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All welcome to come along for a chat, cuppa, local organic gardening tips, seed saving and plant swap! Gold coin donation.
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Wednesday, October 27, 2010

How to Grow, Harvest & Save Basil Seeds

Basil is one of our most popular culinary herbs and belongs to the mint family. Basil is used to make pesto sauce, flavour many dishes and salads, and is well accepted as the perfect partner to tomatoes. It is traditionally used in Italian, Mediterranean and Thai dishes, blends beautifully with garlic, thyme and lemon and also works well with fish, pasta, cheese or eggs.

Other uses include drying leaves for potpourri and using fresh leaves as a herb tea to help with digestion. Basil can be frozen in ice cubes and leaves can be preserved by blanching in vinegar or oil and then blended with cheese, pinenuts or other seeds/nuts to make pesto which freezes well if sealed with a layer of olive oil.

Basil Varieties:

There are a number of delicious varieties to grow.  
  • Sweet basil is one of the most common varieties grown but there’s something for everyone in the basil family.  
Other varieties include:
  • Lemon (Ocimum americanum) and Lime basil both of which suit seafood dishes, soups and salads.
  • Cinnamon.
  • Nufar (a mild flavour with just a hint of anise).
  • Greek Mini (a compact small leafed basil which particularly suits pots as it only grows to 30cm).
  • Thai (Ocimum basilicum) which has a sweet anise-clove fragrance and hint of mint and citrus - flavours that go well in curries.  
  • Of course, for a change of colour, there’s also Purple basil.

Basil flowers are a beautiful temporary addition to any garden with the added benefit that they attract pollinators and also provide free seeds for next season.

Tips on How to Grow:

Most basils are annuals and are very easy to grow. They like a soil ranging from slightly acidic with a pH of 5.5 to 6.5. Seeds can be sown directly into moist soil (moderately rich) in a full sun position any time from spring to mid-summer or into a seed raising mix to a depth of not more than twice the size of the seed. When two pairs of true leaves appear, seedlings can gently be pricked out of the seed raising mix with a bamboo skewer and gently transplanted.

Tip pruning basil helps prevent plants becoming woody too quickly and pinching off flower heads will keep the plant putting its energy into more leaves not flowers and seeds. Once flower heads start to form, the plant slows down leaf production so it’s important to keep pinching these flower buds off.

When harvesting basil leaves, use a pair of secateurs or scissors to cut it back to about 6mm above a node, leaving enough foliage for the plant to keep photosynthesizing and producing more growth. If you remove all the ‘solar panels’ your basil plant can’t get enough energy from the sun to keep growing!

When Seed Heads are Ready to Save:

When you are ready to save seed, allow one plant to flower and leave at least one other to keep producing leaves. Flowers will form on long stalks and stay green for some time while flowering.

This is the ideal time to snip them off the plant.

Eventually they will start to turn brown which house mature seeds inside.  

How to Harvest:

To harvest the basil seed heads, using a brown paper bag and secateurs, snip off the flower heads at the base and drop into the bag. Any mature seeds will fall into the bag. To fully dry the seeds, peg the bag up to dry in a warm, well-ventilated space. Once dried, they are ready for processing!

How to Process: 
Basil seeds can be a little stubborn to remove from the seed heads which each hold several seeds. However they are very tough and can take rough treatment!  Here are some ways you can process them depending on what materials you have available.

  • Add the seed heads to a clean calico bag or pillowcase. Rub them vigorously between your hands, scrunching the bag regularly to remove the chaff and allow the seeds to drop to the bottom of the bag. 

Alternatively, use a rolling pin to crush the seed heads.
  • When you can see all the seeds, tip them out onto a shallow tray ready to blow the chaff off.  

  • Another tool you can use is a strainer or sieve with appropriate sized holes or mesh to allow the seeds to remain while the chaff is rubbed through the bottom and onto a tray.

  • Gently blow the chaff (plant matter) off the tray or use a small pastry or art brush to remove it. 

  • Then you'll have clean seed you can package in a small self-seal bag. 
  • Remove all air from the bag first after adding your seeds and pop in the freezer for a couple of days to kill any stowaway insects like weevils! 
  • Then store in a dark, cool place until you need them for planting. 
  • Make sure to label with the variety, date and source. 

Plan on plenty of pesto next season!


  1. Any secrets for how to get basil seeds to germinate? I've had some in a plastic planter for about three weeks now and they show no sign of life. Think it might be due to the cold and lack of sunlight at my house, though.


  2. Depending on where you live Zev, and the season, it may be too cold for them to germinate. Or possibly they are too old and unviable. To germinate, they need to be kept warm and create humidity with a cover over your seed raising mix. Hope this helps.

  3. Try closing them in a ziploc bag and open for a few minutes daily to ventilate, keep them on a windowsill, that how i start mine in winter...not sure where you're staying but South African winters are not that cold...Good luck

  4. how long will it usually take for sweet basil to bear seed?

  5. When the plant is mature, if it is well watered, it may take 2-3 months to start flowering and develop seeds but if it is dry, plants often 'bolt to seed' much earlier. You shouldn't have to wait too long!

  6. How long will the collected seeds last for? And what is the best way to store them? Thanks

    1. Sorry for the delay in replying. If stored correctly, your basil seeds can last up to 5 years. Read our post for how to store your seeds: http://eudloseedsavers.blogspot.com.au/2011/09/how-to-store-seeds-correctly.html. Hope this helps!


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