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Summer-blooming bulbs bring vibrant colors and lush foliage to gardens during the warmest months of the year. To get the most out of these plants, which include favorites like dahlias, lilies, and gladioli, we checked in with bulb specialist Brent Heath, part of the team behind Brent and Becky‘s. Here, Heath offers advice on planting and feeding the bulbs once the ground thaws in spring, and tells how to encourage them to make new plants.
Understanding Summer-Blooming Bulbs
The world of summer-blooming bulbs is diverse and colorful. Understanding their general characteristics, planting strategies, and care requirements will set you on the right path to a vibrant garden.
Types of Summer-Blooming Bulbs
Summer-blooming bulbs come in a wide variety of shapes, sizes, and colors. Some popular options include:
- Dahlias: Known for their large, showy flowers
- Lilies: Fragrant and elegant, with trumpet-shaped blooms
- Gladioli: Tall spikes of colorful flowers
- Canna lilies: Tropical-looking plants with bold foliage and flowers
- Begonias: Shade-loving plants with delicate blooms
Each type of bulb has its own specific needs, but many share similar care requirements.
Choosing the Right Bulb Varieties
Choosing the right bulb varieties for your garden will depend on your regional climate, soil type, and garden design. Popular options like dahlias and gladioli are known for their striking appearance and relatively easy care, but it’s important to select varieties suited for your specific conditions.
There are early, mid-season, and late-blooming varieties, giving gardeners options for a continuous display of color throughout the summer. Choosing a mix of these can ensure your garden stays vibrant from early summer until fall.
When and Where to Plant
The timing of planting is important for summer-blooming bulbs. Most should be planted in the spring after the danger of frost has passed and the soil has warmed. Choose a location that receives full sun to partial shade, depending on the specific bulb’s requirements. Well-draining soil is essential to prevent bulb rot.
Starting Off a Flower Bulb Right
Proper planting techniques are fundamental to the health and longevity of your summer-blooming bulbs. The right soil and planting depth can make a significant difference in how well your bulbs perform.
Choosing the Right Soil Type
Summer-blooming bulbs thrive in well-draining soil rich in organic matter. As Heath explains, “Bulbs do best in free-draining soils, though summer-blooming bulbs are a bit more tolerant of wet feet, compared with ones that bloom in the fall, because the cooler spring dormant period is hospitable to fungi.”
If your soil is heavy clay, consider amending it to improve drainage. Heath recommends adding a layer of compost above the clay, instead of mixing the two, which creates something of a bog. Layering the compost allows the bulb’s roots to drain and reach into the clay, which is great for holding nutrients and moisture.
Proper Planting Depth and Spacing
The general rule for planting depth is to place bulbs in holes that are three times as deep as the bulbs are tall. However, there are exceptions—true tubers, like dahlias and liatris, should be buried only as deep as the crown.
Spacing depends on the type of bulb and its mature size. Refer to the planting instructions that come with your bulbs, as they can vary significantly between species. Some, like dahlias, can grow quite large and may need extra room to spread out. Proper spacing ensures that each plant has enough room to grow and access nutrients without competing with its neighbors.
Using Raised Beds and Containers
For those with limited garden space or poor soil conditions, raised beds and containers can be an excellent solution for growing summer-blooming bulbs. Raised beds offer better drainage and control over soil quality, while containers allow for portability and placement flexibility.
To use containers effectively, choose pots with adequate drainage and fill them with a high-quality potting mix. Grouping different bulbs together in a single container can create a stunning display of mixed colors and forms.
Nurturing Your Summer Bulbs
Once your bulbs are in the ground, they require ongoing care to flourish. Proper watering and delayed fertilizing are key to producing healthy plants with abundant blooms.
Watering Requirements
Summer-blooming bulbs generally need consistent moisture throughout their growing season. Water deeply and regularly, especially during dry spells. However, be cautious not to overwater, as this can lead to bulb rot. The soil should be moist but not waterlogged.
Fertilizing Strategies
Contrary to popular belief, fertilizing at planting time isn’t always necessary. Heath advises, “A lot of the advice out there advocates adding a pinch of fertilizer to the hole when planting, but it’s not necessary and it can burn emerging roots.” The bulbs already contain the nutrients needed for their first year of growth.
For subsequent years, Heath recommends a sustainable approach: “It’s better to have a more sustainable nutrient base provided by compost. But if you have to fertilize after year one, use a slow-release, organic version like Espoma Bulb-tone.” Compost tea applied as a spray stimulates the life of the soil, reaches the roots faster, and can be applied at nearly any time of the year.
Overall, soil should have a high amount of organic matter instead of relying on synthetic fertilizers, which provide an initial boost but leave the plant in a slump afterward.
Mulching and Weed Control
Applying a layer of mulch around your bulbs can help conserve moisture, regulate soil temperature, and reduce weed competition. Organic mulches like straw, wood chips, or shredded leaves are excellent choices.
Regular weeding is essential to prevent competition for nutrients and water. Hand-pulling or using a hoe will keep your bulb bed clean and healthy.
