Guide to Summer Gardening

Summer is a time to relax and enjoy the fruits of your labours. The main worries are watering and pest control. It is all too easy to allow plants, particularly if they are in tubs, to dry out in hot weather. Make a regular point of checking the garden, especially the vegetables, for signs of disease and insect damage.



Plant out summer bedding plants. Prune shrubs after flowering. Apply fertilizers to all established plants. Keep an eye open for pests and diseases and spray as soon as they are noticed. Remove dead flower-heads. Take softwood cuttings of shrubs and perennials.

Thin out hardy annuals. Provide support for plants. Plant out dahlias and fuchsias. Lift and store spring-flowering bulbs if necessary.


Protect strawberries from slugs – put down slug pellets.

Spray fruit and vegetables against pests and diseases.

Plant out tender vegetables such as tomatoes, marrows, sweet corn and celery.

Continue sowing green vegetables and salad crops, plus roots such as carrots, swedes, turnips and radishes.

Provide support for peas and beans.

Sow runner and French beans.



Trim hedges as necessary.

Continue dead-heading, feeding, and pest and disease control.

Lift and divide bearded irises.

Continue shrub pruning as necessary, after flowering.

Lawns might benefit from another feed.


Continue feeding and spraying against pests and diseases.

Protect fruits from birds by draping netting over the bushes.

Remove old leaves, and unwanted runners, from strawberries.

Make sowings of spring cabbage, turnips, carrots, lettuces, winter radishes, beetroots, early peas and winter spinach.



Plant autumn-flowering bulbs.

Propagate plants from semi-ripe cuttings.

Continue dead-heading, and pest and disease control. Continue feeding, too, if you feel plants need a boost.

Continue hedge trimming.


Plant strawberries, either in a bed in the open ground, or in strawberry containers.

Prune raspberries as soon as the fruits have been picked. Cut out old fruited stems to ground level.

Lift onions and shallots, dry off and store.

Sow spring cabbage, winter spinach and salad crops.

Cut and dry herbs for winter use.

Continue with feeding, and pest and disease control.


Most people today buy plants from garden centres or high-street chain stores.

The beauty of a garden centre is that plants are sold in containers and so can be planted at virtually any time of year, provided they are hardy and the soil is in suitable condition. Plants can be bought in full flower and planted immediately you get them home. An advantage of the garden centre over the chain store is that one has a much wider choice of plants. Usually, if you are unable to obtain the variety you want, there is a good chance that the garden centre will have another, very similar.

Very often, plants offered by chain stores are pre-packed with roots wrapped in polythene to keep them moist.


The majority of garden centres sell good quality plants, and the plants are well cared for while they are waiting to be sold. Even so, it pays to inspect plants carefully before buying, just as you would with any item that you buy in a shop. The following guide will help you to select quality plants: Make sure that plants, such as shrubs, trees, roses, conifers, perennials, and so on, are not loose in their containers. This would indicate they had not long been potted, and would therefore not transplant well when you got them home.

Ideally, there should be a little root showing through the bottom of the container to indicate that the plant is well established. Ensure the compost in the container is moist. If plants have been allowed to dry out their growth may have been checked and they may later lose their leaves.

Ensure there are no weeds or moss growing on the compost surface.

It goes without saying that plants should be completely free from pests and diseases. Growth generally should be sturdy – not thin, weak and lanky.

Foliage should be healthy – not showing brown marks, spots or other discoloration. It should not be yellowing, nor have brown edges. Similar comments apply to spring and summer bedding plants. Summer bedding plants should be just coming into flower when they are offered for sale – with one or two blooms open and a number of flower buds to follow. The plants should be sturdy and short jointed, particularly subjects such as geraniums and fuchsias. Summer bedding plants should have been well hardened off (acclimatized to outdoor conditions) before they are offered for sale. It is not too easy to tell if this has been done, but if the plants look very sappy, soft and lush, then suspect that they have just come out of a warm greenhouse, in which case they would receive a check to growth if planted straight away in the open ground. Plants such as these are best avoided.

Alpines – most of the above comments apply to alpines and rock plants. Many are offered just as they are coming into flower and can be planted even when in full bloom if grown in containers such as pots.

