Knowing how to grow rosemary is one thing, knowing it is a perennial that I can harvest all year round is also wonderful. However I hate going out to collect it on a cold and wet evening in the UK during Winter! So I have been experimenting with how best to preserve it at home.
When we preserve a fresh herb we are looking to remove the conditions that would otherwise allow for bacteria to grow. In our examples we shall be removing moisture by drying the rosemary. We will also look at freezing to reduce the ideal breeding temperature of germs. You can also learn about oil infusions as a way to preserve flavour.
- Air dry rosemary by hanging in a cool dark place
- Drying Rosemary stems on a wooden block in the sun allows the flavour to be preserved.
- Using an oven to dry rosemary can also be effective, but be sure to watch it as it can quickly cook and you won’t have preserved rosemary as much as crisp rosemary
- Using a microwave can preserve the taste quickly and rosemary leaves need only be added, not the stems as well
- Using a dehydrator set to herbal can be really useful for preserving rosemary
- Freeze rosemary leaves in ice cube trays either in water or olive oil, the flavour is really well preserved and will last in the freezer for some months
- Freezing the rosemary sprigs individually and then combining them to take up less space really helps with preservation.
- Oil infusion with dried rosemary is a great way to preserve the flavour but an oil infusion with fresh rosemary is not so great for preserving in a healthy way and caution should be taken as we outline further below!
Special warning must be made of oil infusions using fresh herbs as they can encourage botulism, if not correctly prepared. So let’s dig a little deeper and hopefully you will find the right method for your own home.
Preserve Rosemary By Drying
By far the easiest and most traditional method of preserving fresh herbs! We love to dry our lavender in the same dark and airy beam! It really does look the part!
Pick your rosemary in the morning, the heat of the day will cause essential oils to evaporate and the aroma and taste will be diminished.
- Take around 10-15 sprigs of rosemary between 9-12 inches in length. Give them a light shake to encourage any bugs to leave. We are an organic garden so do not need to wash the sprigs to take any chemicals off, if you are not do this now! Then dry the sprigs.
- Tie them together with an elastic band. Do not be tempted to go all cute Instagram photo and use twine. It will hold the sprigs too tightly, you want air to be able to circulate around the leaves. So loosely use the elastic band.
- You can use a piece of twine to pull through and create a loop. This will then hang easily from any hook or nail. We have a set of book shelves that we made from old scaffolding boards, they are in a dark but airy room. We also use a few internal doors that have a breeze, but not direct sunlight. I am very short so this is not an issue!
- Check occasionally that it is not becoming a dust trap and no mold has developed.
- 2-4 weeks later the pine like leaves should be brittle and the stalk should snap with any pressure applied.
- To remove the leaves take the sprigs individually by the end of the growth. Hold between thumb and forefinger then with your other hand run your fingers down the length of the stalk to make the leaves fall away. They will drop off, so have a sheet of cheese cloth waiting or if you are drying to scale a large bowl!
Your hands will smell divine for a very long time! Use containers that can be sealed like Kilner jars or we use old coffee jars – the posh ones that have a rubberised glass lid. Store in a cool, dark place. Any kitchen cupboard or larder will be ideal.
This is a perfect method in a location where you will not get any chance of a surprise downfall. So may rethink it in the UK. Although we do get hosepipe bans so that would be your ideal time.
- Cut sprigs of rosemary that are 9-12 inches in length, make sure to avoid any stems that are about to flower. If you use chemical sprays, wash and dry the sprigs.
- The sunshine will be doing the work to preserve the flavour here, so lay the sprigs out on a wooden block in full sunlight. One layer thick and fan them as much as you can. Do not use a metal tray as it will heat up and essentially cook the rosemary.
- Depending on the wind you may need to weigh down the cut end of the sprigs. Check every 2-3 hours and turn the rosemary over.
- A full day of sunshine may have done the trick, check to see if the stalks are bendy. If they are bring them back out again the next day. When the stalks snap, then you know they are dried enough.
- Strip the leaves by holding the new growth between finger and thumb, then run your other finger and thumb down the length of the stalk in a firm grip. The needles will sort of ping off easily, but make sure you are ready to catch them! Use a cheese cloth or straight into a large bowl.
- Then store as above in a sealed jar.
Low and slow! If you have used chemicals to grow your rosemary, wash them thoroughly. If not just make sure that you cut the sprigs and shake them a little to remove any wildlife that may be happy there.
- Do not walk away or leave the oven unattended during this process. Heat it to the lowest setting 100 degrees Celsius is roughly 200 degrees Fahrenheit.
- Using a baking tray lined with baking paper spread out the sprigs of rosemary.
- You will keep them in the oven with the door slightly ajar for around an hour. Keeping the door ajar will allow for the moisture to leave the oven!
