Below are some of the results I've managed to get after many long hours of battle in the Bryce Tree Lab.
I'm sure all of these can be improved, so they just represent a better starting point than the deformed twig things that Bryce throws up as standard.

   

SHAPE
Tree:
Elm
Gravity: 59.60
Randomness: 81.56

BRANCH / TRUNK
Distribution:
34.69
Branches per Segment:
2 / 17
Segments:
11 / 12
Branch Start Angle:
108.81
Branch End Angle:
101.94
Trunk Thickness:
2 / 52
Branch Thickness:
35 / 53

FOLIAGE
Shape:
Elm
Scale:
2
Number of Leaves:
2

Distribution: Spiral

Notes: Estimated size: 24meg
   

SHAPE
Tree:
Scotts Pine
Gravity: 50
Randomness: 70

BRANCH / TRUNK
Distribution:
15.94
Branches per Segment:
2 / 5
Segments:
7 / 13
Branch Start Angle:
63.94

Branch End Angle:
63.44

Trunk Thickness:
2 / 40
Branch Thickness:
40 / 63

FOLIAGE
Shape:
Scotts Pine
Scale:
2
Number of Leaves:
2

Distribution: Spiral

Notes: Estimated size: 29meg
   

SHAPE
Tree:
Spruce
Gravity: 48.56
Randomness:
22.73

BRANCH / TRUNK
Distribution:
22.56
Branches per Segment:
1 / 13

Segments:
12 / 14
Branch Start Angle:
92.19
Branch End Angle:
90.44
Trunk Thickness:
2 / 40
Branch Thickness:
46 / 59

FOLIAGE
Shape:
Spruce
Scale:
3

Number of Leaves:
8

Distribution: Staggered

Notes: Estimated size: 1meg
   

SHAPE
Tree:
Hornbeams
Gravity: 86.27
Randomness: 70

BRANCH / TRUNK
Distribution:
26.52
Branches per Segment:
3 / 15

Segments:
5 / 14
Branch Start Angle:
65.44
Branch End Angle:
65.44

Trunk Thickness:
1 / 40
Branch Thickness:
8 / 42

FOLIAGE
Shape:
Hornbeams
Scale:
2
Number of Leaves:
2

Distribution: Spiral

Notes: Estimated size: 19meg
From the photos I've seen this is a big tree - perhaps not obvious from this render!
   

SHAPE
Tree:
Apple Tree
Gravity: 30.15
Randomness:
42.52

BRANCH / TRUNK
Distribution:
10
Branches per Segment:
1 / 1

Segments:
5 / 17
Branch Start Angle:
59.19
Branch End Angle:
75.81
Trunk Thickness:
2 / 38

Branch Thickness:
70 / 90

FOLIAGE
Shape:
Apple Tree
Scale:
3
Number of Leaves:
7

Distribution: Spiral

Notes: Estimated size: 1meg
   

SHAPE
Tree:
Ginkgo (Maiden Hair)
Gravity: 50
Randomness: 70

BRANCH / TRUNK
Distribution:
10
Branches per Segment:
4 / 14

Segments:
5 / 17
Branch Start Angle:
52.71
Branch End Angle:
91.67
Trunk Thickness:
2 /
40
Branch Thickness:
70 / 90

FOLIAGE
Shape:
Ginkgo (Maiden Hair)
Scale:
4
Number of Leaves:
4

Distribution: Spiral

Notes: Estimated size: 42meg
I have no idea what this tree should look like, I just thought it looked cool.
This tree may be more than some computers can handle, if so set Branches per Segment to 2/14
   

SHAPE
Tree:
Fir Tree
Gravity: 91.52
Randomness: 70

BRANCH / TRUNK
Distribution:
7.85
Branches per Segment:
2 / 10

Segments:
10 / 15
Branch Start Angle:
85.81
Branch End Angle:
91.67
Trunk Thickness:
2 / 24

Branch Thickness:
54 / 70

FOLIAGE
Shape:
Fir Tree
Scale:
3
Number of Leaves:
4

Distribution: Spiral

Notes: Estimated size: 2meg
   

SHAPE
Tree:
Horse Chestnut
Gravity: 61.35
Randomness:
100

BRANCH / TRUNK
Distribution:
64.27
Branches per Segment:
3 /
14
Segments:
10 / 11
Branch Start Angle:
107.19
Branch End Angle:
46.31
Trunk Thickness:
1 / 50

Branch Thickness:
31 /
60

FOLIAGE
Shape:
Horse Chestnut
Scale:
4
Number of Leaves:
1

Distribution: Bunched

Notes: Estimated size: 64meg
Setting the Distribution to 10, setting the other numbers and then changing Distribution to 64.27 should make this more managable