Using Biennials Effectively

How difficult it is to make a hard-and-fast rule dividing the annuals from the biennials! Then there are some of the true biennials like the Evening Primrose for instance, which shed their seeds in the autumn and these will lie in the soil until early the following year before germinating. They thus grow and flower in one season and so seem like an annual. Then there is a number of perennials like the wallflower or sweet william which are always grown as biennials because they do better that way.

The biennials will be raised in a seed bed very much in the same way as cabbages for planting out later, may be transplanted if necessary into further beds, and will finally be planted out into the place where they are going to grow. ,


As the seed of biennials are sown during the dry months of May, June and July, it is necessary to fork into the top 50 mm (2 in) sedge peat at the rate of one bucketful per square metre. If the soil is sandy and dry, damp the peat thoroughly beforehand. If it is heavy and tends to be wet, use the peat dry. In addition, work into the ground ‘meat and bone’ meal at 105 g/m2 (3 oz per sq yd). Make the bed really firm by treading, and follow this by a light raking, so as to get the surface down to a fine tilth (getting all the particles of soil down to a size smaller than a grain of wheat). The drills can then be drawn out shallowly, the right distance apart.


Here the land should be dug shallowly. Proper composted vegetable refuse should be incorporated shallowly at the rate of one bucketful per square metre. This work should be done early so as to allow frosts and cold winds to act on any clods there may be and break them down. This, of course, can only be done if plants are to be set out in the spring. When planting is to be carried out in the autumn, the shallow digging and composting must be followed by a good treading to get the ground firm and ready for setting the plants out.

The compromise is to thin out the plants in the seed bed and to transplant them to a nursery bed. Here they may go on growing until they are finally planted into their flowering quarters in the spring. The nursery bed should be well enriched with fine organic matter like sedge peat, so that an abundance of fibrous roots may be produced.


Having prepared the seed bed, the drills will be drawn out 150 or 225 mm (6 or 9 in) apart, and about 12 mm (% in) deep, and the seeds of the biennials will be sown in these drills very thinly. To enable the beginner to do this, it is a good plan to mix the seed with five times the quantity by bulk of sand or pulverized dry earth. Some will prefer to sow the seed by stations, and in this case they will place 2 or 3 seeds every 150 mm (6 in) along the drills, later thinning down to one seedling per station, should the germination prove to be 100 per cent.


Those who do not sow per stations will have to thin rigorously and either waste the plants that are pulled out or transplant them into other prepared beds 150 or 225 mm (6 or 9 in) square, depending on the final height of the plants themselves. Never allow the plants to grow in rows thickly, for the final success of a plant is always determined in its early stages.


The plants should be dug up from their nursery beds with as good a ball of soil as possible. They should be transferred to the spot where they are to be planted in shallow trays or boxes, so that the ball of soil does not break away. Good-sized holes should be prepared with trowels so that the roots with their ball of soil around them may fit into their new position with the minimum of disturbance. It is important to water the plants in at this stage and what is known as ‘ball watering’, i.e. watering round the ball of soil recently inserted to the ground, should be carried out once a day for three or four days after planting if the weather proves dry.


Never allow the biennial to remain in the bed after it has finished flowering. Pull it up and put it on to the compost heap where it can rot down and form manure. Keep the ground well hoed between the plants to eliminate weeds. In dry weather put on top dressings of lawn mowings or other similar material as mulch.

BROMPTON STOCKS May be described as half-hardy biennials. The plants are erect and have narrow leaves, the edges of which are usually waved. They grow to a height of about 450 mm (18 in) and flower from June onwards. They may be had as crimsons, mauves, whites or roses. It is usual to sow the seed in June or July either in the open in a sunny bed or under cloches. Some sow in boxes in the greenhouse though this is really not necessary. Despite thin sowing it is necessary to transplant the stocks when 25 mm (1 in) high, 100 mm (4 in) apart. As the stock is very liable to black leg, the soil used in boxes and frames is sterilized or the No-Soil compost is used instead. The plants are finally set out into their permanent beds 225 or 300 mm (9 in or 1 ft) square, and in the north it is usually necessary to cover them with cloches in the winter. Some northern gardeners prefer to leave the plants in the frames until the spring and then plant them out permanently.

Most of the growth of Brompton Stocks is made during the second year and that is the reason why little room need be given to them the first year after sowing. Good varieties are Empress Elizabeth, a large flowered bright rosy carmine. White Lady, a large pure white, and Giant Mauve.

