April is the month when you are unsure about how and when you will start your seedlings. The desire to get an early jump on the year is governed by the weather and the temperature of the soil. Often I start a few flats of greens in March with the hope of transplanting them into soil by mid-April. If I can get peas into the soil by late March, even better. But such regularity is difficult as the conditions for each year changes.
This Spring has been slow in coming with fits and starts of warm and cold weather. I have four flats of vegetables and flowers sitting on a table under grow lamps inside hoping that higher and more consistent temperatures in the next week or so will permit me to move them to my greenhouse for the first stages of hardening off and transplant.
The first set of greens has been placed in the soil though they still require their evening blanket of a cold-frame top. This year in New England, like so many others, has but two seasons: winter and summer. There appears to be little in the form of a gradual warming. Rather it is cold, then a week or two of moderate temperatures, then full-on summer. That is what makes April so maddening as we see the increased light of the days and appearance of warming. But it does not come.
So seedlings sit waiting like many of us for the warming days ahead and ability to grow and flower.