Pollination of Orchid Flowers
There are several methods by which orchids (like other plants) can be propagated. These are by:
- seed
- division
- mericloning
- stem propagation.
- offshoots (keikis)
Here, we will concern ourselves only with the first option, Propagation by Seed. This is mainly how plants ensure their survival (orchids are plants): the male pollen-grains are deposited on the female stigma, then from each pollen-grain, a thin thread grows into each little egg-cell to fertilize it and a seed grows.
Orchid seeds are extremely small; they do not have any food in the seed grain, just the embryo. This helps in their distribution by air currents. Once the seed settles in a place, it will only grow when there are fungus-like organisms, called micorrhizae, which pre-digest any food that is then available to the orchid embryo. Only when the seed forms a healthy symbiosis with the fungus, will both of them continue to grow.
Orchids have been around for millions of years and have had to adapt to climate and geologic changes. They have come up with many solutions to the problem of how to achieve fertilization. Many orchid flowers have evolved together with certain insects and depend mutually on each other’s survival.
In the many different ways orchids attract pollinators, you can see nature at her whimsical best. Some orchid flowers are shaped similarly to the female of an insect species, so the males attempt ‘pseudo-copulation’, with no other benefit but that the orchids are fertilized in that manner. A good number of orchid flowers have strong scents. Some attract carrion flies with their horrid smell, and others emit a lovely fragrance that lures bees or other insects. Most angraecoid orchids are white, attracting night-flying moths. Some flowers are very brightly coloured, the bees come and - no they get no honey – they get the pollen shot at them with a hair-trigger mechanism; it sticks to their body until it gets rubbed off on the next flower they visit. A few orchids are pollinated by hummingbirds. Several orchids do provide some food. There may be sweet nectar in the bottom of a flower and many lady slippers have edible bristles on the inside of their pouch. When the insects crawl inside to nibble those delicious hairs (yecch!) they are trapped and can only escape through the place where they must touch pollinia or stigma.
Now let us look at a Phalaenopsis flower to see how we can pollinate it, (with our trusty toothpick).
Since a number of taxonomists are of the opinion that the orchid family is a part of the lily family and most of us are more acquainted with flowers other than orchids, I will correlate the structural features of a tulip flower to those of an orchid. In a tulip flower and in orchid flowers, there are six floral segments – three outer sepals and three inner petals. In the orchids, one petal is shaped differently from the others to guide the pollinators to the ‘right place’. As with tulips, the centre of the flower holds a stem – the continuation of the flower stem/ovary, which in orchids is called the “column”. At the end of this stem, in tulips, there is the sticky stigma. In orchids, this stigma is not at the top but slightly beneath the top and it is a little cavity. Surrounding the stigma in tulips, there are six pollen-bearing anthers. In orchids, these anthers are part of the column. The pollen-grains are wrapped in little sacks that sit at the end of the column under the anther cap and are loosely attached to the column by a thin thread called viscidium, which detaches rather easily. Orchid pollen are not dusty but waxy, to ensure safe transfer to the next flower.
The lady slippers are built on the same 3+3 system, like tulips etc. with further changes. Our main concern in these structural differences (in the case of slipper orchids) is the fact that the stigma is at the back of the column, behind the front-facing staminode. Some orchid breeders cut off the pouch of the mother plant in order to get at the stigma a little easier.
Some orchid flowers become pollinated inside the bud before they even open – not a desirable trait when we want to have pretty flowers to look at, but an apparently necessary development in areas where there are no more natural pollinators; these flowers are said to be “cleistogamous”. Please, do not try to grow these self-pollinated seed pods – they would just make more cleistogamous buds. Most orchids prefer to be fertilized with pollen from a different plant, ensuring genetic versatility. You have to understand that several orchids are so far apart in their genetic make-up that they do not cross-breed. For instance, any flower in the Laelia (Cattleya) group can be crossed with any flower within the same group, but you would not get any seed if you tried to cross these flowers with anything else, for instance in the Oncidium or the Vanda group. Zygopetalums are infamous for not accepting any pollen from another (even closely related) orchid; if you tried this, the result will always be another Zygopetalum – other plant’s pollen will not fertilize a Zygopetalum; they rather achieve selfings.
The success rate for artificial orchid pollination can often be improved when this is done during the time when the natural pollinators would be around: morning, afternoon, evening, night - moonlit or dark. I have found that out of 100 attempts at pollination, perhaps only 20 may result in viable seed.
So now that we know where the stigma is and what the pollinia are, we can put some pollen on the toothpick and bring it onto the sticky surface of the stigma. Sometimes, you can first dip that toothpick into the stigmatic cavity to pick up some of the moisture there. That can assist in holding the pollen in place during transfer. It is a good idea to have the mother plant standing on a large surface with a clean white paper underneath. Often the pollen roll away before they are securely placed and they are easier to find on a large piece of white paper. Then the names of both (potential) parents are recorded in our studbook with the date and other information and give this cross a number. Write that number also on a little label and put this label close to the pollinated flower.
Then we wait. It takes at least six months for a fast-ripening orchid seed capsule to mature; it can take over a year for others. When you notice that the capsule is starting to turn just slightly yellow at the stem end, you can cut it off and put it inside a letter envelope with its label. Try to get the seed planted right away, if possible. Please, make sure you always keep your labels with the plants, capsules, seeds etc.
One more thing: Please, try to use only healthy, strong plants to carry seed. It is a heavy burden on an orchid plant to carry a seed pod; at times, it means certain death for the mother plant.
And please, do not create plants just because you wanted to ‘see if it works’. Do make seed only when you think they would be VERY desirable or it is the only way you can keep a rare species going. It takes as much effort to raise a bad cross as it takes to make a good cross – why bother with something undesirable?
Ingrid Schmidt-Ostrander - Canadian Orchid Congress