INCREASING YOUR STOCK OF PLANTS

There are several methods of raising new plants, but there is no ‘best’ way. Sowing seeds is a relatively inexpensive way of producing large numbers of (lowers for the garden – it is the standard way for annuals but beset with drawbacks for most perennials. Border and rockery perennials require a vegetative (non-seed) means of propagation if you want to reproduce a named variety – seed rarely produces plants which are completely true to type. Dividing up a mature clump is, of course, the easiest method of vegetative propagation, but not all perennials can be split up in this way and even when practical you have to disturb an established plant. Cuttings are a much more practical proposition in most cases if you want lots of new plants – the cuttings are usually taken from non-flowering shoot tips but roots, leaves and small basal snoots are also used. Don’t try to guess the correct method to use. Look up the plant in the A-Z guide and employ the recommended technique.

SEED SOWING

Looking through the seed catalogues is one of the joys of gardening. Many gardeners begin their horticultural experience with a packet of Virginia Stock or Nasturtiums, and perhaps we move too quickly to buying in bedding plants and container-grown specimens – forgetting the thrill of starting from scratch. Growing plants from seed is perfectly straightforward if you follow a fewsimple rules. The first decision to make is whether you are going to raise the seedlings indoors for planting out later (the Half Hardy Annual Technique) or sow the seeds outdoors (the Hardy Annual or the Biennial Technique). Half Hardy Annual Technique

CONTAINERS Use a seed tray, pan or ordinary flower pot. Drainage holes or cracks are necessary. Wash used containers before filling – soak clay pots overnight.

COMPOST A peat-based seed compost provides an ideal medium for germination – sterile, light and consistent. Fill thecontainerwith Baby Bio Seed and Cutting Compost. Firm lightly with a piece of board. Sprinkle the compost with water the day before seed sowing -it should be moist (not wet) when you sow the seeds. Scatter them thinly and cover with a thin layer of compost – small seeds should not be covered. Firm lightly with a board. Nowchoose the standard’under glass’method or simple ‘windowsill’ method.

STANDARD ‘UNDER GLASS’ METHOD

COVER Place a sheet of glassover the tray or pot and put brown paper on top. Keep at 60°-70°F and wipe and turn the glass every day.

SIMPLE ‘WINDOWSILL’ METHOD

COVER Place a transparent poly-thene bag over the pot as shown. Fit with a rubber band. Keep at 60°-70°F in a shady spot.

LIGHT As soon as the seedlings break through the surface, remove the polythene bag and move the pot to a windowsill which does not receive direct sunlight. Turn the pot regularly to avoid lop-sided growth – keep the compost moist but not wet.

PRICK OUT As soon as the first set of true leaves have opened the seedlings should be pricked out into trays, pansor small pots filled with Potting Compost. Handle the plants by theseed leaves-not thestems. The seedlings should be set about Iva in. apart. Keep the container in the shade for a day or two after pricking out.

HARDEN OFF When the seedlings have recovered from the pricking out move, they must be hardened off to prepare them for the life outdoors. Increase the ventilation and move the container to a cool room or to a cold frame. Then move outdoors during daylight hours; finally leaving them outdoors all the time for about 7 days before planting out. !

Hardy annuals for growing in flower beds. Half hardy annuals where late flowering is acceptable.

Timing March-April for hardy annuals, but let soil conditions be your guide. The soil must be warm enough for germination, and dry enough to allow you to make a seed bed. Hold up operations if the weather is cold and wet, even though it may mean being a couple of weeks late – the plants will catch up by flowering time. A good guide that sowing time has arrived is the appearance of annual weeds. September is a suitable time for sowing many annuals (e.g Larkspur, Limnanthes, Virginia Stock, Cornflower and Pot Marigold). These autumn-sown annuals will bloom earlier than spring-sown ones.

PREPARE SOIL A well-made seed bed is necessary so that the seeds will have enough air and moisture, and the tiny roots will secure a proper foothold. Choose a day when the soil is moist below the surface but dry on top. Lightly tread over and then rake until the surface is even and crumbly.

MARK OUT THE BED

You can scatter seed over the allotted area but this will make thinning and weeding difficult. It is much better to sow the seeds in drills at the recommended distance apart . Note that drills are set at different angles to avoid a regimented appearance

Mark out zone for each variety with a pointed stick

Note overlap to avoid sharp dividing lines

Space left for bedding out a half hardy annual in late May or early June

PREPARE SEED DRILLS The depth of the drill depends upon the size of the seeds. A general rule is to ensure that the seeds will be covered with soil to about twice their size. Remember that you should never water the seed bed after sowing – if the soil is dry then gently water the drills before sowing.

