Far Out Flora

Cerinthe Seed Germination Experiment

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I have been testing whether or not it is necessary to soak Cerinthe seeds to help them germinate.  All the literature says yes.  I am in week 10 of my experiment using Cerinthe ‘Pride of Gibraltar’ (Cerinthe major atropurpurea) and turns out…soaked seeds did about 100% better.

Cerinthe ‘Pride of Gibraltar’ - Cerinthe major atropurpurea from Rene's Garden

Cerinthe ‘Pride of Gibraltar’ - Cerinthe major atropurpurea from Rene's Garden

Quick shout out to Rene for giving me some Cerinthe seed she collected from her garden for my next round of experiments.  Rene’s Cerinthe above looks great with her succulents.  Rest of images are mostly for transplant Cerinthe seedlings, and text follows the experiment.

Cerinthe ‘Pride of Gibraltar’ - Seedlings

Cerinthe ‘Pride of Gibraltar’ - Seedlings. They are near a west facing window and average indoor temp is 68-72F.

Here is what the literature says to do:  Sowing seeds can be done inside or outside after soaking the seeds for 24 hours.  For outdoors, wait until after last frost and plant in ¾ inch deep 4-6 inches apart.  For indoors, sow seeds in moist not soggy soil.  Provide a strong light source until plants are 4-6 inches tall, then transplant outside.  Since I was starting the seeds indoors, I researched and compiled typical steps to sow seeds indoors.

1) Soak seeds for 24 hours
2) Fill cell type flat with seed starting soil
3) Keep soil moist, not soggy
4) Plant seeds ¾ inch deep one per cell
5) Cover tray and keep it at 70 degrees
6) Give it 8 hours of indirect sunlight
7) Uncover after seeds germinate.  Seeds germinate in 1-3 weeks
8) Keep soil moist, not soggy
9) Transplant outside after they reach 5 inches, approximately 4-6 weeks, and after frost has past

Getting ready to transplant the seedlings

Getting ready to transplant the seedlings into 4 inch pots.

My Experiment: Two groups of 18 seeds were used to test soaking methods.  Group 1 was soaked for 2 hours using hot tap water from sink; Group 2 was not soaked or treated in anyway.  Both groups used non-treated or genetically modified seeds (can find seeds at Renee’s Seeds).  They were germinated indoors under typical apartment lifestyle resources and hand watered using a hand pump spray mister.  Also, the remaining cells in the center were used to germinate other veggie/annual seeds.

Only handle seedlings from the leaves, never by the stems.

Only handle seedlings from the leaves, never by the stems. Touching the stem can severely damage new seedlings, while the leaves can handle some damage.

My Experiment Step by Step Details:
1) 18 seeds were soaked for 2 hours in hot tap water out of the sink which was 100F.  After the first hour, the water temperature at dropped to 70F and stayed at 70F for the entire second hour.  The other 18 seeds were not treated or soaked.
2) I filled a 72 cell pack liner insert with a lightweight potting soil up to the rim.  The liner insert was placed in a tray bottom, and used a 3 inch tall clear plastic dome.  The soil content was Ultra Potting Mix from American Soil & Stone. Contents:  Coconut coir, horticultural sand, scoria, agricultural lime, and trace mineral fertilizer.
3) The seed were sown ¾ inch deep on the outer right and left sides of the liner tray, one per cell.  The soil was already moist, and after sown, I wet the soil using a hand pump mist sprayer, and placed the dome on the liner.
4) Until all the seeds germinated or the first two weeks, whichever happens first, the liner was mist daily in the morning between 5 – 9 AM.  The liner was kept on a shelf near a west facing window.  The temperature in the house stays between 67-75F.  We get between 8-10 hours for medium to bright light.
5) Most seeds all germinated well before the two weeks.  After that time, watering continued until they started touching the top of the clear plastic dome.  At that point, the dome came off.
6) Misting continued daily for 1 more week, then started weaning off the water going to every other day and every third day.
7) After the plants average size was 3-4 inches, I transplanted into 4 inch pots and slowed watering down more and start exposing to outside temperatures.  The soil was a Medium Bodied, All-purpose Potting Soil from Sloat.  Contents:  Fir bark, Canadian peat moss, horticultural sand, mushroom compost, wheatstraw, cottonseed hulls, cottonseed meal, chicken manure, and gypsum (used as a pH adjuster).
8) After the plants average size are 4-6 inches and established good roots, they will be transplanted outside in containers and in the garden.  I am estimating that they will be ready to transplant by week 11.

