'Loamy' soil

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fanaticactus
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'Loamy' soil

Post by fanaticactus »

I have often been confused by the terms applied to cactus soils. I understand mineral and organic soils and, I think, soils with peat vs. peat moss. But when a cactus soil recipe calls for a 'loamy' soil, what exactly does it mean? To me loam has always meant a rich, dark, organic soil. But I know not many cacti like something that rich, preferring much 'leaner'. And does 'decomposed forest products' indicate a fair degree of organic material?

Thanks if you can differentiate all these for me. Currently, I'm using mostly pumice and crushed stone with just a few dashes of a commercial soil with the least organic material I can find except a bit of organic for a slightly more acidic soil on Gymnos, Echinopsis/Lobivia, and some Echinocereus. And obviously, a lot more organic for Epis and other tropicals.
Catch a falling star--but don't try it with a cactus!
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greenknight
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Re: 'Loamy' soil

Post by greenknight »

Loam contains sand, silt and clay. Plants grow well in it, so it often is high in organic matter, but that's not what makes it loam.
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Aiko
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Re: 'Loamy' soil

Post by Aiko »

Here's an article I wrote about ten years ago on loam. You might find it useful.
It's ideal for sowing, I must say!


Loam as substrate [This article has been published before in Succulenta, volume 92, 2013, issue 2]

Every now and then I came across the advice of using loam as (part of) the substrate of my succulent plants. For different reasons loam was advised specifically aimed at Lophophora, Ariocarpus and mesembs. Now there is intentionally good advice, and unintentionally bad advice on all sorts of matter. And a few years back I had set my mind to find out for myself whether the advice to use loam would turn out to be a good advice or bad advice. After using loam for a few growing seasons I must conclude that I do not regret using loam as a substrate for my succulents, of which many mesembs. In this article I will further explain my findings on the use of loam as (part of) the substrate of my succulent plants.

Properties of loam
Since I have been using loam as (part of) the substrate of my succulent plants, I noticed loam has a few very distinct properties:
1 – Loam is very hard when it is dry
2 – Loam is very soft when it is moist
3 – Moist spreads through loam quickly and evenly
4 – Loam dissolves in water easily
Of these four properties I consider the first three to be positive for succulent plants. And it is these three properties that make me recommend using loam for sowing, to grow seedlings in, and to use loam for plants that are prone to rot due to excessive watering. Let me explain the three positive properties and the fourth less positive property a bit further.

1 - Loam is very hard when it is dry
Once previously moist loam as dried out, you will notice the loam has turned to a very firm substance. Especially f you have mixed pure loam with sand, grit or pebbles, the mix could turn out to be as hard as concrete when fully dry. With minor force you can break the loam into smaller pieces or even shatter it to fine dust again, if you want to. Using dust fine loam will mix better with other ingredients, if you like to mix your own substrate.

The hardening of loam should have no negative effect on your plant rooting. Dried out loam should even provide a very specific advantage. If the dried out loam is inside a plastic pot, you will notice the sides of the plastic pot will feel really firm. It is hard to compress the sides of the pot without some force. The content of the pot does not give way easily. This means that loam can be used as an indicator for moist content inside a plastic pot. Especially useful for the lower part of the pot, since that is usually out of sight and takes a bit longer to dry out. Even if you think a pot has fully dried out, there might still be some moist hiding in the bottom part. Especially for plants that are prone to rot due to excessive watering, this is not what you want. While with loam the top part of the pot may feel hard, the bottom part might still be a bit soft if you squeeze the bottom part of the pot. If the bottom part also feels rock hard, you might feel safe to oblige your plant with some needed watering again.

Unfortunately loam takes a bit longer to dry out compared with other substrates / mixes. Especially after a cold dark week and a lack of sun intensity loam might need quite some time to dry out again. While with loam you can get an idea of how much moist there is left thanks to the level of resistance the loam inside the pot will give when you squeeze the pot. This will give you an estimate if it will take too long for your plant to dry out again, and you need to take measures. If you fear it will take the pot too long to dry out, the loam will tell you and can help you to save your previous rot prone plant by replanting it in some dry substrate.

