What I learnt today: preparing a bed for lawn seed and broadcasting

Today – for the first time in about seven months – I sat in a classroom with the other apprentices on my course. It was amazing. I had missed talking as a group, finding out what we had all been up to and working together. These kinds of college days remain a rarity, as we will be studying from home every week except for practical days. Today we worked on the following:

  • Soil cultivation, preparing for a lawn
  • Seed broadcasting
  • Calibrating a broadcast spreader
  • Hand scarifying with a rake
  • Hand aerating with a fork
  • Top dressing
  • Ident walk

We kicked off the day with some soil cultivation, preparing a bed for lawn seen broadcasting. Preparing a bed for any use is time consuming and – in some cases – back breaking. For example, if the practical test pare required a 20m² bed to be prepared for planting vegetables, good luck! This likely means you will be double digging the area or at least digging to a depth of about 30cm. Then, you will rake this over, tread it in and rake level.

Fortunately, lawn establishment only requires the top layer of the soil for the roots. As such, we worked on simple digging, which involves inserting the bottom third to two thirds of a fork into the soil and tousling it. This allows for gaseous exchange in the soil and alleviates compaction without digging too deep. After that, we roughly raked over the soil with a soil rake, combing through it and flicking away any large rocks, while also giving larger clods a good bash to break them down. Then comes the penguin walking, or treading in, which involves putting all of your weight into your heels and methodically taking very small steps across the soil. This presses the soil in and firms it up as when you cultivate, it adds more air into the mix and raises the level.

Once we made our way zig zagging back and forth over the bed once, we used an industrial rake to rake it over again. Unlike soil rakes, which have wider teeth and are primarily used to move material, industrial rakes have very fine teeth and are about 1m wide. They are used to break down clods and gently create a level without moving the soil around too much. Importantly, they also have a long flat bar when you turn it upside down, allowing you to smooth the surface of the soil and create a presentable, flat level.

Buddleja ‘Buzz Velvet’, Hand scarifying and aerating, Preparing bed for lawn planting, seed broadcasting and pretty patterns by Jordan.

Once we had finished leveling off, we began working on broadcasting grass seed. As grass seeds are so fine and accurate broadcasting is important to grow a strong, consistent sward, measurement is key. As per the box instructions, the grass seed had to be cast at the rate of 30g/m². Our prepared beds were 4m², which made it easy to make out these 1m² boxes, as all we had to go was place a stake in the middle of the original square.

To provide even distribution, the broadcasting is done in two passes (i.e.: from North to South, then from East to West). This means that the volume of seed recommended per m² needs to be halved. In our case, this means that 15g of seed will be broadcast per metre squared. When sowing seed, it is important to factor in a certain loss of seed to animal feeding. As such, it is common practice to add an extra 10% on top ‘for the birds’. This made our total seed volume 33g/m² and 16.5g per pass.

Broadcasting seed is best done with broad passes, using your hand or a cup/ container. Try to keep each pass as even as possible and fill in any gaps when making the final pass. When all the grass seed had been broadcast, gently rake over the soil to lightly cover the seeds. The last step is watering, very lightly, to avoid puddling, seeds pooling in one are and the soil level being disturbed. Use a rose adapter on your hose or watering can to diffuse the water and pass over it a few times with a spray, as opposed to a drench.

I had a wonderful day working with my classmates again and having a laugh while we learned some new skills. I can’t wait for our next practical day next month!

The brassica ‘triangle of U’

Today was our first day back at college since we broke up for summer. And by ‘back’ I mean back behind a computer studying from home. I have been missing the learning aspect of college, as well as the day of respite it offers from the working week. Nonetheless, I do miss our classes in person, when we could chat during breaks, wander around the college grounds and learn about plants the best way I know: through touch, smell, sight, sound and, occasionally, taste. Next week, we will get to do this, as we go for a safely distanced day of practicals. I can’t wait.

Today, we covered tonnes of content, from legislation and health and safety to plant nomenclature and how much it costs to plant a hedge (a lot, if you were wondering). One thing that jumped out at me – and by that I mean: confused me – was the concept of the ‘triangle of U’ when talking about brassicas. I’m going to do my best at explaining what exactly that is and hopefully help myself figure it out along the way. Just to warn you, as much as the ‘triangle of U’ sounds like the name of an angsty indie song, it’s actually very scientific and delves into the evolution of plants. So strap in!

The Triangle of U is a theory first published in 1935 and named after the botanist Woo Jang-choon’s Japanised name “Nagaharu U”. This is a theory about the evolution of plants in the brassica family (Brassicaceae). The basis of this theory is that three ancestral brassicas, which were diploids, combined to create three common brassicas, which were tetraploids. Before we jump into the ins and outs of the theory, let’s get some terminology out of the way:

  • Genome: this is the genetic material in a living organism
  • Diploid: ‘Ploidy’ refers to the number of complete sets of chromosomes found in the nucleus of a cell. In somatic cells, the chromosomes exist in pairs. This is known as diploidy, and the cells are referred to as diploid (2n). Except for human sex cells, which are haploids (containing a single set of chromosomes), the rest of our cells are diploid, containing chromosomes from each of our parents.
  • Tetraploid: While diploid cells have chromosomes in pairs, polyploidy (when a normal diploid cell acquires one or more additional sets of chromosomes), means that some cells can reach up to twelve sets of chromosomes. Tetraploid cells have four sets of chromosomes.

The relationship between these brassicas is best shown through the diagram below:

Triangle of U Simple1
Adenosine at English Wikipedia based on work by Nashville Monkey at English Wikipedia / CC BY-SA (https://creativecommons.org/licenses/by-sa/2.5)

While this may look intimidating, once you break it down, it becomes a lot easier to understand. The AA, BB, CC, AABB, etc. differentiate between the three diploid species (AA, BB, CC) and the remaining tetraploid species (AABB, BBCC, AACC).

After that, it is important to note the ‘n=’. This is simply referring to the number of pairs of chromosomes present. In Brassica rapa (or AA), for example, there is a total of ten pairs of chromosomes. In the tetrapolid cells of Brassica juncea (or AABB), there is a total of 18 chromosomes present, as the number of chromosomes in AA and BB have combined.

What we observe is that the diploid species, or the Brassica nigra, Brassica rapa and Brassica oleracea, are the ancestral genomes, with only set of two chromosomes. When combined, these produce Brassica napus, Brassica carinata and Brassica juncea, species with tetraploid cells.

Since this discovery, an ‘allohexaploid’ has been created, which would sit in the middle of this triangle. It combines the three different sets of chromosomes to create AABBCC.

If your brain hasn’t melted by now, here’s the horticultre element: these derived species make up the bulk of the brassicas you know and love today. Brassica oleracea has many cultivars which produce these favourites: brussel sprouts, broccoli, cauliflower, kohlrabi and more!

I can’t say I have a comfortable understanding of this just yet, but hopefully I can review this in a few months and make a little more sense of it then!