Hi everyone.

Laurie - Firstly let me say that I live in a temperate area of Australia so my cultural methods may not necessarily suit you and other growers who are in colder areas so you need to be aware of this, but I too have heard it said many times that you shouldn't let water lie in the cup of bromeliads.

Let me say that I have a couple of thousand plants (including Canistropsis billbergioides) which are growing in an open garden or just under the cover of shade cloth with no overhead protection from the dew or rain and I've never emptied out a plant cup yet, and my plants haven't suffered because of it.

Every time I water my plants, they are watered overhead, and the leaves, cups and potting mix all get watered, in fact the water will saturate the potting mix to the extent that the excess will run from the bottom of the pot. This why it's so important to use a well draining potting mix. Even when I bring flowering plants into the house they still get watered in the same way.

To answer your question, you just have to ask yourself, what happens to these plants when they are growing "in habitat" and it rains? There's no one to hold an umbrella over them to prevent water entering the cup and it therefore gets full of water. Indeed that's why many bromeliads are commonly referred to as "tank bromeliads"

The following article from Encyclopedia Britannica is well worth reading and after reading it you will understand that a bromeliad cup full of water, is part of a natural on-going process for maintaining life in the bromeliad family.

See: https://www.britannica.com/topic/Life-in-a-Bromeliad-Pool-1688529#ref740325

The advice of "never letting water rest in the cup" may have come about from people in areas where the water quality is very poor (Unlike the natural rainfall these plants would get in the wild where they are found); or it could be a misunderstanding of the advice to occasionally empty out the cup (or vase) when you regularly use "foliar fertilizer". The reason behind this is that the fertilizer "run off" will lie in the cup and may cause damage due to a build up of harmful fertilizer salts. In cases such as this it is advisable to empty or flush out the cups with fresh water every few weeks to prevent this build-up.

I hope this has helped to explain things for you and your friend.

All the best, Nev.

Ok, Thank you. I will tell her watering via the cup is safe and the plants preference. Thanks for you thorough reply. I grow plants, and she does not. I hated giving advice I was not qualified to give, so thank you.