Break open one of gardenia’s wrinkly husks, with its thick fibrous hull, and the seeds inside are tiny. Cuttings taken in early spring, or a branch air-layered while still attached to the shrub, both give plants identical to the parent; keep the air around them moist and you get new gardenias in weeks rather than years.
Gardenia can be increased in three ways, and they do not give the same result in the same time. Use this table to pick the method that matches what you want and how long you are prepared to wait.
| Method | When to start | How long it takes | Result |
|---|---|---|---|
| Cuttings | Beginning of spring, on stems not yet woody | About 8 weeks | Identical to the mother plant |
| Marcotting (air-layering) | On a branch left attached to the shrub | 3 to 4 months at most | Identical to the mother plant |
| Sowing from seed | Indoors in early spring, in a tray | Sprouts in 2-3 weeks, flowers in 3-4 years | Slight variations from the mother plant |
Cuttings are the quickest route to a true copy, while seed is the only way to end up with something new.
Cuttings and marcots come true to type, so it pays to know which gardenia you are copying before you start. The varieties below are the ones most often sold in garden centres and catalogues.
| Variety | Flower | Best use |
|---|---|---|
| late summer Beauty | Large double, long flowering | Shrub border, scent by a path |
| Kleim’s Hardy | Single, star-shaped | Low edging, containers |
| Frostproof | Double, narrow petals | Informal hedge |
| Veitchii | Double, very free-flowering | Conservatory and house plant |
The cultivar ‘Frostproof’ takes its name from flower buds that tolerate late frosts, a trait noted by growers; whether its wood is any hardier than other cultivars’ is not established.
Gardenia jasminoides ‘Veitchii’ is a good choice for indoor fragrance, as this cultivar is known for producing scented white flowers through the cooler months when grown under glass.
Some gardenias sold in warm regions are grafted onto Gardenia thunbergia rootstock for resistance to root-knot nematodes, and a cutting taken from the top loses that protection.
The best way to multiply gardenia is cuttings, even though this technique isn’t always crowned with success.
You can also try marcotting (also called air-layering). It’s similar to cuttings, except that the branch remains attached to the plant.
Basically, the goal is to wrap the branch with a clump of moist soil.
Roots will develop. Then, simply cut the branch off and plant it to a pot!
Every couple weeks, check the moisture and add water if necessary.
Voilà! Your marcot is going to sprout roots in the area with the soil. This will take around 3 to 4 months at most. At this point, you can cut the branch from the mother plant at the bottom of the marcot and pot it up. Remember to keep the plant away from direct sun at the beginning, until roots develop more.
Seed pods form on flowers if you haven’t deadheaded them. These are shaped like a wrinkly husk. The hull is rather thick and fibrous.
Once you’ve recovered the small seeds inside the husk, you can start sowing them in a blend of potting and garden soil.
Sow the seeds indoors early spring, in a tray. Cover with a light layer of soil. Keep at room temperature and mist often to keep the soil moist but not drenched.
Depending on the weather in your area, keep them indoors in their pots for their first winter, or transplant them to the ground in fall to let them develop roots.
The shrubs should bloom within 3-4 years. When growing from seed, expect slight variations from the mother plant because of cross-pollination.
