Should We Plant Bulbs in Fall or Winter?

You may have noticed a theme in our recent blog posts: autumn is a busy time in the garden! While our plants may be active in the spring and summer, fall’s a time in which gardeners and homeowners have plenty to do preparing for winter and the spring to come. One of these tasks pays off beautifully—fall is the right time to plant the bulbs of many flowering plants. In this blog we’ll take a look at how and when to plant bulbs, which bulbs we should plant in fall, and whether or not planting bulbs in winter is a good idea. Let’s dig in!

Gardzen Executive Summary

· Fall is a great time to plant many types of bulbs

· Not all types, however—some bulbs should be planted in spring

· Fall weather offers the right mix of air temperature and soil conditions to help bulbs establish good roots before winter dormancy

· Bulbs need to be planted correctly—in the right location, with the right soil conditions, and the correct orientation

· Generally speaking we shouldn’t plant bulbs in the ground during winter, but there are other alternatives to start bulbs after the frost comes

Why We Plant Flowering Bulbs in Fall

Let’s not bury the lede: fall is the right time to plant the bulbs of many types of flowering plants. The reason for this is pretty simple: fall hits a sweet spot for conditions that best encourage early bulb growth. The soil is warm enough to encourage initial root development while the air temperature is cool enough to discourage premature sprouting or stem/foliage growth. The bulb puts out its initial roots and then has the winter months to rest before spring arrives and it can take advantage of its developed roots and prepared soil to grow and produce the beautiful flowers we look forward to.

Which Bulbs Should We Plant in Fall?

There’s a long list of bulbs that are best planted in fall. This is only a partial sample of the many bulbs that are best planted in autumn for spring blooms, but we hope it helps as a starting point:

· Daffodils

· Tulips

· Snowdrops

· Hyacinths

· Crocus

· Allium spp.

Bulbs to Plant in Spring

We’re including this to avoid some potentially problematic and costly confusion. Some bulbs are best planted in spring as the growing conditions in that season are better for them, these include:

· Dahlias

· Gladiolus

· Lilies

· Cannas of all types

· Begonias

· Geraniums

Again, these bulbs should be planted in the spring and we’re putting this list here so they don’t get mixed in with our fall planting bulbs.

How to Plant Fall Bulbs

So now that we know which bulbs we should—and shouldn’t—plant in autumn, how do we go about planting them?

The first thing to consider is timing. The best time to plant autumn bulbs is when the nighttime air temperatures are consistently below 60F/15-16C. Generally, you’ll want to plant as soon as the temperature moves into the preferred zone so that your bulbs have time to develop before the first freeze sends them into dormancy. When these temperature conditions occur will depend on your climate zone and location, but in Zones 3-5 the temperature is generally right in late September or early October. For those of us in Zones 6-10, the right nighttime temperatures can come anywhere between October and December depending on local conditions. This is why we always suggest talking to a garden club or your local cooperative extension for advice tailored to your region.

The next step is soil and location. Different bulbs for different species and varietals prefer different soil conditions, so it pays to research which plants you’re putting in and what they like. In general, most fall-planted bulbs will need at least partial sun to keep soil temperatures warm enough that root growth occurs. They’ll also generally thrive in a loose, rich, well drained soil—though there are exceptions! And please remember that we’re planning for the spring, so consult your garden sun map and review your own experiences in your space to ensure that the resulting plants will have the sun, shade, and soil combination they need to thrive and produce blooms.

The final thing to consider is planting depth and spacing. This isn’t complicated, but it does often depend on the varietal of plant in question so (once again) do your research. We can make some generalized suggestions however. Larger bulbs should typically be planted 4-6 inches/10-15cm apart. Smaller bulbs can be planted a bit closer, 2-4 inches/5-10cm apart, but it’s best to err on the side of caution and give them a bit more space. Planting depth is fairly easy: most bulbs should be plant at a depth equal to two or three times their height. So for example if a bulb is 2 inches tall, we can plant it 4 to 6 inches deep. This takes a lot of the guesswork out of things as the bulbs serve as their own unit of measure and their own ruler!

Plant bulbs with the flat side down and the pointy end up. The flat side is where the roots come from and the pointy end is where the stem comes from, so it’s important to get them oriented correctly. Cover loosely with rich, well draining soil, water deeply after planting, and then keep the soil moist until the frost comes. A good layer of mulch always helps protect your bulbs from temperature swings and frost, so adding some as an insulating layer is a good idea.

That’s it! Your bulbs are plants, watered, mulched, and putting out roots that will help ensure a wonderful array of blossoms in spring!

Can We Plant Bulbs in Winter?

Generally speaking, planting bulbs in the ground during winter isn’t a good idea. The bulbs will at best have a delayed development in the spring and at worst may not survive the winter. There are ways to start bulbs over the winter months, but that generally involve planting them in containers in a controlled environment rather than putting them directly into the ground. We’ve written about that before here, and we may cover it again in a future article.

If you have experience planting bulbs in winter—or some advice about regular bulb planting in the fall—please let us know. Likewise, reach out if you have any questions and we’ll do our best to answer them. Gardzen is all about community and we love to hear from you!