Water Absorbing Crystals For Container Garden Soil

How to Increase Moisture in Container Garden Soil

I thought I’d talk about a great product you may not have heard of before – water crystals, aka water gel – that can make your outdoor container gardening watering requirements a bit easier. These little white granules are a type of absorbent polymer that can absorb up to 400 or 500 times their weight with water (there are different brands on the market – there may be variances in their absorption rates). When hydrated, the water crystals swell up, holding the water, and will look like little pieces of ice. Plus, water crystals are non-toxic and safe to touch with your hands. They are eco-friendly too, decomposing harmlessly over time. They can be purchased at big-box stores, many garden centers and online.

Container plants can benefit from having water crystals added into the soil.If you have a number of planted container gardens and hanging baskets, you’ve probably run into the issue of having to do more frequent waterings in the hotter months. Many of us live in very hot climates, or our summers get awfully hot, and I find that during the height of summer I may have to water my container plants two, if not three times a day! That can pose a problem if no one is at home during daytime hours. A drooping, stressed-out plant is not a good thing, and sometimes a plant can’t even handle this situation once, let alone many times. So, watering of potted plants can become quite an issue for the home gardener.

How to Mix Water Crystals Into Soil Before Potting the Plant

These crystals can absorb a lot of water, thus will get very large. This is one issue to keep in mind, as the expanding crystals can literally push the soil out of the pot, so be very careful with how many you add to the container’s soil. I would suggest you use less than the package’s label says to. It’s up to you, but many of us using them do find that if we use the amount stated on the label, that the moistened crystals do indeed push the soil over the top of the container. Perhaps you might want to expert by adding soil to a small pot, mix in some crystals, water and see what happens. This might help you get a better idea of how many to add in.

Also, thoroughly mix and incorporate the water crystals into the soil – don’t get too many in one spot. As they swell they can push a plant right out of it’s pot!

Here’s a highly suggested method/trick to help you figure out the right amount of water crystals to use: water the crystals FIRST before you mix them into the soil. The crystals will adsorb the water like a sponge and immediately turn into their gel-like substance. I assure you that you’ll be very surprised at how much larger they become. Then, keep adding water until it is obvious that they can’t possibly absorb anymore water.

Then, mix them into the soil. Then go ahead and fill the container. You can either wet the soil again before putting the plant in, or just skip this second watering and plant the container.

However, here is a general guide of how much to use in relation to a pot’s size – again remember to experiment first to determine how much the crystals you’ve purchased will expand when moistened:

 6″ pot = 1 tbsp. dry granules
 8″ pot = 3 tbsp. dry granules
10″ pot = 4 tbsp. dry granules

How to Use Water Absorbing Crystals in Already Potted Plants

Here’s a few tips on how to incorporate these crystals into container soil that has plants growing in it. This is reverse of the above instructions, but I recommend that you add in the granules DRY.

First, thoroughly moisten the soil. Then, using the handle of a wooden spoon or pencil, poke holes down into the soil all around the plant. A good rule of thumb to follow is to poke one hole for every inch around the diameter of your container. Make the hole about 2/3’s of the way down the depth of the soil.

Using about 5-10 or so DRY water crystals per hole, carefully drop them down into each hole. Then water well.

Note: I will mention that if I were wanting to ADD these crystals into an existing planting, I’d go to the trouble of unpotting the plant(s) and going through the steps as listed above for adding moistened crystals to loose soil. Then I’d repot the plant. It really isn’t that much of a hassle, and you’ll have the assurance that the crystals are distributed better throughout the potting soil.

Watering Tip for Container Gardens and Hanging Plants Using Water Crystals

A last tip I’ll pass along is to how to get the greatest water absorption of the crystals once they’re mixed into the soil in your containerized plants.

Try this: water the container until water just starts to come out the bottom drainage hole, then move on to the next container until water is just beginning to drain from that one, and so on. Then, go back to the first one, water until the water starts draining out of the bottom, and so on.

You’ll likely be surprised at just how much more water the crystals in each container can hold. It seems that the crystals don’t necessarily suck up all they can absorb instantly.

I hope this information on using a simple product like these water absorbing crystals helps make your container gardening efforts more successful and less tedious to tend to.


  1. I have used these crystals for several years in many different applications. Just two important notes.
    1) Do NOT let the crystals get into a drain as they can cause serious clogging in the pipes.
    2) Do NOT use where your animals might be tempted to taste them.

