CO-Horts Blog

Monday, March 25, 2019

Top houseplant watering myths

By Irene Shonle, Director CSU Extension in Gilpin County

I live in the mountains, and both March and April can be frustrating for a gardener’s soul. I see reports of crocuses and snowdrops down below, but we are still white and frozen up here. This is when I turn to houseplants to save my sanity. 

Late winter houseplants at my house
Houseplants can be such a boon for the winter-weary, but they can also pose frustration for those who have trouble keeping them going.  In this post, I am going to bust the top three myths that lead to poor watering habits (probably the number one killer of plants).

The most pervasive myth is that you should always add a layer of gravel or other coarse material at the bottom of pots to improve drainage.  This is an extremely common recommendation, and while it seems plausible, it actually does the exact opposite! Soil scientists have known for at least the past hundred years that water does not move easily from layers of finer textured materials to layers of more coarse textured. Instead, the water will not move from the finer material to the coarser until the finer soil is completely saturated. This is called a perched water table. Bottom line- your entire pot should have the same high-quality soil in it, and nothing else. If you need to improve drainage, mix perlite in the soil throughout the pot. Also, make sure there is a drainage hole in the bottom of the pot, though, or the lack of drainage could cause root rot.
 In the cup on the left which is filled entirely with potting soil, water sits at the base of the container while, in the cup on the right which was filled halfway with gravel, water sits above the gravel - From The Garden Professors Facebook page
The second most common myth is that you should always water on a schedule.  This is popular because it’s easy, but it does serve your plants well. For one thing, plants often need less water in the cooler, darker days of winter – perhaps a plant that needs watering every couple of days in the summer might go a week in the winter without needing it. For another thing, if you have many houseplants, they may not all need the same schedule of watering. Some might need a drink every couple of days while others would prefer not to be watered more than every couple of weeks. My orchid cactus will only come into bloom in the early spring if I don’t water it at all starting in November! There are other plants that respond to dry periods with a flush of blooms, and still others that won’t flower unless kept consistently moist. Get to know the needs of each plant, and cater to those. Don’t water any plant if the soil is already quite moist – poke your finger in the soil to see if it needs water or not.

The final myth of today is that droopy plants always mean it’s time to water. If the finger test mentioned above indicates a very dry soil, then yes, water quickly before you lose the plant.  But double check before you water – plants that are developing root rot due to too much water will also droop, and water is the last thing they need!

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