Have you ever wondered why we plant spring-flowering bulbs in the fall? We’ve been doing this for so many generations that this now appears quite normal, but in fact we don’t plant bulbs then because we have to, but because it’s more convenient for the merchants to sell them to us in the fall.
Let me explain.
History of a Delayed Planting
Logically speaking, the ideal time to plant bulbs of tulips, daffodils, hyacinths, crocuses and other spring-flowering bulbs would be in late spring or early summer when their foliage turns yellow and they go dormant. That way, the gardener knows exactly where to find them in the garden and digging them up is therefore easy. Just divide them and replant them, it’s that simple. There is absolutely no reason to delay their planting until fall. Remaining dormant under the soil in the summer is part of their growth cycle. They then start growing again when temperatures drop in the fall.
If, while gardening, you accidentally dig up bulbs—and that certainly happens often enough! —, most gardeners know enough to replant them immediately… and that is precisely what you should do.
However, if you want to sell spring-flowering bulbs, a late spring planting season is not at all convenient. They would have to be dug up, cleaned, checked for insects, diseases and blemishes, sorted by size, packed, shipped and ready for sale in just a few weeks. Even then, they’d have to compete for your attention with all the beautiful annual and perennial plants already in bloom that fill garden centers at the same season.
That’s why Dutch growers, who supply more than 75% of the hardy bulbs sold around the world, have learned that if they keep the bulbs in warehouses under strictly controlled temperatures and humidity, mimicking the conditions found underground, they can delay planting—and therefore sales—until fall.
This gives them all summer to harvest, clean, sort, pack, etc. And it means they can take advantage of inexpensive means of transportation, such as container ships, to deliver the bulbs. There’s no need to rush! If even if bulbs dug in June don’t reach local stores until September, the usual scenario, that gives most gardeners over two months to plant them, something you’ll want to do before the soil freezes.
Soil Temperatures Not a Factor
It’s amusing to hear so-called experts insist on the importance of waiting until the soil cools down in the fall before you plant your bulbs. You often hear temperatures like 50 or 60° F (10 or 15° C) bandied about, but hardy bulbs from previous years, already in the ground, are going through whatever temperatures Mother Nature throws at them and still do fine.
I imagine a poor gardener going out every day with a meat thermometer to check the temperature of the soil, waiting for the right moment before planting his bulbs. Yet soil temperature is just not an important factor in planting bulbs: they were designed by nature to be underground, no matter how hot the soil gets! Some grow in soil that becomes baking hot in summer, yet they thrive.
As a result, there is simply no need to take soil temperatures into account when planting your bulbs. Just plant the bulbs even if the soil is still warm and let Mother Nature cool the soil down as fall progresses.
So When Should You Plant Bulbs?
It’s always best to plant bulbs a few weeks before the soil starts to freeze, as hardy bulbs need to start producing their roots in the fall. You don’t want the ground freezing to any great depth before they’re well rooted. In most climates, that means any time between late April/early June (the beginning of the bulbs’ dormancy, depending on the variety and climate) and mid-November.
(There are a few bulbs that should be planted as soon as they arrive in stores: read more about them in the article 6 Bulbs to Plant Without Delay.)
So there you go! There is actually a vast window of opportunity—over half a year!—for you to plant spring-flowering bulbs, but the reality is that they only come on sale in September in most areas, so plant them then or wait a month or two: it really doesn’t matter, as you long as get them into the ground before it freezes. And just leave bulbs of previous years in the ground year after year: it’s their natural environment and that’s where they do best!