I've had this problem a few times and have usually found that gently pressing on the compost can be enough to get the capillary action going. Failing that, do the first water using a really fine rose or even try spraying the compost quite heavily with a hand sprayer. Subsequent waterings from the bottom should be fine so long as the compost doesn't dry out again.
These days, if the compost is in the least bit dry, I tend to fill the seed tray with compost, stand it in a tray of water, water it from the top, leave it to soak through for 10 mins, then leave it to drain for about 20 mins, then sow the seed and pop it back in the watering tray for a couple of mins until the surface looks moist, then leave it all to drain for 20 or 30 mins before popping in the propagator / wherever. Sounds a faff but it isn't really - if you're sowing several trays at the same time you get a nice rhythm and routine going.
Heaven is ... sitting in the garden with a G&T and a cat while watching the sun go down
Capillary action - obvious really but never thought to check whether the OP had considered that. Just as well that at least @Topbird and @Busy-Lizzie still have working brains
I used a fine rose in the end @Busy-Lizzie. Although I saw your post later, otherwise I would’ve done what you said about leaving the tray in water as well, to see if it started soaking it up. Will try this next time, probably tomorrow.
@Topbird thanks for the tips, I like the idea of the heavy misting. I’ll bear that in mind.
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These days, if the compost is in the least bit dry, I tend to fill the seed tray with compost, stand it in a tray of water, water it from the top, leave it to soak through for 10 mins, then leave it to drain for about 20 mins, then sow the seed and pop it back in the watering tray for a couple of mins until the surface looks moist, then leave it all to drain for 20 or 30 mins before popping in the propagator / wherever. Sounds a faff but it isn't really - if you're sowing several trays at the same time you get a nice rhythm and routine going.
It's all about getting that capillary action going...
Just as well that at least @Topbird and @Busy-Lizzie still have working brains
@Topbird thanks for the tips, I like the idea of the heavy misting. I’ll bear that in mind.