Which Substrate for Which Plant: The Selection Guide

Most substrate advice is written for a plant in a greenhouse in the Netherlands. You are growing in an apartment in Israel, where the summer is long and dry, the tap water is hard, and the air conditioner runs for five months. What the plant sits in has to answer that. The question is never "which is the best mix". It is "what does this plant, in this pot, in this room, in this season, need to do". Three things decide it: how fast the roots want to dry, how much you want to be involved, and whether the plant lives in a cabinet or on a shelf. Soil-Free Mix is the default for aroids in pots. Monstera, Philodendron, mature Alocasia, anything with thick roots that rot if they stay wet. Coir, sifted perlite, pumice, LECA, pine bark and activated charcoal. It holds enough water to forgive you for a few days and drains fast enough to forgive you for overwatering once. If you are not sure, this is the answer. Terra-Lux is pure mineral, for semi-hydro. Pumice, tuff and zeolite, no organic matter at all. Nothing in it breaks down, so nothing sours, and there is nothing for fungus gnats to breed in. That makes it the mix for cabinets, for anyone who has fought gnats and lost, and for growers who would rather manage water and feed precisely than guess. The trade: it holds no nutrients of its own, so you feed at every watering. See the fertilizing entry for the EC numbers. Succculent Mix is for succulents and cacti, and for nothing else. Coir, perlite, tuff, charcoal and zeolite, tuned to dry fast. Putting an aroid in it means watering twice a week all summer. Zeolite Base is not a mix, it is an additive. A natural mineral that holds surplus water and nutrients and releases them slowly, buffers pH, and adds air. Ten to fifteen percent by volume into any of the mixes above makes the pot more forgiving, which matters most in August. Zeolite Boost is the rescue version, a powder for a substrate that has gone tired and compacted. If a plant has been in the same pot for two years and the mix has slumped into a dense block, this buys you a season before a full repot. Activated Charcoal is a filter. It binds toxins and excess fertilizer, keeps a closed environment from going sour, and stops smells. Mandatory in terrariums and in any closed propagation box. Five to ten percent by volume in a normal pot. A word on what not to use: garden soil and bagged potting compost. Both are built to hold water around a plant that lives outdoors in moving air. In a pot indoors they suffocate aroid roots. This is the single most common reason a rare plant dies in its first month in a new home. And do not reuse old substrate. It has lost its structure, it carries whatever salts you fed it, and it may carry fungus gnat larvae. Substrate is the cheapest part of the plant.