When buying pre-packed plants from a chain store – shrubs, roses or perennials, for instance -it is more difficult to inspect them closely.

Try to find out how long they have been on the shelves. They can, of course, deteriorate if kept for too long. Ideally, they should be bought as soon as possible after they have been delivered to the garden centre.


Hardy plants should be planted immediately if the soil is not too wet or frozen. However, if they are in containers they can be kept that way for as long as necessary. But do keep them watered. If you cannot plant prepacked plants immediately, they can be kept in a cool garage or shed for up to a week. Unwrap the tops to prevent condensation, but keep the roots wrapped to ensure they do not dry out. If you find you cannot plant them for several weeks, they should be heeled in, in a spare piece of ground. Choose a sheltered, shady spot. They will then remain in good condition for several weeks. Summer bedding plants are tender and must not be planted out until all danger of frost is over. The usual planting times are late May and early June. If you buy them before, keep the plants in a cold frame to give them frost protection. Don’t forget to water them regularly, and they will undoubtedly benefit from weekly liquid feeding.

Planting in Summer


Summer bedding plants (the half-hardy annuals and perennials) are planted out when all danger of frost is over. This may be late May in the south, but is generally considered to be early June in colder, northern counties. If you are in any doubt it is better to delay planting for a week or so – the first week of June should be safe enough anywhere in the country.

We have already considered these plants for containers, but many people like to plant them in special beds, generally of formal shape, perhaps around the house or patio. They can also be planted around permanent features such as shrubs.

The site should be sunny for most bedding plants, but impatiens (or busy-lizzie), mimulus, fibrous-rooted begonias (Begonia semperflorens) and bush fuchsias will flower well enough in light shade.

The bed should be dug over beforehand, broken down, firmed and levelled, and a general-purpose fertilizer worked in several days before planting.

A bedding scheme traditionally consists of the following elements: an edging of a low-growing plant such as lobelia, alyssum, ageratum or dwarf French marigolds and a main ‘carpet’ of plants, which could consist of just one type of plant, say salvias, geraniums (pelargoniums), antirrhinums, dwarf bedding dahlias, African marigolds, petunias, and so on. Alternatively, you could mix together several different kinds, aiming for pleasant colour harmonies or contrasts. The main carpet could again be formed of low or dwarf plants, a little taller than the edging. However, this gives a flat-looking scheme. So to provide height some taller ‘dot’ plants could be introduced at random over the bed. Dot plants could be standard or half-standard fuchsias, geraniums or heliotropes; or foliage plants such as Abutilon striatum ‘Thompsonii’, Eucalyptus globulus or cannas (Indian shot). The latter do flower in a good summer.

As for colour combinations, you might like to get away from this traditional red, white and blue theme formed of an edging of lobelia and white alyssum, and a carpet of red salvias or geraniums. Here are a few alternative suggestions:

An edging of mauve or blue ageratum, a carpet of pink fibrous-rooted begonias, mixed with violet Verbena venosa, and dot plants of bush or standard fuchsias.

A carpet of orange-red geraniums, interplanted with blue or purple petunias, and dot plants of standard geraniums also in orangy red. (There’s no need always to have an edging.) A carpet of scarlet salvias, with Verbena rigida, an edging of mauve ageratum, and dot plants of silver-leaved Senecio maritimus. A carpet of blue petunias and yellow antirrhinums, and dot plants of tall yellow African marigolds.


Many people plant spring-flowering bulbs and perhaps some of the better-known summer-flowering kinds, but autumn-flowering bulbs seem to be somewhat neglected by all but the most enthusiastic gardeners. Yet they are just as easy to grow, and bring a welcome splash of colour to the garden, combining beautifully with shrubs and other plants noted for their autumn leaf colour and berries. Some suggestions:

Amaryllis belladonna produces deep pink trumpet-shaped flowers on 450mm (18in) high stems in early autumn. It needs a warm sunny position with well-drained soil. Plant 100mm (4in) deep and 300mm (12in) apart in August.

Colchicum speciosum is a crocus-like plant with mauve flowers; it grows about 200mm (8in) high. It will thrive in sun or partial shade and likes well-drained soil. Plant in July or August, 75mm (3in) deep and 150mm (6in) apart.