CANTERBURY BELLS Tall plants that have bell-shaped flowers. They usually grow to a height of 600 to 900 mm (2 to 3 ft) and flower in June, July and August. The seed should be sown at the beginning of May in a sunny spot out of doors under continuous cloches. The land should be enriched with sedge peat at one bucketful per square metre. It is important to sow early, as most of the growth of the canterbury bell is made the first year. Some gardeners sow the seed in boxes in the greenhouse and then when convenient to handle plant out into a finely prepared bed, 150 mm (6 in) square. Sowing by stations 150 mm (6 in) apart in a seed bed out of doors saves a great deal of handling and transplanting. If possible the plants should be set out into their flowering positions early in August either 300 mm (1 ft) square or 300 by 225 mm (lft by 9 in).

CHEIRANTHUS This is really the Latin name of the family of wallflower, but is commonly used as the name for the Siberian wallflower Cheiranthus allionii. This bears beautiful deep orange flowers from May onwards and averages 300 mm (12 in) high. The seed should be sown in May in the seed bed. In the north it is advisable to delay the transplanting into the flowering position until March the following year. EVENING PRIMROSE There are two main biennial evening primroses, both of which should be sown in seed beds in June or July. They should then be transplanted in September, and will flower the following summer. Oenothera biennis, the common evening primrose, is the pale yellow fragrant sort that flowers from June to September, and usually grows about 1.2 m (4 ft) in height. Golden Yellow is the golden yellow fragrant variety that gives plenty of colour from June to September, and often grows 1.5 m (5 ft) tall.

FORGET-ME-NOT Though usually considered as a blue-flowered plant, it is possible to have pinks and whites. The flowering takes place in April, May or June according to variety, and the flowering stems may be from 300 to 375 mm (12 to 15 in) long. The seed should be sown in May in the seed bed. When station sowing is not practised, handle into further beds 150 mm (6 in) square. As a result they should grow into quite good plants by October, when they can be planted into their permanent positions. Forget-me-nots appreciate phosphates and potash; work steamed bone flour into the soil where they are to grow at 105 g/m2 (3 oz per sq yd), and give wood ashes if possible at a similar rate.

Good varieties are Royal Blue Re-selected, a very early free flowering deep indigo blue. Marine, a bright blue but not so tall as Royal Blue; and Victoria, a very bright blue, probably the earliest of the three.

FOXGLOVE A plant that quite likes shade and is often grown in a wild garden or in the margins of shrub borders. There are four biennial border species listed. The seeds are usually sown in a seed bed in a half shady part of the garden early in May. It is important to thin out the seedlings when quite small and transplant them into other borders that have been enriched with peat, so that they may grow on. The planting into their permanent quarters is usually done in September. An interesting variety is Foxy. It grows 300 mm (3 ft) high and is compact and bushy. The flowers are spotted and very attractive. Digitalis gloxiniceflora is the Giant Spotted Foxglove which produces masses of large flowers covered with spots, from July to September on stems 1.5 m (5 ft) high. Digitalis monstrosa may be had in various charming colours on stems 1.2 to 1.5 m (4 to 5 ft) tall from July to September. The common Foxglove is Digitalis purpurea which flowers about the same time as the others and grows about 1.2 m (4 ft) tall. The flowers are purple.

HOLLYHOCK There are a few species of hollyhock which are truly biennials and the plants of which may be raised in a similar manner as for wallflowers. The spot where the plants are to grow must be deeply dug and heavily manured because the plant is a deep rooter. Althaea cannabina bears large solitary rose flowers with a yellow base from July onwards, and usually grows about 1 m (3 ft) tall. A. ficifolia bears pretty yellow and orange flowers in July and August and grows 2 m (6 ft) high. The common hollyhock that most people know is really a perennial but is usually scrapped after two years for it gets so badly attacked by rust. A dwarf 600 mm (2 ft) variety is Silver Puffs. The flowers are double, fringed and pink. Summer Carnival on the other hand grows 2 m (6 ft) high and produces double flowers 100 mm (4 in) across of many differing colours, scarlet, rose, pink, yellow and white.

