Posted 4w ago by @omnommia

Determining the amount of water used for watering the plants
Does anyone know how greg computes for the amount of water it suggests?

The book I'm reading said to get a third of the volume of soil (or a quarter or even a fifth of it) to determine how much water to use. But, the amount I'm getting from my computations are far larger than what greg is suggesting me. Though, I may be computing incorrectly. If anyone is wondering how I computed for it, I'll attach screenshots of my process below. I've added computations for getting 1/3, 1/4, and 1/5 of the volume.
I'll also attach the screenshot of what greg suggests me.
#PlantParent #NewPlantMom #HappyPlants #PlantsMakePeopleHappy #NewGrowth #PlantAddict
Best Answer
Hi @omnommia @HoyaAddict! Happy to shed some light on this, it’s a great question.

First, here's general info on the amount of water to give your plants:

- @strawberrymoon is right that if your pots have drainage, the best rule of thumb is to water until a little bit of water comes out the bottom. It's actually not well-understood whether "rinsing" your soil is good or bad. The bad: may carry off some helpful nutrients. Houseplants require very little nutrients though (perennials and fruiting plants more). The good about rinsing: plants deposit sugars into the soil which are usually consumed by friendly bacteria. In potted plants there typically isn't much living matter so these "plant excrements" can accumulate. Also, there's often a little bit of salt and other minerals in the water you pour onto your plants which can accumulate. Letting the water flow through your soil may rinse these excess materials away. It's unclear whether it's a net positive or negative. Personally I think it's best to just water until you see a little bit of water come out the bottom.

- If your plants don't have drainage, watering the exact amount your pot can hold (or less) is extroardinarily important to avoid creating conditions where fungus grows in the soil, causing #RootRot.

- Your book is right that the pot volume matters. You can think of it as a cup that's holding water. Bigger cup = can put more water in.

- The soil composition also matters. Sandy soil = there's less surface area for water to cling to the soil particles, so it will hold less water. Soil with smaller particles (more densely packed) like clay and loam (the most common potting soil) can carry more water.

- Pot type also matters. "Porous" terracotta, some stone, and wood pots will absorb some of the water you pour, while non-porous glazed clay, metal, etc pots will not absorb water so more will sit inside of the pot available to the plant.

- Plant type matters. Succulent plants are unable to rapidly increase their uptake of water, while non-succulents can "slurp up" the water more immediately and quickly after watering.

- Finally, exposure to sunlight matters. Sunlight contributes the most to water consumption. It both causes the plant to photosynthesize more quickly (consuming water), and it also causes water to evaporate from the surface of the soil.
@omnommia maybe @alex or @Kiersten knows. I wished I knew. It might be an algorithm in their system that does it.
no idea, honestly i think if your plants are in appropriately sized pots it’s perfectly fine to just water till all the soil is soaked (basically until water comes out the drainage hole)!
@strawberrymoon I've actually been doing that! But I'd also read it could wash away some of the precious nutrients from the soil so I've been meaning to change the way I water them
@omnommia i don’t think that’s too much of an issue, just repot once every few years and the soil should retain enough nutrients for the plants to grow well. if you’re really concerned though you can mix in some worm castings (basically acts as a slow release fertilizer) into the soil :) your plant will tell you if they’re not getting enough nutrients, they’ll start yellowing or getting weak/lanky growth etc.
@strawberrymoon that's reassuring to know. thank you!
@omnommia np!! also i checked your oasis and i see you’ve got mainly flowering plants- those need more fertilizer than regular houseplants so i can see why you’re concerned. most plant soils come with fertilizer mixed in so it should be ok, just make sure to feed the perennials next year when they start growing again (probably early spring for most, idk much about flowering plants tho so it’s better to do your own research)
@strawberrymoon thank you for everything!
This also confuses me, I have three different Hoya all in the same soil, same pot and same distance from window. My largest Hoya (in size) is said to need 79ml, my two smaller Hoya (merilli and Pottsii) are said to need 110ml. I don’t understand the discrepancy at all.
Now, to your question about Greg:

- The water amounts are based on the pot diameter, pot drainage, plant type, and exposure to sunlight. We don't currently know your pot volume, but we will in the future!

- Because our predictions can't be perfect right now (we don't have enough info), we err on the side of "less water" to avoid over-watering plants. Most plants can do fine with a bit less water, but too much water will be fatal.
Thanks @KikiGoldblatt for tagging me :)
@alex wow! thank you so much! it's amazing to find out how greg processes and calculates for everything it suggests! i have newfound appreciation for this app.
@omnommia happy to help and thank you for asking! We’re working on a new Tips & Guides feature that will help explain some of this :). We do our best to calculate automatically where we can, and also share info to help everyone learn what plants need.
@alex Thanks for the info, I’m guessing this means a fungii Hoya needs less water than my others? Seeing as all other variables are the same except for the variety of Hoya

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