3/09/2018 - Darkness
- Ruvan Asagao
- Sep 3, 2018
- 4 min read
Things are still rather quiet in the garden. Ever since the heat and drought dissipated gray, overcast skies have been pretty much constant. In addition, night temperatures have been dropping quickly as well (sometimes dipping beneath 10°C) resulting in small, underdeveloped flowers which don't even want to open fully during the day.
Having experienced a very similar scenario last year I am starting to reach a couple of conclusions: Ipomoea nil only starts flowering naturally around mid to late August in my region. Critical night length (9 hours) was reached on the 4th this year. Night temperatures also start dropping significantly around mid to late August. Combine this with the long periods of overcast skies we've experienced during August these last two summers and you have the perfect formula for getting just a few scrawny flowers compared to the wealth we've been seeing in July this year.
The above scenario seems quite common for my region and will be a a strong possibility every season.
However, this year I've been having some relative success getting some of the plants to flower early. It has been apparent that a lot of the plants I planted earliest (end of March-early April) were the ones to start flowering way before I expected. The reason being that the critical night length lasts until early May in my region, forcing them to flower shortly after germination. This is somewhat similar to how a lot of Japanese growers work. Giving seedlings a short-day period to induce early flowering (usually 16 hour nights for around two weeks or until signs of a flowering response are observed) .
I will probably have to focus a lot more on this process in the future to ensure earlier and better flower production (and hopefully seed yields as well). However, this also comes with a couple of inherent problems:
I may need to start germinating my seeds earlier in the year. I would probably start germinating the plants indoors around early March. However, the weather is very unpredictable during spring and up until mid May there is no guarantee the plants can go outside. Some years we're lucky, some years we're not. Space is extremely limited inside and the vines can reach quite a decent length after 2 months of growth. This means the number of plants I can grow is greatly reduced even with severe pruning of the vines (I also overwinter a bunch of my favourite pepper plants every year which requires some space).
Additionally, the brightest space in the house is way too cold for germinating plants during late winter/early spring. I would need to start heating the room which would waste a lot of energy as it is not properly insulated (it's actually a veranda). On the other hand I could use another room but I would definitely need to provide additional lighting. This again would mean increased energy usage but is likely more economical than heating the entire veranda for 2 months.
Using artificial lighting would completely defeat the purpose of starting early though. As I would have complete control over the night length (as long as the room is completely dark during night hours). This can be seen as a positive though as I could practically start and flower plants whenever I wanted.
I'm still not keen on the increased energy usage though and this way I would only be able to grow a very limited number of plants at one time. This would also increase costs and as a non-profit setup this is something we'd like to avoid as much as possible.
This has lead me down another avenue of thinking. Namely, artificially manipulating the dark period by covering up the plants with a lightproof material. This process could be used anytime the night length is shorter than the critical night length. It's a little more labor intensive but should be just as effective.
I have actually already been conducting some early experiments along this line in the beginning of July but never got round to posting about it on the blog.
I acquired a few lightproof bags originally meant for vacuum sealing which seem to be the perfect size for fitting in one or more trays of seedlings or a single small sized potted plant. By covering up the plants every night for 9+ hours for a week or two flowering should be induced.
Having to do this with a high number of well developed plants would be a large amount of effort though. Covering and uncovering them individually every evening and every morning can take up a large chunk of time which could otherwise be used for watering and training the vines.
So it seems easier to use this method when the plants are still young. As one bag will fit many seedlings at once. Also, cotyledons are much more receptive to changes in night length so it is highly advisable to use this method while they are still present on the plant. Cotyledons can survive for several months on healthy, well maintained plants though but will drop quickly on nutrient deficient plants. Large plants transpire a lot more as well and the small amount of air in the bag might possibly pose a problem, although I haven't observed any so far.
It seems this method may be the way to go for now but more experimentation is certainly needed before deciding to keep going with it in the long run.
On a completely other note the Ipomoea lobata has finally started flowering. It's a very vigorous grower. The vines get quite long quite fast. I ignored the plant for a while and it has become hopelessly entangled with a couple of its neighbours. It is very unique with one-sided racemes of flowers opening in a gradient of red fading to yellow, cream and white. Apparently this one is a perennial so I might try and see if I can manage to overwinter this one.
Comments