Why take the plants out of their pots Most plants that are sold in stores come in these little plastic pots we are talking about. I have some succulents in pots ( small, medium, sized) and 3 dwarf citrus in large pots. In terms of what to put in the bottom of an indoor planter for drainage, you should add a drainage hole if you can, assuming there isn’t one there already. It’s important to understand that the perched water table does not drain, the water stays there unless plant roots draw the water up, or it evaporates away when the potting mix dries out, in which case the plant won’t survive! Perlite and vermiculte are materials which are used as soil amendments, and both are minerals that are made more porous by expanding them with heat, much like popcorn. Putting stones around plants in a tray is a great way to increase humidity for indoor plants that need more moisture. You are completely incorrect in your article. What's worse is that these annoying insects can be incredibly prolific during their rather short lifespans, generally only living a single week as an adult gnat. Reducing the volume of growing medium available to the plant roots will reduce root growth space and overall root volume, as well as available moisture, thereby decreasing the plant’s drought tolerance and potential maximum growth size. Gravity is self-explanatory, it’s the ever-present force on this planet which pulls everything down! Overwatering a potted plant can cause root rot, a disease that results in the slow death of the plant. I’ll show you how to test this, all you need is some empty soft drink bottles. Why should I not put rocks in the bottom of my planter? I do not agree at all with your explanation and your graphics on gravel drainage. The pwt will NOT be “higher up in the pot”. you said it yourself, the perched water table will always be the same height. Fill in your details below or click an icon to log in: You are commenting using your WordPress.com account. Hi Javier, thanks for your comment. Plants that have different soil drainage (aeration) requirements can be combined in a landscape planter if they are in their own separate pots. If you pour water from the top, the medium will act like a sponge and prevent a certain amount draining out of the bottom, that is the perched water table. With these pots, it was a traditional practice (and still is) to sit a very loosely fitting stone over the hole to stop the potting mix falling out. In general, it’s not necessary to put rocks in the bottom of plant pots. Remember, the downwards force is due to gravity, which we can’t increase, a lower layer of another material won’t change the adhesive forces between the growing medium and the water molecules, nor will it alter the cohesive hydrogen bonds between water. The problem would be even worse in glazed terracotta pots, which don’t seep moisture from their sides and stay wet longer. This weekend I took out of the pot a lemon tree which was planted in 70% expanded clay balls mixed with 15% coco peat and 15% compost all the way through the pot. Double potting makes it possible to sink individual potted plants into the landscape (or remove them) without disturbing the roots. Here are the facts about using gravel in potted plants. The more moisture retentive growing medium/potting mix available, the less often a plant will need to be watered, as long as the pot is not too big. From the University of Illinois Extension, Urban Programs Resource Network – Successful Container Gardens, Choosing a Container for Planting – Drainage Is Critical to Plant Health: From the University of Tennessee, Institute of Agriculture, Agricultural Extension Service – PB1618, Growing Media for Greenhouse Production, we see that reducing the depth of the pot actually increases water retention and. Hi, I also altered the composition all the way through the pot, the expanded clay balls are 5-12mm diameter and they retain little moisture, similar to perlite. For example, molecules of water are able cling to each other. Put rocks on your soil! It is not recommended to use Styrofoam peanuts for potted plants now, because they may break down in water and soil, leaving you with sunken in containers. Plant pots fail to drain because the capillary action that suspends the water in the soil is stronger than gravity. Succulents and cacti naturally grow in sandy soils that drain quickly. The secret to improving pot drainage is to alter the composition of the potting medium, by mixing something with a larger particle size all the way through it, and there are several different amendment materials for this purpose. The reason why I chose expanded clay balls is because they don’t float as easily as perlite. Some plants require extremely well draining potting mixes in containers. That is not right. Mixing either of these amendment materials right though a potting mix will increase aeration, improve drainage and reduce the height of the perched water table. Put a layer of gravel in your plant’s drainage tray, or down inside a decorative planter, then sit your plant pot on top. Simply take your plant saucer and add a single layer of pebbles, which can include either small decorative stones or simply some small rocks you find outside. If not, then see for yourself. Follow Deep Green Permaculture on WordPress.com, How to Make Compost in 18 Days Using the Berkeley Hot Composting Method, How to Use Replaceable Filter Face Masks for COVID-19 Coronavirus Protection. Different growing media will have different perched table heights, the more absorbent materials will have higher perched water table, and the less absorbent ones will have lower levels. Drainage Holes There may be conflicting advice about how to keep your container garden plants from drowning. Putting rocks at the bottom of the pot doesn't change that. The gravitational force can only exert a limited downward pull on the water against the upward pull of the capillary action, and no more. Beds. Since any decent quality potting mix must retain some moisture, it needs to contain material which will absorb and retain moisture, much like a sponge does. If you have a large planter, it can take a lot of potting soil to fill it completely. Should You Put Gravel or Rocks at the Bottom of Plant Pots for Drainage? gravel in bottom of plant pots for drainage, how did the tradition of putting gravel at the bottom of pots originate, how to increase drainage in pots and containers, the correct way to increase drainage in pots and containers, http://oregonstate.edu/dept/nursery-weeds/feature_articles/physical_properties/physical_properties.html, Gardening Calendar (Australian Temperate Climate) – December, Gardening Calendar (Australian Temperate Climate) – November. Water each with the same volume of water, wait till they drain, and then observe the perched