As difficult as it is to think about, autumn is creeping up on us and the cooling weather of September and October is a perfect time to plant fall bulbs for an early spring flower show. Knowing what bulbs to plant in fall and the intricacies of planting bulbs in the fall can be tricky, and this blog seeks to simplify the subject to ensure your garden is flourishing come spring!
In this blog, I will cover:
- The difference between hardy bulbs and tender bulbs
- Which bulbs are hardy for zone 3 and zone 4 gardens
- What healthy bulbs look like
- Where to plant fall bulbs
- When to plant fall bulbs
- How to plant and establish fall bulbs
- How to care for fall bulbs in the spring
- And how to care for fall bulbs after they bloom
The Difference Between Hardy Bulbs and Tender Bulbs
Our natural world is unique in so many ways. For example, plants reproduce in several ways. Seed is likely the first thing that most people may say, but plants also reproduce by cuttings, rhizomes, tubers, fleshy roots, corms, and bulbs.
Bulbs are incredible plant structures that store the nutrients and framework for growing a new plant. In addition, they are protected from many adverse weather conditions to ensure the vitality of the next plant generation.
People often think of bulbs as a general category of plants that start growing from the ground from anything that is not a seed or a cutting. Genuine bulbs have five structures: a basal plate, scales (think onion), a tunic or skin, a shoot or eyes, and lateral buds.
For this blog, I will clump fleshy roots, corms, rhizomes, and tubers into our discussion on fall bulbs.
Flowering bulbs are divided into two groups: hardy bulbs & tender bulbs.
Tender bulbs are also referred to as spring bulbs.
Spring bulbs are planted in the spring because they cannot tolerate our cold Canadian prairie winters. Spring bulbs are often started early indoors to get them a jump start on growing. This category includes Gladiolas, Begonias, Caladiums, Cannas, Callas, Dahlias, and unestablished Lilies.
Hardy Bulbs also called fall bulbs
They are called hardy and fall bulbs because they can tolerate our winter and are planted in the fall.
Fall bulbs require two things:
- Fall bulbs need time to get their roots and other structures established.
Strong and healthy roots are required to uptake water and nutrients in the spring to support flowering. Root development occurs when the soil temperature hovers around 10-15 C.
Other structures, like leaves and flower buds, begin to form to be ready for spring flowering. The ideal scenario is to have them begin to establish and then stop growing. And then there is a winter pause in growth.
- Fall bulbs need a cold period (vernalization period) to initiate the flowering process.
Fall bulbs need a minimum of 10-13 weeks of cold below 4 C (40 F) – something we in Zone 3 have no problem accommodating!
Bulbs that are Hardy for Zone 3 & 4
- Allium – provide round purple, pink, or white flower displays atop a stem anywhere from 25-100 cm (10″– 36″) tall. Depending on the variety, alliums are long-lived and don’t require frequent replanting.
- Crocus (Chysanthus) – these short 5-10 cm (2″-4″) colorful flowers often show up while there is still snow on the ground. They naturalize easily and don’t often need replanting. Crocus flowers close at night.
- Snowdrops (Galanthus) – these are early blooming white drop-like looking flowers on short plants that go dormant in the heat of summer, plant these in groups of 10-25.
- Daffodils (Narcissus) – these delightful, frilly-edged, trumpet-shaped flowers have a longer life span, likely needing replanting every four or more years. If they get too thick, they will need to be divided as the foliage turns yellow. Deer also don’t like daffodils, Yay!
- Tulips – come in a massive array of colors and unique styles. Most tulips need to be replanted every 1-2 years. Tulips close up at night.
- Grape Hyacinth (Muscari) is a member of the lily family. This 10-15 cm (4″-5″) tall plant bears blossoms that look like upright clumps of grapes above grassy-looking leaves. Give them a try in the front of a flowerbed, in alpine rock gardens, and woodland gardens. They come in shades of purple, white, and light blue.
Fall Bulbs Usually Bloom in this Order in the Spring
- Crocus & Snowdrops – as the snow is melting
- Daffodils – in early to mid-May
- Tulips & Grape Hyacinth – mid to late May
- Alliums – bloom in late May and into June
What Do Healthy Bulbs Look Like
Healthy bulbs are firm like potatoes. Their outer skin should be intact, sometimes it is rough, and other times it is smooth. It depends on the variety.
Scratches or dents indicate that there has been some physical injury, and a break in the skin can be a vector for disease or infection. Bulbs shouldn’t be soft or squishy; they are never to be oozy or moldy.
Keep fall bulbs dry and cool in the interim before they are planted to keep them from getting moldy. Only plant firm, dry bulbs in the fall.
Where to Plant Fall Bulbs
Site Selection is one of the keys to growing great flowering fall bulbs. Choose a spot that will display the flowers well, has adequate light, rich soil, and good drainage.
Sunlight Requirements for Fall Bulbs
All bulbs need light and warmth to start the growing process. Pick a site in a sunny, warm location that gets at least 6-8 hours of sunshine. Check the light growing requirements for your specific variety so that you have the right sun exposure.
