Before I get to the critique, I'll answer your question - generally, simple curve should indeed be drawn from your shoulder (since generally they benefit from a smoother, more flow-focused execution). It will definitely get easier with practice, so always consciously try to avoid drawing them with your wrist.

Starting with your arrows, you're doing a great job here - you're capturing them with a great deal of confidence and fluidity. That carries over quite well into your leaves, where you're capturing not only how they sit statically in space, but also how they move through the space they occupy.

That said, there are a few things you need to watch out for. First and foremost, the process of construction is one that is built upon very tight, specific relationships. Each phase of construction establishes very specific rules. So for example, with this more complex leaf construction, that general leaf shape you started with establishes the boundaries to which this leaf will extend. So when you add the flow lines for the individual arms, it's important that you extend those lines to the perimeter of the outer shape - no overshooting or undershooting (or anyway, to the best of your ability). It doesn't matter if in maintaining those tight, specific relationships you end up moving away from your intended reference image - each stage makes these assertions, and we need hold to them to avoid contradictions in our constructions, which in turn can undermine the solidity of what we've built.

For what it's worth, it also appears that you're skipping the stage with this particular leaf of creating simple leaf shapes for each "arm", then merging them together as shown here.

Continuing onto the manner in which you're building up your edge detail, there's a bit of a mix. There are cases where you're doing it well - like this one where you maintained tight relationships and built the edge detail right onto the structure that was already present. There were a couple however where, as shown here you end up zigzagging your detail back and forth (instead of building it up bit by bit). This is an issue I address here in the notes, and tends to result in a much weaker relationship with the previous phase of construction.

Moving onto the branches, your work here is looking good - you're extending your segments fully halfway to the next ellipse, allowing them to overlap well to achieve smoother and more seamless transitions, and you're also showing some thought to how the ellipses themselves should get wider/narrower as we slide along the length of a given tube.

Looking at your plant constructions, as a whole these are very well done - save for a few issues that I want you to keep in mind. For the most part though, you're building up solid structures, working in a step by step manner from simple to complex, and capturing a strong sense that each of these exist in three dimensional space.

The issues that I wanted to call out are similar to (if not the same as) what I mentioned about your leaves. Primarily there are areas where the relationships between your constructional steps are looser and more vague - think of each phase of construction as building up a scaffolding. The scaffolding is what determines how the next stage can be built up. There will inevitably be circumstances where a choice you've made deviates from what you need to reproduce your reference image, leaving us with two options: do we hold to what we've built, or do we try to bend the rules to get back on track to what we were aiming for? Doing the latter unfortunately breaks the illusion that what we're constructing is 3D - and so it is not the correct choice. Instead, treat the reference image as a source of information - we're not focused on reproducing it and creating a pretty drawing, but rather using that reference to help us work in a particular direction, and to help us make decisions as we build up our structure.

To that same point, make sure that you draw each and every form in its entirety. Avoid cutting things off - like the petals on these cactus flowers - where they're overlapped by another form. Drawing everything in its entirety helps us understand how each form sits in 3D space, and how it relates to the other forms that exist in that space.

Lastly, remember that as discussed back in Lesson 2, form shading shouldn't be something you worry about in your drawings for this course. It looks like there have been some cases where when getting into the detail phase of your drawings, you got a little more distracted by the idea of "decorating" those drawings. What we're doing in this course can be broken into two distinct sections - construction and texture - and they both focus on the same concept. With construction we're communicating to the viewer what they need to know to understand how they might manipulate this object with their hands, were it in front of them. With texture, we're communicating to the viewer what they need to know to understand what it'd feel like to run their fingers over the object's various surfaces. Both of these focus on communicating three dimensional information. Both sections have specific jobs to accomplish, and none of it has to do with making the drawing look nice.

Furthermore, remember that the filled black shapes we draw when capturing texture are themselves cast shadows specifically - always think about how the shadow shapes you draw relate to the specific forms that cast them.

Now, I've pointed out a number of things to keep in mind, but as a whole your drawings are certainly looking great. Keeping these things in mind will help ensure that you continue to benefit as much as possible from these exercises - after all, each drawing is itself an exercise in developing your spatial reasoning skills.

So! I'll go ahead and mark this lesson as complete.