SOW SEED Seed must be sown thinly. Mix very small seeds with sand to help ensure an even spread. After sowing, carefully rake the soil back into the drill and then firm it with the back of the rake. Apart from gentle watering if there is a long dry spell, nothing further need be done until after germination apart from protecting the area from birds. Cover the surface with twigs or stretch black thread over the seed bed. At the first stage reduce the stand to one seedling every 2 inches. Lift out unwanted plants very carefully – you must not disturb the ones you propose to retain. Repeat this thinning about 10 days later, so that the young plants are at the distance apart recommended for them in the A-Z guide. Thin out September-sown seedlings in autumn.

Biennial Technique

Timing

Hardy biennials which will be transplanted into beds in autumn. Hardy perennials which will be transplanted into pots in autumn. Nearly all named varieties of perennials fail to breed true from seed, but you might not mind having a mixture of colours – let a seed catalogue be your guide. The real problem is that you might have to wait several years before perennials reach flowering size.

PREPARE NURSERY BED This is a special plot of ground set aside for raising seedlings. Follow the rules for preparing the soil for hardy annuals – Step Q] above.

PREPARE SEED DRILLS Follow the rules for preparing drills for hardy annuals – Step [3J above. The drills should 2 I be 1 ft apart and labelled with the name of the variety sown. apart. Firm the soil around plants.

PLANT OUT In autumn when the plants are 1.5 -2 in. high, lift up each plant with a trowel and transfer it with its soil ball to the bed or border where it is to flower (hardy biennials) or a small pot filled with Potting Compost (hardy perennials). Gently water the plants into their new home.

SEED TYPES

Standard seed

Nearly all seed used for propagation is bought in packets shortly before the time of sowing. This seed will have been carefully selected and cleaned by the packager.

Dressed seed

The grower will have dusted the seed with a fungicide or insecticide/fungicide before packaging.

The packager will have coated the seed with a clay Pelleted seed mixture to enable the easy handling of small seeds. Thechore of thinning is removed -sow at half the final spacing and merely pull out or transplant alternate seedlings after germination.

Saved seed Some seed is usually left over after sowing I I – nearly every variety can be saved for next year if you put the seed in an air-tight tin and keep in a cool place.

Home-grown seed

Annuals and biennials can be propagated from seed collected from plants growing in the garden. Collect the seed when ripe and allow it to dry thoroughly before storing in an airtight tin in a cool place.

Self-sown seed

Many plants produce self-sown seedlings around them – Nature was propagating her own long before Man arrived! These self-sown plants can be left where they are or transplanted to another spot. The drawback is the same as for home-grown seed – the pollen may have come from inferior or even wild plants and the resulting flowers are generally poorer and more varied than those raised from shop-bought seed.

DIVISION

Division is a form of propagation which is often forced upon you. Spreading border perennials will often deteriorate after a few years if not lifted and divided. In this way you can increase your stock and regenerate the plant at the same time.

Choose a mild day in spring or autumn when the soil is moist but not wet. Dig up the clump with a fork, taking care not to damage the roots more than necessary. Shake off the excess soil and study where the basic divisions should be. You might beable to breaktheclump with your hands, taking off pieces bearing both shoots and roots. If the clump is too tough for this technique then use two hand forks or garden forks. Push the forks back-to-back into the centre of the clump and prise gently apart. Treat the resulting divisions in a similar fashion or tear apart with the fingers. A sharp knife may be necessary for tough rootstocks.

Select the divisions which came from the outer region of the clump – discard the central dead region of an old plant. Replant the divisions as soon as possible and water in thoroughly.

Always check in the A-Z guide before lifting a perennial. Some dislike disturbance and may take several years to recover. Others which can be moved may have a distinct preference for either autumn or spring.

Carefully dig around the clump of rhizomes and raise them gently so that the roots are retained. Shake off the excess soil and with a sharp knife divide up each rhizome into sections, so that each piece bears leavesor buds above and roots below. Throw away all old and diseased pieces and then replant each section at the same depth as the original plant. Summer is the usual time for dividing rhizomes.

Bulbs and Corms

Most bulbs and corms spread to form clumps in the garden, and these require lifting and dividing every few years. The best time for this task is when the foliage has died down. Lift the clump with a fork and separate with the fingers. Replant the large specimens at once in areas where flowers are required next year, but move the small offsets (bulblets or cormlets) to an out-of-the-way spot. Plant them 2-4 in. deep and leave them undisturbed until they have reached flowering size in 2 or 3 years time. Once they have flowered they can be lifted and moved to the display part of the garden.

A cutting is a small piece removed from a plant which with proper treatment can be induced to form roots and then grow into a specimen which is identical to the parent plant. Stem-tip cuttings are popular-short piecesof non-flowering shoot tips which are ideally soft and green at the top and rather firm at the base. Some border perennials produceyoung shoots around the base of the main stems in spring – Lupins, Delphiniums and Paeonies are good examples. These shoots are pulled away or cut off at ground level with a sharp knife to provide basal cuttings. A third form of cutting is obtained by gently pulling off a side shoot from a main stem, making sure that some of the old stem (’heel’) remains. These heel cuttings usually root very easily.

