Carnivorous Plant Propagation

How do I propagate my plants?

How do I stimulate seeds to germinate?

Smoke for germinating Australian native seeds?

How do I propagate my plants?

There are many methods of propagating these plants. Methods used by CPers include leaf cuttings, root cuttings, stem cuttings, air layering, dividing clumps, separating growth crowns, seeds, gemmae, daughter tubers, adventitious plantlets, and tissue culture methods. But all methods will not work for all plants. For example, the only effective way to propagate Byblis liniflora is by seed, while Drosera capillaris can be propagated by seed, leaf cutting, or occasionally false vivipary. All pygmy Drosera species, like D. roseana or D. pulchella produce small modified leaves (called gemmae) which detach and should be planted, without delay, in a manner similar to seeds. Exactly which method will work depends upon the plant you are growing. You will have to ask around or experiment on your own. Once you know the method to use, any of the CP books in your library will tell you how to proceed.

How do I stimulate seeds to germinate?

Most CP seeds germinate in normal CP growing conditions. Prepare a pot as you would a pot for a mature plant, then sprinkle the seed upon the surface. Do not bury the seed. Keep the pot moist, as you would for a growing CPs, and wait. Germination takes longer than garden vegetables – if some CPs germinate within a few weeks, most veteran growers are pleasantly surprised. Some CPs take months to germinate. When you sow seeds, do not give up on the pot until two years pass. Patience is the key word. Plant the seeds, then try to forget about the pot – a watched pot never germinates. Some CPs require special treatment to germinate, like chemicals, cold treatments (stratification), extreme heat (from fires), or slicing the side of the seed. You'll learn about these techniques elsewhere in these pages, and in other books, and on the internet - see our links page for more details.

The stratification of seeds is necessary in the case of Sarracenia and some other genera. The preferably fresh seed should be dried for five or six days to minimise any fungus difficulties. Put the seed, together with a plug of moist Sphagnum moss into a medicine phial, or sealable plastic bag, together with a label containing the plant details, seal the container, and place it in the non-freezing section of your fridge. Leave it there for about six weeks during the winter. After that time sow the seed into its normal potting media. This process simulates the conditions of the seed's natural environment, where the parent plant drops its seed during autumn, and it remains dormant during the winter, to germinate when temperatures and daylight hours increase in the spring.

VCPS operates a good seedbank, with fresh seed obtained from various world-wide sources.

Smoke for germinating Australian native seeds

By K. W. Dixon & S. Roche, Kings Park Botanic Garden, Perth Western Australia

Fire has played a significant role in the evolution of Australian flora at least since the arrival of arid conditions in the mid-Tertiary (Kemp, 1981). For many taxa, response to fire has moulded plant growth and been responsible for the derivation of analogous structures and life forms often in disparate taxonomic groups. In the fire-prone floras particularly those of Mediterranean zones, fire has been shown to be crucial for the recruitment from seed of a wide variety of taxa. For seeder or fire sensitive species and fire ephemerals, habit burning is the single most important cue for triggering germination of the dormant soil seed bank (Bell et al., 1993; Meney et al., 1994). For many fire responsive taxa, germination of viable seed under controlled conditions has been difficult or impossible using conventional treatments other than excised embyro culture (Meney et al., 1994) or special treatments including hormonal applications (Bell et al., 1993).

The Role of Smoke in Germination

Following the discovery that smoke stimulated germination of the rare South African plant Audounia capitata (De Lange and Boucher 1990) the exploration of benefits of smoke-mediated germination has expanded to different continents with applications in nursery, land management, and rare flora conservation.

As crude smoke or aqueous extracts applied to seed directly, or to the surface of the seed trays, or as smoke to the soil surface in habitat sites, germination has been stimulated for a wide variety of species (Brown et al., 1955).

The study of Dixon et al. (1995) found that smoke applied in a variety of ways was able to stimulate germination in Australian species both in situ (in bushland) and ex situ (nursery and laboratory). This study established, for a wide variety of species, the importance of smoke as a cue for germination with resultant and sometimes spectacular improvements in germination.

Smoke Stimulated Germination of Australian Species

Research by Dixon et al. (1995) has shown that smoke is a key principle in breaking seed dormancy in a wide variety of native Australian species. Though this study has concentrated on Western Australian plants, general principles have emerged regarding the benefits of smoke for germination:

Smoke can promote earlier and more uniform germination under controlled greenhouse and laboratory conditions.

Smoke enables germination in species previously thought difficult or impossible to germinate by conventional methods.

Smoke substantially promotes germination in species with low levels of germination.

