Orchids are plants, therefore they have roots.
Most of our greenhouse-raised orchids are epiphytes – why? They come from the tropics. The climate in the tropics is conducive to plant growth; many plants thrive under tropical conditions, so there is heavy competition for growing space. All orchids probably started out growing on the ground, like most other plants and some orchids still do, for instance Cypripediums and Orchis which come from temperate climates. But in the tropical climate under fierce fighting for living-space, many orchids started to seek out better places, with more light to grow in. That is when they started to climb into shrubs and trees. Other climbing plants, like Virginia Creeper have stubby little roots, Pole-Beans wind around a stick and Sweet Peas have tendrils which help them to get away from the ground. Our epiphytic orchids have adapted their roots to help support their ascent into higher growing places.
Orchid roots consist of an inside core (cortex) which is very tough and carries nourishment and an outside covering (velamen) which is quite a marvellous material: it absorbs water, fertilizer, oxygen and clings to any substrate so well that at times it is impossible to remove these clinging roots from whatever they are attached to. In this way, epiphytes are not only well anchored, but also well able to utilize any moisture or food that comes into contact with these roots, which can grow for very long stretches (several meters), in the wild. One very important function of epiphytic roots is the exchange of gases – to take in oxygen. They must be exposed to moving fresh air, wind, fans blowing or whatever you can provide. Another job for some roots is to photosynthesize. There are orchid species which live in climates which change dramatically from very wet to very dry. These plants can become deciduous, going dormant in the dry season (Chilochista); some of these may stay without leaves. Others let their roots take over when there is not sufficient moisture to support leaves – these are called “Leafless Orchids” (Polyrrhiza). Some orchids (Cyrtopodium) have roots that grow upward, making the plant look like a birds nest; in this manner, they can catch moisture from the air (dew and guttation); they also trap insects and dead plant material to practically make their own aerial compost. Of course, in addition to the pseudobulbs, which are mainly storage organs, many roots are providing temporal storage for foods, mostly starches; this is particularly important for seedling orchids which first grow roots and the leaves come much later. Sometimes one can find that even though a plant is dead, its roots will continue to grow. It has even happened that out of the old roots there grew little plants, just as keikis grow from old flower stems, (Paphanatics).
The appearance of orchid roots varies with the species. Some can be big, round and fat with a diameter of 2 cm or so, others can be fine, like hair. Their colours can be white, grey, silver, brown, purple, red or green. They can be smooth, scaly, thorny or warty. Some experienced people can tell at a glance what kind of an orchid they see, just by looking at their roots.
One thing that I had been told – and I found that it is true, is that each orchid’s roots grows according to their environment; when you change this environment, the plant has to grow a different set of roots. For instance: when you have a plant that has its roots hanging outside the pot, they will not do well when you stick them inside the pot, covering them with growing mix. Even if you change the plant’s growing mix, (for instance from bark to peat or vice versa), or if the water is very different from what the plant is used to (from prairie water to West coast water), it takes the plant a long time before it has grown the new roots for these new conditions. In the meantime, the plant will falter.
That is why it is generally advised to re-pot at a time when new roots are beginning to grow. By this it is meant that the new roots are just barely breaking through the stem – do not wait until they are a few centimetres long: they break off easier than glass. Some orchids keep their roots for many years and others must grow a new set of roots each year. For this particular reason Lycastes and Miltoniopsis need to be repotted annually. Most orchids, under our temperate conditions, grow during the summer. Therefore look for fresh roots tips in the spring and try to repot then – never mind if the plant has flowers; just be careful. Roots are more important than flowers. Without roots, the plant will decline and die. As long as the roots show fresh tips, you can water and fertilize regularly – the plants want to eat and drink! When the velamen has covered the tip of a root, the plant may want to rest – or you have neglected it and it is shutting down. Some people suggest that you water with plain water first to avoid burning the dry roots with fertilizers and only after things are moist, apply the food. Others use a very dilute solution and water with that continuously. Just remember to flush out the growing mix at least every other month, with clean, warm water. One very useful bit of information I have learned is that roots need vitamin B to grow well. So try to find a fertilizer that has this substance printed on the label. Your orchids, their roots and of course their lovely flowers will thank you.
Ingrid Schmidt-Ostrander - Canadian Orchid Congress