Knowing when each plant should be sown is an important factor in growing a flourishing garden. Unfortunately, the planting guidelines on seed packets or in gardening magazines are rarely precise enough to be helpful. For better results, information from local gardeners, frost date guidelines, biological cycles, and even the phases of the moon can be used to pinpoint the ideal planting time for each vegetable, flower, or tree.
Many gardeners understand that getting each plant in the ground at the right time is vital for growing a healthy garden, but what do you do when the information on the seed packet just says ”plant in spring”? When the host of a national gardening program tells you it’s time to plant squash, how can you be sure that statement is accurate for your region? Correct planting times can’t be chosen according to a date on the calendar, but there are a number of reasonably accurate methods for determining them.
Contact Local Gardeners The easiest way to find out when a particular plant should be sown or transplanted is to contact a local nursery, garden center, or agricultural extension, or find an experienced gardener through a local gardening club. This way, you can simply provide the name of the plant and what part of town you live in and you’ll get a fairly accurate estimate. When asking for advice, don’t just accept a fixed date. Be sure you understand how the expert determined the planting date they suggested.
Planting Relative to the Frost Date Another method is to choose planting times relative to the last and first frosts in the region. The U.S. Department of Agriculture’s system of plant hardiness zones is the most popular guideline for predicting frost dates in North America. Similar maps have also been created for Europe, placing inland Britain in zone 8 and the British coasts in zone 9. Central Europe falls into zones 7 and 6, with the Mediterranean in zone 10. Detailed zone maps have been developed for individual countries and can be found through an Internet search or by asking at your local garden center. Soil temperature is another factor determining when a plant should go into the ground. For accuracy, rather than relying on weather forecasts to tell you soil temperatures, use a soil thermometer to take measurements exactly where you want to plant at a depth of 3-4 in (8-10 cm). While using predicted frost dates and soil temperature to choose planting times works most years, it still exposes plants to the risk of an untimely frost.
The Old Farmer’s Almanac This venerable old book, first published in 1792 by Robert Bailey Thomas, provides a planting timetable and detailed weather forecasts for each of 16 regions throughout the U.S. and Canada. The publishers claim Thomas’ weather forecasting methods, which are now supplemented by modern science, have been 78 to 80 percent accurate since their conception. Unfortunately for non-U.S. gardeners, the weather information will be difficult to use unless you know which region of the U.S. is similar to your own.
Phenology The name of this method is Greek for “the science of appearances”. Annual occurrences--or “appearances”-- in the growth of plants and the behavior of wild animals are used to determine when cultivated plants should be sown, fertilized, sprayed, or pruned. Although the principle has been used since ancient times, it’s becoming an ever more exact science with practitioners around the world keeping detailed records of the yearly cycles in their gardens. Because this method allows nature to indicate appropriate planting times, it’s quite precise.
Planting by the Moon While this system won’t tell you which month to plant in, it can help determine which week of the month the ideal planting time will occur in. To calculate this time, the system takes into account how the moon’s gravitational pull affects plant growth. In general, above-ground crops are best planted while the moon is waxing (rising), while root crops should be planted during the waning (declining) moon. For example, it’s recommended that flowers and fruit plants be put into the garden when the moon is waxing.