A good way to think about orchid roots is to think about car tires. Tires do an important job, get worn out doing their job, and eventually get replaced. Orchid roots are the same way – they do an important job, get worn out doing their job, and eventually get replaced. Orchid plants generally initiate new root growth during the start of the growing season. Roots will emerge from new shoots; it is rare that roots will emerge from older growths. In some orchid types, you’ll actually get new root tips branching out from OLD roots; Vandaceous types including Phalaenopsis and Neofinetia) do this, and I’m sure others can, too.
So if you find that your orchid doesn’t have quite the robust root system you were expecting, don’t worry too much. Orchids want to grow new roots, but they’ll do so when the season and growing conditions are right.
Your job as a grower is to create conditions where new roots can grow AND extend. That means having the proper media and moisture level in the media for roots to grow into. It’s always annoying when an orchid starts to make new roots, but then the roots stop growing. This happens because the root couldn’t find water (and, in some cases, something to cling to). So when you see new roots emerging, make sure the roots can find some moist media, such as damp sphagnum moss or thoroughly wetted bark.
Keep in mind that the vast majority of orchids want aeration at the root zone, which is why overwatering is the number one killer of orchids. Too much water (usually because there’s too much media in the pot) will drown the roots, and you’ll end up with a rootless, and stressed, plant. One great thing about orchids is how tough they are. Consider a garden plant like a tomato. A few days without water, and that thing is in trouble. This is very true for many plants, especially ones grown in containers. Orchids, on the other hand, can handle lack of water for weeks, and in some cases, even months. This very ability to handle dry conditions means that orchids can usually recover from loss of roots, although it can take awhile (months or even a year) before they re-establish, and it’s best keep them very humid in the meantime.