These orchids native growing habitat is in trees where the flower spikes can lean out into the atmosphere. Here's a quote from this site.
You might want to do some reading here. You can do a search at the bottom of the page of the last link.
Dendrobiums are a funny orchid. After blooming, cut off the flower spike. Dens tend to drop all their leaves and leave nothing but the cane. Do not cut the canes as long as they are firm and are not dead. This is where your next flower spikes will come from.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.