Best Cloning Cubes for Propagation and Seed Starting

What a starter cube is made of

Every rooting cube is solving the same problem. Roots need water, air and something to hold onto, all three at once, in a block small enough to drop into a tray of fifty. A medium that holds too much water drowns the cutting; one that drains too freely dries out between visits. University extension guidance puts it simply: the medium has to be porous enough for aeration and drainage while still retaining water and nutrients.

The four materials split cleanly into two camps. Stone wool and foam are inert: they contain no nutrition and no biology, so everything the plant gets comes from the solution you feed it. That is a feature in a commercial room where the recipe is controlled to a decimal place, and it is extra work on a bench of thirty cuttings. Composted peat and coco sit at the other end. They carry some fertility of their own, hold water differently, and in one case arrive with a fungus already living in them.

The second split is conditioning. Stone wool arrives dry and has to be saturated with pH-adjusted solution before use. Foam, composted peat and coco arrive either sterile and ready or already moist. That single difference is the one most growers notice first, and it is why a sheet of A-OK and a bag of Root Riot feel like different products even though both end up holding a cutting.

One caveat worth hearing before you pick a side. An inert medium is not a disadvantage and an organic one is not automatically better. Virginia Cooperative Extension warns that a rooting medium should be low in fertilizer, because excessive fertility damages or inhibits new roots. The reason stone wool and foam dominate commercial propagation benches is precisely that they start at zero and stay there until you decide otherwise.

The three at the top

Three products take the top spots, and the ranking rests on how much work each one asks of you before a cutting goes in. OrganiPlug is first because it arrives finished. Grodan A-OK is second because it is the most versatile block on the bench once it is conditioned. Oasis Rootcubes is third because the foam is sterile and ready, with a drying habit that needs watching.

That sequence is about workflow, not quality. Every one of the three roots cuttings reliably in the right hands. What separates them is how many decisions sit between opening the package and sticking the first cutting, and how forgiving each is if you miss a day.

Each of the three gets its own section below, with the full range of counts and formats. After that come Root Riot, Rapid Rooter and Botanicare CocoPro, which cover the rest of the shelf and win on different grounds entirely.

Ventana Plant Science OrganiPlug

The OrganiPlug is a 1.25 by 1.25 inch plug of coco coir, peat moss and bio-char, held together by an all-natural food-safe binding agent. It comes pre-moistened and pH balanced in a lightproof resealable pouch, and it contains Trichoderma. There is nothing to soak, nothing to adjust, and nothing to throw away if you use half a bag.

That is the whole argument for first place. Open the pouch, set the plugs in a tray, insert the cutting about halfway down the plug, and keep the humidity between 70 and 100 percent. Mist the leaves straight away. The plug is already at the moisture content the manufacturer wants it at, so the first thing you do is the thing that actually matters rather than a twenty-minute conditioning step.

The ingredients are OMRI listed, the binding agent is food-safe, and the finished plug is 100% compostable and Kosher-certified. Those are not marketing adjectives on this product, they are the reason it exists — a plug that can go into a certified operation and then into a compost heap without a second thought. If you have ever pulled stone wool out of a finished crop and wondered what to do with it, that difference lands.

The one thing that surprises people is the white growth. Open a pouch that has been sitting a while and you will often find a fine white fuzz across the plugs. That is the Trichoderma doing exactly what it is in there to do, and it is a good sign rather than a contamination. It is also the single most common reason someone emails us about this product. More on what that fungus is actually doing is in our piece on beneficial microbes in hydroponic growth.

Three formats cover the range. Loose plugs in a pouch suit a bench where the count varies week to week. The pre-filled trays suit a room that runs the same number of sites every cycle, and the tall tray exists for species that want more depth under the cutting before transplant.

If the plugs dry out in storage, rehydrate them with clean water and carry on. There is a longer write-up of this product and the growers using it at commercial scale in why VPS OrganiPlugs are the clone plugs top growers trust.

Grodan A-OK stone wool

Stone wool is spun mineral fibre and it is completely inert, which means it holds back nothing and contributes nothing. Everything the cutting receives comes from the solution you put through it. That is the whole reason A-OK has been the default on commercial propagation benches for decades, and it is also the reason it demands a conditioning step that none of the organic plugs do.

