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Sunflower leaf discoloration

jc7843jc7843 Posts: 2
Hi all, first time poster and newbie gardener here! 

We are growing sunflowers for the first time. Here are some details: 
  • They're American Giants, grown inside my apartment in the UK, from seeds, starting two months ago. We've kept them inside due to reading online that it might be too cold with the weather we've been having where we live. The plan is to put them outside during the daytime only, over the next month or so on dry sunny days. When they get as tall as the ceiling they'll just have to be outside and whatever happens happens. 
  • They've seen a decent, though not amazing, amount of daytime sunlight (partly due to a UK climate, partly due to only having an East-facing aspect. For about half of the nights so far, I've had a mains ceiling light turned on in an attempt to give them a bit of a boost. This was just instinct, I've never read anything about this practice. 
  • The six plants are now all between 125 cm and 155 cm tall. The thinnest is 7 mm diameter and the thickest 12 mm diameter at the base. All have about four sets of leaves and all have 'shed' they initial set of leaves. 
  • We have been watering them between once a day and once every three days, depending on the weather. We've tried to keep at least the top one inch of soil constantly moist/ damp. We are really worried about underwatering and overwatering. Some days have seen totally dry soil on the top 1 cm, some days have seen some specks of white-coloured mould on the top of the soil. Most watering has been done in the evening which I just read is maybe not as good as in the morning so we'll adopt that approach from now on. 
  • Some of the plants are in pots with no drainage, some do have drainage holes. However, we've never seen water emerge from the drainage holes after watering. We thought this was a good sign, as it may mean we're not overwatering, but then the mould would presumably contradict that. It gets very warm in the apartment and the air is still. We know that outside would be ideal but have just been waiting for better weather as we'd hate to kill them all off with rain, wind, and/or cold. 

Our concern is...

The leaves on all of the plants have in the last week or so become discoloured (see photos). The problem has been getting slightly worse over time I feel, so we are really keen to identify and act on this problem fast. We massively appreciate your help, so thank you in advance! 


  • BrexiteerBrexiteer Posts: 955
    They will be fine outside. Mines been out for the last 6 weeks 
  • DovefromaboveDovefromabove Posts: 83,739
    Totally agree ... mine are outside planted in the garden and have been for a while. Harden yours off and plant them outside ... they need more sunlight than they are getting.

    Also exposure to breezes will strengthen the stem, bug yours will need more support than usual because they have been grown indoors, so make sure they have sturdy stakes. 

    Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.

  • jc7843jc7843 Posts: 2
    they need more sunlight than they are getting.
    Many thanks for your quick reply. Do you think this is the reason for the discolouration? Or was it just a suggestion for good practice? 
  • DovefromaboveDovefromabove Posts: 83,739
    Can’t can’t really tell but I suspect that leaves that are very tender from having been kept indoors have now been scorched by strong sunlight coming through the window. 

    These are some of mine 
    sturdy enough to manage without stakes so far, even in a windy Norfolk garden 

    *note to self : (I must weed out that chickweed 🙄)

    Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.

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