It is okay to plant fall bulbs near deciduous trees that lose their leaves in the fall because they won’t be leafed out by the time the plants from the bulbs emerge.
Bulbs will grow earlier and faster in warm south-facing areas than in shadier, cooler locations.
Soil & Drainage Requirements for Fall Bulbs
Bulbs grow best in good quality, loose, fertile soil that drains well. Avoid planting bulbs in hard, clay-based soils. If the soil is hard, enrich it with organics to soften it up. Avoid planting bulbs in wet areas or areas with standing water. Bulbs will rot when the soil stays damp.
When to Plant Fall Bulbs
It is best to plant fall bulbs 5-6 weeks before the ground freezes solid. Trying to pin that date down is a lot like betting on the birth of a baby — when exactly that will happen is a good question!
Here is a guideline of approximate dates for planting fall bulbs in horticultural zones 1-4
Zone 1 & 2: early September
Zone 3: mid-September
Zone 4: late September / early October
How to Plant Fall Bulbs
Planting fall bulbs properly is a combination of correct depth, spacing, watering, fertilizing, and mulching.
How deep to plant fall bulbs?
The correct planting depth depends on the individual type of bulb and the soil conditions.
The Rule of Thumb for Planting Bulbs: Plant at a depth of 2-3 times the measurement across the bulb (diameter) or the largest dimension and measure the planting depth from the bottom of the bulb. Most packages will give precise measurements for the variety.
Plant the bulbs at the recommended depth for soft and pliable soils, but for harder soils, plant a little shallower.
How to Space Fall Bulbs
Bulbs can be planted individually or in clusters. Plant larger bulbs like Tulips, Alliums, and Daffodils 15 cm (6″) apart, but smaller bulbs like crocus & grape hyacinth can be as close as 5 cm (2″).
How to Prepare the Site
Once you know whether you’d like to plant in clusters or individually, you can move forward in digging the hole.
Arrange the bulbs on ground level first to give you an idea of the diameter required, and then dig a hole to the depth and width appropriate for your planting.
It’s a good idea to add bonemeal or superphosphate (0-20-0) to the bottom of the hole to provide a little extra phosphorous to encourage root development. For more details on fertilizer macronutrients like nitrogen, phosphorous, or potassium – see my blog called ‘How to Understand Fertilizer Labels’. Always be sure to follow package directions for recommended fertilizer amounts.
Cover the hole 1/2 way up with soil and water the bulbs well. Then cover the hole entirely, so that it’s level with the rest of the flowerbed. Finally, add mulch. Mulch is great for insulation — it levels out the soil temperature to minimize the effect of the freeze-thaw cycles that happen in the fall, mid-winter, and early spring. For more about the benefits of mulch, check out my blog called ‘What is Mulch? Making Gardening Magic with Mulch’.
Remember to label your plantings so you know what you’ve planted! Even if you think you’ll remember all the plantings and what they were, you might forget as our winters are long. If you’re like me, you will not!
Caring for Fall Bulbs in the Spring
Fall bulbs require very little spring care. They will probably surprise you with blossoms before you even notice them emerging.
One note for spring care is to notice if the ground is parched and water the bulbs when the first signs of growth appear. Water deeply, remembering the depth they were planted in the fall, but avoid watering often as they will rot if they stay too damp. One good drink of water will probably be enough.
One other thing to remember is that flowers from fall bulbs make great cut flowers! Allium, Tulips, and Daffodils work wonderfully as cut flowers. Cut them when they are still in bud for the best results. For more on fresh-cut garden flowers, read my recent blog called ‘The Best Secrets to Making Cut Flowers Last’.
Caring for Fall Bulbs Once They are Done Blooming
Once the flowers have faded, caring for the bulbs is essential for them to enlarge and reproduce.
As the flowers begin the die back, give the bulb a light application of fertilizer (10-10-10, 20-20-20, 15-30-15, or another organic or natural fertilizer of your choice) to keep the leaves healthy. Maintaining leaf health is key to bulb health and growth.
Cut off the spent flowers so the plant’s energy focuses on bulb development rather than seed development. Allow the leaves to stay, don’t cut them off, but let the leaves die back naturally to provide as many nutrients to the bulbs as possible. The bulbs bulk up as photosynthesis continues in the leaves.
If it looks too ugly to let the leaves die back, try interspersing the bulbs among other perennials in the garden, and as the other perennials emerge and grow, they usually mask the dying leaves. People tend to notice the growing perennials more than the fading ones.
Hardy bulbs are perennials and can stay in the ground after they have established and blossomed, producing a new crop the following spring.
Sometimes clumps get massive and need to be thinned; this is especially important for Daffodils. Dig out the bulbs after the foliage has died back and split them up. You can store the bulbs in a dry, dark place until it’s time for fall planting.
Wrapping up Fall Bulbs
Garden preparation in fall is already spring gardening, and fall bulbs are like putting insurance in place for an early show of spring flowers as the rest of the garden is waking up. If you haven’t tried them, give them a go. You’ll love them!