The A-OK plug comes in two footprints. The 1.5 inch plug measures 1.4 by 1.4 by 1.6 inches and arrives 98 to a sheet, 30 sheets to a case, 2,940 plugs in total. The 2 inch plug measures 2 by 2 by 1.6 inches, 50 to a sheet, 30 sheets to a case, 1,500 plugs. Both heights are the same at roughly 40 mm, so the difference is footprint and spacing rather than depth.

Saturate before anything goes in. The manufacturer's instruction is a 1.5 EC nutrient solution adjusted to pH 5.5 to 6.5, applied either as a coarse spray or by submerging the sheet for up to a minute, then left to drain. Stems go half an inch into the saturated plug, and cuttings should be no more than fourteen days old. Skip the saturation and the plug wicks moisture out of the stem instead of into it.

Do not squeeze a saturated plug to force water out. Stone wool holds its air and water balance by structure, and wringing it collapses that structure permanently. Once the plugs are running, the irrigation cue is weight: when the wet weight falls to around half, irrigate again at 1.5 EC and pH 5.5. There is a fuller treatment of solution pH and EC in optimizing pH and EC for improved yields.

Beyond the square plugs, Grodan makes two shapes that solve different problems. The Macro Plug is a 1.5 inch round, 1.57 inches high, with a slit rather than a hole so a cutting pushes straight in — useful when the stem is soft and a drilled hole would crush it. Grow-CUBES are loose cubes of stone wool sold by volume, used to fill a container rather than to hold a single site.

The shrink-wrapped single strip is the one to reach for on a small bench. A strip of 98 costs less than a bag of groceries and leaves the remaining sheets in their wrapper, which matters because an unwrapped case starts drying the moment it is opened.

Oasis Rootcubes

Rootcubes are an engineered hydrophilic foam rather than a mineral or an organic medium, and the thing that sets them apart is that they arrive sterile and pathogen-free with nothing to condition. The foam also has a low cation exchange capacity, which means nutrients become available quickly and salts do not accumulate in the block the way they can in coir.

That combination suits high water use crops. Hydroponic lettuce, tomato, herb and onion germination all run well in Rootcubes, and the same sheets handle foliage plant propagation without a change in method. The sheets are cut to the industry standard 10 by 20 tray footprint, so they drop into trays and domes you already own.

Two sizes are listed. The 1.25 inch cube comes 104 to a sheet in an 8 by 13 grid, 20 sheets to a case, 2,080 cubes. The 1.5 inch cube comes 50 to a sheet in a 5 by 10 grid, 20 sheets to a case, 1,000 cubes. Both carry a 3/8 inch hole, which is a comfortable fit for most herbaceous stems and a little loose for very fine ones.

The honest caveat is drying. Rootcubes hold their air to water balance well, but foam gives up moisture at the surface faster than composted peat does, and a tray left uncovered on a warm bench will show it within a day. A humidity dome solves it completely. The second consideration is end of life: the foam is not compostable, which is a real difference from the coco and peat plugs above and worth weighing if that matters to your operation.

Both cases carry the same price, which makes the choice purely about site count and cube volume. Twice as many cubes at 1.25 inches, twice the root volume each at 1.5 inches. Pick by what the cutting goes into next.

Root Riot and Rapid Rooter

These two are the composted cubes, and they share the trait that makes them the easiest entry point into propagation: they arrive moist and go straight into a tray. No saturation step, no pH meter, no drain time. For a grower rooting twenty cuttings on a kitchen bench, that is most of the appeal.

Root Riot is made from composted natural materials and ships spongy and moist in a sealed bag. The moisture target is specific and useful — moisture should just come to the surface when the cube is squeezed, and the cube should be spongy rather than saturated. If a bag has dried in storage, re-wet the cubes in a bowl of lukewarm water. Each cube carries a pre-formed hole in the top.

The method for a cutting is short. Cut diagonally below a node, keep a couple of leaves, dip the cut end in rooting gel, and push the stem into the pre-formed hole just far enough to support it. Cover with a clear lid. For seeds, drop the seed into the same hole and keep the tray warm until germination. Transplant once roots are visible.

Rapid Rooter works on the same principle with a different recipe: sphagnum peat moss and composted tree bark held together by a plant-based foam polymer. It is the one composted plug here that does want a soak. General Hydroponics calls for fully immersing the plugs in pH-balanced water at around pH 6.0, or a very mild nutrient solution, for roughly two hours, squeezing four to five times during the soak, then squeezing out the excess so the plug is thoroughly damp but never dripping.

