Your plant isn't getting enough light.
Ideally indoor plants need to have a view of the sky. Ask yourself, where you want to place the plant, can it see some sky? This doesn't mean there has to be direct sunshine on the foliage. In fact I don't recommend positioning your indoor plants where they will receive a lot of direct sunlight. A few short hours of direct morning sun is ok.
If your plant says its "low light tolerant" then when you're deciding where to place it, see if you can read there, without turning a light on. That should give you a good enough indication of whether there is enough light for your plants.
Also note, a plants tolerance for low light, does not mean no light. All plants need some form of light, either natural or a grow light to survive.
You water your houseplants too much.
Plants do not need to be watered as often as you might think, and, watering them on a schedule is often a sure fire way to drown them. Most people don't realize there is a huge correlation between how much light a plant receives and how much water it will use, so be sure to adapt your watering to your environmental conditions.
So how much water is too much water? That really depends on the plant, however it is important to note that it is not the amount of water given to a plant when you're watering it, but how often you are giving the water. I usually allow most of my plants to dry out the top soil before I give them another drink.
Plants will show you signs that they are thirsty, some plants (hello peace lily) are a lot more dramatic than others, but the signs are there if you know what to look for. Such as:
- wilting and drooping foliage
- lacklustre and loosing colour
- wrinkling stems and leaves
- leaves curling in on themselves
- crispy leaves and leaf tips
- yellow leaves.
You potted your plant in a pot without a drainage hole.
There's no other way to say this, plant's NEED drainage! If you've got a pot without a drainage hole, it's for housing a plant in a nursery pot, NOT for planting into! If you use these cover pots, make sure when you water the plant you tip out any excess water that's drained. If you don't, your plants could be sitting in water which leads to root and stem rot and ultimately plant death.
And that's it, the 3 most common mistakes new plant parents make AND how to avoid them.
Want to learn more? Check out my mini course How to get started with houseplants.
I'll teach you the fundamental principles you need for getting started with houseplants and you'll be able to avoid many of the common mistakes new plant parents make.