Growing Succulents from Seed: An Honest Introduction

Part of the A Beginner's Guide to Succulents: What They Are and How to Keep Them Alive.

Seed propagation is the slowest and lowest-yielding way to multiply succulents, and for most house collections it is also unnecessary. Leaf and stem propagation give faster, more predictable results for the genera most beginners grow. Sowing seed earns its keep when you want a species vegetative propagation cannot produce: a CITES-listed plant, a difficult-to-source botanical species, or a genus that does not have stable named cultivars in the first place. Here is the rest of the picture.

Part of the Beginner's Guide to Succulents.

When seed propagation makes sense

Seed is the only realistic source for several rare or protected species. Astrophytum asterias (Zucc.) Lem., listed on CITES Appendix I, is exported as legally produced seed but almost never as legal mature plants. The same is true for many Mammillaria with restricted Mexican distributions. Lithops N.E.Br. and Conophytum N.E.Br. species do not propagate from leaves, and dividing a clump only multiplies a single clone. If you want twenty Lithops showing the natural variation from a wild population, seed is the route.

Seed also gives you genetic diversity, which matters if you keep a population for breeding work or to see how far variation goes within a species. A single offset is one genotype repeated forever; a pan of seedlings from a wild-collected (legally documented) seed lot is a window onto the species itself.

Genera that grow from seed reliably

The following genera germinate well at 22 to 25 °C (72 to 77 °F) under bright indirect light, on a thin layer of fine mineral substrate, in the closed-bag setup described below.

Genus	Time to first germination	Typical germination rate
Astrophytum Lem.	3 to 7 days	around 80%
Lithops N.E.Br.	5 to 10 days	around 70%
Echinocactus Link & Otto	7 to 14 days	60 to 75%
Ferocactus Britton & Rose	7 to 14 days	60 to 75%
Mammillaria Haw.	10 to 28 days, variable by species	40 to 70%
Conophytum	10 to 21 days	50 to 70%

These figures assume fresh seed (under 18 months old for cactus, under 12 months for Lithops and Conophytum) and sterilised substrate. Older seed germinates more slowly and at lower percentages; Astrophytum seed older than three years rarely tops 30%.

Germination rate is not survival rate. From sown seed to a potted, viable seedling at one year, expect 30 to 50% even with good technique. Losses come mostly from damping-off in the first month and from desiccation when the bag is opened too quickly.

Genera you should NOT grow from seed

Three groups disappoint reliably from seed.

Echeveria DC. segregates badly. Even when both parents are named cultivars, the F1 generation is a wide spread of forms, colours, and rosette geometries. A few seedlings may resemble one parent, others will look nothing like either. If you want a particular Echeveria clone, take leaves from the clone, not seed.

Crassula L. 'cultivars' behave the same way. Crassula ovata (Mill.) Druce 'Hummel's Sunset', the cream and red form, exists only as a vegetatively propagated clone. Seed from 'Hummel's Sunset' produces ordinary green-leaved jade plants. The cream variegation is a chimera maintained by the original tissue layers and is not transmitted through pollen.

Most Aloe L. hybrids in the trade, particularly the small hybrids from breeders like Kelly Griffin or Karen Zimmerman, are clones. Seed from a hybrid mother fertilised by an unknown pollen donor yields plants that may share some features with the named hybrid but almost never reproduce it. For these plants, take offsets.

Seed is sexual reproduction, and sexual reproduction shuffles the genome. Anything you value because it is one specific phenotype must be propagated vegetatively.

Sources for legitimate seed

Four sources cover most of what a serious grower needs:

Mesa Garden (Belen, New Mexico, USA): the long-running specialist for cactus and other succulent seed, with detailed locality data on most listings. Steve Brack ran it for decades and the catalogue remains a reference.
Cactus-Mall and similar UK suppliers: cactus and succulent seed packets with reasonable provenance, useful for European growers avoiding US import paperwork.
Köhres-Kakteen (Erzhausen, Germany): one of the largest cactus seed catalogues in Europe, with strong Astrophytum, Mammillaria, and Turbinicarpus offerings.
Society seed exchanges: the British Cactus and Succulent Society (BCSS) and the Mesemb Study Group (MSG) run member-only exchanges with material donated by experienced growers, including Lithops and Conophytum lots that almost never reach commercial channels.

Avoid bulk listings on general marketplaces. Seed sold as "rare cactus mix" on auction sites is frequently old, mislabelled, or chaff, and the gamble is rarely worth the lost year.

Substrate and pot setup

Use a sterilised mineral substrate. A 50:50 blend of fine pumice (1 to 2 mm) and akadama (1 to 3 mm) works for most cactus and mesemb seed. Sterilise the substrate by soaking in boiling water for ten minutes, draining, and letting it cool to room temperature in a covered container. This kills the fungal spores that cause damping-off.

The container should be transparent so light reaches the surface, with drainage holes. A clear plastic pot, a takeaway container with holes punched in the base, or a purpose-made seedling tray all work. A 4 to 6 cm depth of substrate is enough; deeper pots only hold excess water near the new roots.