There are, however, a few general rules. Use a sterile rooting medium and plant the cuttings as soon as possible after severance from the parent plant. Some form of cover will be required to ensure that the cuttings are kept in a humid atmosphere, and do not be tempted to keep pulling at the cutting to see if it has rooted. The appearance of new growth is the best guide.

Types of Containers

For difficult subjects you may require a propagator with undersoil heating. For nearly all perennials, however, the plant pot or rooting bag is satisfactory

Rooting bag 0 Cut central hole and add water to compost as instructed 0 Place pots in a cold frame – shade glass and ventilate on hot days. Water gently when necessary. In frosty weather cover glass with sacking

Polythene bag method 0 Place 4 canes in the pot and drape a polythene bag over them. Secure with a rubber band. Stand pot in a bright spot away from direct sunlight

Cold frame method

Pick off leaves which turn yellow or start to rot. Look for signs of rooting in 4-6 weeks – new growth is the best indicator. Also, a rooted cutting will not lift if the leaves are gently tugged. Plant rooted cuttings separately into 3 in. pots containing Potting Compost

Root Cuttings

Some perennials can be propagated by planting sections of their fleshy roots – examples include Phlox, Anchusa and Oriental Poppy. Insert 1 in. pieces vertically into Seed and CuttingCompost for half their length, then coverthem completely with a layerof sharp sand. Water in and transplant into individual pots when new top growth appears.ROCKERY PERENNIALS ‘Rockery perennial’ is a vague term used to describe a dwarf herbaceous perennial which is suitable for growing in a rock garden – it is impossible to be more precise. Such plants are often referred to as alpines because many of them (the true alpines) were originally collected from the slopes of the Himalayas, Andes, Atlas Mountains, European Alps, Rocky Mountains and so on – the intrepid traveller can still find these true alpines growing in the wild. The Edelweiss of the Swiss Alps has become the classical representative of this group – low-growing and extremely hardy with a passion for sun and gritty, free-draining soil. Many true alpines can be grown outdoors as rockery perennials but some of the choicest examples have to be kept in an alpine house – a cool or cold greenhouse with a low-pitched roof. The reason for housing these difficult plants indoors is that they cannot stand our winter winds, frosts and rain – at home they spend all the winter months tucked up under a thick blanket of snow.

Not all rockery perennials are true alpines. Some come from lowland sites such as deserts and the seashore – others are the product of the plant breeder’s art rather than the work of Nature. The Aubrietia in your garden is quite different to its ancestors growing in the wild.

A mixed bag, then, of low-growing but often spreading perennials which are usually grown in a rockery or rock garden. Success with a rock garden depends upon proper siting, construction and planting. . . . and there are pitfalls at each stage. Siting first, and you should pick an unshaded spot as nearly all rockery perennials are sun lovers. A few require shade and these can easily be accommodated against a rock-face which receives little or no sun during the day. Never, never try to build a rockery under trees-the drip from the wet foliage in summer and the blanket of fallen leaves in winter can be fatal.

Having found the right site you must now think about construction. Order your stone – find a local source if you can as the cost of transporting rocks over a large distance can be prohibitive. Slabs weighing between 50 and 250 lb are what you require, and you should not attempt to construct a rockery on your own unless you are used to heavy work. The best of all stone types is tufa, a porous limestone which allows root penetration.

Before you lift a single stone you must make sure that the drainage is adequate. If there is the slightest problem then you must build a soakaway of pebbles or broken bricks on which the rock garden should be constructed. A long time ago Reginald Farrer described badly-made rockeries as clogs’ graves, almond puddings and devil’s lapfuls, and textbooks provide detailed warnings against such eyesores with the stones sticking upwards. Always try to make the rock garden look like a natural outcrop with the stone slabs sloping gently backwards and with most of the bulk and all of the undersides buried in the earth. Cutting a rockery into a sloping lawn is the easiest situation although with care (and some skill) you can build one on a level site.

Use a planting mixture rather than ordinary soil for building up the structure and for filling the gaps between the stones – mix 2 parts soil, 1 part peat and 1 part grit or coarse sand. Never use fine sand – it would do more harm than good. Planting is the final stage, and it would be a poor rock garden which relied on rockery perennials alone. Dwarf conifers, low-growing shrubs, dwarf bulbs and a few annuals all have an important role to play and there are an infinite number of possible arrangements. The best plan is to go along to your local botanical garden (or the R.H.S. Gardens at Wisley if you are in the London area) and write down the names of the plants you will find in the rock garden. A few must be planted vertically in cracks between the rocks in order to keep winter rain off the leaves.

We have dealt at length with the rock garden but it is not the only or even the best place for rockery perennials in a small garden or a level site. A raised bed or a sink garden shows off tiny, choice alpines to perfection whereas they can be lost amongst the large stones and spreading leafy sheets found in the rock garden. Many alpines flourish in the cracks between the bricks in old walls or the paving stones in pathways, and there is always the front of a small border where they can make middle-of-the-border plants look like giants. Somewhere in every garden there is a place for at least a few rockery perennials.

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