Top dressing and soil mixes -- thread offshoot

[amanzed]

vapester asks about top dressing and mix-ins.

Originally Posted by vapester

sooooo, my agave and succulent collection is growing pretty quickly and i don't know much about this. Is this a preferred top soil for pots and ground plants ? And if I find it, a very small 1/8" is what to look for ?? I've been wanting to change to a nicer top dressing for my potted plants. I mainly just use fine orchid bark, tho one plant i did use crushed gravel. But i felt it maybe keeps the moisture in too long. There is an A1 or rock place near my house in Wilmington that prob has the stuff.

Ronald Chisum gives the Short Answer to why we top dress.

Originally Posted by Ronald Chisum

Top dressings and soil mixes are worthy of their own threads. Ornamental dressings are frequently used on show plants. In my area, some nurseries use a lot of perlite in their mixes to insure good drainage. Perlite floats and will easily wash out of the pots. Rock top dressings prevent this washout while maintaining evan more rapid drainage near the base of the plant. I suggest you join a Cactus & Succulent Society if there is one anywhere near you. Members can fill you in on some of the best ways to cope with your particular needs. RON

I have been collecting agaves, crassulas, and sansevierias for about 15 years, since my late 20s. When I started, I didn't even know I was starting a collection. I really didn't know about growing medium or top dressing.

Now I collect many more genera. As my plants multiplied, I hungered for more ways to grow and present them. Like Ronald Chisum says, you can learn a lot by going to shows and local cactus and succulent society meetings or study groups. (Here in L.A., CA, I joined Cactus and Succulent Society of America and the nearest affiliate, San Gabriel Valley Cactus and Succulent Society.) At a recent SGVCSS study group, for example, the master stager of show plants for California Cactus Center demonstrated some of his most useful techniques.

In this hobby, some people even specialize in taking trips out to the desert and collecting attractive sand and gravel for top dressing. One favorite, for instance, is the neatly sorted, coarse sand from around ant colony entrances.

Talk about a niche product!

--dean
sentientmeat.net

PS Speaking of that, what is the current thinking about the ethics of field-collecting soil, aggregate, or rock? At some point, it was all collected somewhere! But better a gravel pit than a wilderness preserve, to use extreme examples for sake of argument.

[Matt Maggio]

Originally Posted by amanzed

PS Speaking of that, what is the current thinking about the ethics of field-collecting soil, aggregate, or rock? At some point, it was all collected somewhere! But better a gravel pit than a wilderness preserve, to use extreme examples for sake of argument.

Gosh... this could be an interesting thread. There's much to say about soils in general.

Let me address your last thought through the lens of someone in the United States, California to be more precise. Collecting mineral resources in State Parks as well as National Preserves, Parks and Monuments is almost always strictly prohibited. That being said, non-commercial "hobby" collecting is permitted on lands managed by the U.S. Forest Service and the Bureau of Land Management (BLM). All collecting must be done by hand tools and accessed by foot... I guess a wheelbarrow could suffice. "Absolutely no mechanized or heavy digging is permitted and no visible scars on the landscape may be left behind"( Gem Trails of Southern California, 2003). They allow some collecting, but make it as difficult as possible - motorized vehicles are usually prohibited on the side trails into these lands. Be advised that the rules are constantly changing and park lands are being expanded quite readily. That's about all I know regarding the law on collecting mineral resources on public lands in California, and soil may be a different story. If you get permission from a property owner, you should have much greater leeway.

Moving into ethics, you're right... purchasing material from a supplier doesn't necessarily equate to environmental friendliness, but such has its benefits. It's a means of obtaining materials in accordance with private property rights - a company for example obtains rights to a property, the mineral resources on it, then sells pieces of that property to the consumer one boulder or bag of sand at a time. The localized areas where commercial mining or quarrying occur can be heavily damaged. But nonetheless, an environmental benefit is that the activity is typically concentrated in one area. Furthermore, these rock supply companies help satisfy a market demand that may otherwise be filled by widespread disturbance of pristine areas.

