June gardening: what to plant and what to tidy this month

This June has commenced with a welcome week of sunshine, not a moment too soon after an unseasonably frosty April and a rainy May.

After June 21st, the longest day of the year, we can look forward to increasingly warmer temperatures and extra sunlight.

Flowers and plants are in full bloom; and there’s lots to harvest in the vegetable garden and fruit containers (think of all those strawberries!).

Still, let’s not get ahead of ourselves: there are plenty of jobs to keep on top of including weeding, deadheading and watering. A little work now will bear fruit later. Here, you’ll find the best tips for this month, from clever hacks for better berries to a note on nipping out chrysanthemums, depending on whether you prefer a spray or a single stem bloom.

Coriander time

I wait until this week to sow coriander for leaves rather than flowers and seeds. Sown in a polytunnel through summer it gives leaves all winter then flowers in spring. Go belt and braces and sow ‘Confetti’ from suttons.co.uk.

Tired geraniums

After their workhorse-like procession of flowers and foliage, my hardy geraniums are starting to look a bit tired and gangly, and I have just taken the shears to them, to encourage a flush of fresh foliage and hopefully some new flowers too before long.

If you are considering buying a few, choose a modern variety such as ‘Rozanne’ which is less prone to the midsummer collapse and will flower until the frosts hit.

Bay tree trim

This is a good moment to reshape a topiary bay tree, using secateurs so that you don’t hack all the leaves in half. Overgrown bay trees can also be hard pruned now, but take out about a third to half of the growth each year over two or three years.

Bolting mustard

Oriental mustards are day-length sensitive and, if sown early, will bolt ahead of midsummer. Now that has past we can expect chunky and leafy plants from new sowings. Real Seeds (realseeds.co.uk) has a particularly interesting selection.

Honesty policy

It is time to sow honesty, a biennial which will flower in early summer next year, before producing those gorgeous glass-like seed pods next autumn. Sow now into seed trays and plant out as soon as the plants are large enough.

Tomato support

How sturdy are your tomato supports? We pop in a little cane as we plant them, forgetting what brutes they can be, and it is about now they start to lean and topple. It’s not too late to push a good sturdy stake into the ground next to each.

Feed for thought

Liquid feed all summer long is the key to the happiest and most floriferous gardens. Comfrey liquid is brilliant, and I’m particularly keen on Maxicrop’s seaweed extract-based fertilisers (maxicrop.co.uk).

Naughty dogs

Dogs, lawns and summer are a bad mix. If your dog can’t be trained to go in a corner, the grass will soon sprout burnt yellow patches. On dry days wash away the worst using a watering can fitted with a rose.

Mind the gap

It is a shame to struggle on with gaps in borders when quick-growing and bedding plants are available. A fuzz of lobelia or a blowsy begonia may not be in your long-term plan, but you can afford to take a chance.

Nipping out

It’s time to decide whether you want a single impressive bloom on each stem of your chrysanthemums or a spray of smaller flowers. I lean towards the former, but if you want the latter then nip out the growing tip now.

Enjoy last-gasp asparagus

June 21 marks the official end of the asparagus-picking season, so enjoy a last weekend of fresh spears. Then back off and leave the plants to grow into ferns, building up their resources for next year’s harvest. Water occasionally during dry weather and weed carefully between rows now, too.

Under the rose

Roses are in bloom, but they always look better with underplanting to disguise their lower, less interesting bits and complement the flowers. Consider hardy geraniums, salvias and alliums to waft around and through them.

Banana drama

For pure drama, you can’t beat a hardy banana, Musa basjoo. They are spectacular and easy – they only need winter protection in the first few years. This is the time to get one settled in; find them, and other subtropical beauties, at palmcentre.co.uk.

Crunch time

Keep sowing short rows of quick-growing salad crops such as spring onions, radishes and lettuces (the latter in shade if you can, or they will bolt – sow in the evening if the weather is hot), for a constant supply of crunchy salads.

Sheer beauty

If your border is graded upwards from front to back, inject a little drama with “transparent” perennials such as Verbena bonariensis, bronze fennel Foeniculum vulgare ‘Purpureum’ or Sanguisorba officinalis ‘Red Thunder’.

Cultivate carpet

Sow Viola biflora now, a hardy perennial that will form a carpet below shrubs and trees next spring and early summer. Sow seed in pots and cover with grit, then leave in a cool greenhouse until they germinate (plant-world-seeds.com).

Bathe baskets

It is much easier to water a hanging basket that has been consistently watered, so water every day when the weather is warm: once they dry out you need to dip them in a sink or basin overnight until they are rehydrated.

Trim magnolias

Magnolias need only ever be pruned if they are outgrowing their space: it is always better to allow them to find their own shape. But if you must, do it now. A winter prune can lead to dieback and in spring magnolias can bleed.

Ease citrus out

Move citrus trees outside, but make the transition gentle. They will bloom and fruit more after lots of sun, but it can be a shock at first. Shade with horticultural fleece for a day or two, which will keep them cosy at night too.

Shrub cuttings

To make more rosemary, lavender or sage plants, take cuttings of fresh growth. Strip lower leaves and insert several around the edge of a terracotta pot of gritty compost. Cover with a plastic bag, water, and set out of direct sun.

Oil strike

The essential oils in lavender are at their most potent when the flashes of the petals are only just showing, and so this is the time to pick them for culinary use or for the making of lavender pillows. Hang small bunches in a dark, airy place to dry them for storage. From May to September you can visit beautiful Somerset Lavender and see around 20 different varieties in bloom.

Being green

If the overblown gaudy flowers of bedding baskets are not for you, consider going all green with a basket full of graceful Glechoma hederacea ‘Variegata’, known as trailing nepeta. Find them in garden centres among the bedding plants.

Poppy love

Oriental poppies can look ragged after flowering. Cut them back right to the ground to get rid of the brown foliage while they are dormant over summer and you will soon enough get a flush of new green leaves to replace them.

A fiddly job

Aphidscan cluster around the buds of roses, distorting them as they try to bloom. Use thumb and forefinger to wipe them off now or mist with a mild soap mix.

Peas in our time

This is perhaps your last chance to sow sweet and tasty maincrop peas (any later you will need to switch back to a quick-maturing early variety). Sow direct, and thickly – one for the birds, one for the slugs, and one for yourself.

Flaw and order

Hollyhocks almost always suffer from rust and lose their lower leaves. You can partake in a dull and time consuming spraying regime, or you can just accept their flawed nature and plonk something in front of them.

Just a trim

My honey spurge, Euphorbia mellifera, does not reliably flower every year, and I don’t mind because the foliage is so dramatic. It did this year, but now it is time to trim off the old flowers and get the plant back to its shapely self.

Bee friendly

“The sound of spring bee activity is music to my ears. The queen bumblebees, large and often noisy, start to emerge from overwintering sites from February and feed voraciously as they search for nest sites,” says Jean Vernon. Encourage bees into your garden with bear’s breeches (Acanthus mollis and A. spinosus), flowering currant (Ribes sanguineum) and early-flowering borage (Trachystemon orientalis).

Better berries

The slug is the enemy of the strawberry patch. Lifting developing fruits up now on a bed of straw prevents them from touching the ground and becoming susceptible to rots which let in slugs and ants. Better berries will follow.

Spider sense

Red spider mite can drain the life out of your greenhouse and conservatory plants over summer. Prevention is easier than cure: keep the humidity high by damping down greenhouse paths and misting frequently.