After that it is straightforward. A 2 to 4 inch cutting, cut at 45 degrees, the bottom inch stripped bare, inserted into the pre-drilled hole so the stripped stem is fully enclosed. Hold the room at 75 to 80 °F with 16 to 18 hours of light under a dome. Keep no more than a quarter inch of standing water in the bottom of the tray. Clones and seedlings are generally ready inside one to three weeks, once roots show through the sides or the bottom.

One instruction on Rapid Rooter is worth repeating because people get it wrong: when you transplant, do not strip the plug material off the roots. The whole plug goes into the next container. Pulling it apart tears the root hairs that the last three weeks were spent growing. The same holds for every plug in this guide — there is more on timing and technique in transplanting plants into a larger container.

Store what you do not use properly. Both manufacturers say the same thing in different words: seal the remainder in an airtight bag, keep it dark and cool, and the cubes stay usable. Left open on a shelf they dry hard, and a rehydrated cube never quite recovers the structure it had.

Botanicare CocoPro

CocoPro Plugs are the straight coco option. The coir is thoroughly washed and buffered, then dehydrated and compressed down to roughly 35 mm across and 9.5 mm high, which is how a case of three thousand fits into a box you can carry. They rehydrate on the bench with whatever nutrient solution you are already running.

The compression is the point. A coir plug at full volume takes a lot of space and a lot of freight, and most of what is being shipped is water. Compressed and dehydrated, the same three thousand plugs arrive in a box around 16 by 20 by 15 inches at 37 lb. That changes what a bulk propagation re-stock costs to get to the door, which is not a small consideration for a room running thousands of sites a cycle.

Washed and buffered matters too, and it is the step low-grade coir skips. Raw coir carries sodium and potassium from the coconut and will swap them for the calcium and magnesium in your feed, which shows up a week later as a deficiency nobody can explain. Buffering pre-loads those exchange sites so the plug behaves predictably from the first irrigation.

These are a commercial product in commercial quantities, and the smaller of the two counts is still 1,400 plugs. If you are rooting dozens rather than thousands, one of the bagged options above fits the bench better. If you are rooting thousands, the freight arithmetic is the reason this product is on the list.

Soaking a cube before you use it

This is the step that separates the materials in practice, and getting it wrong is the most common reason a tray of cuttings fails for no obvious reason. Three of the five media here need nothing at all. One needs a two-hour soak. One needs a pH-adjusted saturation with a measured EC. Treating them all the same is how a grower ends up with half a tray rooted and half a tray black at the base.

The logic is simple once you see it. An inert medium starts with no nutrition and no pH buffer, so the first solution you put through it becomes its chemistry. A pre-moistened organic plug has already been brought to its working moisture and pH at the factory, so adding water only pushes it past where it should be.

Two details that are easy to miss. Stone wool should never be wrung out after saturation, while Rapid Rooter explicitly wants to be squeezed four or five times during its soak and then squeezed again to shed the excess. The instructions point in opposite directions because the materials are structurally different, and following the wrong one does real damage. Stone wool that has been squeezed has lost its air channels for good.

The other is that a soak is not a feeding. Virginia Cooperative Extension is blunt about fertility at this stage: excessive fertility damages or inhibits new roots. The 1.5 EC that Grodan calls for is a conditioning strength, not a veg feed, and the water Rapid Rooter wants is pH-balanced rather than nutrient-rich. Full-strength solution in a propagation cube burns the root initials before they ever emerge.

Starting seeds in a cube

A seed asks less of the cube than a cutting does, which is why seed starter cubes are where most people meet this category. There is no wound to callus and no leaf transpiring against a stem with no roots. What the seed needs is steady moisture, warmth, and darkness until it breaks the surface — and the hole in the top of the plug already gives it a chamber that holds all three.

The method barely changes between products. Place one seed in the hole of a saturated or pre-moistened cube. Grodan calls for a single seed placed with clean tools into the hole of the saturated A-OK plug. OrganiPlug wants the seed halfway down the plug, in a warm dark place at high humidity. Root Riot asks only that the seed goes into the hole and the tray stays warm until germination.

