How To Grow Sweet Peas

A most popular annual, the sweet pea (Lathyrus odoratus) is not difficult to grow, though the richer the soil the better the results. Given good cultivation it will produce stems 2 ft. long bearing four, five or more florets. Elegant, graceful and fragrant, with the exception of yellow, it will provide every colour of the spectrum and dozens of different tones or shades. It is a ‘cut-and-come-again’ annual; indeed, every other day blooms should be gathered to keep the plants in full production.

The ‘Spencer’ type, trained up canes in ‘cordon fashion’, will grow to a height of 14 ft. though this means that all side shoots need to be removed during the growing season and every few days there is the business of tying or ringing the thick haulms (stems), and once or twice during the summer kneeing, or layering is called for. On the other hand, if the sweet pea is allowed to go its own way brushwood or wire to the height of 8 ft. will not be too tall.N1508067


Land enriched with farmyard manure at the rate of one barrowful to each strip of 15 ft. by 4 ft., dug in autumn or early winter into the second spit of soil and fortified by half lb. of bonemeal, will give the best results, or good garden compost at the same rate will serve. Failing that peat may be used. A big bucketful to the square yard, fortified by a 1/4  lb. of artificial fertilizer containing nitrogen, phosphates and potash in the ratio of 20:10:10, obtainable in granular form, has proved a very good substitute.

The whole area where the sweet peas are to be grown should be double-dug and the bottom spit treated as suggested. If the soil has been used the previous year for a crop that has been manured, nothing at all need be added. Acid soils should be given a light dusting of lime in January or February. Sweet peas revel in sunshine and dislike draughts, so give them a sheltered place.

When to Sow

In the North sow from late September to 7th October. In the Midlands and the South, from the 5th to the 21st October. It is best to sow in a shallow frame, otherwise the plants tend to get drawn – the aim is short, stocky plants.


Six seeds to a 6-in, pot, sown an inch from the edge is ideal; or if boxes are used. Sow the seeds 2 in. apart each way. Sow ¾ in. deep. Use a moist compost of 3 parts of sieved loam, 1 part of peat and 1 part of coarse sand. Cover the pots or boxes with thick layers of paper to prevent drying out; replace the framelights after placing slug pellets between the pots or boxes. Set a couple of mouse traps, for mice find the seeds irresistible. Inspect after a week and as soon as the shoots appear remove the paper. Water if necessary, and after a day or two open up the frames and do not replace the lights unless frost is threatened.

In hard or severe frosts keep the lights down and cover them with old carpets or sacks. Never let the sun shine on pots and boxes if the soil within them is frozen, since a quick thaw does great damage to the plants.

Springtime sowing will require a greenhouse. When the plants have four leaves pinch out the growing points to induce side shoots. When these are 1 in. long, harden off the plants by placing the pots or boxes in a frame or under the south wall of the greenhouse.

For a late spring sowing the seeds may be sown in. deep, like garden peas. Always put down slug killer.


Never plant out until the soil on the plot has been reduced to a fine tilth. Then erect the canes if the plants are to be grown cordon style. A strong support at each end of each row will be necessary, with a cross-bar at a height of 5 ft. Double rows, 2 ft. apart, are best, as this helps when it is time to layer.

Stretch strong wire from the end of each cross-bar, insert 8 ft. tall canes, 7 in. apart and secure them to the wire.

Using a trowel, make holes to receive the plants on the outside of each cane, to facilitate layering. If the plants are to be in circles, they should be planted inside the circle of hazel sticks or brushwood. If a circle of netting is to be made, plant first and surround with the netting. Spread the roots and return the soil, so that it just covers the white collar of the plant. If a plant has a brown collar, reject it. It may grow to a height of 3 or 4 ft. and then collapse. Always surround each plant with small twigs. Black cotton stretched across the twigs will deter sparrows.

The Climbing Plants Sweet Peas support

May is a month of vigorous growth. The cordon plants by now will have been restricted to a solitary stem by removing the weaker of the side shoots, of which there may be three or more. Tie in the early stages, very loosely, using raffia. At 1 ft. in height the big sweet pea metal rings may be used. Pinch out side shoots and tendrils to channel the sap into the one stem.

When the plants are grown ‘naturally’ side shoots are left alone and the tendrils are not removed.


Never allow the land or the plants to become dry. Water the former and spray the latter.


Early in the season buds which should develop into flowers sometimes assume a frozen appearance and drop off. This is not a disease and eventually nature will correct the trouble. It will even occur, on occasion, in the middle of the flowering season. It is caused by hot days and cold nights, or excessive rain, and there is nothing to worry about.

Kneeing or Layering

This is a task only for the cordon-growers, and a somewhat bewildering one for those who tackle it for the first time. If possible, it is best to visit a local grower and help him layer his plants. Broadly speaking, when the plants are 5 or 6 ft. tall, in mid-June, six plants are detached from their canes and drawn out at an angle of 45, the next six, in order, are placed where the first six have been and so on right to the end of the double row, until there are six vacant canes left, for the first six detached to fill. This means turning the corners at the two ends of the row and great care is needed. But the growing point of each plant should rest near the cane up which you require it to climb.

The stems are laid in a row close to the line of canes. Each plant will lift up its head within a few hours and within three days it will be possible to start the tying process again. Flower stems at first will be twisted and should be cut off, but once the plants have grown a foot or so up the canes, if they are kept tied, the stems will be just as straight as previously, and there is still another 6 ft. or more of cane for them to climb.

The Natural Method

Since only exhibitors require flowers with very long stems, the easiest method is to grow the plants much as garden peas are grown, with brushwood or netting for support. Four or five times as many blooms may be cut. Keep the plants weed-free, kill the aphids and, above all, keep cutting the flowers.


If the land was well prepared in the winter, feeding should ‘hardly be necessary. However, if the flower stems are short, give the plants a liquid feed.


Special vases are filled to the brim, quite firmly, with thick bulrushes. The vase is thoroughly soaked in a bucketful of water. The stems of sweet peas are arranged in the shape of a fan. Exhibition sweet peas are straight of stem, and with four, five or six florets evenly placed. Gappy blooms should be avoided, as should any that have been marked.

Choosing Varieties

The most popular sweet pea is the ‘Spencer’ which grows tall, has exceptionally long stems, and carries 4-6 florets per stem. ‘Galaxy Hybrids’ also tall-growing, will carry as many as nine or more florets per stem, but they are not so nicely placed. The shorter type known as `Knee-Hi’ grows into a nice bush, needs little support, and will reach a height of 4 ft. with stems about 1 ft. long. Some dwarf types are less useful if cut-blooms are required – ‘Little Sweetheart’ varieties grow to 1 ft. and ‘Colour Carpet’ 6 in. ‘Bijou’ and ‘Dwarf Pigmy’ will sometimes grow to a height of 3 ft. but the flower stems are short.

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