Salad Days: There Are More Questions...

With most experiments I've ever conducted (either in a professional capacity or my own amateurish potterings), the results often garner more questions than answers*. You may recall I concluded in last month's Salad Days there may be a slight advantage if winter indoor pea shoot growing is started off in a propagator.

However this answer inspired the following additional questions:
  1. Were the results repeatable, or a one-off?
  2. Would later growth or potential cropping times be affected?
  3. Would using a heated propagator make a bigger difference?
  4. Is there a difference in windowsill growing upstairs vs downstairs? (I was speculating the difference in height might have helped January's emergence/growth)
  5. What difference (if any) did soaking the peas first make to germination times? 
  6. What difference does windowsill aspect make? (I'm currently using south facing windowsills; I found last year I had to switch to westerly when the light and heat in March seemed too strong for my shoots)
So this month I've been trying to find answers to questions 2-4 (entirely) and number 1 (in part) and I've put questions 5 and 6 away for later. I've been  measuring the growth of the original peas and also started 3 new identical pea trays (same types of tray, growing media and the same seed variety and numbers used): 2 for upstairs (1 in a heated propagator, the other in the unheated propagator used last month) and 1 for downstairs (in an unheated propagator placed in the equivalent position on the windowsill). The above picture shows the upstairs peas happily growing away post emergence and after they'd reached the height of their respective propagator lids earlier this week.

Results of the growth observations (Question 2)

Although both trays had their lids removed from the first measurement onwards, the increased growth observed with the peas started in the tray with the propagator lid on continued for the rest of the growing period. Whether the increased yield at the time of picking is significant needs further investigation and is probably minimal for my scale of growing. NB some of these shoots were used to make the yummy Sprouted Lentil and Pea Shoot Salad :)

Results of the heated vs unheated propagator and upstairs vs downstairs emergence rates (Questions 3 and 4, plus a little bit of 1)

The peas started in the upstairs non-heated propagator emerged the earliest and have the highest germination rate. There is very little difference to choose between the emergence rates for peas placed in the kitchen (downstairs) non-heated propagator and the upstairs heated propagator. I'm now measuring growth rates and on average so far they're at 85mm (kitchen) and 105mm (upstairs, both propagators). I'll continue with these measurements over the next few weeks.

The pea emergence start day and overall curve for the non-heated propagator is similar to that seen last month, so it looks like the results are repeatable for propagator use at least.

Overall verdict

It's been an interesting few weeks conducting these experiments. It looks like I can save some of my electricity bill by not using heat for my indoor growing**. I like that I managed to pick my pea shoots a week earlier than last year, though whether I've significantly increased the actual crop obtained each time is questionable (though on a commercial scale there should be an advantage, they will be using giant propagators i.e. greenhouses and polytunnels ** after all...).

However for both the upstairs vs downstairs comparison and cropping times, there are too many variables not eliminated from these experiments. This year's earlier pickings could be due to e.g. better light levels this year; the poorer performance downstairs seen so far might not be due to lower light levels as I first pondered, but to lower temperatures (heat does rise after all), or both.

What is certain though at the end of this post, is I still have more questions than answers!

* = A bonus point to everyone who remembers this was a song by Johnny Nash ;)
** = so I've started off my chillis instead
*** = I don't have either of these, hence my windowsill growing and propagator ponderings

One further question: how's your salad progressing this month? Tell all in the comments, or add the link to your blog post in Mr Linky below...


  1. Lovely looking pea shoots VP, I've got as far as getting some dried peas... Not much to say about salad this month, it is all rather slow, but at the end of a rather long post that is mostly about foliage I have added an update. Am off to sow peas, and not in the propagator which is good, more room for other things!

  2. Hi i've just found your blog and this post is really interesting. I have never really studied what grows best where, i just do it, so it was lovely reading about your experiment. Thank you

  3. Complete admiration for your dedication!

  4. gorgeout peas! mine are on a heat mat which perhaps your observations of less-heat-downstairs indicates I should unplug. Mine are too slowly emerging IMHO. Great food for thought! Thank you for your research.

  5. Your experiments are indeed fascinating!! I was convinced that my heated propagator was the bees knees and would ensure quicker germination but perhaps that's just another myth?!! My salad is doing fine despite me sowing it much later than I ever have done before, in December. There was a moment a week back where I thought it wouldn't make it but it's looking great now. Really turned a corner. I am intrigued by all this peashoot growing though, do you eat the shoots?

  6. When you say unheated, what kind of temperatures are we looking at?

  7. Update on my salad challenge just posted - should soon be able to start growing proper lettuce now that spring is nearly here. Champing at the bit....

  8. Janet - just read your post, you've had a lot of fun this month!

    Joan - peas don't mind slightly lower temperatures, so I reckon our centrally heated home is sufficient without the need of extra heat from the propagator

    Anna - your propagator is great for starting chillis, peppers, aubergines, tomatoes and cucurbits all of which need higher soil temperatures for germination. Since this experiment finished I've proved heated propagator chillis emerge much faster than their unheated propagator cousins.

    NMK - I can't say for sure as I haven't been measuring the temperature. It will be at least 18 degrees centigrade during the day as that's what our thermostat is set at. However with sunny days + a south facing windowsill + double glazing it must exceed that quite a bit. We found last year that very cold nights can grind things to a halt if you have thick curtains. Even with double glazing windowsills get quite chilly at night. I'm sure using an unheated propagator has meant night time temperatures have been maintained at a relatively warm level.

    TTG - thanks for your post. Yes it's proper lettuce sowing time now - only indoors though :)

  9. Oops managed to miss a couple of you in my earlier reply :(

    njgf - welcome and thanks :)

    Angie - thanks. I need to do much better science with this stuff though!

  10. Finally linking you can see nothing is happening but I have my veg garden plans finally and I am starting seeds indoors.

  11. Donna - it was great to see your plans for the year :)


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