Cactus and mesemb seeds need light to germinate, so spread a thin layer of finer particles (0.5 to 1 mm) across the top, giving the seed a level surface rather than crevices to drop into. Mist with rainwater or boiled-then-cooled tap water until the substrate is uniformly damp but not flooded. Sow by tapping seed from a folded paper card across the surface. Do not cover with substrate. Mist lightly again to settle the seed against the grit.

The Fleischer (closed-bag) method

The closed-bag method, named after the Czech grower Zdeněk Fleischer who popularised it in the 1980s, solves the central problem of cactus seedling cultivation: very young seedlings dehydrate within hours in normal room humidity, but rot within days in continuously soggy substrate. A sealed clear plastic bag holds relative humidity at 95 to 100% while the substrate slowly releases moisture from below, keeping the cotyledons turgid without saturating the rooting zone. That sealed environment is what makes root establishment possible during the first six weeks.

The setup is straightforward:

After sowing, place the pot inside a clear plastic bag (a freezer bag or zip-top sandwich bag works for a single small pot).
Inflate the bag slightly so the plastic does not touch the substrate surface, then seal it.
Set the sealed bag in bright indirect light at 22 to 25 °C (72 to 77 °F). Direct sun cooks the inside of the bag within minutes; a north-facing window or a position 30 to 60 cm from a fluorescent or LED grow strip is correct.
Leave the bag closed for 4 to 8 weeks. Do not open it to mist, fertilise, or check for "freshness". Every opening drops the humidity and shocks any seedling that has recently germinated.

Condensation inside the bag is normal. If it obscures the surface for more than 24 hours, the substrate is too wet; this usually corrects itself by week 2.

Germination timeline by genus

Within the closed-bag environment at 22 to 25 °C, germination unfolds in this rough order:

Days 3 to 7: Astrophytum cotyledons emerge as small green domes, often with the seed coat still attached at the tip.
Days 5 to 10: Lithops seedlings appear as paired translucent leaves no larger than a pinhead.
Days 7 to 14: Echinocactus and Ferocactus push up small ribbed bodies with visible early areoles.
Days 10 to 28: Mammillaria species germinate over a broad window. M. zeilmanniana Boed. is often quick; M. plumosa F.A.C.Weber is famously slow.
Days 10 to 21: Conophytum cotyledons appear as small fleshy pairs, sometimes flushed pink in bright light.

If nothing has emerged by week 4, the seed was probably too old or the temperature too low. Heating cables or a warm shelf above a refrigerator (which often runs at 22 to 24 °C on top) can recover a slow batch.

When to open the bag

Begin opening the bag at week 6 to 8, when the seedlings have one or two true tubercles (cactus) or a second pair of leaves (Lithops and Conophytum). Open in stages over 7 to 14 days:

Day 1: cut a 1 cm slit at the top.
Day 3: enlarge the slit to 3 cm.
Day 7: open the bag fully but leave the pot inside it.
Day 10 to 14: remove the bag entirely.

This gradient lets the seedlings adapt their cuticle to lower humidity. A bag opened all at once after eight weeks usually causes the seedlings to collapse within 48 hours; the cotyledons cannot yet manage stomatal water loss at 50% RH. The shock is a function of transition speed, not final humidity.

After the bag comes off, mist the surface every 2 to 3 days for a month, then water from below by standing the pot in a shallow tray of rainwater for ten minutes once a week.

First repot

Leave the seedlings in the original pot for 9 to 12 months. The first repot is appropriate when the seedlings are 5 to 10 mm across the body for cactus, or when Lithops have completed their first leaf-pair replacement.

Tip the contents into a shallow tray and tease the seedlings apart with a wooden cocktail stick or a soft paintbrush. Pot individually into 5 cm (2 inch) plug pots in the same fine mineral mix. Keep newly potted seedlings in shade for a week, then return to bright indirect light. Withhold water for four to seven days to let any broken root tips callus.

Survival from sown seed to potted one-year-old is typically 30 to 50% even for an experienced grower. Beginners should expect closer to 20 to 30% on the first attempt.

Common failures

Seed buried too deep: cactus and mesemb seed needs light to germinate. Seed pressed into the substrate or covered with grit will not germinate at all. Surface sowing is correct.

Tap water with chlorine or chloramine: chlorinated water is fine for established plants but kills germinating seedlings. Use rainwater, distilled water, or tap water boiled for ten minutes and cooled. Standing tap water overnight only removes free chlorine; chloramine remains unless boiled.

Saturated substrate: a pot with standing water at the base rots seedlings before their roots reach below the surface layer. The substrate should be evenly damp, not running wet, when the bag is sealed.

Damping-off fungus: white or grey fluff at the substrate surface, followed by collapse of seedlings at the base. Treat early outbreaks by dusting cinnamon powder (which contains cinnamaldehyde, a mild antifungal) or sulphur powder thinly across the affected area. Severe cases require disposal and re-sowing.

Bag opened too early: removing the bag at week 3 or 4 desiccates seedlings that lack a developed cuticle. Stay sealed until at least week 6 unless mould demands intervention.

Freezing the first winter: first-year cactus and mesemb seedlings have no cold tolerance. Keep them above 10 °C (50 °F) the first full winter, even species whose adults survive frost in the wild. Hardening-off comes in the second and third year.