Seed Raising and Care
Of course there is no guarantee with these seeds and how well any of the plants that may grow from them will develop, however the potential benefit from good record keeping can be in invaluable for others who may follow. Please consider the possibility of contributing to our need for feedback from as many people as possible as to the success or failure of the seed raising. Many of these plants have been barely tried in the past, so even the simplest of advice such as a good potting media that worked or anecdotal notes such as ‘autumn sowing was better than spring’ would be useful. Of greater interest still, would be for those who have the time to record plant progress at monthly (initially), three monthly or yearly intervals.
Simply, seeds need to be stored in a completely dry environment. Until you’re ready to sow your seeds you may need to consider where and how to store them properly be it for weeks or months. Many succulent seeds can be stored for years, but only if certain conditions are met. Dampness and high temperatures are the enemy of seed in storage. The kitchen is a particularly poor place to store seed packets as the humidity can be absorbed by the seeds reducing their viability. Keeping the seeds cool is relatively easy when they are refrigerated, but make sure the seed packets are in a glass container with a metal lid as this will make them totally impervious to moisture in the refrigerator. Storing the seed packets in a glass jar is also recommended if keeping seeds elsewhere in the house. Over time, even small plastic bags will absorb moisture. Rather put all the plastic bags in a glass jar and add silica gel satchels to absorb moisture. Silica gel can be reconditioned in a microwave.
Mid spring, or when temperatures are between 15’C - 25’C, is usually the best time to sow most succulent plant seeds. Sow seeds in black pots or trays that can hold at least a 40 mm depth of potting mix. All-purpose seed raising mix for general plants can be used. Any potting mix that is generally used for succulents can also be used. A twelve month slow release all purpose fertiliser may be mixed into the soil before sowing the seeds. Be aware that some modern potting mixes already have fertiliser added. The best fertiliser we recommend is one which has a relatively low nitrogen level (such as that used for Proteas). Add any fertiliser at half the recommended rate on the label except for Brachychiton seed (high nitrogen fertiliser at recommended strength is preferable for this genus). Before sowing smaller succulent seeds, gently flatten or pat down the potting mix to create a relatively even surface. When watering, use only as soft, gentle spray to prevent splashing and the dislodging of any seeds or seedlings. Many growers cover newly planted seeds with glass or plastic sheets which must be removed soon after germination occurs. A covering material is often used to increase humidity and provide shade. Extra shade cloth may also be necessary during this period. The ideal conditions for raising seedlings soon after germination is to keep them in a humid environment for at least a few weeks, which is preferably out of direct sunlight, especially where the summers are hot and dry. Once the seeds are planted keep them damp, watering at least once daily, and never allow them to dry out, even for a day. After germination, constantly moist soil is still critical for up to 2-3 weeks, however humidity in the air can slowly be reduced. Over one or two months any shade or covering is gradually removed. By the second or third month plants can be moved or replanted in exposed sunny conditions outdoors. The more exposure the plants then receive, the more colour, shape and form are achieved. Watering should continue until plants are established, after which a low watering regime can become the norm. Overwatering, over feeding, over shading will only produce weak, soft green plants of little appeal.
23.11.13 UPDATE: On14 November 2013 I received a copy of relevant and interesting article from Robert Parsons of the Department of botany at Latrobe University, Melbourne. It was an article of his from The Journal of Arid Environments (1997) 37:453-459, titled, Carpobrotus modestus (Aizoaceae), a post-fire pioneer in semi-arid southern Australia. While the article covers primarily details of how this native Carpobrotus responds well to fire affected land, where it regenerates extensively and then slowly over subsequent years almost disappears from the vicinity. The article logically explains all the reasons for this and also discusses how seed of this plant failed to germinate repeatedly in propagation trials. Robert discusses how fire and heat in habitat broke down dormancy protection in seed. He also found greater germination in animal droppings. This all conclusively supports the theory that the Carpobrotus seed have long survival strategies and a very hard protective coating to last years, on or in the soil, waiting for the right conditions for germination. Therefore water, rain or your propagation trials even with a heat bed might fail. I have had many people contact me to say their seed has failed to germinate. Very useful information indeed!
Interestingly, I can only hypothesize that indigenous people who once prized Carpobrotus fruit, either carried fruit far and wide or inadvertently as 'droppings' also contributed greatly to the plants wide distribution range. This activity rarely occurs now.
Sowing Large Seed
Large seeds are considered to be match-head sized or larger (3 mm +). Large seeds are generally slower to germinate than small seeds and in some cases these seeds can take weeks or months to germinate, but it is not uncommon for a few late starters in a seed tray to germinate up to a year after sowing. As a general rule, the larger the seed and the thicker the seed coat, the longer it will take to germinate. It is a god idea to soak large seeds in warm water overnight before planting as this reduces normal germination time by at least half. Seeds need to be slightly buried. Either push the seeds into the potting mix (see photo below) or lay them on the surface and cover them with more potting mix or sand so that they are fully covered. It is important not to let the seeds dry out after planting. This is critical. To speed up germination of thick, hard seeds growers sometimes abrade or scarify the seeds, using sandpaper or a file. The intention is to wear away a small portion of the seed coat and accelerate the absorption of water. An extension of this form of treatment is the cracking, chipping or cutting away of part of the hard seed casing with a sharp knife or saw blade. Take care not to damage any of the white inner seed which is very delicate. Abrading the seed coat is done before soaking in warm water. Large seeds produce large seedlings, so do not plant them too close together on in shallow trays or pots. If you have several seeds of a plant and only really want one good one to grow, then why not plant all of them in a moderate sized pot and as they come up you can select the healthiest and most vigorous seedling and weed out the weaker ones around it.
Sowing Small Seed
Small seeds vary in size from dust-like up to the size of coarse sand grains. The smaller the seeds, the more difficult it is to handle and sow. If packets of seeds are opened outdoors be aware that even a small breeze (or a sneeze) can blow them out of your hands. It is best to plant seeds on a calm day or alternatively plant them under cover. No pre-treatment is required fro most small succulent plant seeds before planting. Just lightly sprinkle the seeds onto the surface of your propagating potting mix. The type of propagation mix you use is not as important as having a topping of coarse washed river sand (or aquarium sand) on top of the propagation mix. When seeds are sprinkled over the surface and gently watered in, the seeds will trickle down among the larger grains of river sand, where they will get some shade as well as essential support as they begin to grow between the grains. If you have unsteady hands, or would like to have a more even seed distribution over your seedling tray, mix the dry seeds with half a cup of fine dry river sand then just sprinkle this sand out evenly as you would for the seeds alone. Try to use very fine sand which preferably is similar to the seed size. Anyone experienced with raising plants from seeds will be aware of the problem in spreading seed evenly. This method is highly recommended as it gives a more even spread of seedlings. Germination will usually occur in a few days to weeks, while stragglers may take months.
- Most of this information about raising succulent plants from seeds is from our book on propagating succulent plants by Attila Kapitany & Rudolf Schulz 2004. For more information on propagating succulent plants see Succulents: Propagation here »»