Many of the most familiar bulbs in the flower world are spring-blooming species. But, in order to bloom, these spring-bloomers need to be planted several months earlier. The general rule of thumb is that spring-blooming bulbs require a period of cold-chilling and thus should be planted in the fall. But fall is a long season, and some bulbs require a more precise planting time within the fall window.
Considerations for Planting Spring-Blooming Bulbs
There is no perfect moment, calendar-wise, for planting bulbs. The ideal time to plant your spring bulbs depends on where you live and seasonal weather conditions.
To break dormancy and ensure flowering, most of the more common spring-blooming bulbs (like tulips, daffodils, hyacinths, and crocus) must be exposed to temperatures of 40 degrees or colder for at least 12 to 14 weeks. Exposing bulbs to these cold temperatures stimulates them to turn on flower formation and initiates root growth. Most spring-flowering bulbs must be planted in soil for several weeks before the ground freezes for their root systems to develop.
Planting these bulbs too early in the fall can be detrimental because the bulbs may start to sprout too early. Sending up foliage too early depletes the energy that a bulb needs to get through the winter and bloom in spring. So, if your area is experiencing a long summer and temperatures are still quite warm at the beginning of fall, hold off planting until temperatures begin to cool down.
Here are the general rules of thumb for planting spring-blooming bulbs:
- Gardeners in the coldest USDA Zones (1 to 4) should plant bulbs in late August and early September. Don't wait for the official start of fall on the calendar to plant your bulbs.
- Gardeners in Zones 5 to 7 can't trust the calendar, either. You must wait to plant your bulbs until temperatures cool down, especially during the day. Temperatures might start to cool in September in some years and in October in other years. It's better to err on the later side. You can even plant bulbs into November and beyond if the ground has not yet frozen.
- Gardeners in warmer climates, Zones 8 and higher, need to purchase pre-chilled bulbs for the best success. Winters in warmer climates are not cold enough for the bulbs to receive the chilling period they require.
If You Forget to Plant Bulbs in the Fall
The guidelines mentioned here are the ideal planting times, but sooner or later, every gardener buys bulbs and then forgets about them or doesn’t get around to planting at the ideal time. Take heart; all is not lost.
Most bulbs on the store shelves were dug early in the summer and then stored for shipping. If the bulbs you forgot to plant are still plump and firm in later fall or early winter, they’re still viable and can be planted. Storing bulbs out of soil all winter will cause them to wither and die. The important point is to plant your bulbs in the soil as soon as possible.
Before the Ground Freezes
The old adage says, “As long as you can get your shovel in the ground, you can plant your bulbs.” It’s hard to believe, but they are better off in frosty soil than they are sitting in your garage or basement. Spring bulbs have been known to send out roots in soil that’s just above freezing. So, if you’re planting late in the season, plant as deeply as possible, even a few inches deeper than recommended. Once the ground freezes solid, mulch the bulbs with a few inches of leaves, straw, or some evergreen boughs. It might take longer in spring for the shoots to surface from the extra depth, but they will eventually.
After the Ground Has Frozen
Once the ground has frozen and the soil is too hard to dig, you might be tempted to toss your bulbs into a dark corner of the basement and forget about them until spring. But spring-blooming bulbs are not like dahlias, gladioli, or other summer-blooming tender bulbs that can be stored away for winter. Remember, spring-blooming bulbs need to develop some roots and experience a period of chilling to be able to sprout and flower next season. Bulbs only have enough energy stored to get them through one dormant season. They need to grow next year to replenish themselves, so you really need to get them into soil somehow.
You have two options if you find yourself in the predicament where the soil has frozen and you can't dig.
- Pot them up. Plant the bulbs in large containers filled with potting soil. Plant the bulbs at the proper depth in the container, and make sure the bulbs are not pressed up against the sides of the pot, where they can freeze. For proper insulation, there must be plenty of soil between the pot sides and the bulbs. Store the pot in an unheated garage, porch, or even a basement window well. The bulbs need to be properly chilled but not exposed to extremes. Water the pot lightly once a month if it dries out, but don’t allow the soil to remain wet. Move the pot outdoors in mid-spring, and either let the bulbs bloom in the pot or transplant them into your garden once they have sprouted. Transplanting into the garden will give the bulbs more time to establish themselves and become stronger for next year.
- If you can’t dig into the ground, plant on top of it. Spread your bulbs out on top of the ground, and then cover them with at least 6 to 8 inches of added potting soil. To keep the soil in place and deter rodents from making a meal of your bulbs, enclose the area with chicken wire or hardware cloth. You can remove the enclosure in the spring. Mulch the mound of bulbs after it freezes solid.
Planting your spring-blooming bulbs on time is the best guarantee for spring blooms, but it's also possible to plant them late. Even if they don’t put on much of a show the first year, they should get better with age.