I think it all applies to every herb, or anything grown near outside or in dirt. The thing about botulism is that while it's rare but really serious. I mean you don't want to get salmonella but unless your immunocomprimised you will probably just feel real lousy. Botulism is a whole other ball game, it basically causes TOTAL muscle paryisis-that includes the ability to breath without machines.

Here's a link on proper canning from the USDA

and

Here's a link to the CDC to scare your pants off

No safer than the basil oil.

Now rosemary, being sturdier than basil, MAY survive a sterilization process. You'd have to basically FRY the rosemary at 300 degrees for 2 hours to make sure no spores survive (just ONE botulism spore can divide and grow and make enough toxin to put you six feet under).

But my advice is always to make herb-flavored vinegar or alchohol, not oil.

Make it as you need it with fresh, dried or frozen rosemary. Within two or three hours, if the herbs are crushed to release their oils, it doesn't taste any differently than if it sat in the oil for a longer time.

Sterilization at home can be accomplished but it really diminishes the flavors and without proper equipment is tenuous, at best.

When I've wanted to give herbal oils as gifts, I put just the oil in a pretty bottle and dried herbs in a small container with instructions how to make it. Always included in the instructions is the admonition to refridgerate and use it within three days.

Martie

Thanks everyone, guess I will just buy it at a specialty store.

It's easy to do at the last minute... just gently heat some oil and add the rosemary for a little while. You can use it right away either warm or cooled. You can do this with most herbs.... they give up their oils quite quickly when heated.... just don't get the oil HOT because then the oils can be lost as vapor.

This was in todays newsletter from Cook's Illustrated:

Food Science: Are Flavored Oils Safe?
A test cook recently needed to make garlic oil ahead of time but first
wanted to check for safety. Our consulting food scientist confirmed
that garlic oil must be refrigerated and even then used within a few
days. Oil creates a favorable anaerobic (absence of air) condition
that encourages any botulism present on the garlic to grow.
(Commercially sold garlic oil contains an acidic additive that kills
any bacteria.) There is a similar, although smaller, risk for
herb-flavored oils (herbs have fewer nutrients than garlic for
bacteria to feed on). If you're considering giving a homemade
condiment for a gift, flavored vinegars are a better bet--the
vinegar's natural acidity kills harmful bacteria, making them safe at
room temperature.