When you hear “bulbs” you might think of springtime plants – tulips, daffodils, iris, and others. But did you know there are plenty of summer-flowering bulbs that you can plant in the spring? 

These bulbs and tubers can offer a colorful summer display and, with proper care, are perennial so they will come back year after year. While you’re planting summer bulbs, it’s also a great time to tend to your spring-blooming bulbs like daffodils to help them prepare for next year’s blooms. In this article, we’ll walk you through what summer bulbs you can plant and how to plant and care for them, as well as how to look after your spring-blooming bulbs.

Planting Summer-Flowering Bulbs in Spring

Planting summer-flowering “bulbs” (a term that includes corms, tubers, and rhizomes) in spring can yield spectacular flowers in summer. Alameda County’s Mediterranean climate—with wet winters and dry summers—can be ideal for these plants if you plant and care for them properly. 

Choosing which summer-flowering bulbs to plant in your garden

The list of options is long! Below are a few popular species of summer-flowering bulbs for Alameda County, and within each category, there may be dozens or hundreds of different varieties. In general, these flowers will bloom sometime between June to August, though exact timing may be dependent on your microclimate and part of the county.

• Alliums: more than just onions and garlic—there are dozens of varieties that are ornamental and bred for their blooms. Varieties like Globemaster offer giant orbs of tiny flowers, Schubertii looks like a firework mid-explosion, and Sphaerocephalon are small, dainty blooms that are perfect for a border or small space.
• Dahlias: tubers that are prized for their wide variety of vibrant, intricate flowers. They come in thousands of shapes and sizes, from single-flowered to small pompons to enormous dinner-plate varieties, and the plants can range from 1’ tall border or container varieties to 6’+ giants.
• Gladiolas: known for their tall flower spikes lined with colorful, funnel-shaped blooms, gladiolas are often used in cut flower arrangements. They come in just about every color under the sun, and their verticality makes them great for small spaces.
• Lilies: grown from true bulbs and known for their fragrant, trumpet-shaped flowers that bloom in early to midsummer. Lilies can be highly toxic to cats, so take care if you have pets that may want to nibble the leaves.
• Canna is sometimes called “canna lily” but is not a true lily. These are bold, tropical-looking perennials grown from rhizomes, and produce blooms successively from summer through fall.
• Tuberous begonias: unlike the flowers above, begonias prefer shade and protection from the hot summer sun. Their small size makes them perfect to tuck into a garden bed or use in a container.

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There are also many California native “bulbs” that fit our climate well. These are typically planted in fall, because they need winter rain to grow, but they bloom in late spring to summer and can survive on almost no summer water. If you’re interested in dry-loving bulbs, consider natives like Mariposa lily (Calochortus), Ithuriel’s spear (Triteleia laxa), blue-eyed grass (Sisyrinchium bellum, actually an iris relative), or soaproot (Chlorogalum). Make sure to purchase these from a reputable nursery and do not collect them from the wild directly.

When choosing a variety, consider your environment like irrigation and sun. Most summer-blooming bulbs will need full sun for at least 6 hours during the day to produce flowers, and many will need regular and deep watering in our dry climate. If you want to reduce excess water usage, make sure to group plants with similar water needs together so you aren’t over- or under-watering. Some bulbs are also more adapted to dry summers and can handle minimal irrigation once established. For example, Crocosmia is a corm that produces fiery orange or red blooms and can thrive in California’s summer-dry conditions after it’s established. Gladiolus byzantinus, a species of gladiolus, is an easy heirloom that blooms in early summer and can do well even in heavy clay soil.

Finally, wind might be an important factor for choosing summer-blooming bulbs. Taller plants like dahlias will need staking and support, as their hollow stems can break easily. Tender plants like tuberous begonias can also be damaged by wind, especially when the plants are young. You may want to find planting spots that are protected from afternoon winds, or choose varieties that are shorter or have smaller and lighter blooms to support.

Planting and caring for summer bulbs

When and how to plant

Summer-blooming bulbs should go into the ground in spring after the danger of frost has passed. In Alameda County, this is typically March through April, depending on your microclimate. Most bulbs, corms, and tubers are planted about three times as deep as the bulb’s diameter. Check the label for specific instructions for your variety.

Give these plants room to grow and for air circulation. Dahlias can be bushy and should be spaced about 2 feet apart for smaller varieties and 3–4 feet for larger dinner-plate types. Gladioli can be planted closer – often about 6 inches apart in clumps or rows. Lilies might be spaced 6–8 inches apart, and begonias about 8–12 inches if in beds.

Irrigation for summer bulbs

Water to Establish, then As Needed: At planting time in spring, if the soil is dry, water the area thoroughly after planting to settle the soil and hydrate the bulbs. After that, many gardeners hold off on heavy watering until green shoots emerge, especially for rot-prone tubers like dahlias.

