Plant Doctor Christopher Satch
New to repotting? Start here!
(AUTHOR’S NOTE: this is tailored to houseplants/terrestrial plants. For orchids, go to the bottom)
So, you’ve finally gotten your first orchid! ( #YAS !) or houseplant. So now what? Generally, when you buy ANY plant, it’s planted in a medium that is conducive to GREENHOUSE growth. So you need to switch it to a medium that is conducive to home growth. Often times, you’ll be sold a plant that is too big for its pot. Maybe the media will be old. In any case, it’s a PLANT DOCTOR BEST PRACTICE to repot any/all of your plants when you bring them home.
Now, before you newbies hit the panic button, does repotting have to happen immediately? NO! You have a good 0-2 week window in which I recommend you repot. Honestly, for my own collection, I repot right after I treat with my pesticides (insecticidal soap ‘n’ such). But feel free to do it sooner, or wait until the 2 week mark. Why such a graceful period of leeway with repotting? It’s because root size won’t immediately kill your plants (unlike insects). It’ll need a bigger home as it grows, but it can be squeezed for a little while.
Anyway, why do we even repot? Good question! It turns out that plants are just as big underground as they are aboveground, but for some reason, folks seem to lose their perception, and wonder why their 48” tall plant stuffed into a 6” container “keeps dropping leaves”. Go figure. In any case, since your plants are just as big underground as they are aboveground, you need to follow the rule of THIRDS! All of the photography nerds just squealed with delight, but it’s not the photography rule of thirds, but rather the plant rule of thirds.
Basically, the plant rule of thirds states that –
ON AVERAGE, for any given plant, the ideal ratio is 2/3 aboveground, and 1/3 belowground is the maximum/ideal ratio.
That means that if the plant exceeds that ratio in height, then the plant will need to be repotted OR (and big or) trimmed back. Most folks just think to repot, but trimming is an option for some plants. If you trim lower than that ratio in the shoots, then you will spur branching in the appropriate plants.
YOU SHOULD NEVER trim the roots unless they are rotting, dead, or you are doing bonsai. You may, however, tear the roots a tad to loosen them during repotting. That’s ok and welcomed. It’s ok if a chunk comes off, but don’t like… eviscerate it lol. An ideal tear of the roots is one where the chunk you tore is still hanging off the main mass. That’s the spot…
Onwards to choosing a pot!
Unless you are super experienced with plants (and you WILL know), do NOT, EVER, grow ANYTHING without drainage. ALWAYS choose a pot with drainage.
Terracotta – this material dries the fastest. Terracotta is porous and allows water to escape evenly. This is a great choice for super large plants, or plants that like to dry quickly between waterings. The downside is that terracotta is heavy, so if you are using it for a bigger plant, be sure you’re probably not going to be moving it often.
Glazed Ceramic – Dries slower than terracotta, and is great if you like more stylish pots. However, the downside to these is that many do not have drainage holes, and of the ones that do, they may not work with a nice saucer beneath to catch what does flow through.
Plastic – Dries the slowest, and is recommended for plants that are small, or plants that like to stay on the moist side, like ferns. The downside is that if you have a dark home, plastic might keep the media too wet, leading to fungus gnats and such. These are best used on plants that get a lot of light to help them retain water for a tad longer.
Metal – You should not use metal pots for plants ever. No exceptions. They often leak, and are often made of cheap metals that corrode and poison the plants over time. Just because they look good in a magazine, does not mean that you should use them.
Choosing the Right Plant Media
I’ll tell you a secret that the plant industry doesn’t want you to know (sounds like an ad, amirite? Lol!). They create mixes upon mixes for all kinds of houseplants that really don’t care much of what they are growing in. Does your monstera NEED a perfect mix of the finest coconut fiber, pacific northwestern cedar bark (fair-trade, of course), ethically-sourced peat, Italian lava rocks, and 100% pure lab-grade perlite? Absolutely not. You can plant most of your houseplants in… just regular houseplant mix.
Now, that being said, you can adjust the mix slightly to accommodate your watering habits. If your pots end up being on the moist side, or you have a plant that wants it drier, mix in some sand. I do so for my succulents, and certain tropicals that just like being moist, but not staying wet. For example, my vanilla vines are planted in 1/3 sand and the rest is potting soil and lava rocks.
If your plants like more aeration, consider adding lava rocks to the mix (but not too many). Don’t be a lava rock head and plant it in JUST lava rocks. Unless it’s a lithophytic species (like my Laelia milleri), then it should not be planted in rocks alone.
If your plants are partially epiphytic, or grow in plant debris (like a lot of ground-dwelling tropicals), then add orchid bark chips to the mix.
I’ll give you a breakdown of common additives below, but I reiterate – IF you are growing regular houseplants and nothing too uncommon, then you can just use orchid mix for orchids, and regular potting mix for everything else. But I know that some of you will try some more exciting plants, and some of them do indeed need to have something adjusted.
