I've been watching an aspen in my front yard this spring, and sending data to the National Phenology Network. (That's phenology, the study of recurring plant and animals phases, not phrenology.) We've had warm weather, cold weather, and windy weather, and blooming violets, crocuses, and dwarf irises, but the aspens haven't done much.
Until now. My aspen is blooming. Kind of.
There aren't any leaves yet, but this morning I noticed some things that reminded me of the fuzz on pussy willows back in Maine. So this afternoon, I took a closer look, and picked one. And... I think that must be the aspen's flower. It looks like a fuzzy caterpillar.
I don't know why I thought the leaves would come out first. They don't for pussy willows, though most of the native shrubs in the pinyon-juniper woods leaf out first, and flower when it gets a bit warmer. But those shrubs have flowers that are pollinated by... I think bees and hummingbirds. The aspens appear to be pollinated by the wind (which is especially strong today), though they mostly propagate by root suckers. I hope I'm not going to be allergic to aspen pollen, now that I live amongst them.
The NPN data sheets ask whether the tree has male or female flowers. I have no idea how to tell. Anyone know?
For illustrations of male and female flowers see http://www.nesbrec.org.uk/articles/SEXING%20ASPEN%205.pdf.
If the URL is munged Google "sexing aspen trees" to find it.
Pictures are P.tremula (European aspen) but P. tremuloides looks similar.
Since that bit of slang has two uses that, in at least some places, occur equally, I'll point out that it's referring to the cat. Although one could make the case for merkins, I suppose.
What I remember from a spring in the Montana Rockies was that the male catkins were long and dangly and the females were short and stout. Male flowers come first I think so they can dry then the females and I think both occur on our quaking aspen. So you might wait and see if another kind of catkin comes along.
That looks short and stout but the violet-ridged thingamabobs look like pollen.
Those are purple anthers that will shed pollen. Many wind pollinated trees disperse pollen before they leaf out because all those green flags get in the way of pollen dispersal. Most people just don't notice such trees flowering because lacking colorful attractants for pollinators, the flowers go unnoticed. In some you have to look very closely to find the female flowers, e.g., filberts. Although quite common, designating seed plants "male" or "female" is technically incorrect. You see each pollen grain is actually a male organism. And hidden with seed producing flowers is a corresponding female organism, which is not the tree itself. They even have different ploidy levels.
Aspen is dioecious, meaning that male and female flowers are on separate plants.
Your tree has male flowers, and it will only have male flowers. Females will be on a different tree.