A few pointers to get started. After that, it’s all about trial, error, and luck.
Geranium and pelargonium cuttings are easily done. It’s also a low-budget way to increase the number of plants in your window boxes.
Pelargonium and geranium cuttings can be done at any time of year, but the roots will not develop if it’s too cold.
There’s plenty of online advice on how to do cuttings properly, including YouTube videos.
Deadheading geraniums and pelargoniums is essential to continued blooms – keep on deadheading, and they will keep on flowering.
It’s also easy. If a pelargonium is properly hydrated, you can just snap the spent flower stem back where it joins the main stem, and it will break neatly. If the plant is dehydrated, then the stem will be rubbery and harder to break, in which case using clean scissors will be better – or just do a spot of watering, and deadhead a bit later.
For geraniums (cranesbills), it’s often easier to deadhead with scissors as the stems seem to have a different consistency.
If in doubt, check the RHS website: RHS guidance. As always, YouTube is good for practical examples – there is a video for pretty much every gardening technique.
When you deadhead, look out for wilting or yellowing foliage, or half-broken branches too – a little tidy up will ensure your plants thrive.
Other types of flowers also need deadheading – tulips for example.
Deadheading a tulip but leaving the stem and leaves intact means the bulb can absorb sunlight through the leaves and store energy to flourish again the next year.
Once the leaves have died down, they can then be cut. Bulbs can be left in the ground if the area is not watered much – and if the tulips are perennials, not annuals – and might then grow again. The alternative is just to dig out the bulbs, keep them or dispose of them, and start afresh the following year. It’s a bit of extra work either way.
Some types of plants – herbs like basil for example – need pinching out. If you prefer a basil plant to grow substantially while remaining compact, rather than straggly, then pinch out – snap – what looks like excess growth. It’s very easy but at the same time a bit heartbreaking since what is being pinched out is new growth. But it is in a good cause. This Thompson & Morgan video shows how to pinch (and grow) basil: Basil – growing & pinching.
Soil in window-boxes will get depleted over time. This doesn’t matter too much if you are simply growing hardy plants – such as geraniums or succulents. These will continue to do fine, especially if you occasionally use fertiliser, and periodically add a few handfuls of fresh compost.
Swapping old compost for new, without the upheaval of emptying a whole window box at a time, is a good compromise. It really depends on what you want to grow, how much soil depletion and pests are a threat to your plants – and how perfectionist you are.
If you become serious about your gardening then you might in due course wish to change all or most of the compost. One of my neighbours prefers a complete soil change for their window boxes every three to four years. This might be a lot of work, maybe something worth outsourcing – see the Contacts pages for a list of potential contractors.
What kind of compost to choose? John Innes No 3 is the usual recommendation and easily obtained from local shops. Some might deliver. If you order your compost online as part of a supermarket shop, it can usually be delivered past your doorstep and even onto your balcony.
The lighter, easier to carry alternative is Miracle-Gro’s Expand’n Gro compost – easily bought online, expands when watered, and said to contain up to six months’ worth of slow release fertiliser. Perhaps not one for the purists, and it needs generous watering at the outset. It is a useful stop-gap. I’ve used it to supplement or partially swap existing compost in my window-boxes and the plants have done fine.
During growing and flowering season, it helps to add fertiliser to the soil (unless the new soil, already laden with fertiliser, has just been used). Tomorite or Miracle-Gro are the most readily available products.
A low maintenance window box means minimal watering and so choosing plants which prefer infrequent, low amounts of hydration. By watering only intermittently and allowing the soil to go a bit dry in between times, roots will be encouraged to go deeper – where moisture evaporates more slowly.
Consider covering the soil in your window boxes with mulch or gravel, mixing water-retaining granules into the soil – some people use sponges.
My own watering solution is a simple plastic picnic water jug. Its design is easier to handle than a watering can, so I can water my plants more precisely. It takes almost the same amount of time to water as with a large watering can. I usually pour two jugs of water per window boxes. In Winter, I water at most once a fortnight, usually once a month. In Summer, when the weather is hot, I double the amounts and the frequency.
An alternative solution is to get a tap fitted under your kitchen sink, and attach to it an expanding hosepipe. These hosepipes are easily bought online.
I once made the mistake of ripping out clover from my window-boxes, thinking they were undesirables. In fact, they’d been planted to prevent other weeds from thriving. Clover provides good ground cover too, which minimises watering.
In the absence of clover, a bit of mulch or gravel can help with moisture retention.
It’s better to keep certain plants within their own separate pot, even if the pots are grouped within a window box. Mint, for example, is invasive and will affect the growth of neighbouring plants – planting it within a concealed pot will allow it to flourish within reason. Lavender, too, is worth planting in the same way. It will likely need less water than other plants in the same window box, so keeping it segregated into its own pot will reduce the risk of over-watering; adding some grit to the soil will also help.