Success is sweet and (in gardening) relatively easy; indeed, the simple make the best gardeners because they pay attention to simple instructions and do not go sailing off in their minds to the Himalayas when the topic at hand is sweet peas.
Failure with this queen of annual plants is guaranteed if, in early May, the gardener trots out with a pack of seed and scratches like a hen and covers the seed a little and sits back. And yet this is the way many people handle sweet peas, possibly in order to have something to complain about for years.
Here is how to grow them. Not utterly superbly, but well enough to knock the average gardener off a chair.
Find a sunny patch of land that perhaps gets broken shade on summer afternoons. It may be as narrow as two feet. One foot, even. It should be as long as can be managed, maybe 12 feet, maybe 20 or 60.
Dig this earth to a depth of 18 inches. There will yet be good days in December for this, but do it immediately if the soil is not sloppy wet. Do not try to pulverize it. The idea is to open it up deep.
For each foot of row sprinkle a handful of ground limestone, not powdered lime, along the bottom, covering it maybe an inch, and spread a shovel of rotted manure every foot or two along the row. Leave the earth in lumps as large as half a cantaloupe. If larger, whack them with the spade.
Early in March, when the earth is dry enough to work without turning into taffy, go over this with a spading fork, breaking it up well but not disturbing it deep down.
It probably goes without saying that if the soil is heavy, as it usually is in Washington, it should be made lighter by incorporating black woods earth (fully rotted leaves, which you collect in the fall) or dampened crumbly peat moss and sand. The addition of these shovels full of manure, however, will go far to tend to the soil for sweet peas.
If you have no manure, then you must use peat moss or thorougly rotted leaves or whatever other humus you can provide.
It is fairly imbecilic to say one has no peat, no sand, no manure, no compost. Get some. You should have had it years ago, and unless you want to settle for pokeweed (which adores us just as we are), you need to produce a soil that is brown and crumbly.
Order the seeds now or in January. I am considering the tall Spencer sweet peas, which grow more than six feet, but there are other kinds that grow shorter, so suit yourself.
On Washington's Birthday plant one seed to one three-inch pot. The dirt in the pot should be moderately light, such as you get by digging up the lawn, salvaging the four inches of earth just below the grass, and mixing it with about a fourth its volume in sand and a fourth its volume in humus. I do not say you should dig up the lawn to do this, but this gives you the right idea of the dirt you should have in the pot. You could also use commercial potting soil, which I am generally suspicious of but which is better than heavy, soggy clay dug from the garden in February.
If you have 20 feet of row, use 20 three-inch pots, each one with one sweet pea seed buried a half-inch to three-quarters of an inch deep. Firm the soil and water it. Cover the pots with a sheet of paper, and once the seeds sprout, remove the paper forever.
When the seedlings have their second pair of leaves, lug the pots outdoors to a sheltered place. You want them to get sun and air, but bring them in if the temperature falls below freezing. A large tray or cardboard box obviously makes this easier than trotting back and forth with one pot at a time.
You want the young plants to be "hard." That is, the growth is firm and not spindly. You do not want plants with soft eight-inch sprouts flopping about the ground. If they are grown too soft -- that is, with too little sun and too much heat -- they will be ruined by a cold snap, or else provide a small feast for vermin such as slugs.
It is a good idea to soak the seeds overnight in a glass of water before planting them. They will swell up surprisingly. If they do not swell up, leave them longer until they do. Virtually all will swell overnight, however, and you do not want to leave them in the water once they swell.
Now, our spring can vary from tropical to frozen. Usually by March 10 the daffodils are in bud well above their leaves and the early ones may be in bloom. Choose a good dry day, which need not be sunny, and take the young plants out of their pots and set them in the outdoor bed you have been preparing, off and on, since December.
If the soil is fairly dry, press hard in planting the seedlings. Not a battering ram, and not stomping with your feet, but firm pressure with your hands. Thanks to your December digging and early March forking over of the bed or row, the soil will be fine and crumbly.
Water the seedlings. If it snows or sleets, prudence suggests a little protection in the way of crumpled newspapers or evergreen branches or something of the kind.
You want the sweet peas to start out cold, airy and sunny. Watering is no problem as a rule in a Washington March. The rain around here is not to be believed. If, through perversity, the season should turn dry, then of course you water.
You also provide pea sticks. These are simply thin branches, about eight feet long and as twiggy as possible, stuck into the ground about a foot or a foot and a half. They can be crooked and they can be set at an angle, tied with cord where they meet, since there will be winds in summer storms and you don't want them to keel over when clothed with the growth of the plants.
Some gardeners use nets instead of sticks, or fence wire. It makes no great difference to the sweet peas. What you want is support up to six feet above the ground, and you want this support to be twiggy enough for the delicate (and strong as iron) tendrils of the plants to cling to.
At this point you have done what is required of you. You may sit back. Of course you may find the young plants reaching vainly the first few inches for something to cling to; if so, provide them little twigs to get them started up the main sticks.
Usually the main stem of the little plant you have set out will wither away and two buds beneath the lowest leaves will sprout, and these will be the real plant that grows to six or eight feet. Some people worry about pinching off the end of the main stem, but as a practical matter the plant will send out these side shoots itself. If it makes you feel better, however, pinch the main stem off just above the second pair of leaves in March.
Thanks to your good well-prepared soil, you will not have to worry much about watering, but if the weather turns dry in late June, then water deeply. The little vines should never suffer drought.
Once they start growing well -- they will mark time for a few weeks in March and early April -- you can give them a mulch. Late April is soon enough. An inch and a half or two inches of shredded rotted leaves or bark will do. The idea is to keep the soil cool and moist.
The sweet peas will begin to bloom in late May or early June. Keep the flowers picked. If they are not picked, they will set seed and flowering will decrease and stop. If they are picked every other day they will keep flowering, sometimes into October.
Purists like to keep the colors separate. I like bunches of them in which the colors are all mixed up, the blue-mauves, pale raspberries, off-scarlets, whites and so on. The colors are delicate. So is the scent, not nearly as strong as it should be, but better than nothing. Sweet peas will be found a good bit more exciting than marigolds, and not really any more trouble, once you catch on to the routine.
In places farther south and west, sweet peas fling up their hands in July, unable to bear hot dry winds or sauna sweats. Here, despite murmuring about our excellent summers, it does not get very hot, except maybe around Labor Day, and I have had sweet peas blooming beautifully right through July and August. If I had treated them better (as I propose to do this year, following my instructions to you, for a change), I do not doubt I'd have had them almost to Thanksgiving.