Crocus speciosus is an autumn-flowering species, with lilac-blue flowers. Provide it with a sunny position in well-drained soil; plant in July, 75mm (3in) deep and 75mm apart.

Cyclamen hederifolium (C. neapolitanum) is a hardy miniature cyclamen whose flowers vary from mauve to pale pink. It grows about 100mm (4in) high. Provide with a cool shady spot and plant during August, about 25mm (1in) deep and 75mm (3in) apart. It is best to use pot-grown plants, as they establish better.

Nerine bowdenii is the Diamond lily. It has heads of pink flowers on 45mm (18in) tall stems. Plant in a sunny, well-drained spot, in August, 75mm (3in) deep and 100mm (4in) apart.

Sternbergia lutea is a crocus-like bulb with bright yellow flowers. Plant the bulbs 100mm (4in) deep and 150mm (6in) apart in August. Choose a warm, sunny, well-drained site.

A dazzling effect is produced by mixing African marigolds yellow antirrhinum, and blue petunias.

Summer Pruning


Some shrubs are pruned in the spring, but others are pruned in summer, immediately after flowering. These include types which bloom in the early summer on shoots formed the previous year. If they are pruned as soon as flowering is over, they will have a chance to make plenty of new shoots in the growing season, and these will produce blooms the following year.

Shrubs which need pruning now include philadelphus (mock orange), kerria or Jew’s mallow, the brooms (Cytisus), deutzias, weigelas and several spiraeas, such as S. thunbergii, S. arguta and S. prunifolia ‘Plena’.

The pruning technique is simple: the shoots or stems that produced blooms are cut back to just above young shoots which are developing lower down the plant.

A word about brooms. Be careful not to cut into the old wood because the plants may die. Just remove the tops of the shoots carrying the dead flowers.


At this time of year some shrubs and trees that have been budded or grafted onto a rootstock throw up vigorous shoots from the roots, known as suckers. Roses, lilacs and rhododendrons are examples of plants that may ‘sucker’. Suckers should be pulled out at their point of origin, which entails carefully digging down to the roots of the plant. If the suckers are not removed they will eventually ‘swamp’ the plant.


Wisteria needs to be pruned in July or August. It forms a framework of old stems from which new shoots are produced each year. These shoots can become very long and must be reduced in length during the summer to prevent them from turning into a tangled mass of growth. Cut them back to within five or six buds of their base. In the winter they should be cut back again – to within about 25mm (1in) of the old stems.

Another popular climber, Clematis montana, and its varieties can be pruned in summer by cutting back the side shoots on the main stems almost to their base. If they get out of hand, they can be cut back severely as they start into growth in spring; the flowers for that season will, however, be lost.


Hedges are trimmed during the summer, but some need more attention than others.

Formal hedges of privet will need clipping at least once a month to keep them looking neat and tidy. The Chinese honeysuckle (Lonicera nitida) is also a fast grower, but not quite as vigorous as privet. It will, perhaps, need two or three trims during the growing season.

Most other formal hedges need clipping only once a year. This is usually done in August. Examples include the Leyland cypress (x Cupressocyparis leylandii), the Lawson cypress (Chamaecyparis lawsoniatia), the yew (Taxus baccata), holly (Ilex aquifolium), box (Buxus sempervirens), beech (Fagus sylvatica), hornbeam (Carpinus betulus), and laurel (Prunus laurocerasus). Box may need to be trimmed more often.

Informal hedges – those grown for their flowers and/or berries – need little or no trimming apart from shortening overlong shoots that may be spoiling the overall shape of the hedge. This should be done immediately after flowering.

Dwarf lavender hedges are grown informally and all you need to do with these is trim off the dead flower heads towards the end of the summer. Do not cut into the old wood.

Most hedges can be clipped with a pair of garden shears, or with an electric hedge trimmer if you want to speed up the job. An electric trimmer does not make quite such as good a job, though, as a pair of really sharp shears. It is inclined to leave ragged cuts.

Hedges with large leaves, such as the laurel, should not be cut with shears or an electric trimmer. These tools cut the leaves in half, which looks unsightly, especially when the cut edges turn brown. Instead, cut each shoot with a pair of secateurs. Of course, this is time-consuming and laborious, but it results in a much better appearance. Informal hedges should also be trimmed, if necessary, with a pair of secateurs to keep their irregular appearance.

