my theory

[joachimM]

In short, the answer to your question is no.

As for the flowers: all "flowering plants" produce flowers (duh...). This includes grasses, rushes and sedges, stinging nettles, birch, willow, oak, etc. These don't have obvious large and coloured petals but often small and green/brown scaly petals. In structure they are identical to what we call flowers. In these flowers the fruit is produced. Actually, this group of plants are called the fruiting plants, the angiosperms.
For an example of a maple flower, see http://newfs.s3.amazonaws.com/taxon-images-1000s1000/Sapindaceae/acer-platanoides-fl-ahaines.jpg
The catkin of a willow is an inflorescence (a bunch of flowers), a stalk containing hundreds of tiny flowers. All willows are either male of female, so a single tree will only produce male or female flowers (just like yew).

On the other hand, we have the conifers (the gymnosperms), which do produce pollen and female parts, but don't have actual flowers nor fruits. Their seeds are not embedded in a fruit, making them non-fruiting plants.
Now I hear you protest, because yew has a reddish "fruit". Also the ginkgo has a stinky "fruit". Structurally, this isn't a real fruit, it's a part of the seed coat that has become fleshy, and fulfills the same function as a fruit in fruiting plants. Through evolution, life always finds a way ...

But this isn't at all what you were trying to say. If it has obvious flowers, does it make a good bow? Not necessarily. Try a horse chestnut, or a catalpa, ...
On the other hand, hazel, various species of maple, hophornbeam, elm, different kinds of oak and hickory... all have tiny scaly green flowers, but will give you awesome bow wood.

There's no shortcut, you just have to get to know the species.

[Lucasade]

Just to take this thought a bit further, does anyone have any theories about the best place for a tree to grow to produce the best bow (for that species)?
The angle I am coming from is that a tree that grows in a stand with others will grow straight and tall to the light, producing a clean straight stave. However a tree that grows in the open will be subject to a lot more wind flex therefore produces stronger wood. So it follows that for any given species there is an optimum growing site where there are enough nurse trees around to make it grow straight, but it is sufficiently in the open to get some but not too much wind flexing.

[joachimM]

I don't think flexing and wind action play any significant positive role. Reaction wood, moreover, can be pretty treachurous.

[mullet]

There has been a couple of really nice bows made from Magnolia on here, one by Gregg b won BOM. And pines do have little flowers. When I come home from turkey hunting in South Carolina my Jeep is covered with green pollen.

[Joec123able]

If you don't know the trees, try posting pics of them here maybe we can identify a few

[PatM]

There has been a couple of really nice bows made from Magnolia on here, one by Gregg b won BOM. And pines do have little flowers. When I come home from turkey hunting in South Carolina my Jeep is covered with green pollen.

A pine does not actually produce flowers. They are gymnosperms.

[mikekeswick]

The easiest way to determine if an 'unknown' wood will make a bow is to cut a little piece, dry it completely in an oven, don't worry about checks just get it completely dry and see how high it floats in a cup of water. If at least half of it is underwater then it is at least 0.50 s.g. so give it a try.
That's my rule of thumb