This is a tactic I use myself for some rot prone succulents on their own roots, like Pachypodium brevicaule. This particular plant is in a mix of about 60% grit and 40% loam. The grit provides excellent drainage, and less loam to ‘hold’ the water. Just in case I have provided a watering at the wrong time, I can take this plant out of the pot and repot in a dry mix. Lucky many mesembs are not at big risk here, but some ‘honorary mesembs’ like Avonia quinaria might benefit from this technique too.

If you consider the hardening of loam to be less desirable, you can counter this property by mixing the loam with some (sieved) topsoil. About one part of topsoil on four or five parts of loam should do the trick and should keep the loam mix soft. Even when the mixture has dried out.

2 - Loam is very soft when it is moist
If you sow a lot of one species and have all the seedlings in one pot, it might be a bit hard to take out one individual seedling without disturbing the others. Especially when the seedlings have rooted well. Taking them out with ease you might want to do if you want to give an individual seedling away to a friend (or take them out to be able to distribute some seedlings for the MSG Plant Exchange Scheme). With loam this is easy! Just splash the loam with a can or spray it with a water sprayer a few times. You will notice the loam will turn soft. If you very gently pull out the seedling, the entire plant will slide out the pot very easily. Leaving its friends undisturbed where they are. Roots of both the remaining seedling as the to-be-donated-seedling will stay unharmed.

Fortunately this principle also applies to weed, like Oxalis. In non-loam substrates, if you try to pull Oxalis out, chances are you will pull the top part of the weed off only. The remaining part will still stay into the substrate. This probably will grow again into a flowering and seed shooting plant and spread further through the greenhouse. But with moist loam you will notice the roots will be pulled out of the pot too, so you have a decent chance of finally getting rid of Oxalis. Or other weeds.

Many mesemb seeds are rather tiny. But if you have bigger seeds to sown, moist loam will make it easier to press the seeds into the soil. This will allow for a larger surface area of the seed to come in contact with moist, and allow for a better germination (be it faster, or a higher germination rate). Because moist loam is a bit sticky, the bigger seeds will prefer to stick to the loam if you press it down, and will less likely still be hanging onto your finger when you pull your finger out. Same technique can be used for plants, like Lithops. With moist loam you can press your Lithops a bit into the soil to mimic they love of pulling back into the soil, as they tend to do in habitat.

3 - Moist spreads through loam quickly and evenly
If you submerge a pot filled with loam into water, you will notice the water will get soaked up very easily. The water will reach every corner of the pot. This will even go smoother if the loam is mixed with grit. By reaching every corner of the pot, every part of a plant’s root system will come in contact with water. This will prevent parts of the roots from drying out. You might notice this might not be the case if you use a substrate consisting mainly of a peaty topsoil.

Because in loam the water gets soaked up easily the water will also spread out throughout the pot evenly, even when less water has been provided. This is very helpful for mesembs that are better off with regularly watering with a limited amount of water. Like Conophytum calculus, Argyroderma or Tanquana species. These tend to crack when too much water is given. These mesembs should be provided with much less water each time, so they are not tempted to suck up more water than the cells of the plant can store.

As a consequence of the ability of loam to soak up water easily, a loamy mix (depending on the mix) might also dry out more evenly because the top part of the loam will suck the moist from the wetter bottom part while drying out. This will allow for a continuously contact of moisture with drying air or sunlight. This can be helpful if you prefer the mix to dry out relatively quick, and want to be careful with moist sensitive mesembs. Like the cracking-prone Conophytum calculus, Argyroderma and Tanquana.

At the same time, loam might sometimes take its time to dry out too (depending on the mix and weather). For some of the mesembs this will not provide a problem. Muira hortenseae, for example, is not rot prone when it is placed in a lightly moist soil during its growing season. I regularly spray my Muiria hortenseae from September to May, or even June (up here in the northern hemisphere of the Netherlands). Because of the cold and lack of sun intensity, the top part of the soil stays quite moist most of the time between November to February.