water table. The growing medium wont be as saturated as the perched water table, but it will still be wet enough for way too long to be detrimental to the plant. I faced this problem recently and wanted to know how to prevent this problem. Rocks contain micro nutrients, which erode over time, Roots latch onto these rocks and can slowly suck these rocks, if the plant lives for many years in one container this could be of use for extra minerals 3. The forces of attraction between water molecules to each due to the hydrogen bonds they form with each other (cohesion), causing them to pull each other up. ( Log Out /  Hope it’s not too cheeky of me to say that my explanation is the only one from first principles and goes to a greater depth scientifically though. From the North Willamette Research and Extension Center, Oregon State University, Physical Properties of Container Media. Cymbidium orchids for example are grown in an orchid mix which is composed mainly of 20mm composted pine bark pieces. As a final thought worth pondering, it’s curious how gardening has as its foundations the applied sciences of horticulture and agriculture, yet it’s filled with so much dogma and myths, very strange indeed…. First, let’s start with the basics: Your favorite potting mix or growing media holds water by means of two natural forces. The problem arises when you do not remove the rock wool from the roots. If this single hole became blocked, water would pool at the bottom of the pot and drain out very slowly, leading to waterlogging. It prompted me to look around. Clearly, the answer is “no.” Not sure if I needed to read an exhaustive treatise to get the answer, but, well, it was fascinating. You’re right, some things in gardening are definitely not intuitive, and if the science is there, we should use it! But otherwise, this is a super easy way to make sure the humidity is just right for your houseplants. Coincidentally, these forces are also how plants get water from their roots to their leaves! There is wisdom in the gardening advice to plant up to the next size pot when repotting, and increase pot size gradually rather than plant into the biggest pot available at the outset. By putting rocks in the bottom of plant pots, you’re effectively making the soil area of the pot smaller, meaning the “sponge” holding the water in is also now smaller. By pushing a few match heads into the soil around potted plants, you can grow outstanding, healthy plants … Here is a simple experiment that can be set up to determine whether adding gravel at the bottom of a pot improves drainage or not. I did some research and put together this article so it can help you as well. For example, molecules of water are able to cling to other materials. Capillary action, which exerts an upward pull on the water, causing it to be retained, saturating the potting medium. Connecting People to Nature, Empowering People to Live Sustainably. If you have potted plants and cats, chances are you’ve found poop in the plant pot on a bad day. Even if you balance it on some gravel for house plants, these won’t help the sponge dry out any faster. Final thoughts on putting rocks in the bottom of plant pots, natural-colored decorative gravel for plant pots. Why Is My Aloe Vera Plant Turning Yellow and Brown? Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Tap the sides gently to settle the potting mix slightly, don’t compress it down. Hi Angelo: INTERESTING, and not all intuitive. With the exception of the rock (or similar item) we’d recommend putting over each of these, stick to keeping the stones either on top or underneath each indoor plant, depending on what you’re trying to achieve. Gravity, which exerts a downward pull on the water, causing it to be drained away through the drainage holes. I might have to set this up when I have time and photograph it. A good potting medium (potting mix) has to strike the perfect balance between sufficient moisture retention and good drainage for plants to thrive. Crocking was supposed to encourage water to pass down from the potting mix into the gaps in the coarse layer below and out through the drainage hole. When filling the pots, just tap the sides gently to settle the potting mix slightly, don’t compress it down. If the physics is true, then the perched water table, the wet bottom layer of the potting medium will be the same thickness in every pot, and the gravel will simply push it up higher in the pot because it’s pushing all the potting mix up higher in the pot. Ignore it at your own risk. Absorbent materials, such as a wet sponge sat upright or a wet bath towel hung from the line, behave the same way. ( Log Out /  I have wondered for years why nurseries don’t have gravel or the like in the bottom of their pots. Should You Put Gravel or Rocks at the Bottom of Plant Pots for Drainage? This won’t completely plug the hole but will stop the soil from getting out. Potted plants have less of an area to draw moisture from than a plant in the ground. It also doesn’t mean that air is circulating more easily inside the sponge. Small stones, seashells, marbles, or the the half-globe crystals from the craft store can act to keep moisture in by preventing some of the evaporation from the soil, just like From the University of California, Agriculture and Natural Resources, Master Gardeners of Monterey Bay. In Memory of Bill Mollison, the “Father of Permaculture”, 3. If you want, I will leave you my contact and I will explain it to you with a practical video. Make sure you check on the water from time to time so you can refill it when the water level drops. Filling the bottom of the pot with coarse scoria, which is light in weight, will eliminate the unusable space in a tall, narrow pot and effectively reduce pot size to a more suitable volume. When the positive side on one water molecule comes near the negative side of another water molecule, they attract each other and form a hydrogen bond, and this creates the strong cohesive forces between water molecules, and this explains why water clings to itself. The way to increase drainage of the perched water table is to add materials throughout all of the potting medium to increasing the air spaces in the mix and reduce capillary action. However, during this If you are working with a liquid nutrient medium (hydroponics, essentially), then no, stones or marbles are not an impediment to growth. Post was not sent - check your email addresses! Sand will improve soil, as it has larger particles than clay or silt, but it’s way smaller than potting medium particles and will clog it up instead, filling the air spaces. You’ve preempted my next article on which explains the proper way to increase drainage in pots, which I’ll publish soon, but your solution is half-way there. 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