Gardenia thunbergia from seed

conroe_joe(9a)June 24, 2004


Most gardenias grown along the Gulf Coast seem to be variants of G. jasminoides, an evergreen shrub; it is a plant everyone knows with a wonderfully fragrant flower. There are many cultivars for this plant that originates in China, Japan and nearby areas. The plant seems to be referred to by a confusing number of names: G. jasminoides veitchii, G. augusta, G. florida, G. grandiflora, G. radicans, and G. schlechteri.

The eastern part of South Africa is home to another species of Gardenia, G. thunbergia. G. thunbergia makes a taller plant and is sometimes called tree gardenia growing up to 3-5 meters. Though various information is provided from different sources, G. thunbergia is not usually reported as cold-hardy. But Silverhill Seeds offers seeds from plants rated as hardy into zone 7. Perhaps the plant is naturally hardier than suspected, or perhaps the seeds are from inland plants of the highveld and mountain forests.

I purchased some last year and they did not germinate; so I will try again. The plant seems like it has too much potential to give up. It too has a wonderfully fragrant flower, it is evergreen suggesting that it will not mind year round rain, and it is reputed to do very well in deep sandy soils amended with organic matter (Conroe).

Seeds of wild plants can be tricky to germinate. Some have requirements for exposure to heat, or rain, or chemicals in smoke. Others just need time, they need a winter or two for the embryo to mature or for germination inhibitors in the seed coat to dissipate. I have a few G. thunbergia seeds left and I'll order some more ($3.00). This time I'll put them out in gallon pots and treat some of them the same way I treat native hollies--just let them sit in sun and rain for 18-24 months.

For some of the remaining seeds, I will purchase a smoke disk and use it to pre-treat the seeds. A smoke disk is a bit of filter paper that is impregnated with chemicals from burning brush--the smoke is passed through the filter paper and the paper collects various bits of smoke. Later, the disk is mixed with a few spoonfuls of water, and the smoke chemicals leach out into the water--seeds to be treated are soaked overnight in the smoke-water.

Cross your fingers for me, maybe I'll get some seeds to germinate. There is no guarantee either of these methods might work, perhaps I'll have to try gibgerellic acid treatments, acid scarification, or some other approach. The fruit of G. thunberia is rock-hard and apparently stays on trees for years--maybe it needs to pass through a giraffe or elephant before germination is stimulated. Half the fun is in trying and learning.


Conroe Joe

Silverhill Seeds

Info: Smoke Disks,

Here is a link that might be useful: G. thunbergia,

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Instead of spending money on smoke disks, why don't you just go to the supermarket and buy "liquid-smoke"? It's in the same section as barbeque sauces and mustard. All they do is take smoke (usually from Hickory wood) and filter it through water and then package it. You can add a few drops to your watering-can every time that you water.

I've also heard that some people take very-dry leaves and set them on fire directly on top of the planted seeds in the pot. Then they water thoroughly to make sure that the ashes seep into the soil and coat the seeds well. In addition to the smoke chemicals, the brief spike in temperature seems to help. I don't know if any of this will work for the Gardenia, though.

They have a specimen of Gardenia thunbergia growing in a conservatory here in Dallas at Fair Park. It might just be easier to drive to Dallas and ask for a cutting. LOL


    Bookmark   June 29, 2004 at 11:05PM
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doolgendoot(NSW Aust)

Hi Conroe Joe,
I planted 11 of these gardenia about 3 years ago, when I purchased them from the nursery they were incorrectly labeled as G. Corinata. Only after searching the internet I realise that they are actually G Thunbergia.
I am planning to propagate them from cutting - do you know how long will it takes before I can transfer the cutting from the pot?


    Bookmark   December 27, 2004 at 7:25AM
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MarcR(z 8 OR)

Depending on temp, moisture and other conditions they should strike in 20-90 days if you pretreat with Hormex or similar rooting agent. You can always start checking for roots after 20 days. If you pull out a cutting with no roots redip it in Hormex and put it back.

    Bookmark   April 11, 2005 at 3:15AM
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Have you seen this site?

If this is the tree you are trying to grow, I have not found the seeds easy to germinate either.

    Bookmark   May 6, 2005 at 11:51PM
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MarcR(z 8 OR)

They are not especially difficult but they do have specific needs. Use smoke papers. Provide night temperatures in the high 40s or low 50s and day temperatures at least 20 degrees warmer. You might need to buy an old refrigerator and set it at the warmest setting to get the needed temperature cscilation. The 20degree variation is more important than the actual temperatures as long as they don't drop below 44F.

    Bookmark   May 9, 2005 at 1:26AM
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