Once the bulbs have sprouted and are growing in early summer, provide consistent moisture throughout the dry season. A good rule is to water deeply whenever the top 2 inches of soil dry out. Well-drained soil is critical – bulbs will rot in soggy, waterlogged soil. A 2–3 inch layer of organic mulch will help reduce evaporation, but keep the mulch from directly touching the stalks of plants, as it could introduce too much moisture and weaken the plant.

Care throughout the season

Summer-flowering bulbs are similar to most other plants you may have in your garden in terms of seasonal care. Check the plants regularly to make sure they’re getting enough water, nutrients, sun, and air circulation and inspect for pests or diseases. Insects like slugs and snails love to munch on the early spring growth, earwigs may enjoy eating the blooms, and critters like gophers can harm the roots, so you’ll want to pay attention to the entire plant throughout the season. Some plants, like dahlias, can be heavy feeders and may need some extra fertilization throughout the season. If fertilizing, make sure to use a fertilizer that is higher in phosphorus and lower in nitrogen, as nitrogen will promote green growth rather than flowers. Follow the instructions on the label. Our article on fertilizing basics and our article on spring-time fertilizing are additional useful resources.

As mentioned earlier, tall and top-heavy plants like dahlias will need staking at planting time to support their large blooms. You can use a variety of stakes for this—a tall stake planted deeply into the ground and loosely tied to the plant will work well for a single plant in a garden bed. If planting multiple plants together, consider using T-posts and garden twine to create a supportive row or lattice.

And of course, the best part: the flowers! If growing these plants for cut flowers, look into variety-specific recommendations on what stage of flower production to cut them for maximum vase life. Some flowers, like lilies, will continue to bloom after cutting, while others, like dahlias, will not. If you’re growing these plants as ornamentals in the garden, make sure to deadhead regularly to encourage more blooms. 

Caring for Faded Spring Bulb Foliage After Blooming

While you’re in the garden planting summer-blooming bulbs, it’s a good time to tend to any spring foliage that needs care. 

When to cut back dying spring foliage

As flowers like daffodils, tulips, and irises finish blooming, you’ll notice that their green leaves will yellow and flop. It may be tempting to cut everything back for tidiness, but patience is crucial! How you treat this fading foliage affects the plant’s health and next year’s blossoms. The mantra is: “Leave the leaves!”—at least until they have finished their job. These leaves may look like they’re dying, but they’re continuing to photosynthesize and create food for the bulb that will power next year’s growth. 

We don’t recommend braiding these leaves or tying them in bundles—while this may make the plant look tidier, it reduces the leaf area exposed to sunlight and can trap moisture, which could encourage disease. It usually takes several weeks (often 4–6 weeks after flowering) for spring bulb leaves to fully yellow and die. During this time, the plants may look messier in the garden, but think of it as a necessary trade-off for robust flowers next spring. 

As you wait for leaves to die back, make sure to deadhead flowers to prevent the plant from using energy for these spent blooms. Once the foliage is fully dead, remove it and any debris. Healthy leaves can be composted, but do not compost any leaves that are diseased.

Dividing and relocating bulbs

Over the years, many bulbs naturalize and multiply. You might notice your daffodils or freesias producing more leaves but fewer flowers, or your iris is forming a dense and tight clump—these are both classic signs that the bulbs are crowded and need division. As a general guideline, you should divide clumping bulbs every 3–5 years to keep plants blooming their best. 

The ideal time to dig up and divide most spring bulbs is after the foliage has completely died back and the bulb is dormant. In Alameda County, this often means late spring or early summer, around late May or June, for many bulbs. Bearded irises are a notable exception, as we divide them in mid-summer (July or August), a few weeks after blooming and when the rhizomes are semi-dormant.

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Use a spade or fork to dig up the bulb clump gently. Dig a bit away from where the bulbs are to avoid spearing them, then lift the clump. Shake off or brush off excess soil, and you’ll see bulbs and any smaller “offset” bulbs attached. Tease apart the offsets from the mother bulbs. Discard any bulbs that are soft, rotten, or damaged. If you have a new spot ready, you can replant divided bulbs immediately at the proper depth in their new home. Alternatively, you can store most bulbs until fall planting time. To store, keep them in a cool, dry place with good air circulation. Paper bags or mesh sacks work well, but don’t forget to label them! Iris are an exception here – they should be replanted soon after division as they won’t survive long storage.

Final thoughts

Summer-flowering bulbs can give you the best of many worlds: a brilliant display of color throughout the season, relatively easy care (especially if you choose a native or low-maintenance variety), and a plant that will come back year after year. There are many kinds of summer-flowering bulbs that can do well in Alameda County, so you can choose whatever suits your garden and your needs best. While you’re in the garden, there are some spring bulb tasks you can also do to ensure a beautiful display the following spring as well. 

Suggested Reference List (For Further Reading)

1. Faith Brown, Marin Master Gardeners – Plant Summer-Blooming Bulbs for Dazzling Color (PDF) 

2. SF Dahlia Society: 5 simple steps to grow dahlias in the Bay Area

3. Butte County Master Gardeners: Summer blooming bulbs

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