Good gardeners are observant. As soon as the weather begins to moderate, gardeners can be found studying their gardens for signs of life, watching the skies for “V’s” of birds flying north, and searching trees and shrubs for tiny leaves. Why? To gather information to make the decision to plant, or not to plant various crops. Traditionally, the first forsythia bloom tells us to plant peas. Observe carefully though. I’ve seen forsythia blooms over a week earlier in town, and almost two weeks before mine on a neighboring farm where it grows on the south side of a big concrete silo. Each location is a micro-climate, so just seeing them as you venture about may not mean the same conditions are right in your garden.
When the lilac blooms it is time to plant beans, cucumbers and squashes. While this might just sound like advice from the “Old Farmers’ Almanac” it is actually termed “Phenology,” the study of the relationship between climate and the life cycles of plants and animals. In this time of changing weather patterns, a working knowledge of phenology is probably more valuable than the old lore of “Plant potatoes on St. Patrick’s Day” or any other task linked to a calendar rather than actual conditions.
Long before there were stacks of gardening books and blogs, long before there was a Weather Channel, gardeners watched for signs of growth in the plants and animals around them to help determine when it was safe to plant valuable seed. Lives depended upon their success and knowledge. There are some scientific basis for the success of phenology-based crops. The first is soil temperature, because some seeds will not germinate until the soil gets to a certain warmth. I don’t need a soil thermometer to tell me when it’s safe to plant out tomatoes. I just need to see borage volunteers emerging in the potager’s interior border.
In addition to planting times, phenology is used to determine good times to transplant, harvest, or to implement insect controls. When the strawberries bloom, I know I need to start spraying Bt on cole crops to prevent caterpillars destroying the young transplants.
Other phenology indicators are when the lilac begins to leaf, plant beets and carrots, and direct seed second round cole crops. Plant potatoes when the dandelions begin to bloom. When white oak leaves are the size of squirrels’ ears it’s time to plant corn. It’s safe to transplant eggplants, melons and peppers when the bearded iris bloom. Crocus photo taken last year…there’s nary a sign of them yet!
With over 50 years of observation, and the last 26 here in north central Indiana, I’ve fine-tuned the phenology to fit my garden’s conditions. The first crocus (which in the past 4 years has ranged from Feb. 17 to March ??? since we’re still waiting!) means I plant onion sets, shallots, snow peas, shelling peas, chinese cabbages, kale, spinach, arugula, lettuce, potatoes, mustard, chervil, coriander and dill. The first dwarf iris blooms means I can set out all the hardened off violas into the potager’s main paths. A daffodil opening indicates it’s safe to plant carrots, beets, kholrabi and hardened leek plants. When the peonies are 4″ tall I set out hardened cole crops (broccoli, cabbages, cauliflower, etc.) I once tried to push the broccoli and cauliflower into an earlier group, but they never head properly, so I’ve learned it’s worth a bit of a wait. It is also usually a safe risk to plant “Royal Burgundy” beans, which can withstand cooler, wetter soils without rotting. When my lilac blooms, the earliest cold-tolerant tomatoes like “Polbig” can be set in the ground, but the rest must wait until volunteer borage seedlings appear.
Do you use observations to tell you when to plant? If so, what are your favorites?