Gardening Calendar: Tasks for Mid Summer

With perennials and annuals in full bloom and the sun at its hottest, watering is often the most important job.

The warmest mid summer days reach temperatures of at least 24°C (75°F), especially in inland areas of southern Britain. But this can also be the wettest part of summer — hilly areas of the north and west often receive heavy rain and thunderstorms for several hours at a time. Humid, hazy spells are common, and night temperatures rarely fall below 10°C (50°F) in inland gardens.

High humidity and frequent rain produce ideal conditions for the spread of disease. To ensure good control of such diseases, dust or spray susceptible plants, such as Michaelmas daisy and solidago, with fungicides as routine — once a disease has taken a firm hold, it is usually too late to expect control measures to succeed.

garden plantsGarden beds and borders

In very dry weather, water liberally to extend the flowering season, but do not give so much water that leaf growth is encouraged at the expense of flowers. It is better to give a lot of water once or twice a week than a small volume every day, since the latter method encourages the roots to grow towards the surface, where they dry out more quickly and find little nutrient.

Give support to taller-growing plants well before they show signs of flopping over — though this should have been done in late spring or early summer. Continue to tie upright plants to their stakes or supports as they grow. Also check that the lower ties are not strangling the stems, which will have thickened by now.

Continue to spray border plants and annuals every four weeks to control aphids and other sap-sucking insect pests. Hoe regularly to control weeds.


Early in mid summer, direct-sow wallflowers and sweet Williams where they are to flower the following year. (Mid summer is too late to sow these biennials in nursery beds.)

As soon as they reach manageable size, set out in a nursery bed seedlings of hardy wallflowers, sweet Williams (and hardy perennials) which are at present in seed boxes or outdoor seedbeds.

Annuals and perennials

The lives of many flowering plants —especially annuals — are shortened if they are allowed to form seed-heads or pods. So dead-head all plants as soon as the flowers fade, unless you specifically want seed-heads for their decorative value later in the year, or you want to collect the seeds for sowing next year. Removing the old flower heads also keeps the garden colourful and attractive.

Continue cutting back early flowering border perennials. Some kinds, such as Achillea taygetea and Salvia x superba, will produce a second flush of flowers by late summer if they are cut back quite severely just before the main flowering is over. In warm, sheltered gardens, delphiniums and lupins may also flower again if cut down right to ground level.

However, do not cut back herbaceous peonies that have flowered; just remove the dead flower heads — the foliage is ornamental, and peonies need to die back naturally.


Keep the plants well watered and give a monthly liquid feed of a general fertilizer. On all but spray and pompon varieties, if large blooms are required, reduce each plant to five flowering shoots by breaking off the weaker shoots.

Bulbs and corms

Lift and store spring bulbs, such as tulips, daffodils and hyacinths, if this was not done in early summer.

Plant autumn-flowering bulbs now — they provide a touch of unusual form among shrubs and trees at a time when flowers are fairly scarce. Excellent types include Amaryllis belladonna, Nerine bowdenii, Sternbergia lutea and Colchicum, as well as autumn-flowering Crocus species.

Stake gladioli plants individually if you want straight stems for cutting. Use wire rings, string or raffia for securing the main stems to the stakes.

Order spring-flowering bulbs as soon as possible — daffodils in particular benefit from early autumn planting.

If dahlias are slow in growth — they should be about 60cm (2ft) tall by the middle of summer — feed them every two weeks with liquid fertilizer. Always apply the feed to the soil when it is damp. In dry weather, water the soil first.

To obtain long stems and good flowers for cutting, disbud a proportion of each dahlia plant’s stems. At the top of each main shoot is a crown bud, with two smaller buds just below. Remove the lower two buds. Alternatively, to obtain a large number of smaller flowers, remove the crown bud, leaving the two lower ones to grow on.

At the beginning of mid summer dig up and divide dwarf and intermediate bearded irises if they have been undisturbed for three years. Tall bearded irises need the same treatment from the end of mid summer onwards, when they have finished flowering.

When replanting bearded irises, cut the best single rhizomes from the old clumps and plant them in a sunny site in soil which has had well-rotted manure or compost as well as some general fertilizer dug into the top 23cm (9in). Leave the tops of the rhizomes above ground level and press the soil firmly on to the roots below. This will ensure that the rhizome gets baked and well ripened in the sun.

After planting the iris rhizomes, cut off the top half of the leaves to lessen moisture loss and possible loosening in the soil by the wind rocking the plants to and fro.


Summer pruning consists of cutting blooms for home decoration, and dead-heading — both procedures encourage new, strong shoots to grow in the directions required to maintain shapely plants. They also assist the next flush of blooms to develop on repeat-flowering plants.

When cutting blooms from newly planted roses, do not cut stems longer than required. Ideally, remove only one-third of the flowering stem produced this season. Roses need all their leaves to produce enough food for the next flowers. Dead-head back to a compound leaf with flower buds in the axil.

As soon as the first batch of rose blooms is over, feed the plants with a proprietary rose fertilizer, hoeing it into the surface soil. Spray regularly with rose insecticide and fungicide.

Shrubs and trees

After flowering, prune deciduous shrubs — such as Philadelphus — by removing faded flowers and cutting out thin and weak shoots.

Watch for sucker growth on grafted rhododendron and azalea hybrids. In bad cases, the wild rhododendron rootstock will take over. Using secateurs, cut off all sucker growth as soon as it is noticed.

Take cuttings of Buddleia alternifolia, callicarpa, campsis, cistus, clematis, cotoneaster, deutzia, euonymus, Hydrangea paniculata, Hydrangea petiolaris, mahonia, spiraea and viburnum. Root these in a cold frame.

Root cuttings of camellia, elaeagnus, honeysuckle (Lonicera), hypericum, pyracantha and rhus in pots under glass. Layer shoots of passion flower (Passiflora) and wisteria in pots sunk in the ground.

Lawn Maintenance

During prolonged dry weather, water the lawn thoroughly once or twice a week, in the morning or evening — a lot of water applied infrequently is more beneficial than a little water every day. Apply water at the rate of 10-20 litres (2-4 gallons) per sq m/yd so that it penetrates to at least 15cm (6in) deep. Brown patches may develop where weeds begin to infest weakened areas.

If the lawn is compacted, spike the surface with a garden fork or lawn aerator before watering. If necessary, apply a selective lawn weedkiller during warm, moist weather, but never in full sun.


Plant of the Month

Sweet peas (Lathyrus odoratus varieties) come in a wide range of colours, including pastel and vivid shades, except yellows and oranges. The most familiar types climb to 1.5-3m (5-10ft). But for a small garden, the dwarf bushy types are ideal and need no support. ‘Bijou’ is an early flowering mixture, reaching just 45cm (1-1/2ft) in height.

Other mid summer flowers suitable for growing in association with dwarf sweet peas include cornflower (Centaurea), godetia, larkspur (Delphinium consolida), lavatera, petunia and verbena.

18. June 2011 by Dave Pinkney
Categories: Garden Management, Gardening Calendar, Plant Care | Tags: , | Comments Off on Gardening Calendar: Tasks for Mid Summer


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