Rapid Rooter adds one step worth copying everywhere. After dropping in one or two seeds, tear a small piece of material from the edge or the bottom of the plug and lay it lightly over the hole. That closes the chamber, keeps the seed dark and stops it drying at the surface, and it costs nothing. Keep the tray dark until seedlings emerge, then get light on them immediately.

Water from below, not above. A quarter inch of water in the bottom of a 10 by 20 tray is the figure General Hydroponics gives, and it is a good general rule for any of these plugs. Pouring over the top washes the seed deeper into the hole and compacts the surface. Seedlings are ready for their next container about a week after the first true leaves unfurl, or once roots show at the sides and base of the plug.

If seeds are going in and nothing is coming up, the cause is usually moisture or temperature rather than the seed. Our guide on what to do when your seeds aren't sprouting works through the usual suspects one at a time.

Rooting a cutting in a cube

A cutting is a leaf and a stem with no root system and no way to replace the water it is losing, which is why the whole method is built around keeping it from drying out long enough to grow one. Everything below — the humidity, the bottom heat, the dome — exists to give the stem time.

Take a cutting 3 to 6 inches long with at least two nodes, cut just below a node, and strip the leaves from the bottom 1 to 2 inches so nothing sits buried in the medium. Those figures come from university extension guidance and they hold across species. Grodan adds one of its own for stone wool: use cuttings no more than fourteen days old, and set the stem half an inch into the saturated plug.

Rooting hormone goes on the basal half inch before the stem goes in, not after. More is not better — Iowa State specifically warns that too much rooting hormone can slow root development, which is a failure mode nobody expects from a product sold to speed it up. There is a full treatment of gels, powders and their differences in our guide to using cloning gels.

The commonest way to lose a tray is too much water, not too little. Virginia Cooperative Extension notes that misting should run during the day only, because overnight misting keeps the medium too wet and encourages rotting. University of Kentucky adds the matching warning about depth: a cutting stuck too deeply into a shallow medium can rot at the base. A cube that never dries down between irrigations is a cube with no air in it.

Sterility is the other half of that. Extension guidance is consistent that the rooting medium should be clean and sterile, because cuttings are attacked by fungi and bacteria that arrive in the medium itself. That is the quiet argument for every product in this guide over a scoop of garden soil, and it is why the Oasis foam being pathogen-free out of the box is a specification rather than a slogan.

Counts, sheets and cases

Almost every one of these products exists in two or three sizes of the same thing, and the cube inside does not change between them. What changes is how many you are committing to and how it is packed. A bench rooting thirty cuttings a month and a room rooting three thousand a week want very different rows out of the same table.

There is one trap worth naming. An unwrapped PRO case of stone wool begins drying the moment it is opened, and thirty sheets is a lot of surface. A shrink-wrapped strip keeps the sheets you have not reached yet sealed. For the same reason, bulk composted cubes want an airtight container once the original bag is broken.

Read that table by the left two columns first. Below about a hundred sites, the composted cubes and the single stone wool strip are the only rows that make sense. Above a thousand, the case pricing turns over and a 2,940-plug PRO case lands under a tenth of a dollar a site. The middle, between a hundred and a thousand, is where the pre-filled trays earn their keep.

Trays, domes, heat and gel

A cube on its own does very little. It sits in a tray, under a dome, usually over a heat mat, with a gel on the stem and a light overhead, and every one of those decides whether the cube performs the way its manufacturer intended. The sheet formats here are all cut to the 10 by 20 footprint for exactly that reason.

The dome is the piece people skip and then regret. Purdue's propagation guidance puts the humidity target above 70 percent at 68 °F and above 80 percent at 78 °F, and University of Kentucky recommends keeping relative humidity near 100 percent for an enclosed unit. No amount of misting a room gets you there. Trays and humidity domes is where the matched sets live.

Heat goes underneath, not overhead. The root initials form at the base of the stem, inside the cube, so that is where the warmth needs to be — Iowa State puts a heat mat's rooting media target at 75 to 80 °F while the air sits at 65 to 75 °F. A mat without a thermostat overshoots on a warm afternoon, which is why heat mats and thermostats are sold together.

One item in this category is not a cube at all. The EZ-Clone neoprene insert holds a cutting with no medium around it, suspending the bare stem in an aeroponic chamber where a mist does the work the cube would otherwise do. It belongs here because it occupies the same slot in a propagation bench and answers the same question. Growers running cloning machines and systems use these rather than plugs, and the trade-off is honest — faster rooting and no medium to transplant, against a machine that stops working the moment the power does.

