Suburban Sue

Focus on Catnip Germination

Catnip - seems to be the marmite of the cat world. Some cats seem to enjoy it and feel the full effects whilst other cats ignore it completely. Our current cat, Leo, is one of those that loves it. My brother-in law's cat is not interested.

Growing catnip (Nepeta cataria) and catmint (Nepeta mussinii) can be a bit tricky and we quite often get enquiries as to why it hasn’t germinated. So having also tried sowing in a pot and leaving outdoors with no success I investigated a little further. I had assumed in my garden that the cat had got there first. 

Catnip needs light to germinate so by not covering the seed when you sow them will aid germination. I found several recommendations for. some moist cold stratification, that is sowing into a moist medium and then keeping the temperature low but not freezing. Some suggested the deep freeze overnight before sowing then moving to a warm moist medium. Deno* in his seed germination handbook found that trials gave the following results:

  • 70oF/21oC in Light the germination was 32-46% in 1-4 weeks
  • 40oF/4oC followed by 70oF/21oC in Light the germination was 40-65% in 1-4 weeks
  • 40oF/4oC followed by 70oF/21oC in Dark the germination rate was 12%.

There were similar germination rates if the seed was fresh or had been stored dry at 70oF/21oC. I would expect a decline in germination rates the older the seed is and while a few may germinate in older seed it also depends on the conditions the seed has been stored in. Most seeds do not like very hot temperatures.

So in early January I sowed some catnip (Nepeta cataria) using moist vermiculite in a ziplock bag leaving a little vent and placed the bag in the fridge at about 4oC (40oF). I looked every week or two to check whether any seeds had germinated. Of course the seeds are in the dark. Nothing happened so about the end of February when I had a little time I brought the bag out to a warmer area and placed it on my propagator in a light room. In a couple of weeks several had sprouted. I ended up with about 30 sprouts which I transplanted to a seed tray and covered with a vented propagator lid (because of the cat). About half of the transplants have so far survived and are about 5 mm tall! 

 Catnip seeds showing tiny sprouts in seedtray

Note to self: It is tricky to get delicate sprouts out of the bag without damaging them - which might be a cause of quite a few not surviving the transplanting. The bags are easy to store in the fridge and while germination is taking place.

Editor's Note: Catnip leaves contain a compound called nepetalactone (cat drug!).  Nepetalactone also repels insects. Double billing.

*Reference: Seed Germination Theory and Practice by Dr. Norman C. Deno