Planting spring-blooming bulbs can be as easy as tossing them into a shallow hole, throwing some soil over them and walking away. And it can also be frustrating to watch squirrels unearth the buried treasures and make a good meal of them. Just a few simple preparations will help you get the best from the bulb planting you do now for next spring’s show.
When to plant
Small minor bulbs like snowdrops, winter aconites, crocus and Siberian squills should be planted soon as possible, and certainly before the end of October. Leaving them out of soil for an extended time causes premature sprouting and dissipates stored energy needed for spring bloom.
Larger tulip and narcissus bulbs can be held in a cool, dark garage (not indoors) to plant in late autumn. Warm soil can stimulate bulbs to sprout in fall, something to avoid. If warm days persist through September and October, it may be necessary to hold off planting most large bulbs until the weather has chilled in November. The soil temperature should be cooled to below 15°C; chilly nights indicate the soil is cooling. If you don’t have a soil thermometer, wait until nights are consistently in the range of 4 to 8°C.
Bulb planting depth
The traditional rule has been to plant bulbs at a depth three times their height, measured from the bottom of the bulbs. Consequently, a tulip bulb standing two inches (5 cm) tall should be buried six inches (15 cm) deep, and a one-inch (2.5-cm) crocus would be buried three inches (8 cm) deep. That’s a fairly good guideline, but there are circumstances when planting slightly deeper might better.
Most spring bulbs are hardy to Zone 4. If planting in colder regions, it’s safer to plant bulbs two inches (5 cm) deeper than recommended to ensure they have adequate insulation from the coldest frost. A layer of leaves and conifer boughs laid over the bulbs will also help hold insulating snow in place all winter. Remember to pull the covering off in early spring to allow the sun to warm the soil.
Bulbs require good drainage to prevent them from rotting and developing fungal diseases. Sandy soil drains rapidly and favours good bulb health, but heavy clay soil holds water and promotes the growth of pathogens. To prevent the buildup of excessive moisture around bulbs, amend the immediate planting area with coarse builder’s sand to a depth of 10 inches (25 cm). Plant the bulbs into the amended soil, gently firming the soil over them. They will have well-drained soil on all sides, which will prevent excess water from pooling around them.
Avoid setting the bulbs on the soil while you work; keep them in a paper bag or other container until they go into their planting holes. Also, don’t allow any of the papery tunic covering them to flake off and remain on the soil. (No sense leaving delicious hints lying about to attract attention.)
Squirrels search the ground for signs of freshly disturbed soil and then dig for a reward. The marks you leave behind after planting bulbs are strong indicators that something delicious is buried underneath and they’ll quickly take advantage of the free meal. The final step in planting a cluster of bulbs is to disguise your work with a thorough drenching from a watering can (not a strong hose stream that could dislodge soil over the bulbs). Be sure there is enough water to erase the marks of your trowel and hands, creating a slightly muddy surface.
Follow this with a four-inch (10-cm) layer of leaves on the soil over the bulb planting area. The leaves can be left in place until the soil freezes or all winter to help conceal your buried treasure. Pull back some of the leaves in early spring (leaving a light covering of scattered leaves in place), allowing sunlight to warm the soil. Although there’s no certainty when dealing with persistent wild animals, this is usually enough to fool a squirrel.