BY LINDA SCHREIBER AND MELISSA SERENDA
According to my calendar guide, spring started March 20 at 11:33 a.m. EDT. Season dates may vary and sometimes have different lengths, according to an astronomical start date and a meteorological start date. Sounds complicated, but it’s actually not!
- The astronomical start date is based on the position of the sun in relation to the earth.
- The meteorological start date is based on a 12-month calendar as well as an annual temperature cycle.
In the Northern Hemisphere winter ends and spring starts at the moment of the March equinox, which occurs every year between March 19 and March 21.
Meteorologists, however, define seasons based on climatic conditions and the annual temperature cycle. They compare the same period of time in different years. The length of the astronomical seasons varies between 89 and 93 days, while the length of the meteorological seasons is less variable and is fixed at 90 days for winter in a non-leap year (91 days in a leap year).
Most of North America and Europe use astronomical spring, while Australia and New Zealand use meteorological spring (note these countries are in the Southern Hemisphere where the seasons are opposite and spring there lasts from September to November). In other cultures, i.e. traditional Chinese calendar and Celtic traditions, the March equinox is considered to be roughly the middle of spring.
Here in Iowa, February and March are considered late winter, and early spring typically convenes in late March and April. Late winter means it’s time to prune woody plants like grapevines and remove weak, diseased or damaged canes of summer and fall-bearing raspberries at ground level. It’s also time to prune deciduous trees and shrubs.
Late winter is also a great time to start flower seeds indoors – petunia, snapdragon, impatiens and salvia; and vegetable crops – broccoli, cabbage and cauliflower five to six weeks before the April planting date; and start seeds of eggplant, peppers and tomatoes eight weeks before planting in mid-May. Check the back of seed packets for indoor starting times. Continue watering holiday plants – amaryllis, poinsettia and Christmas cactus – after the flowers have faded away.
When April arrives, depending on temperatures and moisture levels, the lawn can be raked to remove twigs and leaves and mow at a height of 2 ½- to 3-inches remembering to never remove more than 1/3 of the leaf blade at one time. April is also a time to check fruit trees to control scale and apply a dormant oil spray when temperatures are above 40°F. Remove mulch from strawberry beds in April as new growth begins. Start seeds for basil to transplant outdoors after the danger of frost has lifted. It’s also a good time to repot houseplants into larger containers if needed and begin lightly fertilizing houseplants.
Some vegetables like broccoli, cauliflower, cabbage, kohlrabi, onions and potato pieces can be planted outdoors in April. Seedlings grown indoors can also be “hardened off” or acclimated outdoors prior to planting outdoors. Acclimating plants by placing them out of the wind and sun for a short period of time and gradually increasing the amount of outdoors will help your plants avoid transplant shock.
An important reminder for especially eager gardeners: do not work the soil when it is saturated.
Johnson County Master Gardeners of Iowa 