One or two? Counting cotyledons

A quick botany lesson. Flowering plants ( not including conifers and their relatives) can be divided into two main groups depending on how many seed leaves they have: there are the monocotyledons with one seed leaf and the dicotyledons with two. The number of seed leaves is not the only thing that divides these groups. Monocotyledons can be distinguished even as adult plants because they have usually have narrow, grasslike leaves with parallel veins and flowers with parts in multiples of one or three – think grass, crocus, lilies. Dicotyledons have broader leaves with netted veins (tree-like in pattern). The leaves can be and often are, divided into leaflets. The flower parts are usually in multiples of four or five. They are frequently woody while monocotyledons are rarely so but frequently bulbous.

Now most bedding plants are dicotyledons and when you transplant them you hold them by their seed leaves (never the stem which you can bruise)*. The true leaves, which resemble the adult plant, emerge from between the two seed leaves which rarely resemble the adult leaves. Sometimes things get a bit complicated and the seedlings have three seed leaves. I have seen this a lot on China asters (callistephus) and sometimes on French and African marigolds – it seems to be an Asteraceae thing.

But as I was pricking out (transplanting) a batch of ‘Fruit Punch’ stocks I noticed something very odd – about 25% of them only had one seed leaf. Now this was worrying because the young plant has to grow from between the two seed leaves and if there was only one – where was the plant going to appear from?

At first I was going to discard them but then decided to prick them out separately so I could see what happened to them.

Now it is never a good idea, when pricking out mixed-colour seedlings to sort them out and start with the biggest and leave the smallest to last. This is because the plants of different colours in a mix may germinate slower or faster or be more or less vigorous and if you select only the biggest you may end up with the least attractive colours. I always used to wonder why, when I planted out trays of mixed petunias or busy Lizzies all the whites would be one end of the bed and all the reds at another. I used to blame it on sod’s law but it was actually my fault for being selective with my seedlings and starting off being lazy and pricking out all the big ones and then, realising I needed them all, finally dealing with the weak ones.  So prick them out as they come if you want a well-balanced mix of colours.

stocks one leaf

Anyway, I planted out the stocks on Friday and I am pleased to say that, somehow, the seedlings with just the one seed leaf all developed into healthy little plants, as the photo above of them two weeks ago shows. Going against my own advice, I am planting these out separately because I want to know if these are all one colour! They are being planted in rows for cut flowers so it won’t matter too much if they are not perfectly mixed. Time will tell.

* If you break off a seed leaf when you are transplanting them this will not do the seedling any harm although it will slightly weaken them obviously. This is not the same as these seedlings which all emerged with one seed leaf.


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3 Comments on “One or two? Counting cotyledons”

  1. Georgiana
    May 10, 2014 at 12:18 am #

    Hey! Do you use Twitter? I’d like to follow you if that would be okay.

    I’m undoubtedly enjoying your blog and look forward to
    new updates.

    • thebikinggardener
      May 11, 2014 at 9:14 pm #

      Hello and thankyou for the nice comment 🙂 I do not use twitter. I have been away at Garden Show Ireland so have not updated this weekend but will post a report in the next 24 hours.

    May 29, 2014 at 6:15 am #

    Fantastic web site. A lot of helpful information here.
    I’m sending it to some friends ans additionally sharing in delicious.
    And of course, thank you for your sweat!

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