Dahlias are hands down one of the showiest flowers around. A true showstopper, they come in many different colors, shapes and sizes. (Photo: Shutterstock).


Deryn Davidson, Colorado State University Extension – Boulder County

As spring bulbs such as tulips, daffodils and hyacinth begin to fade, you can look to their heat loving cousins for a splash of color throughout your garden. Enter, summer-blooming bulbs, corms, tubers and other bulb-like structures (often all referred to as bulbs). With a tropical look – large leaves and big flowers – they will wow your neighbors and bring beautiful interest to your garden all summer long.

Summer-blooming bulbs typically come to us from warmer climates and therefore have different growing requirements than spring-blooming bulbs. Late May is a great time to start planting them because (hopefully) any danger of frost has past, and soils are starting to warm up. Soil temperature must be above 60 degrees, otherwise you run the risk of them sitting in the cooler soil and starting to rot before they have the chance to grow. With all the spring rain we’ve been getting, you’ll want to wait to plant until after the soil has had a chance to dry out a little. Since they are not hardy here, you will need to dig them up in the fall, store them over the winter and replant in the spring; an extra step that you will be rewarded for come summer. In contrast, we plant spring-blooming bulbs in the fall and can leave them in the ground since most are hardy here in Colorado.

You can start buying summer-blooming bulbs in early spring from garden centers, nurseries, catalogs, online and sometimes even grocery stores. Earlier in the season you’ll have better selection to choose from, but if you’re looking to buy now, you should still be able to find some gems. If you buy bulbs in person, you have the advantage of individually selecting what you purchase. Be sure to choose the largest and firmest available and leave behind anything that seems dried out or small compared to the rest – larger bulbs, means larger flowers.

Varieties to try:

Dahlias are hands down one of the showiest flowers around. A true showstopper, they come in many different colors, shapes and sizes. From compact pompoms to the ‘dinnerplate’ varieties, you are sure to find some welcome additions to your garden. They have a wide range of heights, from two feet up to nearly 20 feet. The taller varieties typically require staking. Dahlias will be happiest in a nice sunny location where they can truly shine.

Allium are a showy member of the onion family. Grown for their fun, ball shaped flowers that can range from two to ten inches in diameter and come in white, yellow, blue and purples. This is a summer bloomer that can be left in the ground over winter as long as they are protected with a thick layer of mulch during the cold season.

Caladiums are a good choice if you have a shady location. They are grown for their colorful green, pink, red and/or green foliage and do well in containers as well as directly in the ground. They prefer some extra moisture and nice rich soil.

Gladiolus are a gorgeous addition to your garden and make excellent cut flowers too. Hailing from South Africa, they have been bred to come in nearly every color of the rainbow. You’ll also find them in a range of heights, from four feet tall to the shorter two foot dwarf varieties and prefer a sunny location. If you stagger your planting two to three weeks apart you will have continuous blooms until frost.

By Deryn Davidson. Deryn is an Extension Agent – Horticulture at Colorado State University Extension. For more information contact CSU Extension at the Boulder County Fairgrounds, 9595 Nelson Road, Box B, Longmont, 303.678.6386, e-mail [email protected] or visit boulder.extension.colostate.edu.