06 Jul 2022

Summer colour in planters, pots and window boxes

In her column on common gardening conundrums Lynn O’Keeffe Lascar, DSc Horticulture, Craft gardener, focuses this week on pot planting.

Summer colour in planters, pots and window boxes

It’s that time of year when gardeners and Tidy Town groups get busy planting up pots and planters for the doorsteps and traffic islands of Ireland.

Pots and planters are a great way to add greenery and colour to areas that don’t have soil, like patios, yards, paths and areas of hard surfaces in and around towns and villages. Once planted up with frost-tender annual summer bedding and then winter pansies later on in the year, they can bring cheer to the dullest of locations.

They are however a costly exercise, in terms of buying the pots and planters themselves, the compost or soil to fill them, and then the plants which only last the one season and need watering and feeding regularly.

So how can you be savvy with pots and planters?

First off go big!

The bigger the pot or planter the better the plants in it will grow as they’ll have more space for their roots, therefore the longer you can go between watering and feeding, and the less likely it is to blow over.

One big pot will make more impact than three or four small ones and be less work. The only downside is they can get very heavy to manoeuvre etc., so place carefully and fill and plant in situ.

Fill it up...

In a big pot or planter, it’s best to fill at least half with soil or a soil-based compost. This adds longer-lasting fertility and is less likely to dry out. You can also add well-rotted kitchen compost or other organic matter into the bottom half and mix it through. Then fill right up to the top with a peat free multipurpose compost or a specific compost for planters and window boxes, which usually has some extra water absorption ability added.

Some tricks of the trade include lining the pot with a few layers of newspaper before filling.

This helps hold in moisture for pots in a very dry sunny spot, or for plants like sweet peas that hate drying out.

I really like the pots, window boxes and hanging baskets that have a built-in water reservoirs at the bottom. This makes a huge difference to plant growth and how often you have to water, so keep an eye out for those in garden centres.

What to plant?

Plants in pots soon run out of space and fertility. It is quite tricky to keep plants looking well for years in a pot. Some are more suited than others like the houseplant geraniums or cacti. But trees, like bay laurel, or shrubs, invariably look very sad after the first year or two. But buying in annual bedding every year is expensive and somewhat wasteful.

What else can you do?

I buy perennial plants and grow them for the first year in a planter or pot as a feature plant, and then the following winter take them out and either divide them, putting a small bit back in the pot, or plant them on out into the garden. I’ve done this for perennial geraniums, red hot pokers, Hostas, Helenium, Heucheras, alpines or ornamental grasses. I’ll always dot in lobelias or pansies too for that splash of all season long colour and for the way they hang down over the edge of the pot.

A herb planter is a lovely idea, and all bar parsley love to be hungry and dry. So if you’ve a sunny spot, consider planting up with lavender, rosemary, sage, chives and thyme, and then in a year or two when they’ve out grown the space plant them on out into the garden and start with new plants.

The herbs all flower at different times so there’s always colour, and they’re very popular with pollinators. The plants can be bought cheaply in small pots in the herb/veg section of the garden centre. Mint is another one for a pot, but this time a slightly shady location and kept well watered. Mint is best constrained to a pot or it can take over the garden.

Mint has beautiful flowers that pollinators love, and tasty wee leaves for salads, teas and drinks. It also makes a long lasting green for cut flower displays.

A cheap and cheerful idea is to grow from seeds. You can try pot marigolds (Calendula), Nasturtiums, cosmos and dwarf sunflowers. They can all be sown for growing in sunny containers. They’ll be bright and colourful all summer long and attract bees and butterflies.

You can also add the leaves and flowers of nasturtiums to salads for a peppery zing, or the petals of calendula for colour. This is a nice project to do with kids as the seeds are easy to handle and quick to come up. You can then save your own seed for doing it all again next summer!

In shady spots, like north facing patios or window sills, tuberous begonias are your best choice. You can buy the tubers in early spring and bring them on indoors, or buy the plants already flowering in May/ June. You can then dry them out the following autumn, store them cool but frost free (in the garage) and then off you go again next year. The tubers get bigger and flower better as the years go on.

Add in Lobelia, Bacopa or creeping Jenny to fill out the box or planter. Other shady plants for pots include ferns, ornamentals sedges and my favourite perennial Brunnera ‘Jack Frost’ which flowers from March till June, and then still has beautiful silver variegated leaves after that.

Top Tip

Invest wisely in large pots, and perennial plants, that you can divide up and replant.

Lynn O’Keeffe, DSc Horticulture, Craft gardener with the OPW at Portumna Castle Co. Galway and Horticulture tutor with the GRETB.

This series is supported by the Heritage Offices of Laois, Offaly and Westmeath County Councils, with funding from the National Parks and Wildlife Service of the Department of Housing, Heritage and Local Government, under the National Biodiversity Action Plan. For gardeners interested in becoming more wildlife-friendly, why not check out or go to biodiversity/ for your free booklet.

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