Feeding Plants and Pest Control


Most flowers, including herbaceous perennials, dahlias, chrysanthemums, gladioli, roses and summer bedding plants, benefit from feeding during the summer, when they are in full growth, to ensure plenty of blooms.

A top dressing of dry general-purpose fertilizer, or flower-garden fertilizer, can be applied and lightly forked into the soil. A fertilizer which is high in potash will ensure even better results, as this food is responsible for flower production in plants.

If growth and flowering seem to be very poor, try, instead, a liquid fertilizer, which is quicker acting, perhaps even combined with a foliar feed, which is applied to the leaves. Special foliar fertilizers are available from garden centres: they are quickly absorbed by the leaves and so the plants can make use of the foods straight away.

There are fertilizers especially made for particular plants, having the right balance of plant foods, such as nitrogen, phosphorus and potash. For instance, both rose fertilizers and chrysanthemum fertilizers are readily available.

Never feed plants if the soil is dry and they are suffering from lack of water. Give them a good watering first and allow them time to fully absorb it before applying the fertilizer. A good plan is to water in the evening, and feed the following day.

Flower pests

There are several major pests and diseases which appear in the summer in the flower garden. Keep an eye open for the following, and spray the plants as soon as they are noticed:

Aphids (greenfly and blackfly) suck plant sap. Spray with pirimicarb rather than general insecticides such as dimethoate or fenitrothion. Earwigs can be recognized by their rear ‘pincers’. They eat the petals of flowers, such as dahlias. Spray with gamma-HCH or fenitrothion.

Leaf hoppers cause mottling of leaves, especially roses. Spray with fenitrothion.

Slugs and snails eat the soft growth of many plants. Put down slug pellets.

Caterpillars eat the foliage of a wide range of plants; spray with pirimiphos-methyl. Black spot is a major disease of roses. It appears as dark spots on the leaves; spray with thiophanate-methyl.

Powdery mildew appears as a white powdery coating on leaves of many plants, including roses; spray with benomyl.

Rose rust shows itself as rust-coloured spots on the leaves of roses; spray with copper compound or mancozeb.

There are now available proprietary rose pesticides containing both insecticides and fungicides, to control all the major pests and diseases of roses. These save buying a variety of chemicals.


Apply a general-purpose fertilizer, such as Growmore, in spring or early summer. Alternatively, you could apply a dressing of sulphate of ammonia at 28g per m (1oz per yd2) and sulphate of potash at the same rate. Lightly hoe them into the soil surface.

If the leaves become yellowish between the veins, the plants might be suffering from a deficiency of magnesium. In this case water the soil around them with a solution of Epsom salts (magnesium sulphate) and spray the leaves with it, too. Raspberries are especially prone to magnesium deficiency.

Fruit pests

There are several pests and diseases to watch out for:

Woolly aphids, which are similar to ordinary aphids, but are covered in white wool. Spray with fenitrothion.

Capsid bugs. The adult phase damages the leaves. Spray with fenitrothion.

Raspberry beetle. The white grubs eat fruits plus those of blackberries and loganberries.

Spray with fenitrothion or derris immediately after flowering, and repeat two weeks later.

Sawflies. The caterpillars severely damage leaves. Spray with pirimiphos-methyl.

Powdery mildew. (See flower pests, above.)


All vegetables benefit from a top dressing of general-purpose fertilizer, such as Growmore, in the summer. As for flowers, use a liquid fertilizer if growth seems particularly slow or poor. Use one with a particularly high nitrogen content for leaf vegetables such as cabbages and spinach. For tomatoes, capsicums and aubergines, use a proprietary liquid tomato fertilizer.

Vegetable pests

The following pests and diseases may be a problem:

Cabbage root fly. The maggots eat roots. Treat soil with bromophos.

Carrot fly. The maggots eat roots. Treat soil with bromophos.

Cabbage white butterfly. The caterpillars eat foliage. Spray with carbaryl or rotenone.

Club root attacks the roots of the cabbage tribe, causing swollen roots and stunted growth. Dip the roots in a proprietary club-root dip before planting.

