growing secret

[Quasarrgames]

I'll let you in on a secret:

Plants in dim light (that of heaters, crematoriums, etc.) will grow at night, or at least i think they do. They'll only grow at about a fifth of their normal speed, but still, every little helps.

Now i just need to mod me a far-reaching dim lamp for this especially.

[Kaballah]

Pretty sure you're not really gaining anything here, as plants grow at reduced speed in low light anyway, so instead of a period of full (or better) growth speed and a period of 'resting', you just have a continuous period of low-speed growth.

[Jimyoda]

I'm largely copying from the wiki since I already posted these observations there. (This is as of Alpha 10, though I just checked that it's still true under Alpha 11).
Here goes:
Plants need at least 50% light to grow. When a plant lacks light its info window indicates 'Needs light level: 50%. As light rises above 50%, plant growth rate begins to rise above 0%. In normal soil, growth rate increases by 2% for every 1% increase in light level beyond 50%. At 100% light, the plant's growth rate finally reaches 100%.
Heaters and such give at most 60% light. Given all that you can calculate, (60%-50%)*2 = 20%; or 1/5 as you said.

However, from hour 19 through hour 5 plants will rest during which time they will not grow regardless of the light level. Since plants rest nearly 50% of any given 24-hour period, plants in normal soil, lit 100%, really get an average growth rate of about 50%. When lit 60% that average drops to 10%.

Therefore, for indoor plants, always use a sun lamp. If not a sun lamp then at least use a regular lamp. It provides 60% lights up to 7 cells away. A heater, smelter, etc, lights 60% only 3 cells away.

What you'd really need is a mod that eliminates plants resting (which I'm pretty sure this is one).