June garden: what to prune, sow, and water

June is the height of the gardening season

June is the month your garden runs at full speed: long days, warm evenings, and plenty of growth all at once. Spring bloomers are just finishing their show, the first flush of roses is fading, and the soil is still moist enough for one more useful sowing round. Get the right things done now and you reap the benefit all summer.

This article lists exactly what to prune in June, what you can still sow, and how to water once the heat sets in. All with months, measurements, and a clear order, so you can get started right after reading.

Prune spring bloomers right after flowering

Skip pruning now and you get a weaker, straggly plant next year. The rule is simple: prune as soon as possible after flowering, because many of these shrubs already set next year's flower buds in the weeks that follow.

Rhododendron and azalea: pinch off the faded flower clusters with your fingers, do not cut them. This avoids damaging the young leaf buds underneath. Within a few weeks a new shoot grows from that spot.

Forsythia: prune at the latest now, in June, never in autumn. Remove about a third of the oldest, thickest stems right down at ground level and leave the young shoots. Prune in autumn and you cut away next year's flower buds along with the wood.

Lilac (Syringa vulgaris): prune straight after flowering, just below the spent cluster. Do this every year and the shrub stays compact instead of bare at the bottom and wild on top.

Hydrangea (Hydrangea macrophylla), blue or pink: do not prune now. Remove the dried flower heads only if they bother you, but leave the stems alone. Hydrangeas are pruned in March, once the new buds become visible.

Second sowing round: vegetables for late summer and autumn

After mid-June, outdoor sowing gets harder: the soil keeps warming up and many vegetables bolt straight to flower instead of forming leaf or root. June is your last real window for a second sowing round.

Lettuce: sow a new row every two weeks so you can harvest right into September. Choose a slightly shadier spot, because lettuce bolts fast in the heat. Red varieties such as 'Lollo Rossa' usually bolt later than pale ones such as 'Lollo Bionda'.

Radish: this is your last sowing for a smooth harvest, ready in about four weeks. Sow later and the harvest lands in cold, wet autumn soil, which turns radishes woody.

Spinach: a second sowing now gives an autumn harvest in September. Pick a half-shaded spot, because spinach in full July sun bolts almost immediately.

Herbs: parsley, dill, and coriander can still be sown, preferably in a half-shaded spot. After June the soil gets too warm for these herbs to germinate reliably.

Stop sowing: tomatoes, courgettes, and climbing beans no longer have enough time to set fruit before the first autumn frost. Buy young plants of these instead of sowing seed now.

Hedge trimming in June: the second cut

The first hedge trim of the year happened in May. Many hedges now get a second cut in June, though it depends on the species.

Box (Buxus): can be trimmed again now, about two weeks after the first cut. Box keeps growing all season. Keep the hedge slightly wider at the base than at the top, otherwise the lower part shades out and turns yellow.

Conifers (Thuja, Cupressocyparis): trim carefully now, up to twice a season. Never cut into the bare, brown wood: most conifers will not resprout from there.

Broadleaf hedges such as privet and hazel: get their second trim now, right after the first flush of growth. Use hand shears for soft curves, a powered trimmer is too rough for fine lines.

Hornbeam and yew: both can be trimmed now. Hornbeam (Carpinus betulus) grows vigorously and needs shaping twice a year to stay in form. Yew (Taxus baccata) grows slowly; one trim a year is enough, often in August, though a light tidy-up in June works too.

Roses after the first flush: deadhead and feed

Many roses, especially shrub roses, are finishing their first flowering now. With the right aftercare they flower again in August.

Deadhead faded blooms: cut just above the first full leaf below the flower. This sends the plant's energy into new flowers instead of seed formation.

Feed your roses: after the first flush, give a rose fertiliser or a general feed for flowering plants, following the dose on the pack. This builds strength for the next round of flowers.

Water deeply: roses want at least two deep soakings a week in June if it stays dry. Deep watering builds strong roots, a light daily sprinkle mostly encourages leaf disease.

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Mulch against drought and weeds

June is the best time to lay down mulch: the soil is still moist enough, and a layer now saves a lot of watering in the dry months ahead.

When: apply mulch right after hedge trimming, on moist soil, before the end of June.

Which mulch: wood chips (3 to 5 cm thick), leaf mould, dried and unsprayed grass clippings, or gravel for Mediterranean plants. Keep 5 cm of clear space around every stem and trunk, otherwise trapped moisture can cause rot.

Benefits: mulch keeps the soil moister, blocks light to suppress many weeds, and slowly breaks down into organic matter that improves the soil.

Watch out: on a damp, shaded spot mulch attracts slugs and fungi. Under trees on a dry spot it is close to ideal.

Start watering properly in June

June is the first month with a real drought risk. A ten minute shower often only wets the top few centimetres, the roots stay dry.

Test the soil: push a finger 5 cm into the ground. Feels dry there? Water deeply. Still feels moist? Wait a little longer.

Water in the morning: never water at midday in full sun, because droplets on leaves can scorch them then. Morning watering lets the leaves dry out during the day, which gives fungi less of a chance.

Young plantings: anything planted less than a year ago needs at least two deep soakings a week.

Potted plants: these often dry out daily in June and July. Check with a finger in the potting mix and water until it runs out of the bottom of the pot.

Garden calendar for June, week by week

Week 1 and 2 (1 to 14 June): prune spring bloomers, second hedge trim, rose aftercare after the first flush.

Week 2 and 3 (8 to 21 June): sow lettuce, radish, and spinach, apply mulch, start targeted watering.

Week 3 and 4 (15 to 28 June): keep sowing and watering, check hedge growth, remove faded flowers daily.

Week 4 (22 to 30 June): finish off June tasks and prepare the garden for July heat.

Step by step

Step 1: deadhead spring bloomers

Go along the rhododendron, azalea, and lilac. Pinch off faded clusters by hand, do not cut. Allow 15 to 30 minutes per shrub.

Step 2: trim the hedges

Check which hedges are due for their second cut. Box and broadleaf hedges certainly now. Use clean, sharp shears and work evenly along the sides and top.

Step 3: sow vegetables

Prepare a seed bed with finely raked soil. Sow lettuce, radish, and spinach in rows about 1 cm deep. Keep the soil moist until germination.

Step 4: lay down mulch

Spread 3 to 5 cm of mulch over moist soil, leaving 5 cm clear around every stem.

Step 5: feed the roses

Apply rose fertiliser following the dose on the pack and water it in well.

Step 6: set up watering

Test the soil with a finger and water deeply where needed, down to 15 to 20 cm depth.

Frequently asked questions

Should I check my box hedge for box tree moth now? Yes. In June the caterpillar of the box tree moth (Cydalima perspectalis) is active and can strip a hedge bare quickly. Check inside the hedge for webbing and caterpillars. Use a biological product based on Bacillus thuringiensis, chemical pesticides are not allowed for private use. Acting early limits the damage sharply.

My lilac flowered much less this year than last year. What went wrong? It was probably not pruned quickly enough after flowering, or only pruned in autumn. Lilac already sets next year's flower buds during summer. Prune in autumn and you cut those buds away with the wood. From now on, always prune straight after flowering.

Should I keep mowing the lawn when it is hot? Yes, keep mowing, but not too short. Raise the cutting height to 4 to 5 cm instead of 2 to 3 cm. A slightly longer lawn keeps the soil cooler and moister.

Can I ventilate my greenhouse now? Yes, certainly in June. Open it early in the morning and close it late in the evening. On very warm days, above 25 degrees, the door can safely stay open until evening.

See it in your own garden first

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