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I suspect that I might have too much salt in my potting mix as a result of using unwashed builders sand in my potting mix. Should I flush the pots with water hoping to rid the mix of excess salts and is now the best time or would it be better to wait until plants are winter dormant.

The mix has good drainage but I'm still concerned about water logging. Would a dormant plant be less likely to be harmed by water logging than an active plant?

Mark Morgan Lloyd
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Michael Sherpa
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2 Answers2

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I am not aware of builders sand containing anything except sand. So, I wouldn't worry about it.

What is builders sand? Builders sand is a coarse building material, not to be confused with children’s play sand or even beach sand. Readily available at most home improvement stores and landscaping centers, builders sand is a cheap alternative to perlite, another horticultural material used to improve drainage and aeration in soil mixes.

From tinygardenhabit

BUILDERS SAND Builders Sand is a general purpose No.1 river sand which contains the absolute minimum of salts. It is ideal for use as a concrete sand, for basic mortars, children’s sand pits and as a paving stone sub base. In general it has a top particle size of 1.18mm and a bottom particle size of 0.15mm with an average size of 0.4mm.

From firth

I am not affiliated with either site.

The clue that I missed in my references was riversand. In some areas, the sand will be from the beaches. In this case, it may have salts (mainly common salt) from the ocean. So rinsing would be prudent, as quickly as possible.

Rohit Gupta
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  • I just did a quick Google search to no avail but I'm guessing that "builders sand" in USA may be different to builders sand in the UK. In the UK it is what is normally used to make mortar for a brick wall. The sand particles aren't so gritty as sharp sand and are lightly coated in clay which makes it more pliable for the brick layer. Apparently some builders sand can be tainted with salt which on drying exits the mortar and leaves unsightly white marks. I'm guessing I got unlucky and bought poor quality. Thanks for sorting out my typos. – Michael Sherpa Jul 14 '23 at 17:47
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If you are following the salt theory, rinse sooner rather than later. Of course, it might not actually be the issue.

You should not be "waterlogging" the pot when you rinse it. If the pot has proper drainage holes, it's not really any different (and I'd expect it to have already happened multiple times if the pots are outdoors - certainly does in my area) than a heavy rain event. It gets wet, excess water flows out, it does not stay wet for an excessive period of time. If the pot is in a saucer, remove it from the saucer (and dump out the saucer) to drain.

Waterlogging happens when you leave a plant in excessively wet soil for a long time.

It's quite common, for instance, to "plunge" a pot that has dried excessively by completely submerging it in water for several hours - followed by allowing it to drain and then returning to "normal" watering. The plunging does not "waterlog" the plant unless you forget one in the plunge for days-to-weeks.

If the pot does not have proper drainage holes, either make some, or move the plant to a suitable pot.

It's very common for pots without drainage holes to be waterlogged, even without much watering. My theory is that pots without holes are popular in the retail nursery industry precisely because they ensure plant death and purchase of replacement plants...

It's also common for plants left in full saucers of water all the time to be waterlogged.

Ecnerwal
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