What does 'let dry lightly between waterings' mean?
 

Hi, I recently got two new orchids - Isabelia pulchella and Epidendrum parkinsonianum, and care tips about both says they should be 'let dry lightly' between waterings.

Honestly, I don't get what's 'dry lightly' means.
I understand that it's somewhere in between Bulbophyllum (always moist substrate) and Phalaenopsis or Dendrobium (let the substrate dry completely before watering again), but where exactly? And how would I know that I got the right wetness?

Isabelia is mounted with some sphagnum and I put it near Aerangis Modesta, also mounted, very close to humidifier - basically, the most humid corner of my plant shelf. (humidity is 80-90%). Epidendrum I repotted from the pot to hanging net basket with sphagnum/perlite/lava rock mix

Most horticultural terms are so vague they're meaningless. My best guess is "don't keep completely wet."

How to water orchids varies with the immediate growing environment. I haven't grown the Isabella. Epidendrum parkinsonianum does best kept continually moist during the warm days, cooler nights growing season so long as there is plenty of air at the roots. In the long dry season, with cool days and cooler nights, there is often dew at night, so it is not dry for long. It grows hanging down off trees. Many people mount it if they can keep up with daily or almost daily watering.

I do grow both - mounted. The Isabelia (Neolauchea) pulchella is a rambler. it crawls off the mount and doesn't seem to care. Epi parkinsonianum needs to be mounted to manage its dangling growth habit. I found that a little sphagnum around the roots helps maintain a bit of moisture. I grow both outside all year around. (Winter night temps often down to 4 deg C or a bit lower with days more often in the 18-22 deg C range, summer days up into the 29-32 deg C but nights usually 20-22 deg C)

As with most mounted plants, they love daily watering, it's pretty much impossible to overwater a mounted plant.

When it comes to mounted plants, what's the difference between watering and misting?

Epidendrum is big and heavy, and I didn't have anything to mount it on, that's why I chose to make a net basket - it seems to be ok in it - no new growth yet, but no signs of any issues as well (the damage you can see is most probably by snails, it was sold like this, and it doesn't spread). I water every 2–3 days by submerging, usually, the substrate is almost dry when I water

Isabelia was mounted by a previous owner, and seems to be fine too - I hung it very close to a humidifier. If I don't turn it off, it is constantly wet, but I usually forget to add water in time, so it has some drier periods.

And.. what's completely wet when it comes to mounted plants? it's hung above the humidifier, so when it's on, it has tiny droplets of water constantly condensing on it. Is it 'completely wet'? should I turn it off more often / for a longer periods to let it dry?

These both need to dry out between waterings. Mine get a good bath each morning, then dry out under ambient conditions the rest of the day.

Even true cloud-forest plants don't want to have water condensing on them all day - for at least part of the day, even with high humidity very few want to be dripping wet all the time. And these definitely need to go from wet to "much drier" in the course of the day.

Do you have outdoor growing space? What is your current temperature range, what do you have in summer?

I don't think anything "needs" to dry out between waterings. Doing so applies to the requirements of the potting medium, not the plant.

I think that if we focus on "AWR" = air/water ratios - so that it fits the needs of the plants, we and they would be better off.

For example, bulbophyllum, oncidium, paphiopedilum, phalaenopsis, cattleya, and vanda will likely range from a very low-, to very high AWR, with it increasing (i.e., more airy) with each genus, respectively.

And just like everything else "orchid", there are no absolutes - where YOUR plants are on the AWR Spectrum will depend a great deal on your array of cultural parameters.