- Check on them regularly as we find they smell wonderful – even when burning! Depending on their moisture content they may take as long as an hour and a half to dry out. But give them the snap test. Bendy sprigs need a little longer. Ones that snap first time mean you can remove from the oven and strip the leaves.
- Wait until the sprigs are cooled before stripping.
This is a little bit different and I am very cautious with this as your microwave will dry your rosemary out within 60 seconds. Meaning that much more than that could result in a little bit too dry and potential fire risk!
- start by removing the leaves from each sprig. Hold the stalk by the fresh growth between thumb and forefinger. then in the other hand run your fingers and thumb down the length of the stalk to remove the fresh pines.
- Put them on a microwave proof dish single layer thick and set the oven to full power. Give them a 45 second blast. Do not walk away from the microwave at this point!
- Check on them to make sure they are snappy not bendy, be careful as they will be hot to the touch! If they are bendy, give them 10 second blasts until they snap and feel dry to the touch.
- Store them as before, but wait until they are cooled.
- lay your sprigs out on the dehydrator tray single layer.
- Switch to herbal setting and let it work for 1.5 hours. But stick close by as Rosemary can be a bit tricky and may take a while longer. It all depends on rainfall recently!
- Once it has dried to the point where the stalk will snap under pressure you are ready to harvest the dried leaves.
From the above methods you will have stalks left over. We use these in the fire pit to stop mosquitoes from taking over in the evening! Just pop them in dried or use as fire starters. The essential oils that are released help to deter pests.
We also put some stalks in with our wood dust when we are smoking garlic. This gives our smoked meats and cheeses an extra earthy quality too. Make sure to break the stalks down as small as possible and mix in fully.
You can add you dried rosemary to other herbs that you have dried to create different mixes, like Italian Seasoning or Herbes De Provence.
By freezing our fresh herbs we can help to preserve it. Bacteria likes a warmer temperature to breed and therefore the freezer is the ideal place, however we want to preserve the taste as well as protect against illness.
Freeze in ice cube trays olive oil, water
A nice simple way to have a readily accessible source of tasty rosemary is to freeze in ice cubes.
- Trim your rosemary by pinching out the fresh growth this will preserve the most intense flavour. Avoid pinching out any potential flowers.
- Wash very gently under the tap to remove any living pests or bugs.
- Take a clean ice cube tray and put fresh rosemary leaves into each place.
- Gently pour high quality olive oil or water into each pot. Try half or the ice cube tray as water and half as oil. That way you can defrost the ones with water and have fresh rosemary to add to stews or you can fry the olive oil ones.
- 2-3 hours in the freezer and they will be solid, then you can put them into one bag together and keep them in the freezer, with your ice cube tray free for another use!
Freeze Individual Sprigs
For this you will be able to use just enough for one dish each time.
- Lay the sprigs out on to baking paper on a tray in the freezer, keep them separate and flat.
- 2-3 hours later the sprigs will be individually frozen, then you can store them all together as they will not stick to one another. Roll the baking paper and put into an old margarine tub.
- Then use as and when required, much better to reach into the freezer than a cold night!
- You will need a jar or container that can provide a tight seal. Make sure to sanitise it prior to making the oil up. We use the dishwasher on a hot setting and then use paper towel to make sure it is fully dried out. Please note the below warning around moisture.
- Take around 5 teaspoons of dried rosemary to 100ml of good quality olive oil. Place the rosemary into the container or jar. You can mix it with other dried herbs like thyme or oregano too, think about ‘what grows together goes together.’
- Heat the oil to 180 degrees Celsius. Then pour into the jar over the dried ingredients.
- Seal the container and allow the oil to cool.
Professional food producers will use fresh herbs in their oil infusions and introduce an acidity regulator to kill off the bacteria. This is really not advised at home and making up an oil infusion with dried rosemary can be a great way of preserving the flavour and being able to use it in a different way.
It is all about ease of use and making up a set with Kilner Jars that can hold different herb infusions is great for using in dishes that you may not want the fresh herbs in. We even use oil infusions in BBQ’s and apply with a rosemary brush!
Warning For Oil Infusion Related Botulism
We do not use oil infusions as a method of preserving fresh herbs. The moisture in the fresh rosemary sprigs will introduce the perfect breeding ground for Clostridium botulinum which is known to cause botulism. Botulism can be quite dangerous and even deadly in some cases.
If you are using an oil infusion you will need to use it almost immediately and store it in a dark cold place where bacteria is known to not live. Once made use within two weeks. We really learned this the hard way and tried to make Christmas hamper gifts from fresh herb infusions. Not great!
By using dried rosemary in your infused oil you will be able to reduce the moisture present and store the oil for around 3 months. But after this time discard it.
Let us know how you get on with your own preserving!