Zanthoxylum fagara

[thyerr01]

I've been growing a few of these as food plants for Giant Swallowtails as I assume they are the native host plant from Houston southwards along the gulf coast. I have some questions if anyone else is growing this.

(i) Are there differences between the plants natively occurring in Texas and those from Florida, like leaf size/shape or cold tolerance? I have six plants, of which three I ordered online from a nursery in Florida and appeared to be rooted cuttings from two separate plants with slightly different growth habits (pics 1 and 2). These both have large leaves, although one is larger than the other. I have another one I picked up at a nursery in Houston which looks very different. The leaves are a very dark green and much smaller (pic 3).  All of these plants are growing the same bed in a row and experience exactly the same conditions. The remaining two were also bought locally and look closer to the first two, but are growing in a different location. During the freeze over Christmas, -8C/17f, all five with the larger, light green leaves froze back to the base but have since regrown. The small leaved form was almost completely unaffected and lost just the new growth at the tips. Do the native plants on the Texas gulf coast freeze back in the winter?

(ii) Is there any way to determine the gender of these from the flowers? The small-leaved, cold hardy form that I have flowers regularly. None of the others have flowered. These flowers are a little past their prime.

(iii) Has anyone had any luck germinating seed? I have tried a couple of batches of seed I bought online and got nothing, and have found at least one journal article which comments on the extreme difficulty of germinating the seed for this species.

[Silas_Sancona]

23 minutes ago, thyerr01 said:

I've been growing a few of these as food plants for Giant Swallowtails as I assume they are the native host plant from Houston southwards along the gulf coast. I have some questions if anyone else is growing this.

(i) Are there differences between the plants natively occurring in Texas and those from Florida, like leaf size/shape or cold tolerance? I have six plants, of which three I ordered online from a nursery in Florida and appeared to be rooted cuttings from two separate plants with slightly different growth habits (pics 1 and 2). These both have large leaves, although one is larger than the other. I have another one I picked up at a nursery in Houston which looks very different. The leaves are a very dark green and much smaller (pic 3).  All of these plants are growing the same bed in a row and experience exactly the same conditions. The remaining two were also bought locally and look closer to the first two, but are growing in a different location. During the freeze over Christmas, -8C/17f, all five with the larger, light green leaves froze back to the base but have since regrown. The small leaved form was almost completely unaffected and lost just the new growth at the tips. Do the native plants on the Texas gulf coast freeze back in the winter?

(ii) Is there any way to determine the gender of these from the flowers? The small-leaved, cold hardy form that I have flowers regularly. None of the others have flowered. These flowers are a little past their prime.

(iii) Has anyone had any luck germinating seed? I have tried a couple of batches of seed I bought online and got nothing, and have found at least one journal article which comments on the extreme difficulty of germinating the seed for this species.

Tried seed i'd collected off plants in FL. once w no luck..

As far as your ?'s.  Possible the two leaf forms you're seeing are different variants, or the " thicker " ..less-lush leaved looking specimen could also be an different species..  Possible too the thicker leaved " Texas " plant  originated from a population that is farther inland, thus, the thicker leaves reflecting adaptation to more heat / drier conditions than plants closer to the coast where it is moister.. Intrigued myself..  Looking around at observations of the sp. on iNat, seems there can be a good deg. of leaf size variation in different areas too.

I'd assume the "FL." obtained specimens could be ...slightly?  less cold hardy compared to plants obtained from populations in Texas, ..or Eastern / N.W. Mexico, or Baja ( Grows there too )

99% sure flowers are monoecious ( male and female parts on each flower ) so you should see both anthers ( pollen producing parts ) and an ovary on each flower.

Neat plant regardless.. One of the "FL" natives i wanted to try here ( Esp. since it grows not too far south of AZ in Sonora / Sinaloa, and Baja Sur )  Prickly and evergreen could = a decent privacy barrier type plant option, depending on how well it handles our summer heat. ..Bet the swallowtails here would prefer it -over Citrus-  too. 

[thyerr01]

I don't know the full distribution in Texas but Houston is the furthest North they occur naturally. I don't think they extend far inland until you get to South Texas. I had no idea they spread so far west in Mexico. 

I've seen several references states they are dioecious eg. https://www.fnps.org/plant/zanthoxylum-fagara. My small leaved one has never produced fruits or seeds, despite flowering regularly, which I assumed was due to being male/not having a mate. It also has 2-3 times as many thorns on the thicker branches than the larger leaved forms. The only wild ones I have seen in Texas were around Corpus Christi and I don't recall how large the leaves were. 

Ideally I'd like to set some seed from the frost hardy form and avoid having to regrow things every time we decide to have Z8 weather.

Edited May 22, 2023 by thyerr01

[Silas_Sancona]

2 minutes ago, thyerr01 said:

I don't know the full distribution in Texas but Houston is the furthest North they occur naturally. I don't think they extend far inland until you get to South Texas. I had no idea they spread so far west in Mexico. 

I've seen several references states they are dioecious eg. https://www.fnps.org/plant/zanthoxylum-fagara. My small leaved one has never produced fruits or seeds, despite flowering regularly, which I assumed was due to being male/not having a mate. It also has 2-3 times as many thorns on the thicker branches than the larger leaved forms. The only wild ones I have seen in Texas were around Corpus Christi and I don't recall how large the leaves were. 

Ideally I'd like to set some seed from the frost hardy form and avoid having to regrow things every time we decide to have Z8 weather.

Distribution map, via iNaturalist:

I'd bet they're more common inland than what observations have been made.. At least west and south from San Antonio along the edge of the Hill Country.  Those would be the plants i'd try to source if looking for the hardiest of it's population if you can..

There has to be a trick to get them going from seed since i'm pretty sure at least two of the native plant nurseries i'd by stuff from started their stock from seed.. As far as i remember.  Not out of the question they started w/ cutting-grown stock though.

If they are truly Dioecious, very possible that the Texas plant might be male.. Would have no female parts in the flowers when you pull them apart and examine up close if so. With 6 plants, you should have at least 1 female in the group -if-  strictly singe-sex plants. Being the same sp. they all will be compatible.

Didn't realize Texas has another Prickly Lime / Ash as well.. Z. hirsutum.