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I'm trying to germinate Vinca and Petunia flowers from seeds, for over a month now.

INFO

I have multiple environment-conditions setups for the Vinca:

  • Vinca setup 1: Seeds from last-year's flowers, potting mix bedding, inside a pot (in indirect sunlight), sewed 1-2 [cm] into the soil (so they'll be in the dark), soil kept moist, at an average temperature of 25 degrees Celsious.
  • Vinca setup 2: Seeds from last-year's flowers, home-made compost bedding, inside a plastic cup, sewed 0.1-0.5 [cm] into the compost, cup kept in closed closet (so they'll be in the dark), wrapped in plastic to keep moist, at an average temperature of 25 degrees Celsious.
  • Vinca setup 3: Same as setup 1, only with seeds from a pack (bought at a nursery).
  • Vinca setup 4: Same as setup 2, only with seeds from a pack (bought at a nursery).

And multiple environment-conditions setups for the Petunia (same as Vinca setup, only light conditions changed):

  • Petunia setup 1: Seeds from last-year's flowers, potting mix bedding, inside a pot, in indirect sunlight, spread on the soil and covered with light paper (so they won't be in total dark), soil kept moist, at an average temperature of 25 degrees Celsious.
  • Petunia setup 2: Same as setup 1, only with seeds from a pack (bought at a nursery).

ISSUE

None of the above germinated. It has been more than 5 weeks, and according to most information on the internet (and in seeds packages bought from the nursery) they we're supposed to germinate after 2-3 weeks.

I've taken water, bedding, light and temperature conditions into consideration.

Any idea on what may prevent them from germinating? Am I missing something here?

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  • When you say 'Vinca', do you mean Vinca minor or major, or Catharanthus? What part of the world are you in?
    – Bamboo
    Commented Jun 21, 2020 at 16:30
  • I honestly don't know... I grow them in full sunlight outside, so my guess would be Vinca Major, or Catharanthus. Reading on the two, I can't say that the ones I grew last year fell into one category (maybe somewhere in between). The ones bought from the nursery didn't have anything written on the package other than 'Vinca'.
    – orangesomethingorange
    Commented Jun 21, 2020 at 17:03
  • Vinca major and minor are sprawlers - they send out long runners and flower for about 3 weeks early in the year with blue or white flowers, then they're done till next year, and they prefer shade. Catharansus makes a little shrubby plant covered in flowers for a long period, in varying colours - the two look quite different. The confusion arises in USA because of the tendency to call Catharansus Vinca, which it is not - common name for Catharansus is madagascan periwinkle - Vinca has the common name periwinkle, hence the confusion. That's the trouble with common names I'm afraid....
    – Bamboo
    Commented Jun 21, 2020 at 17:56
  • Wait, let's assume I do have Vinca, are you suggesting that these 'long runners' are sent out before the hypocotyl rises above the ground? If so that's a little confusing to me... can you please elaborate on this?
    – orangesomethingorange
    Commented Jun 23, 2020 at 12:42
  • This gobotany.nativeplanttrust.org/species/vinca/major is Vinca major - Vinca minor is just a smaller version. This en.m.wikipedia.org/wiki/Catharanthus_roseus is Catharansus - you can tell from the leaf shape and veination that they look different from true Vinca. Compare with yours. You still haven't said what part of the world you're in and that's important for growing from seed...
    – Bamboo
    Commented Jun 23, 2020 at 13:05

1 Answer 1

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I am going to assume that the vinca you refer to is Catharansus; since I don't know where you are in the world, it's impossible to know whether Vinca major/minor would be a perennial where you are, but Catharansus is usually grown as an annual and therefore might be raised from seed each year.

Where you are in the world is important for seed sowing, even if that takes place under cover or indoors. However, since you do not wish to impart that information, here is a general answer. In the northern hemisphere, Catharansus should be sown indoors early in the year, around 12 weeks prior to the last frost, in temperatures of around 76 deg F. They should be sown into seed starting formula potting soil, not ordinary potting soil and not in homemade compost. Further instructions on how to grow from seed here https://www.burpee.com/gardenadvicecenter/encyclopedia/annual-flowers/learn-about-vincas/encyclopedia__Vinca-article.html

Petunia seed sowing is similar - early in the year, 12 weeks before the last frost, in warm temperatures or on a heat mat, not covered because they need light to germinate, sown in seed starting soil, not ordinary potting mix. Further info on growing from seed here https://www.burpee.com/gardenadvicecenter/vegetables/petunias/all-about-petunias/article10254.html

If you are in the northern hemisphere,then you started too late trying to germinate from seed to have flowering plants this summer. If you are in the southern hemisphere, it was too early, and it seems you did not use seed starting mix for the seeds either. Ordinary potting soil has a higher level of fertilizer which may deter germination or burn seed/seedlings, whereas seed starter has very little or no fertilizer. Note also that home made compost, unless produced using a hot, aerobic composting method where it reaches very high temperatures during the process (difficult to achieve with home composting), is not suitable for use as a planting medium for either plants or seeds (especially in containers), but is useful as a soil conditioner on open ground outdoors.

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  • Thanks for the answer @Bamboo :) now I have some research to do, with all that information. Two immediate questions that pop up are (1) assuming I have Vinca instead if Catharanthus - are you suggesting that I can't grow them from seeds each year? and (2) most guides I read about Vinca suggest sowing 2-3 weeks (15-20 days) before, where did the 12 weeks calculation came from? I'll be sure to check those links when I get home, and in any case, even if this is a failed experiment - I'll try and post some results, to make this Q/A post a helpful one... cheers!
    – orangesomethingorange
    Commented Jun 25, 2020 at 15:25
  • YOu wouldn't need to grow Vinca major/minor every year unless you live somewhere with a very harsh climate; they are perennial plants and, as such, are permanent residents in the garden, usually planted as ground cover, and are usually bought as plants - propagation is usually done by digging up and dividing or taking cuttings. Seeds for this plant are not commonly available. As for seed sowing time, check the link provided, which contains the information; sowing early means you will have good sized plants to put out for summer - 15-20 days is only till germination.
    – Bamboo
    Commented Jun 25, 2020 at 16:42
  • I will enlarge on seed sowing times - the point is, you want good sized plants ready to plant out in early summer - that takes some weeks of potting on and growing on after germination has taken place. If you sow too late, by the time the plants are big enough to flower, summer will either be over or almost over, and given that both petunia and Catharansus are cold sensitive, they will just die without flowering outside at all.
    – Bamboo
    Commented Jun 25, 2020 at 16:47
  • Thanks for the comments @Bamboo and for elaborating on sowing times. I think that now I got what you were trying to say. I wanted to grow Vinca from seed every year for a different reason, but you're right, I might just grow it all year round and propagate from it each year. I will check that it's Vinca and not Catharanthus, since it did die out each year up until now, but that might have been caused by changes I made in my garden. My question still stands for the Petunia, so I'll keep that project going, for the results :)
    – orangesomethingorange
    Commented Jun 30, 2020 at 8:04

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