The 5 Best Bulbs to Plant in Spring for Summer Blooms

Written by Chronicle Staff. Posted in Featured, Home & Garden

Published on May 19, 2021 with No Comments

While spring-blooming daffodils, tulips, hyacinths, and other fall-planted bulbs are great additions to any garden, summer-blooming bulbs also deserve a featured spot in the landscape. Planted in the spring, these summer beauties require very little maintenance and can be tucked right into existing garden beds. Planting spring bulbs means a lush garden, filled with fragrance and color all summer long.

When to plant spring bulbs

Spring Bulbs

Summer-blooming bulbs are most often planted in the spring, as soon as the danger of frost has passed. Though the five bulbs featured below are winter-hardy down to USDA hardiness zone 5, planting them in the spring gives the bulbs plenty of time to get established before the next cold winter arrives. Plus, you’ll be planting them while the bulbs are still dormant and there are no stems or flower stalks that might accidentally be damaged during planting.

 How to plant bulbs

Planting spring bulbs isn’t difficult, but there are some rules of green thumb you should follow when you plant bulbs.

  • First, be sure to plant them at the proper depth. Most bulbs do best when planted two-and-a-half to three times deeper than they are tall. In other words, if the bulb itself is two inches tall, the base of the bulb should be about six inches deep after planting.
  • Next, the majority of bulbs prefer well-drained soils. Do not plant bulbs in boggy areas where they’re prone to rot.
  • And finally, bulbs grow best in soil amended with compost or other organic matter. Work a few shovels of compost into the area before planting spring bulbs.

5 bulbs to plant in spring

There are dozens of summer-flowering bulbs, but not all of them are winter-hardy. While dahlias, freesia, and calla lilies are beautiful plants, they won’t survive the winter in northern climates. But, these five exceptional favorites are both beautiful and winter-hardy.

  1. Oriental lilies: The large, fragrant blooms of Oriental lilies are total show-stoppers in the garden. With scores of varieties available, there’s a broad range of colors and heights to choose from. Space Oriental lily bulbs about a foot apart, and be sure to stake the stems as they grow; their blossoms are heavy, and they’ll need the extra support.
  2. Crocosmia: Just like gladiolus and crocus, this perennial plant technically grows from corms (storage organs similar to bulbs). Reaching about three feet in height, the sword-like foliage is bright green. In mid-summer, stalks of arching flowers extend above the leaves. Common flower colors are red, orange, and yellow, depending on the variety. Crocosmia prefers full sun, and hummingbirds are frequently found dining on its nectar.
  3. Asiatic Lilies: Asiatic lilies differ greatly from their Oriental cousins mentioned above. They are earlier blooming, fragrance-free, and brighter colored. Their flowers aren’t typically as large as Oriental lilies and their stems are sturdier, so they don’t require extra support.
  4. Chinese ground orchids (Bletilla): If you’re looking for a summer-blooming bulb that prefers the shade, the Chinese ground orchid is for you. Though it officially grows from a bulbous rhizome, this plant is generally categorized as a summer-blooming bulb. A terrestrial orchid, hardy down to USDA zone 5 with a layer of winter mulch, the Chinese ground orchid reaches a mere eighteen inches in height. The distinctive, Cattleya-like flowers come in white, purple, or lavender, and over time, the plants will spread and create a nice colony.
  5. Hardy Begonia (Begonia Grandis): With a layer of mulch, this hardy, shade-loving bulb can survive a very cold winter. The leaves of this begonia are shaped like a lopsided heart and are green on top and burgundy beneath. They’re topped in midsummer by masses of pink or white flowers. Though the hardy begonia is late to emerge in the spring, once it does, there’s no stopping it. This begonia naturalizes beautifully and reaches about two feet in height.

There’s no doubt that planting spring bulbs brings a blast of summer pizzazz to the landscape – something everyone can appreciate.

When Should You Plant Spring bulbs?

For root growth and bulb development, early is better. For disease control, late is better. The best time is a compromise between the two.

Dr. William Miller made this suggestion, “Soil temperature for planting should be under 15C (59F), and for tulips 13C (55F) would be better. Below 9C (48F), root growth is reduced as temperatures get cooler.  Root growth for most spring bulbs is nearly zero at 0-1C (33F).” In zone 5 the best time to plant is October.

If you are digging up your own bulbs, and disease is not a serious concern, they should be planted as soon as possible. There is no advantage keeping them dry until the soil cools down. Any damaged or diseased bulbs should be discarded.

If bulbs are not planted on time, they can be planted until the soil is frozen solid. As Miller says, “late planting is better than not planting.” If you still have bulbs after the ground is frozen, plant them in pots and keep them in a cool spot. They will flower in spring and can be planted out the following year.

Planting Spring Bulbs Early

I am a big believer in taking advice from nature. If bulbs that are already in the ground start making roots in August it tells me that this is a benefit for the plant. Starting growth early allows the bulb to make a larger root system before the ground gets too cold. Larger root systems must benefit the plant, or they wouldn’t make them.

The exact reason for making roots early may not be known, but it is clear that bulbs prefer to make roots early in my climate and soil conditions. It then follows that new bulbs should also be planted as soon as possible (usually not available until August). 

The Life Cycle of a Spring Bulb

To determine the best time for planting bulbs it is it is important to understand the life cycle of a bulb.

In winter, the bulb is under ground and not doing very much – it is resting. In spring, it starts to grow and most of our common spring bulbs produce both flowers and leaves. This requires a tremendous amount of food energy which comes from the bulb. The new leaves start to photosynthesize to replenish the food used for early spring growth and to make seeds, another energy intensive process.

By mid-summer the plant has finished its above ground growth and the leaves start to die back. What you do not see is that the roots also die back and stop working. This makes sense since the plant is about to enter into a dormant phase where roots are not required and keeping them is a liability. The plant is now in a state of rest.

Towards the end of summer the bulb senses it is time to start growing again. It first makes roots so that it can have access to water and nutrients. Soon after root initiation, the bulb starts to grow leaves and flowers. These grow until they reach a point just below the surface of the soil. The first time I heard this I didn’t believe it. Why would the bulb grow leaves in fall? So I went out to the garden in November and sure enough almost all my bulbs had green growth just below the surface of the soil.

In hindsight this all makes perfect sense. Most spring bulbs need to start growing early in spring so that they catch the light from the sun before grasses, shrubs, trees and other larger plants shade them. The best way to get an early start is to complete a good part of the growth in fall.

When things get really cold, the bulb goes into a dormant state again, until spring.

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