HONESTY This, though it has lovely purple blooms, is usually grown for its seed-pods, the centres of which are large, circular and transparent and look like moons. Hence the Latin name Lunaria, from the Latin Luna, the moon. It flowers in May, grows to a height of 1 m (3 ft), and the seed should be sown early the previous May out of doors. After thinning, the plants may be allowed to remain there till August when they should be put out into their flowering positions 300 mm (1 ft) apart each way. It is always better to grow Honesty on land that has been manured well for a previous crop. A freshly manured over-rich piece of land tends to encourage too much foliage and too little bloom. The plant will grow quite well in a shady situation. The best variety to grow is the Munstead Purple whose flowers are dark mauve in colour. There is a crimson variety and a white kind as well.

MULLEIN Verbascum. There are over 100 species of mullein but many of them are worthless. There are many good biennials, however, which can all be raised from seed sown in a nice seed bed at any time from mid-April to June. Sow by stations 150 mm (6 in) apart and transplant into permanent positions in September or the following spring.

Verbascum thapsus is the common mullein, the well-known yellow sort which blooms through the summer and early autumn and may grow to 2.5 m (9 ft) high. V. rubi-ginosum bears yellow flowers deeply tinted with red from June to September and only grows 4.2 m (4 ft) high. V. bombyciferum, Arctic Summer, grows 2 m (6 ft) high and bears spikes of yellow flowers.

SCABIOUS As the scabious is generally called the Annual Scabious. It is however strictly a biennial and may be sown in April or May outside, transplanted in August or September into its permanent position and then flowers in June the following season.

SWEET ROCKET The plant looks much like an ordinary stock but has hairy toothed leaves. In the country it is often called Dame’s Violet. It bears spikes of lilac, or white flowers 1 m (3 ft) high and is in flower in June and July. The seed should be sown in May or early June in the prepared seed bed. Sow by stations 150 mm (6 in) apart and put the plants out in their permanent positions in July or early August, 300 mm (1 ft) square. The blossoms are very richly perfumed, and it is a nice plant to have near the windows of a sitting room. SWEET WILLIAM This is strictly a perennial but is invariably grown as a biennial. It flowers in June and early July and can be had in many lovely colours, white, pink, red and mixtures. It generally grows 600 mm (2 ft) tall. The seed should be sown in the seed bed out of doors in May. The plants are set out into their flowering bed in August or September, 300 mm (1 ft) square. The sweet William is happy to grow in almost any soil, and will put up with rather rough treatment. Good varieties are Holborn Glory, a large flowered auricula-eyed strain, and the Unwin Hybrids. The new Extra Dwarf Double Mixed only grows 250 mm (10 in) high and produces 70 per cent double flowers of beautiful colours.

WALLFLOWER Few will not know the wallflower which probably gets its name because it is often found growing naturally in the crevices of old walls. It flowers in April or May growing to a height of 450 mm (18 in). To get the best plants the seed should be sown thinly in May with the drills 300 mm (12 in) apart, though those who omit to sow then may put the seed in during June and July. The young plants should be transplanted when 50 mm (2 in) high into a temporary bed or into their permanent positions. Whenever they are put out into the spot where they will flower the distances in millimetres should be 225 by 225, 300 by 225, or 300 by 300 (9 by 9, 12 by 9 or 12 by 12 in), depending on the size of the plants and the general planning.

It is most important to see that the bed is firm after it has been dug and manured. Firm soil ensures bushy plants. Bushiness is also assisted if the growing points are pinched out when the plants are about 150 mm (6 in) high. Always plant with a trowel and never a dibber.

Good varieties are Cloth of Gold, a large handsome yellow; Golden Queen, a large flowered deep golden yellow; Covent Garden Blood Red, a rich velvety crimson; and Scarlet Emperor, the purest scarlet grown.


Biennials are commonly used in a formal way, that is to say they are planted out in beds on the square or in some regular formation. This bedding out, as it is called, was particularly popular in the Victorian era and is still very popular in France and Germany. It is more commonly used in this country for beds, say in a front garden, or for beds on terraces. For instance, where tulips are to be planted formally, forget-me-nots are generally planted between, and thus you get a very bright late spring display.

The great thing is to have a mass of bloom and to put the plants out so that they have the exact amount of room they need and no more. The soil is therefore completely hidden.

Biennials can be used for planting out in drifts in a shrub border or even in drifts in a herbaceous border. Biennials do well in narrow borders. I often plant them, for instance, in a narrow bed I have around the tennis court which is rather too dry for growing perennials successfully. The biennial is perfect for the more formal position or the more formal aspect in the garden.

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