Trees are not flat!
If you simplify a tree form to the very basics - it comes down to a lollipop form: a round or conical form on a stick.
Each form has a highlighted side, a shadow side, and a drop shadow beneath it.
Keep this basic form in mind as you work - combined with the chosen direction of light - the overall form will look realistic.
Look at the tree trunk - is it straight or curved?
(Curved lines give more grace to the form, create more interest. You can interpret the subject as you're drawing - you are in charge!)
If the trunk is curved - is the top of the tree in the same axis as the bottom?
Visually connect them with a straight line.
Analyze the branches and limbs.
Tree trunk is usually the thickest part (blue shape);
The limbs, that grow out of the trunk are thinner and shorter - (green shape);
The branches, that grow out of limbs - are even thinner (red shapes);
Finally, the twigs - they are the thinnest shapes (yellow).
Also, keep in mind that trees are not flat.
The limbs and branches grow in all directions - all 360 degrees.
Each branch holds its own mass of leaves.
Each mass of leaves is its own 3-D form - with all attributes - shadows and highlights; it also casts a shadow onto other forms.
All the forms (big and small) are subjects to the same light source.
Don't forget the structure of the roots - they also have their shadow and highlighted sides, they cast drop shadows as well.
Are the trunk and limbs straight or curved?
Do they go straight up or leaning?
Define the major leaf masses.
Where is the light coming from?
Mark the tree boundaries and proportions. Add the direction lines for the tree trunk(s).
Layout the front leaf forms. Define them.
Silhouette-draw the back (dark) side of the leaf forms.
Continue with the back side of the tree crown.
Now add texture and mid-values.
Sharpen the pencil and start shading with small strokes. Remember that you can control value with texture shading (more shading in the shaded areas, less shading in the areas that face the light source).
leaves and leaf forms
tree bark
TREE STRUCTURE
overall tree shape matches the photo
proportions are correct
line angles are accurate
DRAWING STEPS
leaves masses are outlined
trunk and branches drawing is accurate.
SHADING
background value shading
bark texture
leaves: texture strokes
3-D quality
ARTISTIC QUALITY
Craftsmanship
Craftsmanship