Good sweet peas can be grown in any sunny, well-drained position without the traditional trenching processes. Most soils can easily be adjusted to suit them.
They may be used to alternate with dahlias or other tall-growing summer flowers which are dormant in winter and spring.
In positions where they cannot conveniently be sown before the late summer flowers are removed, then start them in peat moss containers such as Jiffy Pots.
After the seedlings are well under way, these are planted pot and all; the roots meander through the soft peat wall of the pot when they are ready, without disturbance by transplanting.
Another suggestion is to fill a number of 4-inch flowerpots with a light soil mixture, with a little lime and complete fertilizer added, and sow a few seeds toward the edge of each, later thinning out all but 2 or 3 seedlings. When ready they are knocked out of the pots and planted without disturbing the root formation.
Either method allows another 4 or 5 weeks for late-summer displays to finish or for soil to settle after preparation, also making weed control easier.
Although sweet peas are generally grown on supports such as wire-netting stretched over fences or between specially erected posts, there are other ways to use them attractively. They can be very decorative when grown to cover a simply constructed tripod of garden stakes or a column of wire-netting.
The tripod is simply constructed by setting three 6 feet garden stakes about 2 feet apart to form a triangle and lashing them together where the three cross, say about 3 inches from the top. Seed is planted about 4 inches apart along the triangle formed by the base. Support them by running string or pea-wire spirally about 6 inches apart around the stakes.
Normally the plants will reach the top of the tripod, then tend to spill downwards in a random effect. When extra training is preferred, the height and width at the top of the tripod can be extended by wiring light 3 feet stakes.
A straightforward way to construct the columns is to cut 6 feet wide wire-netting into 5 feet or 6 feet lengths. These are rolled and fastened to form a cylinder of netting 6 feet high and 20 inches to 24 inches in diameter. They are kept firmly in place by wiring them to 2 stakes driven in on opposite sides.
The height of the column may be increased by fixing them 6 inches to 9 inches above ground level. This also makes weeding and cultivation easier. The peas, sown round the base of the column, may be assisted to the wire by light twigging.
Again it is only necessary to place the stakes initially, and these need only be 3 feet to 4 feet high, as the wire-netting in column form is fairly rigid.
Dwarf Sweet Peas: Since the introduction of the new dwarf ‘”Bijou” variety it is now possible to enjoy sweet peas without any form of trellising.
They may be used as borders, in clumps among low plantings, or to spill from rockeries, tubs, or window boxes – provided they are in full sunlight and will not become shaded by taller plantings later. This is important, as “Bijou” will be disappointing where sunlight is restricted.
The upright form of the sweet peas may give the impression that the root system follows a similar pattern. Actually it develops a comparatively wide spread, so results will be better where you are able to prepare the soil for a couple of feet on either side.
Sweet peas are lime lovers – except in already limy soils, spread a full cup of garden lime or dolomite to each square yard.
Then spread a liberal layer of well rotted compost, animal manure, or other organic material such as grass clipping (provided they have been heaped for a least a month and are partly rotted down).
This organic matter is especially valuable to help break up heavy soils and improve the texture of the poorer soils. Where it is unprocurable, a dressing of peat moss or vermiculite would be a worthwhile substitute for these difficult soils.
Last but not least, give a liberal dressing with good complete plant food, using about ½ cup to the square yard. This addition is advisable even though compost or animal manure is used, as these materials, though often high in their nitrogen content, are low in phosphorus and potash. These 2 elements are also necessary for healthy sweet pea growth.
Rake, hoe, or lightly fork the compost, lime, and fertilizer into the first 4 inches or 5 inches of surface soil until it appears to be mixed fairly evenly. Then spade the soil to a further depth of 9 inches or 10 inches, lifting and loosening it rather than turning, so that some of the additives filter downward but most of the top soil stays neat the surface. Healthy top soil is alive with useful organisms.
After preparation give the soil a gentle but thorough soaking and allow it to settle down for a week or so. Before sowing the seed break the surface crust and destroy any weed growth. At this stage it should be just damp.
Sow the seeds, usually about 4 inches apart, pressing them down to about ½ inch, or a little deeper where the soil is light and crumbly.
Give a gentle watering to wet the soil evenly, then no more until the seedlings appear – except in soils which dry out quickly. Over-watering and deep planting are the main causes of poor sweet pea germination.
When germination is poor during wet conditions, it does help to coat the seed with a fungicide before planting. Do this by adding to the seed about ½ teaspoon of copper oxychloride, TMTD, Zineb, or mixed fungicide such as rose spray. Then hold the packet tightly closed but slightly ballooned and shake for a few seconds.
Another method is to mix the seed into a saucer or shallow dish of moist vermiculite or seed-raising mixture. Drain off any excess water. In this moist but airy environment the seed normally germinates in about 5 days, where it generally takes about 12 to emerge from the soil. The sprouted seed needs to be handled carefully when planting into the soil, as roots and shoots are very brittle.
Sow all seeds: The seed of different varieties and colors of sweet peas varies in appearance. Most pink and white are larger and paler seeds, reds may be a little smaller and darker, while blues and mauves are often pinched and appear shrivelled. This variation is not sufficiently constant to determine color by seed appearance, but it is obvious that if only the larger seeds are planted the color range will be very limited. Where you have too much seed, it is therefore wiser to sow an average sample.
Pinch back plants: Young plants may be spindly and inclined to twist aimlessly rather than accept the support offering. If they are cut back to the second or third leaf, the new growth should be sturdier and more eager to climb.
Tendrils: The twining tendrils at the end of the leaf stem give the plants natural support during early growth. Later they are inclined to entangle and deform the flower stems, so where the flowers are valued for cutting it is worth the extra trouble to clip off the higher tendrils and replace this support by tying with raffia or, better still, the covered-wire stem ties readily available, as these are easier to use and certainly less obvious.
Prolong the display and maintain good quality blooms by removing old stems. After flowering begins, water at fortnightly intervals with liquid manure at the strength recommended on the container.
The most troublesome disease among sweet peas over recent years is broad-bean virus, which causes infected plants to yellow and die out. It has been known for some time that the disease is carried by insects such as aphids, but only last spring it was established that a host plant carrying the virus is the common plantain or lamb’s tongue.
This is the dark-green, smooth-foliage perennial with the long, rather brittle flower stem, not the grey, downy stachys or lamb’s ear. Unless there are a number of other host plants yet to be discovered, it appears that the best control of the virus is to get rid of plantain in the vicinity.
Other pests and diseases are rarely troublesome, but should red spider or thrips become plentiful they can be controlled with an all-purpose garden spray. This preparation will also control mildew, but this rarely occurs until plants have passed their prime.
Multiflora types such as Seventh Heaven caused a sensation for several years after their introduction. Very long stems carrying 7 or more flower buds were the outstanding feature. Now these are to some extent superseded by Gigantea strains such as Colorcade.
These have a better color range and more ruffled blooms, which are packed closer and open nearer to the one time. In earlier Multiflora strains the lower blooms had fallen by the time the top buds were showing color.
Bijou is a dwarf, growing in clumpy formation about 2 feet high without support, or to 3 feet if trained. It has a full, bright color range, with ruffled blooms on 6-inch to 9-inch stems.
Soil preparation is the same as for taller types, but full sunlight is essential for this variety.