There is always a chance. I used to work with xChitalpa taskentensis which is also a intergeneric hybrid. We used xChitalpa as the mother and pollinated with various Catalpa species. We did consistently get seed production although at a low rate about 1 seed per 25 crosses. But the seed was viable and produced a very interesting podginee.

Do the second generation plants bloom over as long a period as the Chitalpas? That's one quality where they are a substantial improvement over the Catalpa.

And how about the leaves? As a kid I got tired of raking Catalpa leaves. The smaller Chitalpa leaves are less messy when they fall. I suppose the second generation plants lean more towards the Catalpa.

I hope further developments do not improve too much in fertility. Catalpa seed pods are unsightly and messy -- though I was told years ago that they make good food for cultivated earthworms.

Karl

I have 2 Chitalpas and love the bloom, but they drop lots of leaves and I have considered taking them out, because my neighbors are affected.

Sterility affecting only either the male or the female gametophyte exists, though the examples I know of (in ferns) are cases in which the female gametophyte is fertile but the male isn't.

But in most cases a plant's ability to produce viable pollen is correlated with its ability to produce viable ovules, so it'll be just as useful for pollinating other plants as it is for producing seed. Only thing in your favor on that is that far more pollen than ovules are produced, so given the same incidence of fertility in each you're more likely to get some fertile pollen than some fertile ovules...

Patrick Alexander

There are a number of well known cases where hybridization results in cytoplasmic male steriity. Female fertility is not affected. A practical case involved the radish 'Early Scaret Globe' pollinated by a broccoli. The hybrids were male-sterile and female-fertile. After a few generations of pollination by the broccoli, they became (effectively) male-sterile broccoli that could then be used to breed F1 hybrid broccoli on a commercial scale.

Cytoplasmic components (organelles) may segregate if the hybrids receive some from both parents. In some Oenothera and Epilobium hybrids the seedlings have either green leaves or albino (white or yellow) depending on the direction of the cross. Sometimes the green-leaf types will produce spots or flakes of yellow (or white), indicating segregation of chloroplasts.

Similarly, and in similar numbers, other organelles (mitochondria?) may segregate allowing an occasional anther to become fertile and bear functional pollen.

Not all sterility results from incompatibility of chromosomes.

Karl King

Here is a link that might be useful: Cytoplasmic Albinism

The F2 xChitalpas I have seen have larger leaves than F1 xChitalpas. They have more Catalpa like appearance about 2" wide and 3" long. Inflorescences are similar to Chilopsis with relativley few flowers. Flowers are white and 2" across. Plants appear to be sterile. No idea what the final height of the tree will be.