What is the optimal raised bed depth for Brassicas?

Question

I built two large raised beds in my new garden, but couldn't manage to fill them to the top. The bottom is closed with cardboard and has a layer of prunings and hay 1-3 cm deep. I planted anyway 10 young cabbage plants, 10 kales, 10 broccoli plants. I tried to gather the compost around the points where I would put the small plants. In their actual state, they have an available depth to root of about 7-8 inches, and space on the side about 50cm.

• Would that result in any problem for the plant growth?

• If I am to add some more soil later on, should I replant everything, or I can add directly on the top of the actual "small mountains" on which the plants are?

Notice: I live in Bristol, UK, and here it rains quite a lot throughout the year.

Answer 1

On the depth of the beds, that is very shallow. Fortunately, you can add compost as the plants grow, hilling it up around the stems. The plants will grow roots into the new compost, building plant strength.

Because that is a possibility, I'd recommend it over replanting the starts, as that will set them back a bit.

What looks like a bigger issue is the amount of light in the area. Those stone walls are very protective, and will help during hot summer months, but during spring and fall, they may cause some etiolation on the vegetables. The trees all around don't help either.