The rest of the bench fills in quickly: cloning gels and solutions for the cut stem, propagation lighting overhead at an intensity a rootless cutting can handle, propagation nutrients and supplements for the first feeds, and cloning tents when the propagation area needs its own environment. The full department sits in propagation, and propagation tools and accessories covers the scalpels, labels and dibbers.

For the aeroponic route specifically, our comparison of nutrients, rooting hormones and cloning machines for aeroponic cloning goes through the machines in detail, and Radix rooting hormone stimulator covers one of the additives that goes in the reservoir.

FAQs

The questions below are the ones that come in most often about starter cubes, and most of them turn on the same two things: what the cube is made of, and how wet it is being kept.

What is the difference between a cloning cube and a clone plug?

In practice the words are used interchangeably, and the same product is often sold under both. The only consistent distinction is shape — a cube is square and usually cut from a sheet, a plug is round or moulded individually. Neither tells you anything about the material, which is the thing that actually changes how it behaves. A 1.5 inch stone wool square and a 1.25 inch coco plug are both cloning cubes by common usage.

Do cloning cubes need to be soaked before use?

Three of the six media here do and three do not. Stone wool has to be saturated with a pH-adjusted solution, Rapid Rooter wants about two hours of immersion, and compressed coir needs rehydrating. Root Riot, OrganiPlug and Oasis Rootcubes are ready as supplied. Soaking a pre-moistened plug is not a neutral act either — it pushes the cube past the moisture content it was packed at.

How long do cuttings take to root in a cube?

Under commercial propagation conditions roots are visible in about 5 to 12 days and fill half the cell at 10 to 16 days, reaching a fully rooted liner in two to four weeks. On a home bench, three to six weeks is the realistic figure for most stem cuttings, and some species run far longer. The medium is rarely the limiting factor. Humidity, bottom heat and the age of the cutting are.

Why are my cuttings rotting at the base?

Almost always too much water. A cube held at saturation has no air in it, and the stem sits in the one condition that rots it. Mist during the day rather than overnight, keep standing water in the tray to about a quarter inch, and let the cube dry down between irrigations. Pushing the stem too deep into a shallow cube does the same thing for a different reason.

Can I start seeds in the same cubes I use for cuttings?

Yes, and every product in this guide is sold for both. Seeds are the easier of the two jobs because there is no wound and no leaf losing water. The one adjustment is darkness: a seed wants the hole covered and the tray dark until it emerges, where a cutting needs light on its leaves from the first day.

What is the white fuzz on my plugs?

On an OrganiPlug it is Trichoderma, which is in the plug deliberately and is a sign the biology is active. On an inert medium like stone wool or foam, white growth means something has colonised a medium that started sterile, and that is worth investigating. The material tells you which answer applies.

The bottom line

Pick the material first and the product second. If you want to open a bag and start working, OrganiPlug, Root Riot and Oasis Rootcubes all go straight into a tray with nothing in between. If you want total control over what reaches the root zone, Grodan A-OK gives you a blank slate and asks for a saturation step in return. If you are filling thousands of sites and freight is part of the arithmetic, compressed CocoPro plugs change what a re-stock costs to land.

The ranking at the top of this piece holds for a reader standing in front of a bench deciding what to run next cycle. OrganiPlug first because it removes the most steps and brings its own biology. Grodan A-OK second because nothing else is as versatile once conditioned, and because the 1.5 inch plug drops into every Gro-Block on the market. Oasis Rootcubes third because sterile foam out of the box is a genuine advantage that comes with a drying habit and no compost route at the end.

Whatever you pick, the two rules that decide the outcome are the same. Condition the cube the way its maker says, not the way the last cube wanted. And keep it moist rather than wet, because every one of these media fails the same way when it is held at saturation. Deeper method is in advanced propagation techniques from seed to harvest, and the mycology behind the Trichoderma is in the role of mycorrhizal fungi in nutrient absorption.

If you are sizing a propagation run and are not sure which count fits, call us or drop a comment below. We would rather spend ten minutes working out whether you need a strip of 98 or a case of 2,940 than have you find out three weeks into a cycle.