    Thanks so much for this great site. I am a penny pinching DIY’er (on social security). And am using mostly local rocks, plants etc. for my landscaping. My neighbors really like what I am doing and it is fun to discuss different tricks and ideas with them.

  2. Claudia says:

    Hi Carolyn:
    Thanks for taking the time to mention these tips.

    And thanks for the kind compliment about my site. I try my best to offer information that is of value and helps people save some money whenever possible, too . 🙂

  3. I just read a great article about using the material from silica packets from medicines, shoeboxes, etc as a component in potting soil to help retain moisture. Instead of tossing these tiny packets, open them up and pour them into the dirt — they are designed to hold moisture just like the commercial versions.

  4. Hi Myra:
    Thanks for stopping by and for this tip. But my only question about using the silica in the packets (I am familiar with what you’re refering to) is that I wonder if the silica granules are too small to ultimately make a major difference in the water retention levels one would be hoping to achieve versus the amount of water the large water crystals can absorb and hold.

    To my way of thinking it would seem you’d have to add in a lot of those teeny-itny granules to the container’s soil in order to really make an impact.

    But I have never tried this approach, thus am only speculating at this point. 🙂

  5. Hi All,
    I’ve used these a lot ( I used to do about 50 container and large dish gardens a year for a local commercial garden here). The first time I used them, I found that a lot of my plants got heaved right out of the containers.

    I accidentally stumbled on a technique that helps-pre-wet them and then add them to your containers. Toss the recommended amount into a bowl and add water. They’ll absorb it and expand to about a hundred times the size of that tiny dry granule. Just pour the bowl into a sieve and use the amount you need in your container. In a dry season, they are a true God-send.

    The danger in using them with outdoor containers is when the summer has adequate or an abnormal amount of rain. When your plants start showing signs of being too wet (yellow or brown leaves, powdery mildew, or black death (damping off), you have to repot, if it’s not too late.

  6. marianne hartman says:

    I have used the commercial potting soil with the crystals in them, and that works pretty well too. But, for outside pots, when it freezes it heaves the plants up too! I couldn’t figure out what was going on until a friend mentioned that happened to her.

  7. DIAPERS. For flower boxes, hanging baskets and large flower pots open (clean of course :)) diaper just like on baby –soil/dirt in. Adult diapers are even better. I got them writing to a company for samples. Soak them first.

  8. Garden Seeds says:

    Great post.Thanks for sharing such a useful information with us.

  9. Katherine Cote says:


    What an interesting idea! Have you used diapers in your hanging baskets for awhile? Anything more I should know or do I just put the diaper in whole and fill in with dirt?


  10. Hi Katherine:

    No, haven’t used diapers recently, but that’s because I had to cut back on the hanging baskets I previously had for various reasons – not that I wanted to, just “had to”.

    Another person left me a comment and mentioned she pre-soaks the diaper in water first and then puts it into her basket. Good advice. So yes, put the entire wet diaper into the basket with the plastic side DOWN, fill with dirt and hopefully it will help retain more water for you. But remember, you’ve still got to keep an eye on any basket to make sure it isn’t drying out too fast. Even diapers cannot be a magical “fix”.

    Good luck

  11. Hey Megan:

    Great tip – to pre-soak first. Thanks! 🙂

  12. Trevena says:

    Where do I buy these cystals

  13. Claudia Brownlie says:

    You can find them online (Amazon, eBay, etc.) or in gardening centers. I believe I’ve even seen the crystals at the big-box stores (garden dept.).

  14. I found these crystals online from “Tasty Worms Nutrition” but I need to know whether to order small (0-1mm), medium (1-2mm), or large (2-4mm) crystals. Calls to the company have not been returned. Can you help me with this? They have good prices and I need to buy a large amount. For example, 3 pounds is $22.99 and no shipping fee.

  15. Claudia Brownlie says:

    Hi Diane: I’ve never compared crystal sizes, as the ones I have used weren’t labeled size-wise, but if this will help you … where do you want to use them (i.e. small pot, large planter or spread in a large area in your garden)? Based on the size of the container or area, just use your better judgement a chose a crystal size that isn’t too small or too big for the container.

    These things do swell up a bit with water, thus perhaps the large size you’ve mentioned would be too large for a small pot. I don’t believe you can really make a mistake, except maybe if using the smallest size in a large outdoor garden plot.

  16. where do i get this water retaining crystals

  17. Claudia Brownlie says:

    You can often find this product at garden centers, or you certainly can find it from online providers.

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