Xerophyte: It isn't so much that I *need* extra heat. I live in Satna Monica, where this time of year highs are in the mid 70's and lows are in the low 60's. I'm just trying to get a plant established as quickly as possible, and soil temperature is a key factor in triggering root growth. I figure if I can get the soil to stay above 70, I'll have a better chance of getting some roots and getting them more quickly. If I do go for a mat, I'll be sure that it comes with a thermostat. Caudex1: Thanks for the info. I still don't know if I should bother with a mat, or just move it out into the sun. I know the previous grower wasn't able to give it much direct sun, so I'll probably build a little sun screen for the plant, but try to put it somewhere that the sun shines directly on the pot itself. In a related topic, is the culture for P densiflorum v brevicalyx the same as P densiflorum? I can't imagine there would be any real differences...

What kinds of plants are you growing? I think that generally, one is encouraged to remove the heat mats for two reasons: 1) higher heat encourages faster growth, but if light is insufficient to support this growth, the plants will tend to be spindly, and 2) as the plant growth increases, water demand increases, and bottom-heat plus increased water demand will make the plants dry out faster. I usually find that my fluorescent tub lights put out enough incidental warmth to keep my seedlings in the basement warm enough. But I have also in the past draped my lights with reflective mylar with a small fan for air circulation. This would have the additional advantages of higher light levels due to the reflectivity of the mylar and encourage sturdier plant growth by the slight agitation from the air movement. I might experiment with your latter idea if it is not too much trouble.

"...Is this true?" My guess is that is an attempt by the maker to avoid liability. Seriously, if a horticultural heating mat can't be left unattended - it's useless! I doubt you'd have problems, but you gotta wonder about how much trust you an put into a product which you can't leave unattended. Keep in mind though, that you should be extra careful, whether attended or unattended, using any electrical device around water. In the past I've used heating pads made for sore muscles. I would recommend that before you sow, you put a thermometer in the soil to make sure the soil temp isn't too hot. If it's above what you want (depending on factors such as what seeds you are sowing) place something to provide a layer of insulation. You can usually even use a couple of pencils to lift it up off of direct contact with the pad or metal pan you described. If try a few things, you'll find something that works well. Again, make sure it's safe.

all mats are different. do you have a temp setting? hi-low at least or smth like that? very expensive mats have thermostats. i'd advise to get a temperature reading at the bottom of several differently sized pots using kitchen instant read thermometer. Which is what i do to get an idea of how much the pots heat up. the bigger pot the lower the temp will be at the bottom, since the soil mass is larger, so the heat dissipates more. for small 6" pots it can go up to 95F on high and 85F on middle setting (i just use drugstore heating pads) - that should not be a problem, provided you are waking up/rooting tropicals. the roots outside in tropics heat up that much daily. the bigger 8" pots heat up only to 80-85F which is a very good range for most tropicals and seed sprouting too. pots bigger then 8" are quite heavy, so i don't put go above that size. my heating pads have soft padding around them. so it's not just the hard rubberized surface - so i don't know if yours will be heating up higher if it's bare. i put up on mats flowering anthuriums, African masks (that's how i wake them up into growth, rooted or not), anything that i just repotted like acalyphas, philos, other anthuriums, aglaonemas, aralias, tropical hibiscus, clerodendrum, even thanksgiving cactus. anything that likes really warm temps of say 80s in summer with high humidity. i have never put any orchids on mats though. may be ask in the orchid forum? hoyas should be ok, but i haven't done them, since my mats get very busy in spring. i also root caladium corms, begonia tubers and dormant amaryllises every year. the main thing to worry about is moisture levels - the higher the temps the faster the plants will take up water. so you really need to watch to make sure they don't dry up. i usually water with very warm water too, so as not to bring the temps down. condensation is usually high , but it's been ok for the plants mentioned. sometimes i do punch holes in tents to allow some ventilation. but not for all - African masks for example need 100% very hot treatment to wake up with lots of water. the vent holes are better then just lifting the dome - since that will temps down around the plants fast - which i think is not so desirable, unless they need big temp drop for the night, for example (orchids?). it's better when pots sit directly on the mat with the bottom in contact, not on a saucer. but obviously you need to keep the mat dry and you need to water - so i put them in shoe storage boxes - the plastic sides hold the small pots securely too and i set up individual or common tents. supermarket flower sleeves work well as stiff tents over each pot. you can roll them closed or punch a few holes in them when needed. or you can open them up on top altogether - there will still be enough humidity inside the tall sleeve.