Used a tool to make hole so that you do not compress the soil.

Used a tool to make hole so that you do not compress the soil.

Weekly observations:

weekly observations

Weekly observations

For those of you that really want to geek out…here are the stats above.

4 inch pots done.

4 inch pots done.

Conclusion: No seeds germinated after the 10th day.  Overall, the 2 hour soaked seeds did almost 100% better than not soaking the seeds.  They germinated faster, and seemed to hold up better with my indoor watering and caretaking regiment.  The outside rows in the cell liner dried out the faster and that is where most of the dead plants occurred.  Even of those planted on the outside in worst conditions, the soaked seeds did better.  I transplanted the seedlings to 4 inch pots week 8 and hardening them off to transplant outside.

Cerinthe ‘Pride of Gibraltar’ - Cerinthe major atropurpurea in the Rene's Garden

Cerinthe ‘Pride of Gibraltar’ - Cerinthe major atropurpurea in the Rene's Garden

Another gorgeous photo of Rene’s Garden.  Hey, in many climates it is too late for seeds…just go buy a plant at this point such as at Annie’s. My guys are going in the ground this weekend, and should flower by late summer to fall…thanks San Francisco and your mild climate.

Here is the Skinny on Cerinthe ‘Pride of Gibraltar’:
Type: Broadleaf Annual that self sows
Light: Full Sun / Part Shade
Water: Moderate and Regular (MR) hotter climates / Infrequent But Thorough (IBT) coastal
Zones: 7-10b, hardy to 35°F
Family: BORAGINACEAE
Origin: Mediterranean – Greece

Cerinthe ‘Pride of Gibraltar’ is an airy annual growing about 30 inches tall and half as wide.  It foliage is gray to green, but grown for its vibrant purple bell shape flowers and royal blue bracts.  It can be grown in a container, or in the garden.  It likes well drained soil and can take a light frost after mature.  Propagate via herbaceous cuttings, and self sowing, and direct seed planting outdoors after last frost.

– Far Out Flora

17 Comments

  1. Good experiment Matti! I love harvesting those seeds from the dried plants! Good luck with your seedlings.

  2. Great post! Now I am going back to read all the details again!…

  3. This is very interesting. I have Cerinthe “Pride of Gibraltar” from Renee’s also, but its flowers are pink, not blue. Different soil? Very pretty plant, but a little odd as well. A keeper, though!

    • Hmmm… that’s interesting. I’ve only seen the blue ones.

    • Pink? That’s weird. I’ve only seen the blue ones before. Renee’s has a facebook page (I never knew), maybe they would know. I’d love to hear why yours are pink.

    • I also bought Renee’s Pride of Gibraltar Cerinthe seeds (2011) and they’re growing well; a few which are in a more shaded location are less vigorous (smaller plants) and have pink flowers. The soil is probably pretty similar, as is the watering (drip on both). My guess? Difference in sun.

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  7. I will have to try the soaking experiment.

  8. I planted Rene’s Garden Pride of Gibraltar Cerinthe seeds in my greenhouse in early February. I soaked my seeds, and used the peat starter plugs instead of potting soil. P placed the plugs in a tray and used bottom heat set for 70 degrees. I have to supplement heat my greenhouse at night, to keep it from completely freezing, and if it is cloudy, the greenhouse doesn’t get very warm during the day. I had about 30% germination in a week, about 70% germination now. I moved the tray off the bottom heat after about 2 weeks. I appreciate this detailed report, since I’ve never grown this plant before, and don’t even remember ever seeing it. I will probably plant them outside in about a month.

    • Hi Cindy! Cerinthe as we now know is super easy to start from seed. Once you have a few plants in the garden you’ll always have it, as it reseeds politely. Great plant!

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  10. I am currently growing approx.. 3000 Cerinthe and have spaced a planting apart two and a half weeks. I am growing for an interesting reason…see my progress in 2014……

  11. I find the young plants of Cerinthe are inclined to be very gangly. Does anyone know if pinching out the tips gives a bushier neater plant? The young plants are outdoors in pots, but temperatures at night here are still sometimes down to 0 degrees & I am afraid of killing them. I will probably do a couple anyhow to see what result I get!!

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