Royal Icing Cactus

I've been meaning to try my hand at piping some desert-inspired decorations, so naturally I started with a cactus. To pipe cacti, you'll need stiff consistency green icing in a bag fitted with a #8 tip and a coupler, white icing in a bag fitted with a round #1 tip (thinner consistency than "stiff" is ideal when using a #1 tip), a dusting pouch filled with a 50/50 blend of powdered sugar and cornstarch, several pre-made drop flowers (unless you have the mad skills needed to pipe flowers directly on the finished cacti), a #2 tip…

…and a piece of parchment paper taped to a cookie sheet. 

 Start by piping a line of icing with the #8 tip. If there's a peak left when you stop the pressure and pull the tip away, touch a fingertip to the dusting pouch and tap it down.

 Pipe the "arms" of the cactus. To pipe the one on the right, I held the tip against the right side of the center line and piped a "J". The arm on the left is overlapping onto the center line, just to give the cactus some depth. Set the cacti to dry for about an hour (you can speed up the drying time by placing them under a desk lamp).

 Pipe some drop flowers and allow them to dry.

 Switch the tip on the green bag to the round #2. Pipe a dot onto the backs of a few flowers…

 …and stick them on. As you've probably imagined, this exact species of cactus exists only in my mind; I might have taken some artistic/scientific liberties with its design.

 Pipe some "spines" with the white icing and the #1 tip. Allow the cacti to dry overnight, then plant them on any desert- or Southwestern-themed cake (or even a cake celebrating water conservation). They'd look great surrounded by brown sugar sand!

Drop Flowers

I'm not what you'd call a huge fan of drop flowers; there's something so prefab about them. Basically, you hold a tip perpendicular to whatever surface you're going to pipe on, squeeze out a flower while either holding the bag still or rotating it, and then add one or more dots or a star to the center. They don't have a lot of individuality. However, they're easy to crank out, and if you need 350 icing flowers to festoon an old-school wedding cake, they're probably the right flower for you unless you have nothing but time on your hands. 

The Wilton book from 1986, The Uses of the Most Popular Decorating Tips, has an amusing passage that might lead one to believe that some sort of snobbery about drop flower tips exists: "True drop flower tips have a center rod within the cone-shaped tip. This pipes a ring of petals with an open center." Be that as it may, you can pipe drop flowers with regular star tips, and I don't think the effect is different enough to be noteworthy. Here are three "true drop flower tips" though, according to the Wilton book: 

 Can you see the nail inside? That part where it's welded to the side collects icing like nobody's business. Be sure to clean it thoroughly when you're washing your tips (that's why you'll need this brush or one like it).

When you attach the tip to the coupler, line up the nail with that notch on the side, and it won't rotate around. Now you know what that notch is for, if you didn't already. 

 You can pipe drop flowers on a piece of parchment paper taped to a cookie sheet if you're making a lot of them…

 …or directly on cookies or something else, if you're just practicing.

 Hold the tip at a right angle with the tip touching the surface, and squeeze. My collection of tips that will pipe drop flowers is by no means exhaustive, but I'll show you a few that stand out.

 These first flowers were made with an Ateco #106. I rotated either the cookie or my wrist to form the curved petals.

 I gave all of the flowers in this post a center dot piped with a round #2 tip.

 These were piped with a Wilton #21 star tip held still…

…and these were piped with a twist. 

These were piped with an Ateco #96:

These were piped with a Wilton #224:

These larger flowers were piped with a Magic Tip #191:

And lastly, these tiny daisy-like flowers were piped with a Wilton #16, a small star tip rotated…

…and held straight. 

You can pipe drop flowers in buttercream directly on a cake, but I prefer piping them in royal icing on parchment, letting them dry, and then relocating them (or piping them directly on cookies, of course).