As we head into fall with days getting shorter and nights getting cooler, autumn is a perfect time to think about getting your bulbs into the ground for a magnificent spring bloom. September and October are the ideal months to plant spring bulbs because the days are still clear and blue and the ground is still warm and welcoming. Fall bulbs include such traditional garden favorites as tulips, daffodils, crocuses and hyacinths, but there are many other bulbs that will provide your garden with weeks of color next year.

Planting spring bulbs in the fall

Spring blooming bulbs are not instant-gratification plants since they require a chilling period before they can sprout a stem, foliage and flowers. When you get bulbs at your local garden center they are dormant. They break dormancy only after chilling and winter conveniently supplies the necessary cold for the transition into this activity. To break dormancy and bloom, most spring blooming bulbs need a good 12 -14 weeks of chilling temperatures below 7 Celsius. The bulbs need this time in the ground to generate root growth, which helps to nourish them as well as anchor the plants in place before the ground freezes. It also allows the energy to be stored in the bulb over the winter months. If bulbs are planted past the routine temperature threshold, they will develop roots in spring and may bloom later than normal, but they’ll get back on schedule the following year.

Since bulbs look best when planted in groups of 3-5, you are better off using a garden spade instead of the traditionally used single bulb planter. The advantage of using a spade is that it makes it easier to set bulbs side by side in a larger space. When the hole is dug, sprinkle a tablespoon of a high phosphorous fertilizer in the bottom of the hole, then place the bulb in the ground with the pointed end up. Plant groupings of bulbs in a hole that is about the size of a plate or curving trenches and position the bulbs in the bottom. Once the bulbs are set in place,they should be covered with loose soil and watered thoroughly. If you add a 5 cm layer of mulch on top of the bed, this protection will help to prevent winter weeds and retain moisture. The mulch will insulate the bulbs against severe winter cold and temperature fluctuations.

Positioning bulbs at their proper depth will help to ensure their longevity and blooming capability. Bulbs should be planted in the ground so the bottom rests at a depth that’s two-and-a-half times the bulb’s diameter. You can also perk up the area up by planting bulbs with different diameters at different depths to provide a bouquet of beauty and interest in the spring. For example, give variety to the look by digging a 6-inch-deep hole and place several Dutch hyacinths in the bottom. In a hole next to the hyacinth, plant several grape hyacinths at a 5-inch depth. The two types of hyacinths bloom at the same time in spring and the smaller grape hyacinths create a softening skirt beneath the more massive Dutch hyacinths. If your property drains quickly or it is made up of a sandy soil, plant the bulbs an inch or two deeper to increase longevity and discourage rodents.

This chart by landscape Ontario contains the information you need for successful bulb gardens:

Name of Bulb Height (cm) Planting Depth Comments
Tulips (Darwin, Cottage) 38-76 12-18 Plant 15-20 cm apart in drifts of one colour in full sun.
Species tulips, Kaufmanniana 10-30 7.5-10 Plant 2.5-5 cm apart in full sun, early bloomers for rock gardens and borders.
Scilla 15 5-7.5 Plant 7.5-15 cm apart in clumps, early bloomers for rock gardens and borders.
Muscari 15-25 5-7.5 Plant 5-7.5 cm apart in rich, moist soil.
Crocus (Chrysanthus) 7.5-10 5-7.5 Plant 5-15 cm apart in large groups.
Great for rock gardens. Forces well.
Snowdrops (Galanthus) 7.5-10 5-7.5 Plant 5-7.5 cm apart in moist soil, great for naturalizing, can be forced, full sun or part shade.
Glory of the Snow (Chionodoxa) 10-12.5 7.5-10 Plant 2.5-7.5 cm apart in large groups in full sun to light shade, three to four week blooming period, and excellent choice for naturalizing.
Daffodil (Narcissus) 20-6 18-20 Plant in rich soil, full sun to part shade, great for forcing indoors, great for naturalizing.
Winter Aconite (Eranthis) 10 15 Plant 5-7.5 cm apart, very early flowering, blooms are bright buttercup-like flowers.
Crown Imperial (Fritillaria) 91 15-30 Plant 20-23 cm apart in sweet, well-drained soil, flowers mid-season.
Allium 35.5-91 15-30 Flowers May to June or July for Azureum Blue allium.
Iris (bulbs) 15-23 10-15 Very early flowering in full sun, well-drained soil.