Why isn't my textarea's placeholder showing up?

I am using placeholders for all my form elements and it's showing up in them all apart from the textarea. Just looked at it in safari now, and have realised that my input of type="number" isn't showing the placeholder either.

The page is here and you need to click the 'book now' link at the top of the page.

My html:

<form id="booking" action="single-workshops.php">
	<input type="text" required="required" placeholder="name"/><br />
	<input type="text" required="required" placeholder="your phone number"/><br />
	<input type="email" required="required" placeholder="email"/><br />
	<input type="number" required="required" placeholder="how many in your party" /><br />
	<textarea rows="5" cols="30" placeholder="enter optional message">
	</textarea><br />
	<input type="button" value="submit"/>
</form>

Because you have something as text in your textarea with a linebreak in it.

<textarea rows="5" cols="30" placeholder="enter optional message">
        </textarea><br />

Should be:

<textarea rows="5" cols="30" placeholder="enter optional message"></textarea><br />