The medium we grow our plants in is extremely important, because it dictates our watering schedule, fertilising, and ultimately, the wellbeing of our houseplants. In this blog post, I’ll be breaking down some common growing mediums in terms of their strengths and weaknesses.
Commercial soil-based potting mixes are the most common growing mediums. These will work for most terrestrial and semi-terrestrial houseplants, and tend to be well-draining. They’ll also often include some of the following additives:
- Perlite for aeration
- Vermiculite for aeration and slow release nutrients
- Bark for drainage
Some gardeners like to add moss for water retention for some water-loving plants, but moss almost never comes in a potting mix. I think Osmocote tends to be a safe bet with this growing medium. I will say too, do not get the Brunning’s All seasons Potting Mix. The stuff smells foul, has fungus gnat eggs already in it, and comes with soil mites which come to life when watered. Both types of insects are totally harmless to your plants, but they’re just unsavoury in the home. It’s possible that I may have just gotten a bad batch, but that’s just my personal experience with that product.
Bark/Orchid mix is essentially some bark with a little coco coir and some slow release fertiliser is often used as an orchid mix. These should only be used for truly epiphytic plants. Bark gives the roots something to cling to, and allows water to make its way down the pot slowly enough for the roots of an orchid to get a good drink. It does not really retain water. Coco coir is used to retain water so that watering isn’t too strenuous. Fertiliser, for obvious reasons, keeps your orchid healthy. Orchid mixes tend to hold onto less water than soil, and as such, can be added to potting soil to help with drainage. Once again, Osmocote is just okay for this. I have noticed that the bark at the top of the mix comes in big, generous chunks, but when you get halfway through the bag, it becomes extremely dense with coco coir, which may suffocate the roots of orchids because coco coir compacts over time, and doesn’t allow a great deal of air in when it does so. I understand that this may be because the coco coir falls downwards in the bag and gathers towards the bottom, but if that’s the case, then there should be more bark and less coco coir in the bag.
Sphagnum moss is essentially just dried and processed peat moss, which is used to retain moisture while maintaining a good level or air circulation. Like bark, it is used alone for orchids, but also added to potting mixes for water-loving plants. Though I may have just absolutely trashed Brunning’s over their potting mix, I must say, their sphagnum moss is absolutely great. It comes in long, generous strands that you can use to make kokedama moss balls if you so wish, and the moss is always clean with no extra bits and bobs in it. Would definitely recommend it to more experienced orchid growers who can handle moss for their orchids.
The alternative, of course, is coco coir. Coco coir is cool, but it compacts more easily, and I don’t have that much experience with growing in coco coir on its own. In terms of sustainability, coco coir is more sustainable, from what I hear.
Clay beads solve the problem that the last two growing mediums have: they retain moisture well as well as allowing for great aeration for epiphytes. They’re also far superior in that they don’t make any mess, and never degrade or decompose. Basically, they work because clay wicks up moisture around it and distributes it evenly among the clay beads, and the beads themselves are circular. This means that all beads will touch each other at some point, allowing water to spread evenly throughout all the beads without collapsing on air pockets, provided that there’s enough water. There are some minor problems with clay beads, though. Clay beads should only be used in warmer rooms indoors. Wet clay beads can get extremely cold in the night time if the room temperature is not warm enough. They also need a rigorous rinsing before use to remove dust from them.
LECA has cornered the market on clay beads for hydroponics for a long time, and their prices reflect this. A lack of competition means their prices are ridiculous for what they’re providing: some leftover terracotta rolled into a ball and fired in a kiln. My recommended alternative is White’s Landscaping Clay Pebbles. These do the job just as well, but they’re a dark shade of brown instead of the vibrant orange of LECA beads. However, given that you can buy 10kg of White’s clay pebbles for the price of 1kg of LECA beads (here in Australia, at least), it’s a fair trade. It doesn’t even matter if you use a cover pot, anyway.
Water is also used to grow some plants, but what is there really to say about water? It’ll work for some plants, and it won’t work for others. Soft water works best, and try not to use it in cold spaces.