Now, I understand that some of us are after that "natural" look, and as a rock connoisseur myself, I know that the supply places don't always present the finest materials nature can offer. The rocks are sometimes scuffed, the topdressings cooky-cutter, and the soils hit and miss. Materials are sometimes run through a crushing machine, while soils and DG are sometimes mined from subsurface horizons where heavy metals, salts and clays accumulate. This is no surprise from large commercial operations, where quality must sometimes be sacrificed for efficiency.

For my landscape projects, I usually purchase materials in bulk, but am always watchful of legal opportunities where I can collect materials from disturbed sites, construction sites, road cuts or someone's property. To satisfy my personal need for improved quality in my plant collection, however, I've taken ample opportunity to collect on a small scale outside of protected areas. I tread lightly when collecting, trying not to leave huge craters on the landscape. Rock falls and rubble piles are best in this respect, because the areas are already disturbed somewhat. When digging soil or topdressing, I try and keep it to washes and river banks where my scars will vanish during the next flood. Another tip: wrap your nice rocks in newspaper. This will keep them from getting scuffed, especially on those pesky washboard roads.

As hinted, roadcuts are particular favorite of mine - except for that one near the U.S./Mexico border where the Sheriff thought I was pulled over to pick-up illegal aliens. No officer, just decomposed granite... you understand right? I justify these spots because the falling rocks are a hazard to vehicle traffic anyway. Speaking of smuggling things from Mexico, rocks are not illegal(no not those rocks). I was inspected once coming from Baja with a few buckets full of rocks, and the Customs agent said so. The only problem was with soil, primarily because of the potential for importing pathogens.

It's a lot of work digging desert soil by hand and filling buckets. Why not just buy it? Without a lengthy explanation, it goes back quality, and what I said about where commercial enterprises mine their products.

That's enough for now... lights out...zzzzzzzzzzzzzz.

Matt

[vapester]

this is interesting indeed.....giving me alot more ideas. I work outside and travel round Cali a bit for my job as a Piledriver....so I already work in great locations to collect some good materials. I've always brought home rocks, but i'll start thinking on a smaller scale now. I just finished jobs in Palm Springs and Bakersfiled recently I coulda collected some good stuff from.

[wantonamara]

I live on a fossilized oyster bed. There are places where one walks on shells and nothing else. Hard on bare feet. I collect them for my top dressing. It is unavoidable. they pop up in every shovel full, almost

[amanzed]

Yeah, so far, field gathering desert soils or gravels is only theoretical for me.

It was a step up for me to add any top dressing. Then I found sources for different size gravel, crushed brick, decomposed granite...

Screens and mesh: I bought a few yards each of different mesh sizes of hardware cloth (welded metal mesh), to help screen and sort my materials.

The most useful was a length of metal screen (mesh size typically used for window screens) which I use to screen out fines from my perlite, pumice, and decomposed granite, especially when sharp drainage is called for.

This setup's a bit messy and takes some space, but it's nice to be able to toss together a mix with a certain look (for the top) or drainage vs. moisture retention (for the rest of the medium).

Perlite vs. pumice: A lot of growers I respect use a mix of both, such as 2 parts pumice AND 2 parts perlite to 1 part organics or potting soil (trying to avoid peat), maybe with added low-nitrogen or well-balanced fertilizer. But on the topic of growth medium, I have learned that anecdotal lore and personal preference are the rule, and religious wars abound.

Retail vs. wholesale: My biggest step forward came when I got fed up with paying retail for little bags of rocks or other supplies -- or plants, if I can help it. With hundreds of plants to take care of, I have been on a quest to find wholesale suppliers who deal in quantities I can manage.

--dean
sentientmeat.net

[vapester]

ok, went to Thompson Building materials and got me a bag of decomosed granite, some charcoal/lava rock, and stopped at Armstrongs for a few bags of really nice topping pebbles, the small ones. Its time to kick it up a notch !

[vapester]

btw, the granite i got is also blast media, hope its the right stuff......

[wantonamara]

You mean like SANDblast medium? That is usually silica sand or it is down here in Texas. Usually it is really fine, even for sand. Not sure you got the right stuff either.