The promotive effect of smoke is independent of seed size and shape; plant life form ie. whether annual, perennial, herbaceous, seeder (fire sensitive), or resprouter (fire tolerant).

Aerosol smoke, smoke dissolved in water or direct smoked solids (active clays, sand particles), or direct smoked seeds are effective methods for delivery of smoke for germination.

High doses of smoked water can inhibit germination of many species.

Paper daisies (Rhodanthe, Schoenia) are suppressed by smoking.

Germination over time in response to smoke can change with taxa ie.

a) control and smoked seed attain final germination at the same rate eg. Conostylis species.

b) first seedling emergence occurred earlier in smoked seeds.

c) control germination was limited to the first week or so whereas smoked seeds continued to germinate over a longer period.

d) difference between control and smoke treatment became apparent only after several weeks.

Smoked Water

Smoked water can be useful for direct priming or pre-germination of seeds prior to sowing. Smoked water treated seeds have the advantage of not requiring the use of a smoke tent and the convenience of priming seeds at will. Smoke water-primed seeds may germinate better than smoked seedling trays with the process applicable to handling potentially large quantities of seed such as for land restoration or automated seed sowing devices.

Smoked water is produced by drawing smoke produced from the combustion drum operating as for aerosol smoke, through a container of water. Smoke bubbling is done for approximately 60 minutes and the resultant solution is frozen till required.

Seed to be treated with smoked water is soaked for 12 to 36 hours in a 10% solution of the neat smoked solution and the seed is then sown, or dried then sown as required. seeds treated with smoked water can be watered normally after smoke-water treatment. Although this method has been shown to be useful for a number of native species, caution is recommended as seed of some species can degenerate if soaked in water for prolonged periods. Also, pre-germination as a horticultural practice for seed of Australian native plants requires some experimentation to ensure the process is applicable. In some cases pre-germination can lead to decline in seed quality and viability and it is recommended that species to be treated in this way should be tested for tolerance to imbibing and drying treatments.

The Smoke Chemical – What Makes it Work?

Research is continuing in various laboratories and Botanic Gardens to better understand the sites and mode of interaction of smoke in breaking the dormancy of native species.

A major aspect to be considered is that plants differ considerably in their fruits and in the structure of the actual seeds.

Seeds that are wind-distributed are often produced in large quantities and germinate readily, although their period of viability can be short.

Seeds of many of the fleshy fruits have a firm skin or outer shell. This allows them to withstand the digestive juices of the creatures which eat the fruits and distribute the seeds. In some species actual seed germination is assisted by this process.

A large number of tree and shrub seeds produced in pods have very hard individual coats, which can give them a viability period of many years. Germination of these species can be hastened by exposure to digestive juices or fire in their natural habitat, or by immersing the seed in hot water, rubbing the outer coating with sand paper, or a range of other treatments that break down the outer coating and allow water to penetrate.

Heat and fire also assist seed germination by stimulating fruits such as woody capsules to open and release their seed. Usually the seeds contained in hard woody fruits do not have a firm outer coating and therefore require no additional treatment for germination.

Some carnivorous plants occur naturally in areas where winter temperatures drop below freezing point. Germination of these species is often aided by stratification through placing the seed in a refrigerator for a period of days or weeks during winter, before sowing the seed.

It is by understanding the natural habitats of different plants that we can guess at some of the conditions that might exist in nature where the seeds germinate, then use similar techniques to assist us in our propagation of plants.

It has for many years been thought that fire has been essential to the germination of many species. Although it is certainly of assistance in some areas, as mentioned above, research now indicates that it is the actual properties of the smoke that stimulates germination of a wide range of low heathland-type plants, many of which have been regarded as difficult to propagate in the past. Tests with trees and upper canopy plants have to date been less successful.

Many of the carnivorous plants we seek to grow will germinate readily from seed – some to the point where we may even have an excess of plants. Others frustrate us with their reluctance to germinate, and provide a challenge which many growers regard as one of the fascinating aspects of plant cultivation. It may not be worth the time and effort to try any special germination techniques on plants that propagate readily, but for seeds that are difficult the use of smoke is certainly one of the methods well worth trying. There is still much to be learnt regarding this technique and species that occur in areas not usually exposed to fire may also benefit from the properties of smoke.

Acknowledgments

This research was funded by the Minerals and Energy Research Institute of Western Australia, Rural Industries Research and Development Corporation, Land and Water Resources Research and Development Corporation, with support from Alcoa Australia, RGC Mineral Sands, and wildflower growers and enthusiasts from around Australia.