4 - Loam dissolves in water easily
With thanks to the third property of loam (“Moist spreads through loam quickly and evenly”), I will consider loam to be an (almost) ideal substrate for sowing. All my seedlings are sown in batches in small little square pots. These pots are placed together in a low tray. When I want to water my seedlings, I submerge the entire tray into a big container filled with water, with water getting close to the rim of the pots. This is a very efficient way of watering hundreds of seedlings at the same time. Usually I only have to wait a very short time before every pot has taken up enough water and I can place the tray back into its sunny (bit shaded) position.

But unfortunately there is a danger to this when all seedlings are in a very loamy mix, and is caused by the fourth property (“Loam dissolves in water easily”). When you take out a tray of seedlings from the container after they have taken up enough water, you might notice the remaining water in the container is somewhat mixed with loam. The excess water has taken up some of the loam, and will run from the tray back into the container. In the meantime flushing away a bit of the loam from the pots. This will always be loam from the bottom parts of the pots, thereby causing small holes at the bottom.

The top layers of the loam will usually hold for a long while. Easily when they are dry (when it will be firm). Only after a few waterings you will notice that top parts will (eventually) start to give way when they get wet, again and again. Seedlings will at one time all of a sudden sink into the holes. Or worse, caving in from around the holes and burying your seedlings, loam might cover them. And on top of that, seedlings might get washed away when you take out a tray from the water filled container. You might find them floating around in the container. Can be a frustrating puzzle to place swimming seedlings back to the correct pots and labels…

But there is a simple solution to these horrors. Fill the bottom part of the pots with a decent layer of fine grit to cover up the holes of the pot. This will create a buffer between the water and the loam, taking away the direct contact between the outflowing excess water and the loam.

This fourth property is not all bad. It will help you to clean the roots of a plant without much effort. If your mesemb has been in loam, you can simply pull it out gently (see: “Loam is very soft when it is moist”) and splash the roots clean in some water. The water will dissolve the loam and the roots will be clean almost immediately. All ready to be transplanted in some fresh soil. Or if you like to give one away (via the MSG Plant Exchange Scheme, for example), all ready to be sent. For international distribution, the customs might demand to only allow clean plants to pass, without any remaining soil left on the roots.

Loam and moist on the longer run
When sowing, I usually keep my to-be-seedlings in a zip-locked bag for a while to prevent them for drying out too fast and allow for constant moisture for germination. Although much advice has been given to take seedling mesembs out of a bag as quick as possible after germination, I have not noticed a problem of keeping them in a bag for a few weeks, maybe even months. I have not noticed damping off of seedlings. But being moist for a long time could cause for algae to start growing in the pots, even if you have sterilised the mix beforehand. But compared with other mixes, I do have noticed a difference in speed and intensity of emerging algae on loam, in favour of loam (close finish, though). Also if you sterilise / boil your mix before sowing, I have noticed a difference in smell. Al be it the differences is not that big, the smelly loam will win yet again…

Loam for seedlings on the longer run
In the past, when using topsoil as my sowing mix, I regularly noticed the top part of the mix gets crusty after some time. The crust will form a separate layer with curly edges, and only remains to the lower layers of the soil below, thanks to the roots of the seedlings. Although I haven’t noticed this harming seedlings, it does not look very tidy. But thanks to the properties of loam, the top layer will not get crusty with loam. It usually will just look and behave the same from the start, for multiple years.

If you sow mesembs, you might notice some mesembs seem to be upside down. Thanks to the second property of loam (“Loam is very soft when it is moist”), it is easy to place the mesemb back on its feet and its small root into the soil. I use a small knife for that. If the loam is wet, it is easy to make a hole for the small root with the tip of the knife, and push the little mesemb up right. Gently spray some water and the holes will fill up nicely with loam, covering the root (and cleaning the seedling). This technique can also be applied to repot small seedlings.