[vapester]

...lol, yeah wth right ? i think i'm ok tho, they had a huge pile of the granite and i just wanted a sack, and the guy said he had some already sacked....i'm pretty sure its the right stuff, they just put it in an armex bag, which is baking soda sand blast medium.....but the stuff ain't white, its brown just like the decomposed granite on display. Anyhow I already mixed a soil blend with it today along with perlite for a new agave marmorata i just potted today. Hope its right, i'm 90% sure it is, i'll call tomorrow to confirm.

[vapester]

yeah i got the right stuff, they use random bags to fill orders.......had me trippin a bit...lol.

[Kelly]

Down here in NZ, it's not a xeric region and drainage is our biggest problem, thus I keep my best stuff in pots and plant out the toughies in a limited, house-side space that Im slowly raising. I have to say, agaves and aloes seem to love rocks. They love the heat they gather and radiate, they love the minerals that leach out of them and the texture they provide for anchoring roots etc. Luckily I live in an old quarry so if I want rocks, I just bust some off a wall with a shovel or pick and arrange accordingly. Im convinced they help guard against frost damage with their heat sink properties etc. Not to mention, nothing really beats the look of good rocks. They're aesthetically primo. Riverbed cobbles are common and easily obtained down here, but I find them very heavy for their size and they can compact the soil beneath to the detriment of the plants when used as a top dressing, I find.

I also use flat rocks to create zones of run-off and to direct excess water away from some plants, using a layered tiers and this can be surprising effective; I've lifted a rock after a wet winter and found things pretty dry beneath.

Personally, perlite drives me crazy with it's refusal to remain where you put it, especially if you're anticipating significant volumes of water or heavy downpours etc. I adore pumice because it stays put, doesn't suck up water and improves almost any other substrate you care to name. I just use whatever bagged cactus mix is in the shops and cut it with half pumice; this has a pretty good success rate for moi. I don't think most species of agave and aloe are particularly fussy, though I have used peaty mixes in the past and had some rotting issues. I avoid them now.


What I want to know is- who fertilizes their succulents and what do you use??? Looking at some of my specimens, Im convinced they could do with some very dilute manure or potash, as most other plant groups benefit from these two. Does anyone use a commercial fert? Anyone killed anything with it yet ?

[Boo Hollow]

Originally Posted by Matt Maggio

Gosh... this could be an interesting thread. There's much to say about soils in general.

Now, I understand that some of us are after that "natural" look, and as a rock connoisseur myself, I know that the supply places don't always present the finest materials nature can offer.

As hinted, roadcuts are particular favorite of mine - except for that one near the U.S./Mexico border where the Sheriff thought I was pulled over to pick-up illegal aliens. No officer, just decomposed granite... you understand right? I justify these spots because the falling rocks are a hazard to vehicle traffic anyway. Matt

Matt - You lucked out. I was collecting fallen sandstone from along Highway 129 near Watsonville, California and the California Highway Patrol stopped and decided to check out what I was doing. I simply told him that I was collecting the scree that was falling off of the cliffs, had safety cones set out well before my truck and located in a large turnout area. He informed me that the rocks were State property and that I could be arrested for stealing state property. I was amazed. I had a Ford F-250 long bed nearly full of fallen rocks. I asked him if I needed to unload the rocks to avoid getting cited. He told me that he was still going to write me a ticket and cited some obscure code stating that its is illegal to pull out along a highway but would not arrest me for theft. During this order, a CalTrans vehicle passed by. Minutes later, the CalTrans truck pulled up along side us and asked if there was a problem. The officer informed him I was stealing the rocks and was being cited. The CalTrans guy started laughing and told the officer that I was saving the State money since they have to dump all the materials collected from this stretch of the highway due to some asbestos issues with the rock and in his opinion, I could have all I wanted. The CHP officer let me go. I got the number of the CalTrans guy and two weeks later, arrived on the opposite side of the road, truck and shovel in hand and the CalTrans crew had just finished scraping the road edge and had piles waiting for the picking. When I started to shovel, the other CalTrans guys pulled up with their skip loader and asked how much I wanted. A few minutes later I was on my way with a full truck load of crumbling sandstone and a smile (and no sore back).

