Watch out for our next competition which will be launched shortly with more prizes and a free gift for every entrant.

Continue to plant all types of water plants this month. In most seasons, tender, floating plants such as hyacinth and water chestnut will not be available until the middle of the month. Do not plant out until the water is warm and there is no danger of frost. In cold areas wait until early June.

Feeding

Feed established aquatic plants either with a sachet of properly prepared aquatic fertiliser or a slow-release fertiliser tablet. Push the tablet well down into the compost next to the plant, so that the roots can easily take up nourishment and the fertiliser does not leach into the water.

Spreading algae

Until the leaves of the waterlilies are sufficiently large and numerous, and the floating plants have grown and multiplied, most of the water surface will be exposed to full light conditions and algae will probably become a nuisance. Free floating single celled algae will turn the water an opaque green colour, while blanketweed produces masses of fine filaments that restrict the growth of other plants underwater by shading them out.

Remove as much blanketweed as possible with a net, roughened stick or by hand. Algicides, sold for pond use, control both green water-discolouring algae and filamentous growths. Remove the algae masses as soon as they turn brown, to prevent them from blanketing other plants and also to prevent any oxygen deficiency in the water. Adding barley straw to the pond is another excellent way to control algae and keep the water clear. Although it is sometimes recommended, never use straight chemicals such as potassium permanganate in garden pools.

Water evaporation

Warm weather results in considerable water loss by evaporation. Top up the pool using s hosepipe from the tap. Fill little and often, so that wide temperature fluctuations do not occur in the water.

Waterlily propagation

Propagate waterlilies from ‘eyes’ (dormant buds) which occur with varying frequency along the rootsticks of mature waterlilies. Remove the eyes with a sharp knife, and dress the cut ends with flowers of sulphur. Insert the eyes individually into small pots of good garden soil or aquatic planting compost. Place the pots in a bowl with the water level just covering the eyes. They will produce young plants which will flower in two or three years.

Waterlilies can also be divided. This is the easiest way to propagate them if you want to raise a small number of plants.

Propagating marginal plants

Many water plants can be increased from cuttings taken this month. These include brooklime and water mint. Put the cuttings in pots of mud and place in a bowl. Fill the bowl with water so that it just covers the surface of the pots. The cuttings will root very quickly.

Clumps of established plants, such as pickerel weed, flowering rush and cotton grass are easily increased by division now. Select the youngest and most vigorous outer portions for replanting.

Floating plants

Place new and overwintered hardy floating plants on the surface of the water.

Bog garden

Prick out seedlings of spring sown bog plants, such as primulas, into seedtrays using a good potting compost. Place the pricked out seedlings in a light airy place out of direct sunlight. Weed the bog garden regularly throughout the month.

Give the ground a good soaking a day or two before planting out your own or purchased seedlings and water the young plants in their pots before transplanting. In very hot spells, plant in the late afternoon when it is cooler.

Beans

Continue to sow and plant out broad beans. In mild areas plant out the first dwarf French and runner beans 15cm apart, after hardening them off. Alternatively sow directly outdoors, planting two seeds every 15cm. Remove the weaker one if both survive. Dwarf French beans should not need support but you can use small twigs or canes and string to hold the plants upright and help keep the pods off the ground. In colder areas, sow French and runner beans in pots in a propagator early this month. Erect supports for all climbing runner beans.

Brassicas

Plant out summer brassicas started in pots, once they have been hardened off. Continue to sow calabrese and summer cauliflower for a succession of crops throughout the summer. Sow autumn/winter cabbage directly into the ground, and sprouting broccoli, kale and autumn cauliflower in pots if this was not done last month.

In very mild areas, winter cauliflowers are worth trying. These are sown this month, transplanted four to six weeks later, and will produce heads from March to May next year. If you are planting quick-growing crops, such as lettuce, radishes and turnip, in between the slow-growing main crop of winter brassicas, space the brassicas slightly wider apart and water the vegetable patch more than usual in dry spells.

Sowing carrots and parsnips

Continue sowing early carrots to harvest through the summer. This is the last month to sow parsnips.

Celery

Prick out seedlings of self-blanching celery into individual pots and grow on at 13-15°C. Give an occasional liquid feed (Vitax Balanced Water Soluble Feed is ideal)and keep them moist. Gradually harden them off in a cold frame. When the seedlings have five or six leaves, they are ready for planting out. Grow self-blanching celery in a block of at least 16 plants, spaced 25 cm (10 in) apart. water plants and apply a liquid feed regularly.

Marrows, courgettes, squashes and pumpkins

Harden off courgettes, marrows, pumpkins and squashes grown from seed sown last month, before planting them outside. Make sure that all danger of frost has passed before putting them outdoors.

