How to keep seeds warm - permie ideas please!

Sometimes I just *have* to do something new, regardless of how impractical it is...

I really want to try growing Dragon fruit from seed. (Selenicereus undatus or Pitahaya ) The trouble is that it wants 75F to 85F for germination, although the plant should be happy cooler than that once it's growing.

The web claims it can manage as a house plant, even if it doesn't bloom.

The trouble is that my house rarely gets to 75F - we're looking at commonly 62-64F, and apparently this could really slow germination to the point of of the tiny seeds not surviving.

In the distant past, I used to put heat loving seeds on top of hubby's fish tank... there was just enough room for a few pots and they got lovely heat. Alas, the fish are long gone.

In the less distant past, the transformer of 48" florescent lights did the job. Alas, Hubby's replaced all of those with LED's. (Yes, it lowered the mercury risk, but I am aware of the downsides of LED's. )

So I'm looking for ideas here. I will start the seeds in a shallow tray that's about 9"x6", but that's negotiable. But I need a little heat, but not enough to cook them!

The top of the fridge, especially if there is a cupboard above it, and the top of the hot water tank are usually warm enough for most types of seeds.  My grandfather used to start his tomatoe seeds in those spots...but modern insulation might mean it's not as warm as it used to be.

Seed mats are popular now.  But electricity.

Hang on

Does this mean i can take the seeds out of my dragon fruit sitting in the fridge and grow them?  Got to look this up.

A seedling heat mat is my obvious answer. Now they have some with adjustable thermostats. If I ever needed to buy another I could see that feature come in handy.

I only use it for seeds that need warmer germination temps. I think I have 'cooked' seeds in the past because it can dry out the soil much faster in my climate if I forget to pay close attention.

I need to use lights when I start seeds indoors in February otherwise as soon as they germinate they will start to get leggy and stretchy. If you use even one light that puts off heat you can feel maybe you could build an enclosure to hold the seeds and trap some of the heat from the light. Mess around with ventilation to find the right temp. Maybe it could be designed to run off the sun through a window on sunny days and only need the light heat when you need the light heat.

Keeping the containers covered in some way until they sprout will also heat a little heat.

I hope you get them to go!

We keep our house at 60F in winter and the upstairs bathroom is a bit warmer at ~65.  A four-bank light rack is in that room for late winter seed starting which uses seedling heating mats and previously fluorescent tubes (2 ft length).  I just finished installing LED tubes in one of the light fixtures and decided to torture myself with attempts at starting and growing sweet basil from seed (current outside temps near 0F and lower this weekend). ;-)     It was at least some satisfaction at seeing the thermometer under the lights register ~80F by day and above 70F at night (night: light off/heating mat on).   The heating mat draws 17W of power if that helps at all with the decision.  The LED lamps emit more heat than I would have expected, which is a plus for this purpose.  Since I had to rewire the fixture to by-pass the ballasts for the new bulbs, there is no extra heat come from the transformers/ballasts inside.  Since the color temperature of the bulb can be adjusted with a switch on the bulb, I hope to favor vegetative growth of the plant with a setting near 6000K.  Coming up on a week post planting and no emergence yet, but seed admittedly was a few years old.  Photos below of the new lamps and seed pot underneath as well as source for the heating mat.  If I had to go without the heating mat, would probably use a brick atop the woodstove heated in the evening and placed under the seedlings through the night and next morning, then just using lights as heat source for daytime.  Good luck!

I, too think that the little heated mat is an easy way to go.

Raising the temperature a mere 10 degrees is pretty minimal heating and associated electrical consumption.

If you really want to cut the heating to a minimum, place the heating mat/tray on top of some type of insulation.  Make certain that the tray is covered on all sides except the top.  Assuming that you have some decent potting soil in the tray that is moist, the soil itself should do a good job of retaining heat.  When you go to water, do so with mildly warm water so as to not cool the soil off and make the heating mat have to work overtime.


Good Luck!!!

Eric

Thank you everyone for your replies and ideas.

R Ranson wrote:

The top of the fridge, especially if there is a cupboard above it...

I did that 30 years ago with an older fridge, but our current one works differently, and there isn't enough of a gap between the fridge and cupboard to slide even a shallow tray in. However, I have put a thermometer on top of the fridge to see how it compares. It is possible that if I tent plastic from the cupboard doors to the front of the fridge, it might trap enough heat. Worth experimenting with - thanks!

And wrote:

... the top of the hot water tank are usually warm enough for most types of seeds.

This totally has potential. Hubby stores egg cartons on top of there for his egg business, so I would have to negotiate some space and make sure he doesn't knock the pot to the ground!  Again, thanks!

