Watering When Dry?

[dw0rk1n]

I have been following the rule to water when dry. I have some soil/pot/cacti that get completely dry within 2-3 days. Would you say it's OK to water every 3 days in some cases, or there is some kind of minimum?

[iann]

Probably you'd do better to address why the pots are drying out so fast, since most cacti would be happier staying wet for several days, drying out over a few more days to perhaps a week or two, and only then getting wet again. Are you not wetting the whole rootball? Most of the water running straight though instead of soaking in? Soil mix too porous for your climate? Porous pot just evaporating all the water? Or simply evaporation from the soil surface combined with wicking up moisture through the soil? Or just possibly a massively efficient root system in a fairly small pot drinking all the water in two days?

[peterb]

Also wondering where you live and what your climate/temps/humidity is like?

In Phoenix, I do water every 2-3 days sometimes, in the transition from spring to summer.

peterb

[dw0rk1n]

I thought the opposite, the soil should dry quickly to prevent rot.

I live in NJ. These are house plants.

My mix is equal parts of regular soil, coconut coir, pumice, and coarse sand. The pots are from a regular clay.

When I water, I add about half an inch on the entire surface. I think most of the water soaks in. If I add too much, it runs through.

My guess would be the soil mix is too porous, the pots help as well, and some cacti "drink" fast. I would say Hylocereus undatus and Ferocactus emoryi are at the top of my list.

[cortez753]

I just say NO to sand

[oldcat61]

Hi - just curious; where are you in NJ? I'm in the south, near Atlantic City. Any good GHs near you? I'm running out of places to shop! Sue

[iann]

The soil should dry out to prevent rot, but two days is too fast, as you've found out. If it were two days in an occasional heatwave, or even two days for a month or two at the height of summer, then maybe you'd live with it, but this seems like it really is drying out too fast. You just don't want to be watering every three days all the time. It defeats the purpose of having a soil that dries out fast Some cacti will cope with it, sucking up enough water before it evaporates, and you might not even need to water them for a week or more to keep the cactus fat. Others simply won't cope, slower roots, they'll always be thirsty, you'll always be watering them more, eventually they die.

If you are in the second situation, with some of your plants always seeming thirsty and you having to water them all the time, then there are a few things you can try. Porous, unsealed, clay pots dry out extremely fast, so that's probably most of the reason. You could seal the pots, but it is a lot of effort. You could use a non-porous pot, but they are either less attractive such as plastic or expensive such as glazed clay. You can add a top dressing, which will reduce evaporation a lot but is not so effective when the water can just escape through the sides of the pot.

You can use a more moisture-retentive soil, but that is a double-edged sword, because you don't want to be giving loads more water than the cactus can drink, and praying it will evaporate. If it doesn't evaporate the plant might rot. If it does evaporate, then you're just hastening the onset of salt buildup. You might find that a completely different type of soil will solve the problem, perhaps by allowing the plant to develop more roots that will let it get a drink before the water evaporates.

Overall, I just don't like soils that dry out so fast by evaporation. It eventually, or sometimes quite quickly, leads to a bunch of other problems. Experienced growers often have all sorts of strange habits designed to work around these problems, but much simpler just not to allow them in the first place. I aim for a situation where the pot of soil holds sufficient water for the plant to get a good drink, and holds it long enough for the plant to take it up. There is always compromise, and pots can dry out too fast in summer, or not at all in winter, but it is a good incentive only to water when the plant wants it. I've been known to tip off the top dressing to allow a plant to dry out when I get it wrong

[CactusFanDan]

Most, if not all cacti, seem to grow fine root hair cells and feeder roots in response to water, which allows them to take up water very quickly and efficiently. In times of drought, fine feeder roots die back and become woody on the outside to prevent water loss to the soil. It takes from hours to a few days for cacti to grow these roots, so as a result, your soil mix needs to stay moist for long enough that the plant can grow these roots to help it to suck up water. It also depends on if the plant's at the right temperature to allow it to grow these roots. It might be too hot or too cold for it.