Dig a hole for each plant about 30cm wide and deep. Fill with a mixture of soil and well-rotted organic matter. Use any spare soil to form a mound; this will direct water away from the stem and prevents stem rot. Allow 1m between plants in each direction for the bush types, 1.2m for trailing types; pumpkins require up to 3m. Protect young plants from cold winds for the first couple of days by covering them with a bottomless bucket or box and putting a sheet of glass over the top. Do not let the soil in the planting hole become dry, but do not water too much early on as this just encourages leafy growth. Soak the plants once a week when they start flowering.

In colder areas, start courgettes, marrows, pumpkins and squashes off in pots in a propagator. Sow them four weeks before the anticipated date of the last frost.

Other roots and swollen stems

Prick out seedlings of celeriac and treat them as you would celery seedlings. Continue sowing kohlrabi if you want a succession during the summer. Harvest the first kohlrabi by pulling the swollen stems as required before they reach tennis-ball size.

Salad crops

Plant out lettuces started in pots, once they have been hardened off. Continue sowing lettuces, radishes and spring onions for fresh vegetables through the summer. Continue to sow chicory.

Sweetcorn

in mild areas plant out sweetcorn started in pots. Harden them off thoroughly and plant out after all danger of frost has passed. Plant sweetcorn in blocks of at least a dozen plants to ensure even pollination of the cobs. Space out the plants about 40cm apart each way. In colder areas, sow sweetcorn in pots in a propagator. Sow the seeds four weeks before the last expected frost date.

Tomatoes, peppers and aubergines

Harden off aubergines, peppers and tomato plants. Plant out from late May onwards or when all danger of frost has passed. Start them off under cloches, or wait until mid June in colder parts of the country.

Asparagus

Continue cutting asparagus; if this is the first year of cutting, stop by the end of May.

Globe artichokes

Plant out globe artichokes. Allow a square metre for each plant and dig in plenty of well-rotted organic matter.

Growing vegetables in containers

You don’t need an allotment or vegetable patch to grow your own vegetables. Growing vegetables in containers on the patio or other paved area gives all gardeners the opportunity to harvest fresh, home-grown produce even when space is limited.

Another benefit of growing vegetables in containers is that it reduces any potential problems with soil-borne pests and diseases or with impoverished soil. For example, outdoor cucumbers need a well-drained, rich soil; raising them in growing bags saves having to prepare this. However, it must be stressed that all vegetables grown in containers will need watering and feeding regularly if you are to get reasonable yields.

The larger the container you use to grow vegetables in the better. A 25cm pot is the minimum size and it must have drainage holes. Cover these with old crocks or stones. Filling large containers with compost can be expensive. Use growing bags as a cheap source of compost, they can be used for tomatoes and cucumbers as a first crop followed by a second crop of lettuces or radishes.

Tall vegetable crops, including most tomatoes and trailing varieties of cucumber, will need support, so grow them next to a wall, fence or trellis.

Where the appearance does not matter, put old plastic containers not suitable for flower displays to good use.

If the containers are on a patio, make the planting is as attractive as possible by growing plants with coloured leaves and stems such as ruby chard or red lettuce.

Opt for dwarf varieties (sometimes called ‘mini-veg’ in the seed catalogues) and quick-growing crops such as radishes, spring onions and lettuce.

Most plants are best started off in small pots. You can then plant out the best seedlings into the containers and keep a few spares for filling in the gaps.

Vegetables in containers can be planted much closer than generally recommended as liquid feeding will supply the extra nutrients and the crops will be picked young, before they compete too much with each other for light. Use a Vitax Balanced feed for leafy crops and a Vitax Liquid Tomato feed for fruiting crops.

Try to finish planting all your shrubs this month. Small numbers may still be planted throughout the summer if the weather is not too dry and hot and if the plants are watered regularly.Otherwise it is preferable to wait until the wetter weather in September. Continue to water newly planted trees and shrubs. In addition, spray new foliage each evening to prevent it drying out.

Softwood cuttings

Softwood cuttings are those taken from new shoots produced in mid to late spring. They should be firm enough to handle, but not yet fully ripe. If the leaves are larger than about 2.5cm long, remove all but the top two leaves to reduce moisture loss. If the cuttings are taken in late spring and are woody at the base, dip them in Vitax Rooting Powder to help break down the outer skin and stimulate root development.

Rooting in a propagator should take about two to three weeks. Once roots are well developed, shoots will emerge from the upper two leaf buds. Pot up the rooted cuttings into individual 8cm pots containing a general potting compost. Over the next two weeks or so, shorten the new young sideshoots by half to encourage a bushy branching habit in the new plant.