So the warning is to the fellow rock hounds that the State roads are regulated and indeed it is illegal to remove the rocks from the roadcuts. I found out the hard way.

Cheers.

[agavegreg]

Check the older threads, I believe there is one on fertilizers.

What I want to know is- who fertilizes their succulents and what do you use??? Looking at some of my specimens, Im convinced they could do with some very dilute manure or potash, as most other plant groups benefit from these two. Does anyone use a commercial fert? Anyone killed anything with it yet ?[/quote]

[Boo Hollow]

Originally Posted by agavegreg

Check the older threads, I believe there is one on fertilizers.

What I want to know is- who fertilizes their succulents and what do you use??? Looking at some of my specimens, Im convinced they could do with some very dilute manure or potash, as most other plant groups benefit from these two. Does anyone use a commercial fert? Anyone killed anything with it yet ?

[/quote]

Greg - Start a poll! We do not subscribe to the theory of adding fertilizers to our mixes (except the starter fertlizers already in the bulk mixes from our supplier) and do not fertilize any of our cacti or succulents. Having grown over 1 million dudleya seedlings during the past 23 years, we just have not seen the need. Those customers of ours whom dose the heck out of their plants regret it later as their dudleyas become Dudleya monstrosa and morphologically have lost all association with the parent plant stock. They also are more frequently prone to disease, turgor pressure induced leaf damage, fungal and bacterial infections. Leaf growth is a cube function and not a width and length function. To much fert and water and the leaves outgrow their waxy cuticles and voila, infections. My opinion anyways. Paul Agner prepared a great article on saxicolous plants and their very small required soil quantities. There is a limited nutrient availability for these types of plants, yet they thrive. Trying to recreate the exact soil mix for the plants in question ignores the fact that the environmental condition including photoperiod, water relations, mycorrhizial associations, etc., are not being duplicated. Some myths die hard. Putting pot shards in the bottom of the pot to increase drainage is a good one. The soil above the rock/pot shard interface must become supersaturated prior to transfer of water to the next media and thus, results in stagnation zones of water at this interface. The elemental matching we all strive for has also been disproven in that endemics to specific soil types do not require that soil, they just can survive in that soil. Serpentine plants are a good example. Many plants cannot handle the high nickel and arsenicals in the soil and die when exposed to these types of substrates where others can survive and thrive, but through some adaptation, are out-competed in adjacent soil mixes and cannot thrive and die out. My limestone dudleyas are a good example. I do not grow them in basic soil and they have survived for 10+ years. I am also confident that my Opuntia echios, O. megasperma and O. galapegia are not on the same complex soil matrices that are found on their respective native islands.

Look at the UC Soil mixes and John Innes soil mixes. An attempt to standardize for the industry and still viable today. I am amazed when I purchase the odd plant from the big-box store and find a Euphorbia growing in almost pure peat, and wet gooey soils, and thriving. Same with the plants I get in from the TC people that are using pure peat and lots of liquid ferts and Banrot. Standardization for ones collection is the best basis as it will allow a more normalized watering schedule - my humble opinion. If everything has the same drying rate, then it can be more readily predicted when plants might need to be watered. Remember the days when people thought that cacti grew in pure sand, bought a bag of play sand and watched as their plants slowly perished.

The same goes for the water acidification theory recently being resurrected by some. Buxbaum's theory is dated and even after all these years, is not a standard reference for those cultivating cacti. The hydroponics people and universities have performed countless studies on nutrient uptake based on pH and found that the data supports a more neutral to only slightly acidic water. Some elements do have higher uptake at lower pH, but what compromises are made with respect to the other natural ratios now being out of proportion. The nitrogen and lightning relations are overstated as well. My atmospheric chemistry research and reference materials state that only 5% of the available nitrogen is contributed by lightning. That is a statistical outlier (a number and not a meaningful data set).

Start a poll and let's see what the other members do.