Les Frijos and Eric Hanson:

~A seedling heat mat is my obvious answer.

I know too many people who have had heat mats and they just didn't last, even if they were well cared for. They are sealed, so there's no way to try to repair them when some wire or other breaks. (We have the same problem with bed warmers - I had one that lasted over 25 years, but every one since, has more bells and whistles and limited lifespan.)

Short answer, I'm hoping not to have to go there. I don't mind a little electricity, as it will help heat the house when it escapes the plant area, but I do mind not knowing of a brand of heat mat that will last at least a couple of decades, considering it would get very limited use.

John Weiland wrote:

 The LED lamps emit more heat than I would have expected...

That is worth knowing and possibly testing. Unfortunately, the lights I have are in the front window, so any heat will tend to escape. I'd have to find a place against an inside wall and see what kind of warmth I can get.

In spring, I have a friend who puts fresh chicken shit in the bottom of a deep planter, and soil on top of that, and the chicken shit helps to keep things warm. That is another great technique, but I'm not sure I want to try it inside the house.

Please keep the ideas coming. I might need to combine a couple for example, I have a 2 ft LED bulb, so if a made a frame for on top of the fridge, we might get to the target temperature. A bit of insulation in some key spots might also do the trick.

r ranson wrote:Does this mean i can take the seeds out of my dragon fruit sitting in the fridge and grow them?  Got to look this up.

Yes you can!
I did it multiple times, once for a red, once for a yellow and once for a white fleshed fruit. Germination rate is high!
I just did not manage get it to flower yet.
Good luck!

Nynke Muller wrote:

r ranson wrote:Does this mean i can take the seeds out of my dragon fruit sitting in the fridge and grow them?  Got to look this up.

Yes you can!
I did it multiple times, once for a red, once for a yellow and once for a white fleshed fruit. Germination rate is high!

Yes, but the seeds need to be quite fresh, and they want the germination temperature to be between 75F and 85F which is my concern... sigh...
Is the top of your hot water tank accessible?

In the UK my mother would start "early" seeds in a cold-frame - which is basically a small scale greenhouse with no powered heating.  A frame of wood, or bricks, placed in a very sunny spot with a pane of glass on the top.  Not too big, or it gets hard to lift the glass to water seedlings.
Hopefully you have enough sunny days in the Pacific Wet Coast.  I have heard that it can be Very Wet!

The old timers would put seeds on top of a hot compost heap to keep seeds warm.


If you have wood chips dumped at your location putting the seeds on top of that pile  can keep them warm.

Yes, but the seeds need to be quite fresh, and they want the germination temperature to be between 75F and 85F which is my concern... sigh...
Is the top of your hot water tank accessible?

I am very lucky with my well insulated appartment, which remains at 21 degrees celsius (just below 75F)  through most of the year without heating. Summers can be warmer and cold winterdays are a few degrees lower. So I just need a few degrees more.  For germinating seeds, I use the wet paper towel method. The wet towel with seeds goes into a plastic container or glass jar, which acts like a little greenhouse. I place the container in the warmest spots I have. Depending on the wheather, it can be a window still.
I have never tried the top of the waterheater, but it is accessible, and I will give it a try. They will be out of my sight, so there is risk of forgetting... yesterday I placed some cuttings in such a way that they can profit from the heat generated at the back of the fridge.
You need to get creative here. Find all the heat sources in the house. During cooking, your kitchen is warm, when you sleep, your bed is warm... during the day, the window still? Carry them on your body in a ziplock bag, ask a neighbour or a friend who heat their house warmer, wether your seeds can stay over until germination.... You only need heat for germination. Bring them to work... A lot of people love this, even though they might not like the rest of what you do as much as you do. Retry in summer....
Good luck! I am sure you will succeed somehow. Let us know what worked for you!

After leaving a thermometer in several different spots for the last week, I tidied up the top of our water heater enough to fit a tray with seeds on it. Our tank is insulated, and there's no easy way for me to put the tray under the insulation. The temp is *really* iffy.

1. I hoped that an upcycled plastic food tray over top would be enough to trap the heat.    Not a chance.

2. Then I added a hand towel over top and tucked down the edges.    It helped, but we were still below 70F.

3. The I added a 1" piece of foam - probably not a true "closed cell" foam, but it should slow the movement of heat more than the towel. The towel went back overtop with the edges tucked in. Alas I'm still looking at 67F first thing in the morning when no one's been using hot water all night.

At this point I'm hoping that there's enough heat at times during the day that the seeds will germinate. If I have no success, we do have a dog-warming mat Hubby bought at some point. I would have to do a bunch of things to keep it at a steady temperature - I haven't found it that successful for starting seeds in the past. Alternatively, hubby has a temperature controller that equipment can plug into which might allow me to control a chick lamp to within the target range, particularly if I add some thermal mass to the set-up.

