We must be lucky here. Are you referring to the gum or blackberry ? We don't have gum in our region .. Blackberries is another situation. These bramble/vines are everywhere ... In old pastures n along fence lines, along most roads n freeway. In my garden if I'd let it. It is our largest nectar n pollen flow of each year but extremely invasive.
here are pix's I take yearly n daily records ( 08:00 Coalfield Wx data n notes. Clear n Sunny, 61.6 dgs, 70% hum, Wd: Calm (NNE), Bar: steady @ 1023.3 mbs, No Rain. Yesterday's High: 73.0 dgs n Morning Low: 55.1 dgs. ))..
I have noted flowering/blooming times on calendars for years. I owned n operated a plant nursery for years n just had an interest. Each year varies on the exact week but seem to alway follow a sequence of order/bloom time. So I take note of my earliest blooming plants each Spring .. I have also been a avid weather data/station hobbiest as well ( so keep records ).. Analyzing the yearly Wx n order gives me a window of most flows (big n small). We do have variances n years some flows are limited or really huge depending on droughts, rainfall. temperatures n more but normally we are fairly stable n constant with nectar n pollen flows/blooms.
. This year I put this info to use to build my colony work force to maximum for our blackberry flow n was only a few days late with my peak of colony growth as our blackberries were about one week earlier this milder Spring. It's not an exact science but works for me.