Window box vegetables, What you will need & how to put it all together

Last week I wrote about a solution to lack of space for growing salad vegetables faced by balcony and patio gardeners.
That was the window box vegetable garden.

As I promised here is how I would go about how to preparing a window box for veggie growing.

What you will need.


Get those bulbs and plants out, we're sowing veg, photo / pic / image.

(1) A window box, be it wooden, terracotta, or plastic, as long as it has drainage holes in its base. Of course the deeper the window box the better, but the commonly available six-inch deep boxes will be sufficient.

(2) Your compost. The bulk of the compost you will need is John Innes No. 3 compost, a soil-based compost, which contains grit for drainage, and balanced nutrients to feed your vegetables over an extended period.

In lesser quantities you will also require some John Innes seed compost, this is a traditional mix for sowing almost any type of seed as it contains sufficient nutrients for early development. Both the John Innes composts mentioned are available bagged in all good garden centres.

(3) Some water-holding gel, Swellgel being an example. These are granules which swell upon contact with moisture until they eventually hold hundreds of times their own weight in water.

The stored moisture is then released to the plant as and when it is needed, so that the chance of your vegetable plants drying out is greatly reduced. You will require about 20g of these granules for the average window box

Irish stock.

UK stock.

(4) Rough drainage material such as gravel, broken terracotta or broken-up polystyrene.

Bubble wrap

Bubble wrap, don't dump it recycle it, photo / pic / image.

(5) Some bubble wrap, you can reuse some from packaging you’ve received.

(6) Most importantly, a selection of vegetable seeds. Try to avoid large growing vegetables such as pumpkins, cabbage etc, instead select smaller veggies especially those which have been bred as miniature, compact versions, ideal for gardeners with limited space. Suitable vegetable varieties for window box growing include…

Lettuce:  most loose-leaf varieties, for example Salad bowl.

Carrot: The short rooted varieties only such as Kundulus and Parmex.

Runner bean: The dwarf varieties, Hestia for example.

Beetroot: Pronto speedy.

Spring onion: White Lisbon.

Parsnip: Avonresister, but this will still require a box deeper than 6 inches.

Pea: Half pint.

Radish: Any of the globular varieties such as Scarlet globe.

Tomato: Look towards the cherry tomatoes such as Tumbling Tom, Balconi red, and Tiny Tim.

How to put it all together.

(1) Line the insides of your window box with bubble wrap to help reduce your need to water in summer.

(2) Add a layer of the rough drainage material such as gravel, broken terracotta or broken-up polystyrene to the bottom of the window box. Opting for using broken-up polystyrene means the container will be lighter when you come to move it.

(3) Begin to fill your window box with the compost, mixed with the water-holding gel. Firstly fill it with the John Innes No. 3 compost to within 3 inches of the window box lip, settle this lightly by pressing down with your fingers, and then top up again to within 4 inches of the lip. This compost will provide strong feeding for you veg roots when they reach it.
Next, top up the box with John Innes seed compost.

Take your time and bring this to within 2-3cm (1 inch) from the lip of the window box, thus leaving a space for watering. This is the layer of compost which will host our seeds for the first few weeks until their roots dig much deeper seeking out the richer John Innes No. 3 layer.

(4) Finally for that day, place the box up on the windowsill and water it well. Watering it after you put it up, rather than before, is easier on your back as water filled window boxes can be quite weighty.

You can return to the window box the following day when all the layers have settled in and the compost surface has dried slightly. You will now have a workable soil allowing you to sow your seeds with ease.

More on that seed sowing in my next post on window box veg (part 3).

Further reading: Part 1: Window box vegetable growing for gardeners with limited space.

Part 3: Vegetable seed sowing and watering for containers.

More debate about this topic on our forum,
click The Irish gardeners forum.

Creative Commons License photo credit 1: STML

Creative Commons License photo credit 2: keli_h

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4 Responses to “Window box vegetables, What you will need & how to put it all together”

  1. Window box vegetable growing for gardeners with limited space. | Says:

    [...] Further reading: Part 2: Window box vegetables, What you will need & how to put it all together [...]

  2. Cheese Says:

    I haven’t given much serious thought to the compost I use in my containers for vegetables - do you think John Innes no.3 makes a significant difference to general multi-purpose composts?

  3. admin Says:

    Well Cheese, they are loam-based (clay, organic matter and trace fertilisers) to provide a good reserve of plant foods.
    They also hold water better and are easier to re-wet if they dry out, unlike a lot of peat composts.

  4. Vegetable seed sowing and watering for containers. | Says:

    [...] Part 2: Window box vegetables, What you will need & how to put it all together [...]

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