It is worth trying to propagate many different shrubs in this way; hebes, helianthemums and lavateras, are particularly successful, as are many of the grey-leaved Mediterranean shrubs, such as phlomis.

Completing spring planting of hedges

Finish planting all container-grown hedging plants. Plant with Vitax Q4+ and water newly planted hedges in hot, dry weather, concentrating on the rootball of each plant.

Hedge trimming

Start to clip hedges of privet. This should be done regularly every one or two months from now until late summer.

Late frosts and cold winds are both killers of newly planted summer bedding. You can often save your plants simply by covering them with layers of newspaper. A double layer of horticultural fleece also provides excellent protection. Weight the newspapers or fleece down with large stones or peg them down with wire or canes to stop them blowing away. Remember to remove the protection as soon as the danger of frost or cold winds is passed.

Where thatch or dead moss are a continuing problem scarify the lawn lightly using a spring-tined rake.

Controlling weeds

Treat large-leaved weeds, such as dandelions and plantains, with a stick touch weeder or dig them out by hand. If hand weeding, use one of the specialised weeding tools or a knife to get the roots out. Remove all pieces of taproots as many weeds regrow from small pieces left in the ground. Fill any holes with sifted soil or compost. You can treat small patches of weed with a spot weeder without using chemicals over the whole lawn. Vitax Green Up Feed and Weed nourishes the grass while killing unwanted weeds. Vitax Lawn Clear is a powerful lawn weed treatment that handles even the toughest weeds.

Patches of coarse grass will spoil the look of the lawn but cannot be eradicated with selective lawn weedkillers. You can weaken these coarse grasses if you keep cutting out the clump with a knife. In severe cases, it is best to kill that patch of lawn completely with a total systemic weedkiller and then reseed it.

Controlling red thread

Red thread is common in summer and autumn lawns that lack nitrogen. It shows as patches of mottled, light brown grass and, on closer inspection, you will see pink or red threads of the fungus. Apply a lawn fungicide if conditions are not too dry, or a lawn fertiliser to promote lawn growth.

Mowing

Continue to mow the lawn once or twice a week. If you have a powered machine, change the direction of mowing occasionally to prevent a ripple effect (washboarding) on the lawn. Vary the point on the lawn edge at which you turn the mower, as always turning in the same place will damage the grass.

Increase watering and feed as plants start into vigorous growth. Water weekly or daily depending on the weather and the amount of water the plants need. Give plants a weekly liquid feed or alternatively use one of the Vitax Drip Feeds which are designed to deliver the perfect amount of feed.
Shading, ventilation and humidity
Ensure the conservatory is well ventilated and shaded at all times, especially when it is sunny. Roller blinds are visually more acceptable than a shading wash for a conservatory, and they are also easily adjusted to suit the light intensity. To increase the humidity, set out some shallow trays of water in inconspicuous spots.

Moving plants outdoors

Temperatures inside a conservatory often get very high during the summer and many plants will grow and flower better if they are placed outside over the summer months. A sheltered spot on a patio is ideal for many plants, otherwise find a sheltered part of the garden. Remember to water and feed them regularly and check for pests and diseases. Remove plants from south facing windowsills until the end of summer, as the conditions will be too hot for most plants except desert cacti and other succulents.

Healthy leaves

Remove dead leaves. Clean remaining leaves  (Vitax Leaf Wipes are idea)and check for sun scorch which occurs when the sun’s rays are magnified through unshaded glass. This is particularly likely with some kinds of patterned glass where the pattern concentrates the rays.

Supporting plants

Tie in tips of plants such as rhoicissus. Wherever tall, single-stemmed plants, such as ficus or fatshedera outgrow their supporting canes, remove the canes and replace with taller one.

Controlling pests and diseases

Check frequently for the presence of aphids, whitefly, red spider mite and scale insects. Use Vitax Houseplant Pest Killer to control infestations. A daily misting will also help prevent red spider mite infestation. If plants are infested with leaf mealy bugs, pick the bugs off by hand. If root mealy bugs are a problem, tip the plant out of its pot, wash away the compost, remove the affected roots and repot the plant in fresh compost.

Check for vine weevil. Tip plants out of their pots regularly, squash any grubs you find and repot. Also check newly purchased plants for grubs. To deter sciarid fly or fungus gnat, keep the top of the compost dry by covering it with a layer of fine gravel or perlite. Pick off and destroy leaves affected by mildew, grey mould or leaf spots, reduce the humidity slightly, and use a house plant fungicide if necessary.

