The late T.S. Eliot is well remembered for his line "April is the cruelest month," and I would add March, May and much of June.
Whats we loosely call spring, meaning the season in which plants grow vigorously and come to flower in a time of nice skies and warm airs, is partly imaginary. In spring the gardener has the sharpest disappointments of the year, as a rule, especially in this capital (so favored as a gardening region, offering the best of both North and South). We have our most terrible storms in spring, as far as the garden is concerned, and although we are wonderfully free from late freezes (compared with England, say) we still have what I call cold weather sometimes into the month of June.
As our daffodils begin to bloom in March, our hearts leap up, briefly, but they don't stay leapt up, for all too soon the magical day that so excited us, blue sky, crocuses, snowdrops, scillas, early daffodils, temperature of 65 degrees, is followed by a hailstorm or a drop to 22 degrees and a flurry of snow or ice, and gray skies that look more somber than any sky of the winter.
Then the gardener sees his daffodils flat on the ground, and while they may straighten their stems and stand up once again by afternoon, their recovery does not last long, for at night a freeze once more lays them flat. If this happens too many times (such seasons are mercifully quite rare) the day comes in which the stem no longer straightens and the daffodil is down for the count.
If we have temperature drops to 32 or below -- we need to remember that early spring is invariably variable -- we always have warmer than usual days and colder than usual. Nothing would be more surprising than a spring of settled weather. There is not much to be done about it. The flowers that bloom in variable weather have evolved over the eons to survive in variable weather. A bloom here and there may be doomed, but in general there is nothing to worry about when a freeze "threatens" the crocus or daffodil or emerging tulip. They are born to this.
Some damage can be done, however, by the gardener's inept attempts to "protect" frost-threatened flowers.
I do not protect anything and have no trouble. In the fall, if I have a somewhat tender rose (happier, perhaps, in Norfolk than in Washington) I may give a three-inch mulch of hay once the ground freezes, and weave a few evergreen branches among the rose twigs, but nothing more. If it cannot survive with this reasonable effort, then it is too tender to be worth growing here. But the early spring flowers have managed for centuries without assistance from gardeners with blankets and bizarre notions.
This is a good time to give a bit of fertilizer to such things as irises, peonies and daylilies. I use a simple 5-10-5 formula (bags of fertilizer have the percentages of nitrogen, phosphorus and potash printed on them), a scant handful to the clump, or a rounded teaspoon per individual plant. Ideally this should be scratched lightly into the earth, but sometimes I just get it on the surface and leave it at that.
The simplest way to buy fertilizer in the city is to go to a farm store in the suburbs and get large bags of it. But some gardeners have no place to store bags of fertilizer, and they do well to buy little 5-pound boxes at hardware stores or garden centers, and of course five pounds is sold at a higher rate than 50 or 100 pounds. Gardeners with a sixth of an acre or more should buy fertilizer in 50-pound bags at least, unless they enjoy throwing money away.
It is also a good idea to get a general idea what a bale of peat moss costs, then wait for a special sale and buy several bales. It is a great comfort to have a couple of extra bales, so that when you need it (as in planting rose bushes or similar projects) you have plenty of it right there and don't have to dash out and buy small bags of it at high cost.
When you get a new bale of peat moss, open the top and run the hose in it until water flows out. Repeat this, when you think of it, three or four times. Then when you need it, it will be damp and ready to use. Otherwise it will be dry as dust.
If you need the peat and the bale is perfectly dry, the thing to do is get the dry peat dug out into a bucket, fill the bucket with water and with your hands swish it around until it is fully sodden. Then squeeze it dry, and it is ready to mix with the earth. This is great trouble, especially if you're planting a number of things. If your bale is presoaked and ready for use, you will give thanks you thought ahead for a change.
Since I do not use sprays for aphids or beetles or ants or anything else in the garden I cannot give much advice on that topic, and leave you to your own devices, with the fairly obvious warning they are poisonous and frequently not necessary.