leaves are solid and strong so I know it is healthy just not at ideal culture yet

I'll start this off by presenting my plant. I got it in Oct 2014 as a small seedling and it's had a rather hard life until recently. It got less than optimal care (i.e. neglected) for over a year when I was in the last phase of my PhD. It then got more than half eaten by snails in the one summer I put it outside. Once it recovered from that, it was attacked by a mysterious pest/disease that left awful pitting on the leaves and caused them to shed prematurely.

It is still far from being in great health, but has been doing better and better in the past year, and the pitting seems to be gone (knock on wood).


My conditions:
LIGHT:
Grows indoors, on shelves in a south facing window. In the winter it gets positioned to get full sun as much as possible (whatever sun there is), and since this past winter also had some LEDs above it. In the spring I pull it back slightly from the window so that it only gets a couple hours of direct sun per day.

TEMPERAURE and RH:
Temperature is over 24-35°C in the growing season with a RH of 50-60%. In the winter it's usually 20-22°C during the day, 18°C at night,*and RH is 30-50%. This doesn't stop it from putting out a new leaf in the middle of winter.

POT and SUBSTRATE:
Until last year it was potted in bark. I repotted it in straight leca so that I could water more often, and it had some rather explosive root growth (Kelpak probably has something to do with it). Note that I didn't actually repot it, but picked all the bark out and replaced it with leca, without removing the pot. That was a dumb move, as I've discovered that plants with comparable a leaf size are in much larger pots than mine (15cm vs 10cm). I plan to repot it later in the spring, still in Leca, but still questioning how I want to repot it. Maybe I'll test double potting with it (net pot in a standard pot) or pot it in a normal pot and set that in a glass bowl for both stability and humidity around the roots that venture outside the pot. Yes, the roots currently growing out the bottom of the pot are in sad shape...

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Here are mine:

Grown under LEDs, Cattleya light levels. After they're done with their current leaves, I'll put them even closer to the light bulb.
They get a bit of natural spring light during the afternoon; but direct summer sun is not possible under my conditions, I don't want to end with a bunch of roasted salads.

Temperatures are hard to bear for humans, but plants love the heat.
They usually see 30-40°C during summer days, 15-25°C at night. Winter days 18-25°C, nights 18-22°C.

The main issue is RH, 20-30% in winter, under 10% day and close to 90% night during summer.

Gigantea #1 (longest leaf 23cm) is potted in big bark, allowing for very frequent and thorough watering, keeping the moisture relatively even inside the pot.
Gigantea #2 (longest leaf 12cm) is in tightly packed Sphagnum, and will go in S/H soon.

I water them with tap water and RainMix (MSU for Americans); I also regularly swap fertiliser for a bunch of organic products like aloe vera extract or fish emulsion.
I strongly believe in the power of beneficial microorganisms, and use fungi and bacteria monthly.



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Wow, they certainly live up to their name; it will definitely be interesting to follow these plants! :D

Did you ever find out what was causing that pitting? I remember you posted about that a while ago and don't exactly recall what the consensus was.

Nice looking plants Mr.Fakename! Your large one certainly looks in better condition than mine. I'm surprised by how round your leaves are, while mine are long and narrow. Could be due to the amount of light it gets, I might be pushing it in terms of hours of direct sunlight. Though the leaf color (a light yellow green) is about where they say it's supposed to be at...


No, I didn't.
Last summer I wiped down all the leaves (front and back) with rubbing alcohol, and so far I'm not seeing the pitting develop on the newer leaf, but it would often spread primarily late spring to summer so it's to early to say that I'm out of the woods. My guess at the moment is that it was some sort of microscopic mite. I did visually inspect and wiped the leaves with a rubbing alcohol soaked tissue, but never saw the tell tale signs of mites.

IF the pitting reappears in the coming months, then I'm going back to the original hypothesis that it's some sort of fungal infection.