Managing Foliage and Post-Bloom Care
Shown: Asiatic hybrid lilies (Lilium ‘Malta’) and shasta daisies (Chrysanthemum maximum ‘Little Princess’)
Proper care after blooming is necessary for the long-term health of your summer bulbs. The foliage plays a vital role in storing energy for next year’s growth.
The Importance of Leaving Foliage
After your bulbs have finished blooming, resist the urge to cut back the foliage immediately. Leaving the spent foliage on the bulbs allows them to recharge, developing starches and sugars for next year’s blooms. This process is essential for the bulb’s ability to return and bloom in subsequent years.
To manage the appearance of fading foliage, consider planting summer-blooming bulbs among taller perennials. Heath suggests, “Plant summer bloomers with asters and mums that will tide your beds over into autumn.” This strategy helps conceal the yellowing leaves while maintaining an attractive garden design.
When and How To Trim
Wait until the foliage has completely yellowed and begun to flop over before trimming. This usually occurs in the fall and signals that the bulb has finished storing energy for the next growing season. At this point, you can safely cut the foliage down to ground level.
Deadheading and Seed Collection
Deadheading spent blooms can redirect the plant’s energy from seed production back into bulb development. This simple practice can enhance the overall performance of your bulbs.
Alternatively, collecting seeds from some summer-blooming bulbs, like lilies, can also be a rewarding way to propagate new plants. Allow the seed pods to mature on the plant before harvesting.
Overwintering and Dividing Bulbs
In colder climates, some summer-blooming bulbs may need to be dug up and stored for the winter. Additionally, dividing bulbs periodically can help maintain their vigor and increase your plant stock.
Storing Bulbs for Winter
Not all summer-blooming bulbs are hardy enough to survive winter in the ground, especially in colder regions. Tender bulbs like dahlias and gladioli should be dug up after the first frost and stored in a cool, dry place. Heath cautions that a common mistake is washing the bulbs you plan to overwinter, because you can bruise them, leading to rot.
Instead, gently brush off excess soil and store the bulbs in a container filled with peat moss or wood shavings. Keep them in a location that stays between 40 and 50 degrees Fahrenheit throughout the winter.
Dividing Bulbs for Propagation
Dividing bulbs is an excellent way to propagate your plants and maintain their health. “Divide when the plant is finished growing for the season,” Heath advises. “So that’s May or June for the spring-flowering bulbs, the end of the summer for summer-flowering bulbs. “
When dividing, gently separate the bulbs that naturally fall away from the mother plant. These can be replanted immediately or stored for the winter, depending on the time of year and your climate.
Typically, bulbs ready to be divided will naturally fall off from the mother plant when you dig the clump up, and they can be replanted again right away. It’s different from dividing a hosta, which you physically have to cut. With bulbs, gently tease them apart.
Encouraging Bulb Naturalization
Naturalization occurs when bulbs spread and create new plants on their own, creating a more established and natural-looking garden over time.
Creating Ideal Conditions
To encourage naturalization, provide your bulbs with optimal growing conditions. This includes well-draining soil, adequate sunlight, and proper spacing. To give plants a better chance of naturalizing, Heath suggests spacing them out in a border, where there’s less competition for soil, nutrients, and light.
Companion Planting for Naturalization
Choosing the right companion plants can help create a favorable environment for naturalization. Select plants that won’t overshadow your bulbs or compete too aggressively for resources. Consider native plants that attract pollinators, as these can help with seed dispersal and overall garden health.
Monitoring and Encouraging Self-Propagation
Observing how your bulbs spread and where they thrive in your garden can inform future planting decisions. Self-propagation can be encouraged by allowing seed pods to develop naturally and refraining from disturbing the soil where bulbs are planted.
Troubleshooting Common Flower Bulb Issues
Even with proper care, summer-blooming bulbs can face challenges. Knowing how to identify and address common problems can help keep your plants healthy.
Pest Control
Common pests that affect summer bulbs include aphids, thrips, and slugs. Regular inspection of your plants can help catch infestations early. Use organic pest control methods when possible, such as insecticidal soaps or neem oil, to protect beneficial insects in your garden.
Disease Prevention
Fungal diseases are a primary concern for summer-blooming bulbs, especially in wet conditions. Ensure proper air circulation by spacing plants adequately and avoid overwatering. If you notice signs of disease, such as discolored leaves or rotting bulbs, remove affected plants promptly to prevent fungi from spreading.
Environmental Stress Factors
Environmental stressors like extreme heat, drought, or excessive rain can impact the health and blooming capability of summer bulbs. Providing shade during peak heat, ensuring adequate watering during dry spells, and improving drainage can mitigate some of these challenges.
Our Conclusion
Caring for summer-blooming bulbs requires attention to detail and a bit of patience, but the rewards are well worth the effort. By following these guidelines for planting, nurturing, and maintaining your bulbs, you can create a vibrant and long-lasting summer garden display.
