Shel' dear. I always have put gravel in the bottom of pots to facilitate good pot drainage. I was taught to do that by my Botany professor when I used to work for him and take care of the class greenhouse. He also always put a pot sherd over the hole or holes.
But, I use really big pots when I do that. 1 gallon on up to 25 gallon depending on what I am planting. ;-)
It's why I prefer to remove them! They will only do that if they have some water content.
Sand and dirt tho' do float to the top.
And yes, it was humor which is why it was worded the way it was. I hope to gods anyone that is planning on doing led casting jolly well reads up on it first!
I've got pebbles on top of the soil in my herb pots here outside the door, to keep my hens from eating the potting soil. I don't know why the biddies like the soil, but they do.
The plants are doing a lot better with the pebbles than they did with the potting soil being disturbed and removed all the time.
Jan
But did you put in enough gravel or pot shards to hold the containers down in a high wind? That is the OPs problem.
Gravel doesn't improve drainage. Drilling holes in the pot does that. Gravel does help aerate the soil, getting more oxygen to roots and beneficial bugs.
I respectfully disagree. Did some googling and found LOTS of references. Here is just one:
Good drainage is essential! Make sure the pot has plenty of drainage holes in its bottom. Enlarge the holes or drill more if necessary.
Place a layer of drainage material at the bottom of the container. Old-fashioned gardeners called this "crocking" because they used pieces of broken pots or crocks for this layer. If you'll be moving the container, you may choose to use packaging peanuts, which do not disintegrate but are much lighter in weight. "
I have also used packing peanuts to cut weight in really large pots. Just don't use the biodegradable ones.
It helps, but graveling the bottom of a large pot also is beneficial.
Omelet said:
And, you'd be wrong. This subject has come up on a lot of forums, over the years. It's a myth, and can be proved with simple experiments. An acquaintance explained it best (long, copied/pasted from a davesgarden forum on container gardening):
Water Movement in Soils
Consider this if you will:
Soil need fill only a few needs in plant culture. Anchorage - A place for roots to extend, securing the plant and preventing it from toppling. Nutrient Sink - It must retain sufficient nutrients to sustain plant systems. Gas Exchange - It must be sufficiently porous to allow air to the root system. And finally, Water - It must retain water enough in liquid and/or vapor form to sustain plants between waterings. Most plants could be grown without soil as long as we can provide air, nutrients, and water, (witness hydroponics). Here, I will concentrate primarily on the movement of water in soil(s).
There are two forces that cause water movement through soil - one is gravity, the other capillary action. Gravity needs little explanation, but for this writing I would like to note: Gravitational flow potential (GFP) is greater for water at the top of the pot than it is for water at the bottom of the pot. I'll return to that later. Capillarity is a function of the natural forces of adhesion and cohesion. Adhesion is water's tendency to stick to solid objects like soil particles and the sides of the pot. Cohesion is the tendency for water to stick to itself. Cohesion is why we often find water in droplet form - because cohesion is at times stronger than adhesion, water¢s bond to itself can be stronger than the bond to the object it might be in contact with; in this condition it forms a drop. Capillary action is in evidence when we dip a paper towel in water. The water will soak into the towel and rise several inches above the surface of the water. It will not drain back into the source. It will stop rising when the GFP equals the capillary attraction of the fibers in the paper.
There is, in every pot, what is called a "perched water table" (PWT). This is water that occupies a layer of soil that is always saturated & will not drain at the bottom of the pot. It can evaporate or be used by the plant, but physical forces will not allow it to drain. It is there because the capillary pull of the soil at some point will equal the GFP; therefore, the water does not drain, it is "perched". If we fill five cylinders of varying heights and diameters with the same soil mix and provide each cylinder with a drainage hole, the PWT will be exactly the same height in each container. This is the area of the pot where roots seldom penetrate & where root problems begin due to a lack of aeration. From this we can draw the conclusion that: Tall growing containers are a superior choice over squat containers when using the same soil mix. The reason: The level of the PWT will be the same in each container, with the taller container providing more usable, air holding soil above the PWT. Physiology dictates that plants must be able to take in air at the roots in order to complete transpiration and photosynthesis.
A given volume of large soil particles have less overall surface area in comparison to the same volume of small particles and therefore less overall adhesive attraction to water. So, in soils with large particles, GFP more readily overcomes capillary attraction. They drain better. We all know this, but the reason, often unclear, is that the PWT is lower in coarse soils than in fine soils. The key to good drainage is size and uniformity of soil particles. Large particles mixed with small particles will not improve drainage because the smaller particles fit between the large, increasing surface area which increases the capillary attraction and thus the water holding potential. Water and air cannot occupy the same space at the same time. Contrary to what some hold to be true, sand does not improve drainage. Pumice (aka lava rock), or one of the hi-fired clay products like Turface are good additives which help promote drainage and porosity because of their irregular shape.
