If the stem is long enough, provide a small totem for it to climb on. Philodendrons really react to having support, and will even bring about change in the leaf size and shape.

Are you suggesting that a philodendron that is left to its own devices and left to dangle in mid-air, then it will suffer, but to train the plant 'upwards' on a totem-pole will encourage proper growth.

Yes. I've had some dangle, but will grab onto the wall to move upward. There is a mechanism in the plant that changes its morphology. Shinglers (i.e. Rhaphidophoras) are a good example of this, which start out flat against their support but emerge with larger leaves similar to monsteras.

Not letting the plant dry out too much can also help. You'll get the best results in a humid environment.

Thanks for the help, i've now trained to a moss-pole so i'll wait for some decent growth to return.

I have left cuttings of this sp. to vine along the ground so as to build up stock . They never get large leaves until very well established on a strong support . It can be a difficult species to grow to perfection.

If you have to train it up a pole/support to get maximum growth and it takes years to grow large mature leaves, who tall does the support have to be!!!!!!!

Not that tall , it gets very close internodes when mature .
2m would be ok .

Thankyou very much for your help, there seems to be something wrong with my tropical greenhouse enviroment because it is not such the Philodendron Melanochrysum that is sending out small leaves, other species of Philodendron are also doing the same, in particular Philo.Giganteum whose leaves have started getting smaller for no apparent reason. I also grow ALocasia and Anthurium in the same greenhouse with no problems, its just the darn Philo's dont seem to like it in there and i don't no why.

I have a Philodendron plant which has grown abt two meters however lately it is not producing leaves since last two months. What could be the reason?