[agavegreg]

I was responding to a question by Kelly, and apparently I cut the start of the quote. Allen should start the poll , I barely have time to keep my head above water right now.

[Boo Hollow]

Originally Posted by vapester

ok, went to Thompson Building materials and got me a bag of decomosed granite, some charcoal/lava rock, and stopped at Armstrongs for a few bags of really nice topping pebbles, the small ones. Its time to kick it up a notch !

When adding decomposed granite to soil, be mindful that most graniticly derived soils have a tendency to become very hydrophobic and difficult to rewet when they dry. This would not so much apply to top dressings. It is important also when you screen, to use different sizes of materials, but not to wide a range. A top dressing that is composed of to dissimiliar a particle distribution can form interlaced matrices that can form a hardpan or cake on the top of the soil and force water to channel around the edges and not through the body of the soil. The surface of the rocks looks wet, but there is a limited penetration of water into the subsurface soil.

California Department of Agriculture just published a great article on soil rewetting, wetting agents and penetration of water vs. runoff and is well worth reading. http://californiaagriculture.ucanr.o...?issue=current

[lorax]

For top dressings, I'm really fond of the stuff that came down the volcano in the last lahar - it's a mix of black basalt and bluestone in fairly small chunks, with a bit of rough quartz-included granite thrown in. My Agaves and Opuntias love it. With the bromeliads, I try to grow the same hardy grasses that they'd be growing alongside of in the actual paramo, and use these as companions and grass-mulch type top-dressing. It works particularly well with the larger red Cortaderia in companionship with larger Puya. For terrestrial Tillandsia, though, I use the volcanic stuff or the leaf litter from my altitude blueberries (a xeric plant that deserves mention, but probably not on this thread.)

In terms of soil mixes, I tend towards a mixture of sand and smaller volcanic ejecta with some activated charcoal thrown in for most of my xeriphytes. Some of the endemic bromeliads, however, have special needs and there I do try to match what they grew on where I collected them. This means my Tillandsias are almost all on kaolin-based granular clay.

[wantonamara]

What makes the Kaolin granular? Has it been fried by a lahar in the past? Where one finds kaolin , in my experience, it is smooth and absolutely no drainage.

[Boo Hollow]

Originally Posted by wantonamara

What makes the Kaolin granular? Has it been fried by a lahar in the past? Where one finds kaolin , in my experience, it is smooth and absolutely no drainage.

If Kaolin is found in granular form, it is post mining processed and typically a hard fired almost vitreous clay (means it goes through a phase transformation to a "glassy" phase. Clays in general are not granular but lamellar (plate like) in structure. The Turface products are a vitrified clay product that has been fired. If the base material is Kaolin, it would have a pore cation exchange ration vs. other clays, which have high cation exchange ratios. Depending on the surface charge of the clay particles, they can become hydrophobic, however when wetted, they are slower to dry and can become sticky masses with very poor air space. They have great water holding capacity and this is why they typically congeal into clumps, the solution at the interfaces of the clay particles allows them to attract to each other and dehydration occurs, they bond together into a very dense and hard mass - think adobe. I am still perplexed at their use in cactus soil mixes. My experience is that they stay too wet for too long a period of time and since they have a low cation exchange capacity, I do not see their value. Would love to learn why there is a trend to add Turface to mixes. I prefer pumice, scoria or perlite, depending on the plant mix. Both pumice and scoria can develop nice biofilms on the surface that allows for good breakdown of certain decomposition chemicals in the soil, such as the dreaded anaerobic sulfurous smells and ammonicals. Dollar for dollar, scoria (red or black lava rock) is the most effective media for adding bulk, porosity and enhancing drainage. It does have the drawback of being the perfect habitat for mealy bugs. The weight issue that people complain about is another perplexing issue. Unless one is shipping plants in the pots and is constantly moving the plants around, I do not see a distinct disadvantage to its use. Perlite is another great media to use, yes it floats to the surface, but I have found that this layer has benefits. The drawbacks are also the silica dust that can pose a serious health risk. I always lightly wet my perlite prior to mixing, to mitigate the dust and also help reduce the tendency to float. Wetting the perlite reduces the trapped air and reduces flotation.