Now to the main point: When we use a coarse drainage layer under our soil, it does not improve drainage. It does conserve on the volume of soil required to fill a pot and it makes the pot lighter. When we employ this exercise in an attempt to improve drainage, what we are actually doing is moving the level of the PWT higher in the pot. This reduces available soil for roots to colonize, reduces total usable pot space, and limits potential for beneficial gas exchange. Containers with uniform soil particle size from top of container to bottom will yield better drainage and have a lower PWT than containers with drainage layers. The coarser the drainage layer, the more detrimental to drainage it is because water is more (for lack of a better scientific word) reluctant to make the downward transition because the capillary pull of the soil above the drainage layer is stronger than the GFP. The reason for this is there is far more surface area in the soil for water to be attracted to than there is in the drainage layer.
I know this goes against what most have thought to be true, but the principle is scientifically sound, and experiments have shown it as so. Many nurserymen are now employing the pot-in-pot or the pot-in-trench method of growing to capitalize on the science.
If you discover you need to increase drainage, insert a wick into the pot & allow it to extend from the PWT to several inches below the bottom of the pot. This will successfully eliminate the PWT & give your plants much more soil to grow in as well as allow more, much needed air to the roots.
Uniform size particles of fir, hemlock or pine bark are excellent as the primary component of your soils. The lignin contained in bark keeps it rigid and the rigidity provides air-holding pockets in the root zone far longer than peat or compost mixes that rapidly break down to a soup-like consistency. Bark also contains suberin, a lipid sometimes referred to as nature¢s preservative. Suberin is what slows the decomposition of bark-based soils. It contains highly varied hydrocarbon chains and the microorganisms that turn peat to soup have great difficulty cleaving these chains.
In simple terms: Plants that expire because of drainage problems either die of thirst because the roots have rotted and can no longer take up water, or they starve to death because they cannot obtain sufficient air at the root zone for the respiratory or photosynthetic processes.
To confirm the existence of the PWT and the effectiveness of using a wick to remove it, try this experiment: Fill a soft drink cup nearly full of garden soil. Add enough water to fill to the top, being sure all soil is saturated. Punch a drain hole in the bottom of the cup & allow to drain. When the drainage stops, insert a wick several inches up into the drain hole . Take note of how much additional water drains. This is water that occupied the PWT before being drained by the wick. A greatly simplified explanation of what occurs is: The wick "fools" the water into thinking the pot is deeper, so water begins to move downward seeking the "new" bottom of the pot, pulling the rest of the PWT along with it.
Having applied these principles in the culture of my containerized plants, both indoors and out, for many years, the methodology I have adopted has shown to be effective and of great benefit to them. I use many amendments when building my soils, but the basic building process starts with screened bark and perlite. Peat usually plays a very minor role in my container soils because it breaks down rapidly and when it does, it impedes drainage.
My Soil
I'll give two recipes. I usually make big batches.
3 parts pine bark fines 1 part sphagnum peat (not reed or sedge peat) 1-2 parts perlite garden lime controlled release fertilizer micro-nutrient powder (substitute: small amount of good, composted manureBig batch:
3 cu ft pine bark fines (1 big bag) 5 gallons peat 5 gallons perlite 1 cup lime (you can add more to small portion if needed) 2 cups CRF 1/2 cup micro-nutrient powder or 1 gal composted manureSmall batch:
3 gallons pine bark 1/2 gallon peat 1/2 gallon perlite handful lime (careful) 1/4 cup CRF 1 tsp micro-nutrient powder or a dash of manure ;o)I have seen advice that some highly organic soils are productive for up to
5 years. I disagree. Even if you were to substitute fir bark for pine bark in this recipe (and this recipe will far outlast any peat based soil) you should only expect a maximum of three years life before a repot is in order. Usually perennials, including trees (they're perennials too, you know ;o)) should be repotted more frequently to insure vigor closer to genetic potential. If a soil is desired that will retain structure for long periods, we need to look to inorganic components. Some examples are crushed granite, pea stone, coarse sand (no smaller than BB size in containers, please), Haydite, lava rock, Turface or Schultz soil conditioner.
How about just making the pot with the base wider than the top?
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