I have found that some Solanum, like tomato and capsicum seed are slow to germinate, capsicum (bell pepper) being the most difficult I’ve encountered. While my tomato seed will usually germinate within one week, capsicum can take two or more weeks. What can be done about this? Just add heat.
Here in Melbourne, to get the most out of a growing season, we have to start our capsicum and tomato seed early. We grow our seed indoors in mini propagators and on windowsills during early Spring, when soil temperatures are still too low for direct sowing, so they are ready to plant out later when the weather warms up.
I have had trouble getting tomato and capsicum seed to germinate at this early time, with the cool overnight temperatures and often not much better days.
Capsicum like a temperature range of between 25°c – 30°c to germinate.
You can buy a special electric heat mat to obtain perfect growing temperatures, it’s as easy as set-and-forget, but we can’t all justify the cost for our small home plots.
An alternative that I’ve seen used by Peter Cundall is to simply use a hot water bottle to raise the temperature to an optimum level.
I set up the experiment with two propagators containing identical sets of seed, one propagator will have heat applied and the other will be left with natural temperatures.
I placed a garden thermometer in the propagator that I will heat so I can keep an eye on the temperature.
Each propagator has four tomato seed and four capsicum seed consisting of two varieties of each. Juanne Flamme and Amish Paste tomatoes and Quadrato and Chinese Giant capsicum.
I partially fill my rubber hot water bottle with very hot but not boiling water, if your water bottle is too full it will be difficult to balance your seedling tray on top.
Using Peter Cundalls instructions as guide, I wrapped my hot water bottle in bubble wrap. I didn’t have much lying around the house so used two layers.
I re filled my water bottle with hot water twice a day, once before breakfast and again around dinner time to see if this method will fit around normal work hours.
Hot water bottle
The Tomato seed took four days to sprout and the Capsicum took eleven days.
All seed sprouted, 100%germination rate.
Without hot water bottle
The Tomato seed took six days to sprout and the Capsicum took fourteen days.
Without the hot water bottle, only three of my four capsicum seed sprouted, all of the tomato seed sprouted.
Using a hot water bottle definitely hastens the germination for both tomato and capsicum seed, it may only be by a few days but it definitely helps my piece of mind to have my seed sprout as soon as possible to stop me from panicking and starting over with fresh seed.
The added heat seems to improve the germination rate.
Water evaporated out of the soil much faster in the heated propagator so keep a close eye on your seedlings, they will need to be watered slightly more regularly.
Once the seed has germinated it shouldn’t need the hot water bottle any more.
My tomatoes germinated a lot quicker than my capsicum, as they were in the same punnet I could not separate them out, but the young seedlings didn’t seem to suffer from the extra heat during the extra week it took for the capsicum to sprout.
I used this method for capsicum and tomato seed but it should work with any warmth loving plant like eggplant or chilli peppers.
A good gardener always plants 3 seeds – one for the bugs, one for the weather and one for himself. – Leo Aikman