H-A-L-T Means TLC for Orchids

By Joe Francis, Fairfax Master Gardener
When it comes to growing orchids, H-A-L-T doesn’t mean stop; it means proceed with the knowledge it takes to grow these beautiful plants successfully. Orchid plants require H-A-L-T to thrive; that is, they depend upon:

  • Humidity for the transfer of moisture through the velamen covering of its epiphytic root system
  • Air movement to maintain the root system and plant health
  • Light for completion of its growth and subsequent flowering
  • Temperature to match its inherited genetic growth characteristics

orchid clusterHumidity
A discussion of an orchid’s growing environment begins with humidity, the constant source of moisture to the velamen coating on the epiphytic orchid root system. Total lack of humidity will kill the plant quickly; insufficient amounts of humidity will kill the plant slowly. A delicate kabuki dance takes place between the grower’s control of the watering can and the root system’s ability to absorb moisture and dry out between watering events. This balance is much easier to maintain if the grower places humidity trays filled with water and pebbles beneath the plant to insure that the growing pot sits ABOVE and not IN standing water. Grouping plants in close clusters in their humidity trays will create a humid microclimate.

Air circulation
Air circulation is essential to the drying-out process of the velamen covering on the root system. It insures air movement in and around the leaf surfaces of the plant and prevents fungal infections. It ameliorates the effect of excessive heat in the growing environment, and — in combination with light-misting applications — it quickly controls temperature surges. Air circulation is a 24/7 necessity in orchid culture. It is not uncommon to find the home grower giving short shrift to this essential environmental control. The price is a struggling plant making the slow trek to the compost bin, never having produced a flower and heavily laden with surface fungal growth.