Penstemon seedlings

I am in the process of growing alot of seedlings under lights. I have succesfully grown dianthus deltoids, campanula carpactica, lobelia trailing type, snow in summer, aubrita and pansies etc under the lights but for some reason my pestemon seed leaves go brown and shrivel and the seedling dies. I thought perhaps it was my lights which I found strange as penstemon are from a much hotter brighter climate than most of the other seeds so i took the lights off and placed on windowsill, However ones that have sprouted since the others died are taking ages to develope a true set of leaves and some are starting to die. What am i doing wrong?



  • not sure,perhaps its to hot without ventilation or perhaps changing temperature to sudden.

  • There's really good advice about how to grow penstemon seedlings on ehow.

    Penstemons need light, free-draning soil and should not be watered much, although not allowed to dry out. I just wonder whether the heat from the lights, together with the water in the compost, made it too warm and humid for them.

  • nutcutletnutcutlet Posts: 24,058

    Penstemons germinate very easily without artificial assistance, maybe they thrive on a harder lifestyle. 

  • cairnsiecairnsie Posts: 389

    They germinate no probs maybe i am overwatering them. Thanks for the help i still have quite a few alive with there seed leaves ill just plonk them on the windowsill and see what happens

  • cairnsiecairnsie Posts: 389

    Thanks for the help

  • cairnsiecairnsie Posts: 389

    I tried again same happened this time kept soil much dryer still used lights so i guess it must be lights will try to use normal light from windows with this next batch. Its says on the rhs website to sow in a coldframe has anyone done this. Its weird there failing i have grown lots of different plants and they have all done well.

  • Liz 9Liz 9 Posts: 2

    Hi, I am having exactly the same problem as you so would be interested to hear how things progress.  I am growing Penstemons on the windowsill (no artificial light) and they are germinating then dying off as seedlings (don't think I've allowed them to get too dry or overwatered).  Other seeds are doing fine.

    Wonderd if it was getting too cold in the evening so will attempt to re-locate new batch at night if this new batch geminate.  Interested to hear your comment about planting in a cold frame so might sow a few more today and try them out in a cooler environment as a test to see if I've been killing them with kindness!

  • I do this, Liz. I have a dedicated spot in the kitchen where I put seedlings overnight, away from windows. An alternative is to cover them overnight and I'm also trying that this year.

  • P.S. They grow quite easily from cuttings if you already have penstemon plants.

  • cairnsiecairnsie Posts: 389

    I am onto my third set this time not using any lights just the windowsill. I dont think its temperature fluctations as my spare room keeps a constant and the lights kept the seedlings warm. They were fine and got to the point of just producing there true leaves and died. I have cuttings of penstemon and they doing fine. I figured it was the lights scorching the leaves, perhaps your window has too much direct sunlight as I kept my first set of seedlings very moist, the second set on the dry side so its not moisture levels. My third set have not yet produced true leaves. The leaves just shrilveld the actually seedling stayed upright for a while after this before dying so I dont think it was damping off. I am hoping this set will survive i will see. Another one of my theorys was the soil wasnt deep enough so this time i have sown them in small pots. I have been successful with a wide variety of other seeds so I dont understand why I am having trouble.

  • I'm trying them this year for the first time (electric blue and pina colada pink) Mine were sown in a heated propagator but as soon as  they started to germinate I took the pots into the (unheated) GH. They're still tiny but seem fine. I put a plastic propagator lid over them at night...and the GH still has bubble wrap up which probably prevents too much light getting through.

  • cairnsiecairnsie Posts: 389

    The same thing is starting to happen again. I just dont understand it everything else is doing really well. These have not been grown under lights

    So far i have eliminated: Growing under lights, container depth, moisture levels.

    I dont thinks its damping off as its the leaves that go brown the stems dont collapse imediately. The window they are on is west facing.




  • nutcutletnutcutlet Posts: 24,058

    I sow themin my cold greenhouse when winter has gone away. More light avaiable then as well as warmth.

  • cairnsiecairnsie Posts: 389

    Ill try that as a last resort as i dont think these are going to survive.

  • Looking at the photograph the seedlings appear to be drawn and leggy. I suspect it's a combination of temperature and light. Too much of the former and not enough of the latter.  Did you take them off heat as soon as the first seedlings appeared? The ones that have not shed the seed case are not as drawn as the dying ones which seems to indicate to me that you left them on the heat whilst more seedlings appeared. Drawing (or legginess) of seedlings also indicates lack of light, this condition is exacerbated by too much heat.
      Have another go. As soon as the first seedlings appear reduce the heat, if possible to around 15 to 18 °C and get them into good light, preferable not a window. If you don't have a greenhouse or cold frame line a cardboard box with cooking foil, put the seedlings in that and cover it with a sheet of glass or plastic sheet. Lift the whole box in at night and in rainy weather. This last bit is to keep the box dry.
    Good luck.
  • B3B3 Posts: 4,994
    I am by no means an expert, but I rooted penstemon cuttings in a glass of water, potted them up when they had a bit of a root system and they were fine. Some were then planted in the garden and some left in pots outside, but it remains to be seen whether they survived the winter
    The same worked for gaura as well. 
    In London. Keen but lazy.
  • punkdocpunkdoc Posts: 5,116
    Cuttings are a much better idea. They are very easy and offspring will be identical to parents.
    Either use B3's method, or grow in soil, which is what I do.

    There's one more kid that will never go to school
    Never get to fall in love,never get to be cool.
  • CagzoCagzo South WalesPosts: 139
    I tend to agree with you Punkdoc. My cuttings were always successful,but this year I've planted seeds,kept on the kitchen windowsill. They are on the third set of leaves,and seem quite strong,I'm hoping for varying colours,it was a free packet with a garden mag!
    When I did cuttings,I dipped in rooting powder,and put 3 to a 4" pot,then put them in a cellophane wrapper from greetings cards.I found this didn't cling to them like polyethylene.

    The whole truth is an instrument that can only be played by an expert.
  • hogweedhogweed Central ScotlandPosts: 2,513
    I took penstemon cuttings last year as they are not too hardy here in Scotland. Popped them under a shrub for protection over winter but didn't factor in a foot of snow. Doubt if either the cuttings or the plants will have survived!
    'Optimism is the faith that leads to achievement' - Helen Keller
  • B3B3 Posts: 4,994
    edited 10 March
    Hogweed, read your signature and have faith ;)
    In London. Keen but lazy.
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