Flea beetle produces small holes in leaves. Spray with gamma-HCH.

Potato blight. The foliage turns black and tubers rot; it also attacks tomatoes. Spray with a copper compound or mancozeb.



It pays to remove the dead flower heads from some plants before they set seeds, so that they are able to devote all their energy to making new growth, instead of wasting it on seed production.

Rhododendrons and azaleas, especially, greatly benefit from dead-heading. The dead blooms should be very carefully twisted off. Be careful not to damage the new growth buds immediately below them.

Also, dead-head your lilacs. This is most easily done with a pair of secateurs, again being careful not to damage buds below. Any brooms which have now finished flowering can be treated in the same way. Make sure you do not cut into the old wood; just remove the parts carrying the dead blooms.

Some plants are best treated by lightly trimming with a pair of garden shears. Heathers and lavender come into this category. With both of these do make sure you do not cut into old wood. The flowers of lavender, of course, can be cut before they are over, and dried if desired.

Dead-heading also encourages some plants to produce more flowers. This certainly applies to roses. Cut off the dead blooms with secateurs, together with a length of the flower stalk down to buds or new growth which are forming below. These will then develop and produce more blooms.

All summer bedding plants should be regularly dead-headed. This is normally a weekly task when they are in full flower and will ensure plenty more blooms follow.

It is worth doing the same with hardy annuals, although not all will produce more flowers. The same comments apply to hardy herbaceous plants: some will produce a second flush of blooms if dead-headed, while others will not. In any event, it’s advisable to remove dead flowers for the sake of tidiness. With herbaceous plants, just remove the old flowers, not the complete stem. This is done in the autumn when the stems die down.


Rain and summer gales can flatten some plants if they are not provided with adequate support. Herbaceous plants with tall thin stems, such as Michaelmas daisies or asters, certainly need supporting. Twiggy hazel sticks could be inserted between and around the plants before they make too much growth. They should be slightly shorter than the ultimate height of the plants. The stems will then grow up through the sticks and hide them.

Another way of supporting herbaceous plants is to insert three canes around each clump and encircle the stems with loops of garden twine at different levels. There are also available proprietary metal supports which encircle the stems and hold them in. These can be used year after year, and come in various sizes and heights.

Herbaceous plants such as delphiniums, which have only a few tall thick stems, can have each stem supported by a bamboo cane, placed at the back so that it does not show. Tie in the stem with soft green garden string, but not too tightly or it will cut in.

Hardy annuals with thin floppy stems also need supports. Again, twiggy hazel sticks can be used. Insert them before the plants make too much growth.

Gladiolus spikes will need supporting with individual canes, as for delphiniums, and canes make ideal supports for chrysanthemums. Tall dahlias need something stronger – there are available special wooden dahlia stakes, about 25mm (1in) square. Use one or more per plant and tie the stems loosely with soft garden string.


Spring-flowering bulbs do not need lifting unless you require the bed for some other purpose, such as summer bedding. If you have to lift the plants before the leaves die down, heel in the bulbs in a spare piece of ground. You may find you need to lift clumps of established bulbs after some years, as they have become overcrowded and congested. Do this when the leaves have completely died down.

Once the leaves have turned brown, bulbs can be lifted and stored until planting time. First remove the dead foliage, then lay out the bulbs in single layers in trays to dry off, choosing a warm, dry, airy place, such as a greenhouse or cold frame. When dry, rub off any adhering soil, and store them in the trays in cool, airy, dry conditions until planting in the autumn. It is important to make sure that the bulbs remain dry during storage as even a little moisture between the scales could lead to mildew and decay. However, warm dry atmospheres should be avoided, as these will lead to desiccation.



Growing from seed is one of the major methods of raising new plants, and is very often a cheap one, particularly if you save your own.

It is best to collect seeds only from plants that are true species: those that have been found in the wild and have been unaltered by man. The resultant seedlings will then be true to type, that is, will be virtually identical to the parent plants. If you collect and sow seeds from highly bred plants – hybrids and cultivated varieties (cultivars) – such as roses or dahlias, the resultant seedlings will be very mixed and many will not have the same characteristics as the parent plants. Many will, in fact, be inferior.

