Question
I take care of a variety of plants at work and some of them are getting yellow leaves.  I water them once a week.  What am I doing wrong?

Answer
Could be too much water, could be too little.

Watering plants on a schedule is like using an umbrella on schedule.  Why use an umbrella if it isn't raining?  Why water if the plant is not dry?  Why wait to use the umbrella if it IS raining, why not water when the plant NEEDS it?

Are you with me here?

Water when the soil is dry.  Then water it like nobody's business.  Drench the soil, make sure the pot is soaked, and let it drain.  Now you've watered.  Wait.

If it uses a lot of water, and the soil is dry, water it again in a few days.

If it's still dry in a week, DO NOT water.

Plants use water at different rates.  Some are heavy drinkers, with big, vigorous root systems and large leaves that lose water rapidly.  Some plants use very little water.  They're great for xeriscaping in California or Nevada.  They don't need to be watered more than once a month.

There's also the matter of seasonal cycles.  Some plants burst into growth in Spring and they need more water than the ones that sleep through Spring.

Yellow leaves are the symptom there's a moisture problem.  Correct your irrigation technique, and you will see a noticeable improvement.  Thanks for writing.