When sowing, I prefer to scatter seed evenly on the available surface. Especially with tiny mesemb seeds, I am just happy to get something in the pot at all, and not wasting it due to clumsiness or struggle with paper bags that don’t seem to release seeds easily. So sometimes I get a very crowded centre of my pot with all the seedlings real close to each other. Too close, sometimes. With the same knife and wet loam, I can easily push or drag a seedling to more rural areas of the pot with the side of the knife. The roots will follow the seedling without problems, and you can easily push the roots a bit into the loam if needed. If the seedings are still in their first growing season (or any time when the roots are still small and haven’t spread out much through the loam), no harm will be done to the seedling or to the roots at all.

Loam and pests
A mineral substrate (which loam is, in its purest form) is said to be effective (prevention wise) against some of the pests we succulent growers have to deal with. Sciara flies are said to be attracted by the organic ingredients of topsoil. Also root mealies are said to be more happy with organic substrates that mineral substrates. Viewed in this perspective, using loam (preferable pure or only mixed with sand and grit or split) should provide help in dealing with these pests, prevention wise.

Personally, I cannot vouch for this, as the plants in my collection do not seem to be pested by Sciara and root mealies. Not even in the days when I used topsoil very regularly, many moons ago. But some of my plants do suffer from the ‘regular’ mealies a lot. These critters unfortunately do not seem to mind much in what soil a plant is in…

Where to obtain loam
Unknowingly if loam is easily obtainable in other parts of the world, up here in the Netherlands it is not available in garden centres. There are probably many countries where one could scoop it off the ground somewhere. But in the Netherlands this is not the case. But after looking around for quite a while, I finally found a company that delivers loam for the use of plaster skimming. They were selling loam as a fine powder in 25 kilo bags, or a sandy form in big bags. To be prepared for the next twenty years (give or take a decade…), I invested in an order for an entire big bag. Good thing is they service the 1200 kilos worth to my home. Left for me is to repack the loam into smaller bags and store those in the garage for future use.

With all its ancient lakes, rivers and other water ways, clay is more abundantly available in the Netherlands than loam. Clay does share most of the properties of loam, which the main exception that clay takes quite longer to dry out. If one scoops clay off of the land, one would also bring in seeds of weeds that might have settled in the clay if you only scoop off the top layer. Of course all ready to germinate when you apply water to it in a pot. But clay seems to be a worthy replacement for loam. It even appears my Lithops seedlings will prefer clay above loam. Especially after repotting. I have had times where all of a sudden transplanted Lithops and Pleiospilos went soggy and died. Almost immediately right after transplanting. I suspect this was caused by root damage. I probably have applied watering too early and caused an infection (maybe botrytis?). Should I have waited a few more weeks before watering so the damaged would heal? (Since then I tried that, and for now it seems to have done the trick…)

I have not noticed the problem of sudden rotting of Lithops and Pleiospilos after transplanting them in clay, and watering them not long after. So I am starting to think the combination of root damage and clay might be a better combination than root damage and loam. But I haven’t used clay on large scale and over a long period. Although I praise loam, clay will also stay on my radar for a while. Would love to read anyone’s comments about the practical pros and cons of clay on the use for mesembs, though!
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jerrytheplater
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Re: 'Loamy' soil

Post by jerrytheplater »

fanaticactus wrote: Sun Aug 28, 2022 7:02 pm I have often been confused by the terms applied to cactus soils. I understand mineral and organic soils and, I think, soils with peat vs. peat moss. But when a cactus soil recipe calls for a 'loamy' soil, what exactly does it mean? To me loam has always meant a rich, dark, organic soil. But I know not many cacti like something that rich, preferring much 'leaner'. And does 'decomposed forest products' indicate a fair degree of organic material?

