Gardeners usually use the word bulb as an umbrella term for any plant that has swollen underground structures, which store energy for the next season’s growth and flowering. Although these can be true bulbs, corms or tubers, understanding the botanical distinctions isn’t critical for growing them successfully.
The good news for novices is that most flower bulbs are easy to grow. In general, they’ll thrive when given a sunny spot in well-drained soil that is free of standing water in winter and spring.
When planting, keep in mind the bigger the bulb, the deeper it goes: the depth should be three to four times the bulb’s height. For example, plant large ones (such as giant alliums, trumpet daffodils and crown imperials) 15 to 20 centimetres deep and 7.5 to 20 centimetres apart, and smaller ones (snowdrops and crocuses) five to 10 centimetres deep and five centimetres apart. Bulbs should be buried pointed side up. (If you’re not sure which end is up, position it sideways; it’ll sort itself out.)
The most popular bulbs are the hardy spring-blooming ones. What hardy bulbs have in common is the need for a period of cold dormancy (winter) for flowering. That’s why they’re sold around this time of year and planted in the fall. Crocuses, tulips and daffodils are classic examples—nothing beats them for early colour. There are, of course, many other bulbs, including snowdrops (Galanthus spp.), grape hyancinths (Muscari spp.) and fritillaries (Fritillaria spp.), to name a few. Some, such as daffodils, naturalize and increase in number year after year. Others, such as hybrid tulips, need to be replanted every few seasons.
To confuse you, however, there are also several hardy bulbs you can plant in late summer that bloom a few weeks later in the fall. Two such types are Colchicum autumnale, known as naked ladies because they bloom without leaves (the plant doesn’t flower until the autumn, after it’s lost its foilage) and fall-blooming crocuses (related to the more common spring-blooming crocus), such as the saffron crocus (Crocus sativus), with deep lilac blue blooms and bright orange stamens, which are harvested for saffron. Once these autumn-flowering hardy bulbs are planted, they’ll come back year after year.