- Potting mix – Great for almost everything. Default to this.
- Perlite – creates aeration in the mix. Reduces the weight of the pot, as it is light. Perlite is white, and made of superheated volcanic glass.
- Lava rocks – Great for some terrestrials to have randomly in the mix; great for plants that grow lithophytically. Not great for drainage. You don’t need lava rocks for drainage if you have a drainage hole!
- LECA – literally a trendy, hipster lava rock. See “Lava rocks” above.
- Vermiculite – great for water retention and a source of trace minerals… bad for the environment. I’m torn. It’s such a good soil additive, but the mining of the silicates releases asbestos into the environment at the mining site. I would only use on plants that need need need silicates (like Paphiopedilum and SOME aroids).
- Calcite/Marble chunks – Should be unpolished to aid in effectiveness. Absolutely essential for high-pH-loving plants, alkaline growers, and plants that natively grow on/near limestone (you just have to know your plant. I know that a few Paphiopedilum and a few Alocasia natively grow on/near limestone and do SO MUCH better with these natural pH buffers. In addition to providing alkalinity, these chunks are also a natural source of calcium, an essential mineral for strong plant growth and disease resistance. Just be warned, some plants are sensitive to too many salts (calcium-compounds are salts), so don’t give EVERY plant this treatment.
- Orchid Bark Mix – is usually cedar/piney-type bark mixed with charcoal, perlite, and sphagnum in varying degrees of coarseness and ratios. Most of your orchids can be planted in this. If growing indoors, add more sphagnum. Never hurts to add charcoal if you have hard water to help pull out the excess salts. Best recommended for orchids, alocasia, hoya, and other epiphytes.
- Sphagnum – Made from basically dried moss (what a shocker), if you end up getting live sphagnum, it actually produces acid on its own, so will naturally acidify the media (again, only if alive). Live sphagnum is really only recommended for growing carnivorous plants that are found in bogs, which are naturally acidic anyway. Dried sphagnum does not change the pH. All of my orchid mounts are padded with sphagnum, and all of my indoor orchids have mix with sphagnum in it. Beware because sphagnum retains moisture when wet… but when it dries out, it actually repels water. So, just do what I do and “pre-moisten” the sphagnum on the top of your (presumably) orchids, and then water normally about 5min later. It should absorb much better.
- Charcoal – Whether you are on some kind of cleanse (which actually do more harm than good), or your plant needs it, charcoal shouldn’t actually be used that often. Too much may raise the pH or take away essential fertilizer salts that are needed by the plant. I recommend using charcoal with salt-sensitive plants like calatheas, orchids, and some aroids.
- Coconut coir – For whatever reason, this stuff is trendy, and for the life of me, I cannot figure out why. I actually find coir to be detrimental to my plants, as many sources of coir are contaminated with sea salts (which are contain sodium, which is like… near instant death for plants. Game over). Coir is also even worse than sphagnum in that it is even harder to get moist than sphagnum when it dries out. It does not break down and release nutrients to the plants over time like a good mix additive should. My Plant Doctor’s advice is to steer clear of coir.
A Special Note on Orchids –
Orchids are epiphytes, and need a special mix to emulate growing on trees and being wild and free. You can use varying degrees of orchid mix for most orchids. Terrestrial orchids like jewel orchids can be planted in regular potting mix. Do your research and figure out if your orchid grows naturally with limestone, and if it does, then add sand and calcite/marble to the mix. Many Paphiopedilum like the silica from added sand and vermiculite.
A Special Note on growing your plants in a semi-hydro way –
Semi-hydro has come to mean everything from basically growing your plants in water (yuck) to what sounds like a watering technique that a lot of home gardeners already use. Whatever your definition, let me clarify – bottom watering isn’t really semi hydro because you do indeed allow the plant to get dry. Semi-hydro is (as I understand it) is growing your plants in some kind of LECA and having the bottom roots touch perpetually stagnant water. It’s NOT a good way to grow plants, and I highly advise the hipsters who invented it to come forward and apologize for all the misinformation that they are giving to people. As I’ve always stated – if a plant was meant to be grown in water, then it would be an aquatic plant.
A Special Note on Trellises and Stakes –
You should probably always use plastic stakes, or natural materials (like bamboo or hardwood) for trellises. Trellises are a permanent (or permanent enough) fixture in the pot for the plant to vine up. Because you won’t reuse your trellises for other pots, it’s fine to use natural materials. Hardwood or plastic is best; bamboo or softwood (like pine) is worst because they rot fast. As for temporary stakes (like flowering stakes), plastic is best because you can sanitize them between flowerings, and use them on different plants. Natural materials will carry whatever spores land on them, so may transfer disease amongst your plants. Metals are off-limits as they WILL corrode and WILL poison your soil.
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