A window box brings joy and spring colour | Gardening advice

After a seemingly interminable winter, this weekend is finally a good time to start planting up window boxes, and with two handy tips, you can have them churning out a conveyor belt of colour right up until the first frosts.

Gardening in containers offers a range of benefits. It frees you up to grow plants that might not otherwise thrive in your local soil type; you can raise colour to eye level and beyond, allowing you to decorate whole buildings in living green; and, of course, it provides even those with no garden at all a vital horticultural fix.

However, container-growing does come with two hefty downsides. Their comparatively tiny volume compared to garden soil means they will always dry out quickly, which can mean daily watering at the height of summer. The same goes for fertiliser, which not only is a lot of extra work, but extra expense, too. This combination means that many bedding plants – that have been selected for their sky-high metabolisms to fuel fast growth – can run out of steam from July. But things don’t have to be this way.

First, consider your container. The larger it is, the slower it will dry out, with the added benefit of being less prone to wide temperature fluctuations, too, which can hamper growth. It’s also worth picking a pot made from nonporous material. Unglazed terracotta is filled with tiny pores, which means moisture constantly leaches out. Metals, such as aluminium and zinc, can heat up too fast on warm days and burn delicate roots. Resins and composites, for me, provide the best of both worlds. They not only seal moisture in, but often have thick walls, too, which acts as insulation.

Now, let’s talk growing media. Traditionally, they would have been compost-based, made up of plant fibres, such as environmentally disastrous peat, or wood pulp. These were introduced in the mid-20th century because they are lighter weight and thus cost less to transport, and by extension are more profitable for corporations to flog. Containing few of the minerals needed for plant growth, they conveniently also lock you into the need to buy fertiliser. This breaks down over time so it needs to be repurchased every spring. Growing media also have the infuriating habit of being hydrophobic when allowed to dry out, actively repelling water instead of absorbing it.

Soil-based mixes, by contrast, suffer none of these problems and are usually sold under the label John Innes (a generic term that refers to soil-based formulas – it’s not a trade name). Now, of course, there is a balance here – larger boxes filled with soil-based media will be significantly heavier, so you will need to bear this in mind in relation to the support you have available. However, in the vast majority of incidences, these swaps should be easily accommodated, saving you time and money, being better for the planet and giving you a longer season of colour to enjoy.

So, get on out there this weekend and plant a window box. A simple act that makes your world a more beautiful place and gives us, in our own small way, hope of good things to come. Something I think we could all do with right now.

Follow James on Twitter @Botanygeek