The hardiest Ixoras

[mnorell 281]

The commonly sold Ixora coccinea varieties in the southern states and Florida (Maui Red, Maui Sunset, Nora Grant, etc.) usually go down with the first decent freeze unless kept very protected. Though they generally return from the roots here in my zone 9a climate, they are slow to return and I (and most impatient people) generally wind up buying them anew each spring and replacing the old plants.

In doing research over the years I have noticed the following:

- Ixora chinensis is commonly given a hardiness rating of 20F. Unfortunately I've never been able to procure any plants for testing.

- I was also told by someone in Florida that her I. fragrans, though a brief bloomer, is very fragrant and has tolerated high teens with no damage.

- In an article published in 1965 by the Florida State Horticultural Society, grafting on I. parviflora, sometimes resulting in greater cold tolerance, is discussed. It also describes I. 'Hydrangeaefolia' also known as I. 'Singapore Pink' which endured 25F with absolutely no damage.

- In the same article, another is mentioned: "Ixora colei—An old English hybrid apparently developed of I. coccinea x I chinensis alba parentage about 1870 by E. Cole of Manchester, England. Has massive flowers of pure white as large as 7 inches in diameter when fully open." Also mentioned as having greater cold tolerance than most Ixoras.

Does anyone know anything about hardiness in these or some of the other 200 or so species of Ixora, as well as the many hybrids that have been made? Also sources for some of the above? These are of course very loved and important landscape plants in Florida, but it seems a no-brainer that the hardier forms, hybrids and species would be much more popular in zone 9a/9b areas, where they could be treated as something other than an annual or slowly returning dieback perennial.

[Eric in Orlando 3,919]

I can tell you I. fragrans is not hardy at all. We planted one and a I. finlaysoniana 'Variegata' and they had damage under tree canopy in the low 30sF this winter.

The hardiest ones I know of are I. coccinea and I. chinensis, the old plain red flowering species types. That is what grows at old houses here and have survived for decades, occaisonally freezing down but coming back from the roots, even after the '89 freeze. Those newer hybrids like 'Nora Grant' etc. will grow here but are slightly more tender. Same with those dwarf 'Petite' hybrids. I would love to find hardier Ixora, too.

Others that we are growing but really aren't any hardier than I. chinensis or I. coccinea;

I. casei (sold as 'Super King' or 'Super Queen')

I. longistipula

I. 'Aurora'- larger plant with large clusters of pale orange flowers

I. 'Frankie Hipp'- a white form of 'Nora Grant'

'Aurora'

[epicure3 91]

Slightly off question, but I have noticed that several varieties of Ixora do well here in San Diego if kept somewhat on the dry side in winter. The cool temps don't seem to bother them much. Growth all but stops in the winter, however. I have some that are just now starting to bloom. I have about 5 or 6 plants. Some were definitely misplaced in shade but grow very nicely as a stretched foliage plant.

[mnorell 281]

Eric--

After my initial post I was doing more research and I think what the hardy, fragrant Ixora the woman in Florida had in her garden may very well have been I. parviflora, the rootstock mentioned in the 1965 FSHS article. It was described as having a short blooming season and being very fragrant and pictured with large umbels of small white flowers, and since it imparts additional cold hardiness it makes me think this may have been what she had. I'm wondering if it might not have been one of those 1960s plants that had frozen down and the rootstock (rather than the grafted variety) perhaps came back to make more permanent shrubs. Do you know if this rootstock is still being used? And also, can you comment on whether I. chinensis is indeed hardy down into the low 20s without damage? And do you know of a source for any of these other varieties? They seem very difficult to find, at least via mail-order. I'm very interested to try that 'Hydrangeaefolia'/'Singapore Pink.'

[Eric in Orlando 3,919]

I've never seen Ixora grafted here, they are always on their own roots. Maybe there are some but all the mass produced Ixora I see aren't grafted.

I. chinensis and I. coccinea are similar in hardiness. Below 30F burns foliage and about 28 will cut them back to the roots. Both came back from near 20F in the '89 freeze.

Check with Gardinos or with Top Tropicals for different Ixoras.