Thanks if you can differentiate all these for me. Currently, I'm using mostly pumice and crushed stone with just a few dashes of a commercial soil with the least organic material I can find except a bit of organic for a slightly more acidic soil on Gymnos, Echinopsis/Lobivia, and some Echinocereus. And obviously, a lot more organic for Epis and other tropicals.
Soils are classified by the percentage of each of the three main particles, sand, silt, and clay. These particles are classified by their size with sand being the largest and clay the smallest. Each country has it own system of soil classification and they don't often correspond to one another. A lot of them will use equilateral triangles to calculate the soil classes. I will only speak about the US, since that is where I live and where the OP lives.

If you search for "The Soil Texture Wizard" you will find someone has made a computer program that attempts to provide a way to convert soil texture values from one country to another-but this is getting way over my head.

The USDA has its system of soil classification and soil triangle. The link here is to a USDA site where you can input the percentage by weight of each of the particle sizes determined by sieving the soil sample to remove massive pebbles etc. and then wetting the weighed soil sample and timing how long it takes particles to settle out. Sand is determined to settle out in 40 seconds. Silt in 7 hours. And clay is greater than 7 hours, up to days.

USDA site if you know your soil particle percentages: https://www.nrcs.usda.gov/wps/portal/nr ... 2p2_054167

Kansas State University lab on calculating soil texture. It also gives a flow chart for field ID using feel. Something we all can do ourselves. https://kstatelibraries.pressbooks.pub/ ... structure/
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
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greenknight
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Re: 'Loamy' soil

Post by greenknight »

That's way too complicated, all you need to do is a jar test: shake up a sample of the soil in a jar of water with a little detergent added as a wetting agent, then you see how it settles out. See: https://www.google.com/url?sa=t&rct=j&q ... xsFlBm93OL
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jerrytheplater
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Re: 'Loamy' soil

Post by jerrytheplater »

greenknight wrote: Tue Aug 30, 2022 1:49 pm That's way too complicated, all you need to do is a jar test: shake up a sample of the soil in a jar of water with a little detergent added as a wetting agent,
I know it is too complicated for some. But I want to know the exact technique used when having a soil test performed. That Kansas State lab does go over a field test using feel. That can be done anywhere.
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
DaveW
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Re: 'Loamy' soil

Post by DaveW »

In the UK virgin loam is now almost unobtainable. The original specification was for it to be the top spit (= one spades depth) from virgin meadow land that had never been ploughed and not much of that left in the UK. Needless to say most of which is now sold in the UK as loam is from ploughed agricultural land or simply garden (yard) soil removed from building sites.

That was one of the reasons peat based soilless potting soils were invented (by University of California?) since the old John Innes recipes most Brits used required loam as a basic ingredient. Note we call potting soil in Britain "Potting Compost" as well as the usual rotting material of that name. Presumably pre John Innes the old gardeners used to make their potting soils up with home made compost. The cactus potting soils most used to use were JI 1-2 or 3 with one third extra grit etc in to improve drainage.

Here are the old JI formulas.

https://www.proctorsnpk.com/t/howtomakeyourown

The laughable thing is some firms now sell "Peat Free" JI Composts. As peat is an essential part of all JI Composts that is misusing the John Innes name on a product they never endorsed. Peat usage has become a dirty word to some in the UK since peat harvesting was destroying peat bogs to the anger of conservationists. Unfortunately poorly rotted compost made from garden waste by local authorities is now used by some suppliers instead of proper peat based JI compost.
keith
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Re: 'Loamy' soil

Post by keith »

Isn't loam equal parts sand, slit and clay ? maybe some organic ?
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jerrytheplater
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Re: 'Loamy' soil

Post by jerrytheplater »

If you have equal parts of sand silt and clay you have a Clay Loam. The ranges for Loam are 50-72% sand, 5-28% clay, and 28-50 % silt.

There is no mention of the organic content of any of the Soil Texture Classes. They only go by the mineral component of the soil.
Jerry Smith
Bloomingdale, NJ
45 inches (114 cm) rain equivalent per year, approx. evenly spread per month
2012 USDA Hardiness Zone 6b: -5F to OF (-20C to -18C) min.
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