There are sure to be many plants in your garden or greenhouse from which you can collect seeds: trees, shrubs, conifers, climbers, herbaceous plants, alpines, bulbs, hardy annuals, and greenhouse shrubs and perennials are all possibilities.

Collect the seeds when they are fully ripe but before they are shed by the plants. The main periods for seed collecting are summer and autumn.

Many plants produce seeds in dry pods and capsules which change colour as the seeds ripen, generally from green to brown or black. The pods and capsules usually split open to release the ripe seeds, so collect them just before this happens. Many plants such as hollies and cotoneasters produce their seeds within berries and fruits which generally turn red or orange as the seeds within ripen.

Collect the seeds on a warm, dry day. Seeds which are in dry pods and capsules should be dried off for several weeks in a warm, sunny, dry, airy place, such as a greenhouse or a windowsill, indoors. Spread out the pods and capsules in a single layer on sheets of newspaper, perhaps in seed trays.

Once dry, the seeds should be separated from the pods and capsules. You may have to crush them if they have not split open and released the seeds. Rub the seeds between your hands. The resultant mixture of seeds and debris (chaff) should be separated by gently blowing on it – the lighter debris will be blown away, leaving the seeds for you to collect.

The seeds should now be placed in paper envelopes, labelled and stored for the winter indoors. They must have cool, dry, frost-proof conditions.

Berries are not dried and stored by the above method, but are placed in single layers in moist sand. Use tins with drainage holes, and stand them in a shady, cold spot out of doors. For some seed this period of chilling is necessary to break their dormancy. The mixture of seeds and sand can be sown in spring.


Many hardy and tender plants are propagated from cuttings – prepared shoots which are encouraged to form roots. There are several different types of cutting:

Softwood cuttings are prepared from soft side shoots in the spring or early summer. Many shrubs, herbaceous plants such as delphiniums and chrysanthemums, alpines and greenhouse plants can be propagated in this way. Start by removing some shoots from the plant you wish to propagate and then, with a sharp knife, cut the stem immediately below a leaf joint or node. In general, you should have cuttings of between 75mm and 100mm (3-4in) in length. Cut off the leaves from the lower half of each and dip the base in hormone rooting powder. Insert the cuttings in a mixture of equal parts peat and coarse sand up to the level of their lowest leaves. Water in and place in a warm environment -ideally in an electrically heated propagating case inside a greenhouse or on a windowsill indoors. Some windowsill models are inexpensive and very cheap to run.

Semi-ripe cuttings are prepared and potted up in the same way as softwood cuttings. The shoots used are hard and woody at the base but still soft and green at the top. Semi-ripe cuttings can, if desired, also be rooted in a cold frame. In which case they are taken later in the year, in late summer or early autumn. Many shrubs can be propagated by this method, including evergreens, such as rosemary, and also conifers. Geraniums (Pelargonium), too, are raised from semi-ripe cuttings.

Hardwood cuttings of deciduous shrubs are taken once the leaves have fallen, the cuttings being then completely hard and woody. This is a useful method for propagating black and red currants, gooseberries, privet for hedging, and shrubby dogwoods, or cornus, as well as many other deciduous shrubs. Cut shoots of the current year’s growth into 150-200mm (6-8in) lengths. With gooseberries and red currants, cut out all buds except the top three or four. Insert the cuttings in the open ground, in a sheltered, well-drained spot, at a depth equal to two-thirds of their length, after treating with hormone rooting powder. Leave them for a year, by which time they should be well rooted.


This is a popular and easy method of propagating hardy herbaceous perennials, such as helenium, Michaelmas daisy and rudbeckia, as well as some shrubs and mat-forming alpines. It is best done in early spring or autumn.

Lift the plants with a fork, shake off the soil, and split either by hand or with garden forks, into a number of smaller pieces. Discard the centre of each clump as it will be the oldest part of the plant and will be declining in vigour. Save only the young, vigorous outer portions. Replant immediately. Herbaceous plants benefit from dividing every three or four years to keep them young, vigorous and free-flowering.

16. August 2013 by admin
Categories: Featured, Garden Management, Top Tips | Comments Off on Guide to Summer Gardening


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