Users of Turface, please explain the rationale behind this choice and its benefits and drawbacks. It is expensive when used large scale. Soil science indicates that a soil additive must be at >20% in order for any contributory benefits can be realized. So the mixes where I see people adding 10% of a compound to their mixes makes one pause and wonder what real benefit is gained. Look at the UC Soil Mix System handbook for a better explanation of their studies on this matter.

Cheers

[lorax]

They are on mining waste, usually, and yes, the kaolin has been seriously cooked. What it ends up being is something similar to hydroponic balls. In the wild wild, those Tillandsias grow directly on slightly decomposed sandstone cliffs, which is difficult to replicate properly in the garden.

[wantonamara]

I am an ex "poor pitiful potter", from ages past (70's), and what you are describing is what we would call a porcelain "Grog". I was under the impression that Lorax said she was copying the natural dirt she found these bromeliads growing in. Lorax, is the Kaolin a natural part of the soil and , if so, is it "granular" in Nature . What is the geological process that makes the clay granular. Is it a "post mining" product.

Lorax lives in a place where she is not surrounded by bags of odd gardening products at big box stores, brought to her by the marvels of a mass consumer market. Or maybe I am mistaken here.

On another note....I am always amazed when I receive cactus and Opuntia from growers in Arizona that arrive in solid unadulterated red clay and the plants are very happy. Obviously Mother nature has not read the UC Soil Mix handbook. Mother Nature did not plant that opuntia in the red clay around here either. There lies the problem.

[wantonamara]

oops I see we cross post and you answered my question while I was talking on the phone and not submitting my reply. You must go through a lot to get these materials.

[lorax]

Ok, to answer some of your first post first. We don't have "big box stores" here. We have small, mom-and-pop, speciatly stores and we lack the kind of mass consumerism that's seen in North America.

The only thing I can really buy at the "garden center" (and I use the term loosely, because the store is primarily a hardware that also sells trowels) is bags of bark chips and solid blocks of worm castings. There is a specialty farming store in my city that carries peat moss and coir, which it took me nearly 2 years to find. Everything else I use, I'm scrounging from nature or industrial rejects. The thing that makes it worthwhile is that I do like to hike, and I often discover interesting things that I want for the garden while I'm out collecting myself 10 or 20 lbs of volcanic wastes (this is how I get basalt, bluestone, fertilizer, obsidian marbles, and zeolite) or mine tailings (in the case of the granular Kaolin and some grades of sand and redstone gravel, as well as assorted quartzic substrates). I get orchid and Aroid media by hiking into the forest and collecting bags of leaf and bark mulch and bits of decomposing logs. I've been known to cart home Andesite boulders because they're the best substrate for the mosses I grow, which in turn are the best substrate for the hemiepilythic xeric orchids I'm fond of.

I generally don't refer to soil handbooks, especially US ones, because they have absolutely no clue about the composition of tropical soils. Instead, I try to replicate the areas where I find the plants growing well. Hence, the Puyas are all in limestone-rich soil with fast drainage, while the xeric Vriesas are on chunks of sandstone that I hauled home with the plants in-situ, and the larger Tillandsias on the mine tailings, and so on. My Galapagos plants are on soil I brought back from the islands, because I have no hope of replicating it.

[wantonamara]

I did not realize that Puyas like limestone (lucky for me). I have heard "rich" but then I rotted a puya had changed it. When I repot again I will put in some more limestone gravel. The thing about limestone is that there is limestone and there is limestone. The microorganism that live in the varying strata of limestone change with just a few miles and some plants are incredibly tied to which layer they like. I.E. Madrone trees. They grow on my land but will not grow in the "Cow Creek strata" 3 miles from me. And vice versa.

[lorax]

Well, it would be worthwhile to experiment, Mara. I generally take limestone from an area close to where I find the given Puyas, so they've got the microbes they need already living there. When that's not possible (ie when I'm collecting seed from a provincial park), I generally take a tiny sample of the limestone and use that to innoculate other soil.