Watering Houseplants Part 3: Watering From Below
One of the biggest disservices that I do my houseplants is watering them from below. Even though I know better sometimes I can't resist the urge to fill the sink or a large container with water and setting the plants in the water to get a drink. Watering houseplants from below is a time saver if you have a lot of plants to deal with but you should avoid it when possible.
If like me, you're in the habit of setting your pots in water you may find that a white crust develops on your pots, in bad cases the white stuff will collect on your plant. In the photo above the first image shows the development of a hard white substance on a Monadenium in my collection. In the second photograph the white crust has developed on the terracotta pot of a cacti but if you look closer there is also a brown gunk growing on the cacti. Sometimes when you water too much or when water doesn't drain properly a green slime will also develop on the surface of the soil.
The crusty white substance on my succulent plant and on the terracotta pot are minerals that have collected from the hard water that comes from the tap and fertilizers. When you set your plant in water you allow for minerals and chemicals to collect in the pot and soil instead of being washed out. These soluble salts (like fertilizer) stay behind when water evaporates and eventually the high concentration of these salts in the soil make it hard for the plant to take up water. Soluble salts damage the roots of your houseplants and weaken them to the point where they are vulnerable to pests and diseases. Reduced growth, brown tips and dropping of lower leaves are all signs of high soluble salts concentrated in the soil.
You can remedy this by following these steps:
Avoid setting your houseplants in water when they need watering and don't ever let them stand in water. Make sure you're following the directions on the package of your houseplant fertilizer. If you use commercially available houseplant soil check to see if it comes premixed with fertilizer granules. Don't skimp on your houseplant soil-buy the best you can afford and amend it with perlite. When you water use distilled water or set it out overnight to allow for chlorine to evaporate.
You can remove the white crust from your pots by using a stiff sponge that is moistened and scrapping away the crust or starting over in a new pot. Sometimes when you bring a houseplant home from a greenhouse that has been sitting in water or not taken care of properly you'll find that the soluble salts have already accumulated. In those instances I will usually just slip the plant into a pot that is the same size as the one it is growing in until I can transplant it. Every New Year's Eve I make a resolution to stop watering my houseplants from below-maybe this year I'll keep my resolution.
Watering Houseplants Part 1: Pick Them Up
Watering Houseplants Part 2: Botanicalls