Cactus soil moisture duration?

[chancey84]

Has anyone out there logged the number of days that pass after watering until the soil dries out again? If so, is there a certain time frame to shoot for? It seems as though it could be adjusted by the components in which you choose to use in your soil mixture. Also, how long would you allow the soil to be dry before watering again? Thx!

[milos]

my soil is usually dry after one day in summer how long Ilet it dry depends of cactus

[adetheproducer]

Yeah most of mine are dry in a day in warm weather mabey two or three in cool weather but most in a mineral mix just crushed rocks etc.. I do have a few cacti in heavy organic rich soil so the time drying out is a lot longer with those like a week in summer to get bone dry but thats the point I like those plants to have a more or less moist soil with drought in winter.

[iann]

I'm struggling with the idea that pots are really dry in one day. Not least because even a cactus will suffer in those conditions, because very few will be able to take up a useful amount of water in 24 hours, certainly not enough to hold them for the length of time you should be waiting before adding more water. I suspect if you tip them out of the pot you'll find some moisture even a week later.

I aim for the pots to stay wet for a few days, with the last remnants of moisture remaining for perhaps 1-2 weeks. It varies with different species and the pot size. Small pots dry very fast even if the plant isn't thirsty, but large pots only dry very slowly by evaporation and you have to rely more on the roots to take up the water.

[Brunãozinho]

For genra like Astrophytum and Mammillaria, the soil in my regular plastic pots will be dry after 4 to 5 days maybe, but I would notice that the soil would still be a bit moist if I had to repot the plant.
The soil I use for cacti with tuberous roots dry faster, in 3 days maybe. That is, when the weather is normal here (hot days, sun shining).

For genra that like water, like Gymnocalycium, I have no problems even if I don't let the soil dry out, they can be outside in the raining season all the time and have the soil constantly moist for weeks.
I would say it depends a lot on the conditions of the place where you live.

[DaveW]

How quick potting soil dries out depends on your climate, or the microclimate of your greenhouse. Soils also dry slower in cooler winter months than in summer, or in more northern climates like the UK. Therefore soil mixtures have to be modified to suit your own conditions to provide quick enough drainage and dry out in a reasonable time, as Ian says.

[greenknight]

It also varies with how tightly potted the cactus is. If a plant is large for the size of its pot, obviously it can suck all the moisture out of that pot more quickly than if it were in a larger pot.

[7george]

There is no fixed time I let my soil to stay dry - it could be short, just a day or still some moisture deep in the pot summer (warm) time of the year and also for young plants and seedlings, or much longer, even months for the big plants and during colder season of the year. So I don't water them 'all together' but rather individually according the size of the pot, plant and species.
But the scheme 'once weekly or bi-weekly' can be working well for someboddy with a collection of similar soil, pot size and drenage and plants of one eco group (desert plants) kept in similat or identical growing conditions.
So keeping the soil with moisture for 3 - 5 days would be ideal for an average plant during the growing season but is not always possible in the real life.

[DaveW]

You can use the cheap soil moisture meters and not water again until they show dry, but how accurate these are is open to question.

http://www.ebay.com/sch/i.html?_from=R4 ... _sacat=261" onclick="window.open(this.href);return false;

http://www.ebay.co.uk/bhp/soil-moisture-meter" onclick="window.open(this.href);return false;

Most of them simply work on galvanic action rather than a battery, so don't leave them with the probe permanently in the soil as the tip will corrode away.

[iann]

So keeping the soil with moisture for 3 - 5 days would be ideal for an average plant during the growing season but is not always possible in the real life.

That's a nice length of time, but I know my pots sometimes stay moist a lot longer than that if it is cool and cloudy. It helps to be psychic in England so I can water the day before a week of solid sunshine and low humidity Watering the day before a week of solid rain can be fatal

[7george]

I guess many grown up cacti live in dry soil generally and just several times a season they fuel the body tank with water after the rains. But how many of us growers do this with their collection plants?

[Saxicola]

The roots on mature cacti spread out pretty far, so they don't tap out the moisture nearly as quickly as in a pot. Also, while cacti and succulent can tolerate completely dry soil that isn't what they prefer during the growing season. Ideally, there should be some moisture at all times in the soil. Not wet of course, just don't let the pots go completely dry between waterings. Of course, that does not apply to periods of dormancy.

[DaveW]

Cacti don't like cold and wet. The degree of moisture they will tolerate, or even prefer in warm conditions is very different to that which will rot them in the cold. Though some may get a snow cover in habitat winters they are usually dry cold conditions and the snow forms an insulating blanket throughout the cold season, not melting and providing moisture to the roots until the growing season starts again.

In you contrast that with our UK climate which may not be so cold but we have humid freeze thaw, freeze thaw conditions throughout the winter which cacti planted outside do not like because they are alternatively wetted then frozen again. The problem is even in the growing season, as Ian says, our weather can be unpredictable and often turn cold in summer just after you have watered the plants so they take longer to dry out, therefore we need very quick draining potting soil.

[BarryRice]

I live in a hot, dry climate. I grow my plants in a pure pumice/crushed granite mix (NOT DG). Last year, I carefully used a lab scale to measure the weights of pots with media. Starting with oven-dried media, I found it took about 5-7 days for freshly watered pots to return to the bear-original weights.

I reported the results here, but am not sure of the thread.

Cheers

Barry

[jp29]

The official Tucson (Airport) temperature hit 100°F+ (approx. 38°C+) for the first time this year yesterday (3% humidity) with a couple of 100°F+ temperature days predicted for this coming week - followed by some 110°F (approx. 43°C) temperature days. My back patio thermometer is registering 103°F right now so I will commence my daily hot weather early evening watering regimen this afternoon. Fortunately the Tucson night time temperatures drop into the 75°F (approx. 24°C) range right now and that differential allows CAM to come into play -- the plant stomata are open during the night and they can uptake water and nutrients.

Not always so in Phoenix, which is generally much hotter than Tucson -- I am sure there will shortly be some daytime temperatures in the 115°F (approx. 46°C) range (even hotter) with the night time temperatures remaining very high -- temperatures at midnight have been known to be close to 100°F (approx. 38°C) on occasion. Cacti then go into a summertime dormancy -- no matter how much you water and feed them they simply sit there awaiting the cooler night time temperatures of autumn.