I have built a seed germinating box in which the soil will be heated by a heat cable that will be controlled by a thermostat. what temp should should i shoot for?I need all the input i can get.Help me out fellow Pollen dobbers…Larry Popwell
Most important question- will you cold stratify first? Alain Meilland in his book claims that they sow seed directly, but that is in a mediterranean climate and yours is LA I think. Generally things go best at 4-8 C, roughly 40-45 F for some length of time, like 1-3 months. After that warm is good. On the home page under articles there is a review that I wrote covering all the literature up to last year. Some northerly species must have cold, some tropical types like teas need no chill at all. So it depends a good deal on whether you are breeding from northern or southern derived strains.
Larry, I’m in Los Angeles. I sewed straight from the plant to soil in 2009/2010 and they germinated beautifully. Not just moderns x moderns, but Hugonis and Fedtschenkoana seedlings, also.
I cold stratified this year due to early hip abortion and early harvest to avoid loss of the remaining hips to “wildlife”. We get chill hours, not enough to bring a 500 chill hour stone fruit to perfection, but we do usually get enough for 300 chill hour varieties to bloom and fruit well.
Sorry, Kim, I meant Louisiana, not L.A. Your fine city is a med climate place. Meilland is not clear in his book whether there is heating in the greenhouses where he sows the seed initially. Back in the 30s in San Remo Italy, direct planting was very effective. I think it’s more than just temperatures for stratification, perhaps some combination of warmth during maturation, and day length added in. Vernalization is a really complicated process.
I have cold& warm stratified…now im getting ready to plant … my question now is what is a good soil temperature to germinate in… Larry
I think you’ll see that a wide range of temps is OK. I reviewed a lot of papers doing different things. But average room temp of say 18 C (68 F) is good. Don’t make the roots too warm or you will have terrible problems with drying out as water moves from warmer soils faster. And higher temps promote spider mites if you should ever get them in, which happens fairly often unless you have a strict quarantine of your growing area from all other plant life. For most plants an optimum growth temp is around 25 C ( 75-77 F). But if light levels are low you get a better result at cooler temps. Too warm under low light makes leggy plants. That’s why for most purposes below 70 F is better for the nominal room temp. And not much higher for the root temp.
Don’t forget that light, even fluorescent which puts out about zero heat (IR) as such, warms the soil and leaves. Put a thermometer down on the surface and you’ll see it is warmer than the average room air, by several degrees, varying with the efficiency of air circulation. More air circulation makes more drying too. So you have to trade off several factors at once.
You can prevent spider mites by sterilizing your potting mixture. Wet it very well in a baking dish, cover it with foil and bake off most of the water at 250F. Clean the seeds with soap and water before you plant them.
Here is what I go by for temps on modern rose seeds.
40’s for stratification, 50’s for germinations and 60’s for growing. I plant my seeds in sand I get from the beach.
Thanks everybody… Keep them coming… Larry
You can prevent spider mites that are carried by the potting medium, or the seeds that way (baking soil, washing seeds). But my point was that they sneak in from other things, even plants that may be showing few visible symptoms. And hot and dry is their favorite climate.
Depending on what potting medium you use, cooking can be more or less detrimental. It does things to soil structure if it is soil. Affects organic matter depending on acidity, may tie up added fertilizers by speeding the precipitation reactions. And if the medium is one like I use with added microbes to control damping-off, of course it destroys them.
So the pros and cons have to get considered.
I am living/growing roses just midway Meillands historical location at Cap d’Antibes and actual one at Le Cannet des Maures.
Meilland does not heat seedling greenhouses except for phytosanitary purpose. That is drying wet foliage on a rainy/cloudy spell.
Here late december to january sown seeds experience changing night temps around light freezing that allow vernalisation for the first two monthes. Temps naturally get higher by germination and growing time. Good air circulation for dry foliage and allways wet enough medium are key point. Seedlings stand easily some light late frosts.