Boric acid and sugar water for difficult parents

David said,

“In the lab I have very fast pollen germination using sugar water with a little bit of boric acid. It is 40ppm boric acid and I think I used 7.5% sucrose. In two hours the pollen tubes can be 30x long as the pollen was wide. I wonder if after pollination one tries to gently mist some of this solution (without disrupting the pollen too much on the stigmas) on the stigmas if it can help promote better germination. In the lab boric acid is needed for rose pollen to germinate (for a long time I thought I was doing something wrong because in Krussmans Complete book of roses that detail was left out!).”

If boron is essential and sucrose is very helpful for pollen growth, it seems wise to apply these, especially on reluctant parents, as barring genetic incompatibility these are the likely limiting factors.

CharlesC if you run a controlled experiment, I suggest that you include a Ferrous gluconate test line:,M1


Thanks for the link Henry, it was interesting. Providing a food source for pollen, whether it be a gluconate or simple table sugar, seems to be helpful. I wonder if a spectroscopic analysis has ever been done comparing the chemicals present in highly fertile stigma and pollen versus consistently infertile stigma and pollen. We could then perhaps add whatever was missing.

A question for more experienced minds - Do pistils ripen when ready, beyond providing a bit of sugary fluid. If it gets soft and ripe like say a tomato, then ethylene may be helpful.