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Overwintering cacti seedlings

I am growing cacti from seed for the first time and have a tray of very small seedlings. I don't know what the temperature, light or water requirements are for the winter, however and I was wondering whether I should invest in a heating mat to go under them as they will be kept in the greenhouse which will be heated to 5 degrees. Most of them also look quite red even though I have kept them out of the light quite a lot. Any advice would be very much appreciated. 


  • soulboysoulboy Posts: 429

    Here's a link to an excellent guide to growing and caring for cacti grown from seed:

    October to the beginning of March is the dormant period for cacti and it's usual not to water them during this period, unless they're in a hot environment e.g. centrally heated room when an occasional light watering might be appropriate.

    Most of my cacti are in the living room and get no water in that period and are thriving.

  • I don't understand about keeping them out of the light? Surely cacti, other than the Christmas cactus type, need as much light as possible especially at this time of the year when they are not quite dormant yet.

    My own cacti are the more hardy types and are in a cold greenhouse with no artificial heat what so ever, but like soulboy I will cease watering completely for from about now for the next four months.

    I am not sure whether such extreme drought is suitable for small seedlings which have less water reserves and would suggest that on complete drying out they are given a watering, perhaps every month or so overwinter.

    As long as your greenhouse is capable of maintaining 2 or 3 degrees c on the very coldest nights I would forget about the heating pad.

  • soulboysoulboy Posts: 429

    Yes, Roger, it's not desirable to keep them out of the light, as the article points out the germinated seedlings need light, but not direct sunlight. . Perhaps that's what the OP meant, that they hadn't been exposed to direct sunlight.

  • Thanks soul boy for your explanation. I never avoid direct sunshine even for most - but not all -normal seedlings. I had better read your link belatedly! Thanks

  • thank you  

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