The best I can say about the current set-up is that it can passively sit there, absorbing heat that otherwise would go into the room. That said, a friend gave me his holey wool sweater.  Would swapping that out for the cotton towel help trap a bit more heat? The top of the insulation felt warm to my touch when I slid it under the stuff stored on top of the heater. I need to check just how "warm" warm is!

Here we are a month later and ready for a little update:
1. Yes, the wool sweater seemed to help hold another 1/2 degree C or so. We were still hovering around 20 to 22C which is below the minimum 24C target temperature, but fingers are crossed.

2. Downside is that the seeds are pretty much in the dark. Remembering to check them, and actually being able to see the little critters when they do pop is an issue.

3. With the lower temperature comes slower germination - thus more patience and more checking.

4. But patience wins. Four days ago I spotted baby #1. The stem didn't look ridiculously long compared to the example in a video I watched, but I quickly got it into a pot and on my front window ledge where plant lights give some extra light morning and evening.

5. Today, there were two more babies. The cotyledons really do look sufficiently like the ones in the video that my confidence has risen. It's not like I need 20 of them - 3 is plenty redundancy in case I loose any. They are self fertile according to the web.

6.  I have put the tray back in. More babies are always welcome. I know people locally who like having "house plants" although it seems this will be on the large size as houseplants go. I noticed that all three that have germinated have been right at the back of the tray, closer to the center of the water heater and with lots of insulation from objects behind the little area I cleared. I need to take my chick candling/hatching flashlight down there to make spotting babies a bit easier. We will see what happens....

Unfortunately the video wouldn't let me post it here. I don't know if the URL alone will allow any of you to watch it: https://www.youtube.com/watch?v=mlJpyKEpTek
There doesn't seem to be a lot of info on the web about starting from seed instead of cuttings.

I will update again as things progress.

My wife sprouts dragonfruit seeds from EVERY good dragonfruit she eats, they are not nearly as picky about temperature as they say.

She sprouts a bunch of the blah tasting white ones, too, because are supposed to make super vigorous root stock to graft the tasty buds onto to get fruit in a year instead of five. But she isn’t that far along yet.

I don't have a heat mat or other gadgets to keep temperature constantly above 70F/21C.  However, by the sunny window, solar radiation can warm up the surface significantly.  So I was wondering if the brief hot period is sufficient to make seeds sprout and tested out the idea. I bought one dragon fruit and ate most of it. Then I smeared some pulp with seeds on a damp paper towel enclosed in a ziplock bag. I placed the bag where it received a few hours of afternoon sun. Room temperature fluctuated from 58 to 70F ( 14 to 21 C). I didn't measure the maximum temperature while in the sun but it felt warmer than my body temperature. I started on 1/16 (10 days ago)and we had stormy and cloudy days since. Total warm period would be less than 20 hours above 70F. Nevertheless, today I opened the bag and saw several seeds sprouting! If anyone has seeds that need warmth to germinate, maybe you can try this trick.

Yes, in ecosystems where people can count on frequent sunny days even if it's cold, May's experiment can work well. Alas, the Pacific Northwest rarely qualifies.  I admit we have just had a lovely run of about a week of sunny days, and the germinated babies are on my south window ledge sucking up what sun they can get. However, I'm also quite far north, with trees to the south of our house, so we're only starting to get more than a few hours of direct sun, not blocked partially by deciduous trees, or significantly by conifers.

The articles I read about Dragon fruit, suggested that they would germinate, just take a lot longer. I would add, not only longer to start, but longer for the rate of germination to increase. I went from a single baby and none for 2-3 days, to seeing 2 yesterday that I didn't have time to transplant, to there being about 10 in the tray today!

So January 15 - one baby
January 19 - 2 more to make 3
January 20-23 6 or so came along, but at least 1 didn't seem able to actually produce cotyledons
January 26  10 more - alas, I'm out of space to transplant. I started transplanting 2 babies into each pot, then today, with 10 pots on my ledge with either 1 or 2 babies in each, I have simply left the whole germination tray on the window ledge to see what happens.

I expect finding homes for the babies won't be difficult if I'm able to let them grow up a bit. I haven't seen any sign of true leaves on the early ones, but I recall it takes multiple weeks for that to happen.

To celebrate I made Mango Dragonfruit tea today for lunch. It's a commercial product, but someday, I may be able to provide the dragonfruit part of that. Mangos really don't have a hope here!

My layered system on top of the water heater definitely was worth the effort. I have a few other heat loving crops, like peppers, that might do a better job of germinating if I use the system for them also.