Flowering plants

Remove dead leaves and flowers from azaleas, taking care not to damage the shoots beneath the dead flowers, as they will bear next season’s blooms. Azaleas bought as house plants for Christmas or Easter may be pot-bound now, so water well then repot them into slightly larger pots, using an ericaceous compost. Keep them in a conservatory or cold greenhouse for a few weeks, then move them to a lightly shaded spot in the garden and plunge the pots in holes filled with grit or sand. Water them daily to start with and don’t let the soil dry out.

Propagating from bulbs

The fern produces small bulblike growths on its leaves. To propagate from these, peg the leaf down on a tray of compost into which they can root. Pot up individually into 8cm pots once they have rooted.

Indoor bulbs and corms

Continue to water plants in flower such as lachenalias and vollotas and apply a liquid fertiliser  such as Vitax Liquid Growmore as necessary. Cyclamen will die back and then require less water. After hippeastrums have finished flowering and the foliage has died back, cut off any remaining leaves cleanly above the neck and store the bulbs in their pots in a cool room until the next spring.

Climbers and feature plants

Add a supporting framework as plants grow, and tie in unruly growth.

Bromeliads

Water freely, give them a foliar feed monthly (Vitax Liquid Growmore)and mist  plants daily. Shade forest bromeliads from direct sunlight or they will be scorched. Most bromeliads need good light to produce the best leaf markings.

Cacti and other succulents

Water well in the growing season, allowing the compost to dry out between waterings. Apply Vitax Cactii feed regularly. Keep Christmas and Easter cacti away from direct sunlight.

Orchids

Water so the compost is moist but not soaking wet. Feed with specialist Vitax Orchid Feeds.  To increase humidity during dry, bright spells, spray orchids with clean tepid water using a handheld mister. Stand slipper orchids and moth orchids on a gravel tray and keep the gravel moist to provide them with extra humidity.

On warm, sunny days provide shade for plants, seedlings and cuttings. Increase the humidity by damping down the staging and floor. Provide adequate ventilation, but do not open side or top ventilators on the windward side of the greenhouse on windy days.

Controlling pests and diseases

As weather conditions improve, introduce the predator Encarsia formosa to control whitefly. You may need to make two introductions to build up its numbers sufficiently to keep the whitefly population under control. You can also use Vitax Organic 2 in 1, Vitax PY Insect Killer and Vitax Protective Plant Labels to control pests.

Sowing cinerarias

Towards the end of the month sow cineraria seeds. This will produce plants that will flower indoors from December onwards. Sow the seeds thinly in pans of seed compost, cover lightly with compost, and germinate at a temperature of 10-13 C. Prick out the seedlings into a seed tray as soon as they are large enough to handle and keep them watered and shaded.

Planting out

In mild areas plant out any vegetables raised in the greenhouse once they have been hardened off. Half-hardy bedding plants can also be planted out; many will be suitable for hanging baskets and containers. Move outside roses that have been forced in containers when they have finished flowering.

Taking softwood cuttings

Take softwood cuttings of suitable herbs, shrubs and perennials; take semi-ripe cuttings of clematis.

Cucumbers

Sow seeds as soon as possible if this has not been done. Stop laterals growing from the main stems of cucumbers at two leaves beyond the first or second fruit, unless they are much preferred all-female flowered type which do not make laterals and which fruit on the main stem. Cucumbers with male and female flowers will also need subsequent sub-laterals pinched out as soon as they have made two leaves beyond their first fruit. Remove all male flowers and tendrils.

Melons

Sow seeds as soon as possible if this has not already been done. Plant out any melons raised from seed sown in April into cold frames, one plant to each frame light. Set out each plant on a mound of soil mixed with well rotted compost. Pinch out the growing point when the plant has developed four or five leaves. Avoid splashing or damaging the main stem at soil level, or damping off may occur.

Peppers and aubergines

Transplant young plants into their final positions when they are 10cm tall; a greenhouse border, growing bags or 20cm pots are all suitable sites. Pinch out the growing tips to encourage a bushy habit. Water in and damp down the greenhouse floor to keep the humidity high.

Tomatoes

Twist the stems of cordon tomato plants round the supporting strings, or tie them to canes, and remove sideshoots regularly. Feed the plants every week or ten days from the time the fruits on the first trusses begin to swell, using a high-potash fertiliser such Vitax Liquid Tomato Feed. In a cold greenhouse, plant tomatoes in the border, in growing bags, or in bottomless containers on a gravel base using the ring culture method.

Vines

Continue to guard against powdery mildew throughout the growing season. Thin and train in new shoots.

