Seed sowing planner

How the dates are worked out

Each tree's treatment, depth and timing come from its own page's How to grow section, which we wrote from the Forest Service's silvics, the state extension services and the Woody Plant Seed Manual. Where the page gives no day count, the count comes from the seed manual's chapter on the genus, and the plan says so. The refrigerator route counts back from your sowing date: the cold spell starts that many days before it, a warm spell before that where the seed needs one, and a hard coat is broken the day before the spell begins. The hickories' nuts are soaked from two to four days before it instead, as their pages say. Where a page gives its own temperature for a stage, as for the huckleberries' cool spell, the step gives it too. No stage is ever dated before today. When the longest spell would have begun already, the plan starts today, since each spell is a range. When even the shortest spells cannot finish by the coming spring, the plan sows the spring after and says so. A sowing date that has already passed moves to the same day in the first year the stages can reach. The fall route needs only a sowing window: the winter supplies the cold and, for seed with a double dormancy, the next summer supplies the warmth, which is why those seedlings come up the second spring.

Some seed fits neither route as it stands. Seed that must be sown as it ripens, such as willow, cottonwood and swamp privet, gets the same plan on both: sow it the day it is gathered or arrives. Seed whose page sows it indoors in winter, such as the native azaleas and rhododendrons, is planned for December to February, or for January where the page says so. Where neither the page nor the seed manual gives a day count for the cold, the refrigerator route has no dates, and the plan points to the fall bed where the sources give one. Where no source gives a tested way to sow the seed at all, neither route has dates.

The local dates come from NOAA's 1991–2020 U.S. Climate Normals: for your state and zone, the median of the weather stations there. The last spring frost sets the spring sowing date and the spring look at a fall bed. Seed that comes up in late spring is looked for about seven weeks later. From January until the next fall, a fall-bed plan also says when last fall's sowing should come up. A fall bed can be sown from mid September, or from the first frost where that comes sooner, until the first night at 20 °F. Soil freezes from the surface down as the cold goes on (University of Minnesota Extension), so the ground can still be dug that night. The extension names no temperature, so the 20 °F night is our own reading. Where winters average fewer than 20 nights at or below freezing, the plan warns that a fall bed may not chill the seed. That count is our own reading of the NOAA figures: such winters average 52 °F or warmer, above the 34 to 41 °F the seed manual chills seed at. A ZIP code finds its zone in the 2023 USDA map's ZIP listing and its state in the Census Bureau's ZIP code areas. Without a state and zone, the plan uses April 15 and a fall bed from mid September to mid December. The state and zone you choose are kept on this device for your next visit.

Germination varies with the seed lot, the storage and the weather, so every count is a range and every date a starting point; a seed that sprouts in the bag is sown that day whatever the calendar says. Acorns, chestnuts, chinquapins, buckeyes, pawpaws, magnolias and a few others die when they dry out, so those plans open with the storage rule. The whole process, from collecting sound seed to the first year, is in Planting acorns, nuts and seed; the seedling's first summer is the watering calculator's job and its next twenty years the growth estimator's. For acorns from an oak the list lacks, the leaf test that tells a white oak from a red oak is in Red oaks and white oaks.