Sweet peas are a perfect flower, with elegant shape, abundant flowering habit, good scent and beautiful color range. They do not take up great space and they bloom from May until the heat gets them -- sometimes all summer.
This year, the end of January and early February, I shall again try them. Only one year did I have success with them, with seeds of show varieties from England. Sheer luck.
The seeds are planted one to a 3-inch pot in a reasonable potting soil. If you make your own, try 4 parts good garden soil, 1 part sand and 1 part peat moss, well mixed.
The seeds are planted half an inch deep. Ideally this is all done in October and the little pots are stood in cold frames over the winter, in a bed of ashes.
When about half the seeds have sprouted, the glass sashes are removed. In a mild winter the sashes need to go on only in severe freezing spells. If there is danger of an outrageous drop, to 5 degrees or so, the sashes should be covered with mats.
Experience and loud mutterings from readers have convinced me that few gardeners have any intention of sowing in pots and managing the cold frames all fall and winter. Hence my notes today, in which I say you can do the same thing starting in late January or early February.
You can also start the seeds in larger pots (6 seeds to a 5-inch pot; 32 in a seed flat, but the flat should be at least 3 inches deep, not one of the shallow kind) and grow them on the cool side. Cold frames are best; otherwise, a sunny window.
A temperature of 45 to 55 will work better than the 70 degrees or more of heated houses. The young seedlings need all the sun you can give them. The danger (and the usual thing) is that the seedlings lean toward the light and quickly grow to 8 or 10 inches or more before being planted out in April. They are then soft and floppy and tangled together. It is difficult to harden them off properly.
In this, as in so many other things, do as well as you can and pray for luck.
Some gardeners may have an unheated sunny room, and this should work well.
It is possible to plant the seed directly in the open ground, as deep as 2 inches, about Valentine's Day.
However you proceed, remember the plants need support almost from the time they reach 3 or 4 inches in height. It makes sense, not that that makes much difference to many gardeners, to install the support at the time seedlings are planted out, or at the time seeds are sown outdoors.
You use "pea sticks," any branching sticks that should reach 5 or 6 feet above ground. Or you can use wire fencing or various plant nets or strings.
Now there are many strains of sweet pea, all well described in the major gardening catalogues. The usual vining sweet peas will grow to 7 feet, but some, like the "Galaxy" strain, are good for lower (chest-high) fences, and others do not climb up at all, but sprawl handsomely on the ground.
All kinds may be grown in half-barrels or large (10- or 12-inch) pots. About a dozen seeds are planted in these large pots, and the gardener has his work cut out for him in keeping them going in hot dry weather. But it can be done, and may be worth the effort where there is a more or less sunny terrace and not much other space. They will need daily attention.
I was sorry last summer to lose a 14-inch pot full of rose-colored zinnias, which flourished mightily and bloomed their heads off until I forgot watering them for two days. They never revived properly, and sweet peas are less tough than zinnias.
In the old days gardeners did not so much dig as excavate the ground for sweet peas. It was not unheard of to prepare the bed 4 feet deep, and it was standard to dig 30 inches, or at least 24, with a heavy dosage of manure at the bottom. This was done in the fall, so that when the young plants were set out in March or April the tilth would be perfect.
It is still a good way. I like to think gardeners dug briskly in November and December as recommended here at that time.
Eighteen inches is deep enough. But the manure should be there.
What is wanted is for the seedlings to be firm, about 6 inches high, and used to cold but not bitterly subfreezing weather, and you want them in that state about mid-March. We still have freezes at night then, but the terrible cold is over. Then they are ready to grow rapidly in April and May. If timid, you will not set the plants out until April 10.
The practical trouble is that it's hard to have the seedlings in good condition at the right time. Another hazard is our occasional heat waves in April. People seem to forget we sometimes have temperatures well into the 90s in April, though all daffodil growers are aware of this.
The sweet pea, in short, is not an ideal annual for Washington. But for gardeners who have nothing else to do, or for gardeners who are forever branching out (leaving undone a dozen important operations that should have been tended to) the sweet pea is a pleasant challenge. The result is successful often enough (once is enough to fire up the gardener for some years afterward) for it to be worthwhile.
When I was a kid some neighbors had a farm in Mississippi and one May sent over a big box (the kind dry cleaners used to send clothes back in) full of sweet peas. I never have quite got over it.
This may be the place to say that last February, at the full moon, I planted nasturtium seed outdoors. Complete failure. But it never hurts to try something once, particularly if somebody swears that planting nasturtiums in February gives you lots of flowers in May, long before other people have them.