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Flushing salts from house plants?

I was reading some information about caring for house plants, and several sources recommend doing a monthly or seasonal flush of the plant to rid the soil of salts or other material buildup.  The idea is you place the plant in it's pot over the sink or some place for drainage (wire rack over a bucket), and give the plant a large amount of water until it is running out of the bottom of the pot.  Wait 10-15 minutes for salts or such to dissolve, then do another deep watering to flush the dissolved things out.  

I've never done this before in my 20 years of house plant growing.  BUT I traditionally grow tough/resilient types of plants, I'm not very good about fertilizing, and I tend to pot up/on as needed.  

As I have progressed in my career over the years, so has my salary.. so I have found myself purchasing every more expensive and potentially sensitive house plants.

Do house plants appreciate having their soil soaked and 'flushed'?  Is it necessary?  I water with city treated water, but let the watering can sit for 24 hours prior to watering my more expensive plants.  Rainwater is not an option.  
Utah, USA.


  • PlantmindedPlantminded Wirral (free draining sandy soil)Posts: 1,754
    My instinct is to think that this double flushing may result in some essential nutrients also being flushed out, particularly if you don’t regularly feed your plants.  I use filtered water and this seems to work well with the normal single soak until water runs out of the pot. I also feed my plants during the growing season according to the recommended amounts for each plant.  I think that if you’ve been growing houseplants successfully for 20 years, you’re a proven grower!
  • BenCottoBenCotto RutlandPosts: 4,050
    The internet is rammed with solutions to problems that don’t exist. If the advice is titled a ‘hack’ I would be even more convinced it’s piffle. But what do I know? I grow very few houseplants. You’re right to seek advice from people with experience rather than from folk whose finger is permanently hovering over the re-tweet button.
  • Pete.8Pete.8 Billericay, EssexPosts: 9,872
    It's something I do at least twice a year with rainwater in the warmer months.

    Plant feed is a mix of all sorts of salts.
    Different plants prefer different types of slats, and unused salts build up over time and can cause problems.
    If hard tap water is used too, salts will build up too from the minerals in the water.

    Once they've had a thorough flush, they get a final flush of dilute fertilizer so it's all nice and balanced again.
    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • SkandiSkandi Northern DenmarkPosts: 1,577
    The build up of salts is a real problem in commercial greenhouses where plants like tomatoes are being fertilised every few days all year. I personally doubt Whether it would ever become a problem in a houseplant that is watered once a week and repotted once a year.

  • Blue OnionBlue Onion Posts: 2,933
    @Plantminded Filtered water is a good idea, I have a spare Britta filter pitcher from a previous job site that had nasty tasting tap water.. I could use that for the more delicate sensitive plants.

    @BenCotto Haha, how true.  I tend to avoid houseplant social media, but do read blogs or personal websites for the more rare plants in my collection.  

    @Pete.8 I could manage twice a year, but not with rainwater like you do.  I do typically take my large plants outside on a warm spring day to spray the entire plant to wash off the winter dust.. and maybe again in late summer to remove summer dust.   I do worry a bit as the large planter's soil stays wet for ages/several weeks afterwards.

    @Skandi I expect you are probably correct, I've gotten away with doing nothing so far!
    Utah, USA.
  • PlantmindedPlantminded Wirral (free draining sandy soil)Posts: 1,754
    @Blue Onion, l’d recommend using filtered water for all your plants, not just the sensitive ones.  Replacement Brita filters are quite expensive so search for compatible filters, your plants won’t notice!
  • wild edgeswild edges The north west of south east WalesPosts: 8,879
    I do the same as Pete and take everything outside for a flush through with rainwater. In the summer I water most plants outside as often as possible or put them out in the rain. You will see the salt effects (I use salt fairly loosely as it could be other minerals) with some plants and also with some pots. Crassula Ovata will start to sweat salts if you don't flush the soil and a few other plants will show similar white flecks on leaves. Terracotta pots will often show a mineral build up too. This is just from my experience not from reading about it. I only water with rainwater but I do use fertiliser regularly.
    Tradition is just peer pressure from dead people
  • Pete.8Pete.8 Billericay, EssexPosts: 9,872
    I use seaweed extract every couple of weeks on mine in the growing season and they do get plenty of light in the lounge so they grow quite fast in the warmer months.
    When I flush them out it's a really dark liquid coming from the pot.
    I give them a gentle hose-down too then finish off with some fresh seaweed ex. the let them dry off.
    A bit like a plant's 6 month service :)
    The compost in all my h/plant pots is very free draining.
    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • ObelixxObelixx Vendée, Western FrancePosts: 28,574
    I put nearly all my houseplants outside for the summer once night time temps average 10C+.   They go on our north facing terrace so get minimal direct sun but plenty of light and any rain going so their foliage is rinsed.

    The foliage canopy means rain doesn't often get thru to their pots and compost so I water as neccessary from the tap, once the water butts are empty.
    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
  • bédébédé Surrey Hills, acid greensand.Posts: 1,366
    I flush my lemon tree omce a year after a winter of being fertilised.  If calcium-free water is the stuff to use.  If rain water is not available,   use clothes dryer or dehumidier condensate (aka distiiled water/deionised water).
    "Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
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