Try to finish the planting of permanent containers by early May so that the plants have the long summer period ahead in which to establish themselves. If tender evergreens were not planted last month, plant these now. Finish sowing hardy annuals directly in pots or liners for flowering by the end of June or early July.

Hanging baskets

Harden off hanging baskets by sitting them in a large pot in a sheltered corner during the day. Return them to the greenhouse, conservatory or porch at night. Do not expose them to possible wind damage or the plants may not recover.

Remedying winter damage

Evergreen shrubs which have been severely damaged by frost drop their leaves and often look dead. Don’t discard any plants unless you are positive there are no signs of life; test by scratching the bark to see if there is any green pith showing. Some will not revive until June, when they may re-grow from the base or shoot again from the branches. When this happens, prune out any dead material and reshape the shrub to make a pleasing outline.

Sprucing up windowboxes

By the end of May, most spring flowers in containers will have started to fade and look unsightly. If you have used cheap containers inside an ornamental windowbox it is a simple matter to lift them and replace them with ones ready-filled with plants for the summer. Throw away the faded annuals but salvage ivies and other evergreens such as periwinkle and euonymus, which can either be planted out in the garden or potted up and used again in containers later in the year.

Feeding

Soilless composts contain sufficient fertiliser to keep plants fed for several weeks after planting. After that, you will need to feed plants in seasonal displays regularly. It is best to use a general purpose liquid fertiliser (such as Vitax Liquid Growmore) recommended for flowering plants and bedding. Follow the instructions and do not be tempted to use at a higher rate than the recommended concentration, as this can harm the plants. Plants in coir-based composts may need more frequent feeding and watering than those in peat based composts. Lush, leafy growth at the expense of flowers is usually an indication of overfeeding or too high proportion of nitrogen in the fertiliser.

Watering

As the weather warms up, watering becomes a daily exercise, especially for hanging baskets and plants in small pots which quickly dry out. Use a watering can without a rose to direct water on to the soil rather than the foliage, otherwise it can be wasted. Grouping pots together on the patio can cut down on the time spent watering, as can hosepipe attachments.

If the compost in a hanging basket dries out too much, it can be difficult to rewet. Try taking the basket down and leaving soaking in a sink or bowl of water until the plants have revived.

Protecting against slugs and snails

Check regularly for slug and snail damage (click here for Vitax organic solutions to slugs and snails). Vulnerable plants that are often grown in containers include pansies, petunias and hostas. Slugs and snails will climb up walls, so do not assume that plants in ground floor windowboxes are safe.

Check for other pests and diseases and treat as necessary.

Continue to remove dead blooms from daffodils, tulips and hyacinths as they finish flowering.

Lifting bulbs

Most bulbs, such as tulips or daffodils have finished flowering by now, and it may be necessary to lift them from the beds or borders to make way for summer bedding. Heel in the bulbs in another part of the garden so that they can die down naturally.

1. Provided the flowers have died you can lift spring-flowering bulbs and corms to release the space for other plants. Lift them carefully with a fork, keeping as much soil around the roots as possible.
2. Place the bulbs at a slight angle in a shallow trench so the foliage is above ground. Put netting in the bottom to make it easier to retrieve the bulbs later. Cover the bulbs with soil. Lift and store when the foliage has died down.

Cleaning and storing bulbs

Clean the bulbs of early tulips and daffodils that have had time to die back and store them in shallow trays in a cool, airy shed for replanting in October. Destroy any diseased tulip bulbs that are soft or have prominent brown or grey marks or scars on the body of the bulbs. If they are placed on a compost heap they may carry disease to fresh plantings.

Watering and feeding

Water all plants thoroughly in dry spells. Daffodils in a light, sandy soil will particularly benefit from this. Give gladioli and summer flowering bulbs a general liquid feed (Vitax Balanced Feed and Vitax Liquid Growmore are good choices)

Hippeastrums

After hippeastrums have finished flowering allow the foliage to die back. Cut off any leaves cleanly above the neck and store the bulbs in their pots in a cool place until next spring.

Crinums

Crinum bulbs should be planted 15-20cm deep in a south-facing border. Alternatively, if you live in a cold area, plant them in tubs which can be moved under cover during the winter.

Arum lilies
Arum lilies are often grown in pots in the greenhouse for protection and early flowers but, except in cold areas, they also flourish in the open. Plant them out when all danger of frost has passed, either in moist soil or up to 30cm deep in a pool to grow as water plants.

Gladioli

Continue to plant gladiolus corms for a succession of flowers. Try to finish planting by the middle of the month.

Small alpine bulbs

Gradually reduce the watering of dwarf bulbs which you are growing in a bulb frame or greenhouse as the leaves start to turn brown.