Before we can answer the question of when the best time to plant summer-blooming bulbs, we must determine what summer-blooming bulbs are! Online retailers like Holland Bulb Farms and Tulip World sell a variety of bulbs, perennials, fruit and vegetable plants for planting in spring. Typically out of their assortment we consider “Summer-Blooming Bulbs” to be bulbs like dahlias, gladiolus, canna lilies, calla lilies, caladium, begonias, anemone, pineapple lily, lilies, elephant ears, ranunculus, and a few other specialty bulbs.

Proper planting time for these summer-blooming bulbs will vary based on your location and each different type of bulb. Most summer-blooming bulbs are sensitive to frost, cold soil, and below freezing temperatures. Taking the weather into consideration in your area is the first thing to think about when planning your spring planting for summer blooming bulbs. In addition to considering typical temperature trends in your area, you can also use your hardiness zone as a guide for when and what to plant. Hardiness zones are set by the United States Department of Agriculture and are based on the minimum average low temperature a particular area receives. Plant and flower bulb hardiness zones are based on the lowest temperature they can endure for survival through winter. You can determine your hardiness zone by entering your zip code in the hardiness zone finder on the Holland Bulb Farms website here.

Zone Map

Once you know your hardiness zone you can establish a general time frame for planting summer blooming bulbs. For gardeners in warm hardiness zones (zones 8, 9, 10 and 11) they are typically able to start planting summer blooming bulbs in mid-March or sooner if available. However, most online retailers and catalog companies don’t start shipping until the middle of March which is why this is a good timeframe for planting to begin those areas. Warm climate gardeners (or lucky people as I will refer to them from now on) can start planting summer blooming bulbs in Mid-March. The planting season for these summer blooming bulbs like dahlias, gladiolus, callas, canna lilies and caladium in warm climates can last through late spring. Warm climate gardeners planting in late spring when the temperatures are on the rise will need to be more aware of keeping the bulbs watered once they see sprouts.  For people in places like Florida, California, Texas, Louisiana, and other warm hardiness zones, spring planted summer-blooming bulbs are ideal for your locations and thrive in the warm and sometimes tropical climates.

Hardiness zone 7 covers locations in the middle of the United States, like Tennessee, Oklahoma, New Mexico, Virginia and North Carolina. Temperate areas like Oregon, Washington, and Northern California also have zone 7 hardiness in certain locations.  These areas may get some winter-like temperatures on occasion, but in general, are a bit on the mild side, and once late March rolls around they are ready for planting. If you are in zone 7 and the weather isn’t quite cooperating by late March or your soil seems too cold, you may want to hold off planting tender bulbs like caladiums, cannas, begonias, and dahlias until later in April or early May.

One of the largest hardiness zones in the United States is hardiness zone 6. This zone covers a large portion of the Midwest, states like Illinois, Indiana, Ohio, Pennsylvania, Kansas, Massachusetts, and Connecticut. Even areas in Colorado, Nevada, and Missouri are in hardiness zone 6.  People in hardiness zone 6 are most likely to experience true winter conditions like snow, ice and below freezing temperatures. Therefore, gardeners in zone 6 will need to wait a bit longer to plant sensitive summer-blooming bulbs such as cannas, dahlias, gladiolus etc.  Even once spring appears to be in full swing, the soil may be a bit cold which can cause warm weather summer blooming bulbs to rot prior to sprouting.  Gardeners in zone 6 should wait to plant their summer blooming bulbs outside until the danger of frost has passed in their area. Typically by mid to late May bulbs like dahlias, gladiolus, caladium, and begonias can be planted in the ground in hardiness zone 6.  If you want to get a jump start on planting before May you can start your tender summer bulbs indoors in pots.

Another large hardiness zone is zone 5, which is one of the colder zones in the United States. Gardeners in hardiness zone 5 will experience similar winter temperatures and conditions to gardeners in zone 6. Gardeners in hardiness zone 5 will want to wait until around Memorial Day to get their dahlias, gladiolus, canna lilies, calla lilies and caladium planted in the ground. However, if you have the capacity to start these tender bulbs in containers inside it is recommended to do so. Once the danger of frost has passed you may transplant the bulbs outside.

Zones 3 and 4 are smaller zones, but experience cold temperatures through winter and into the spring months. Summer blooming bulbs should be planted outside started in June. Again, if you are able to start your summer blooming bulbs inside before you can get to planting them in the ground I definitely suggest this!

Many catalogs and online retailers of plants and flower bulbs will send you your items before you are safely able to plant them. They do this to stay ahead of schedule and ensure you receive the items you may have reserved through a pre-order. If you receive flower bulbs, or perennial roots before you are able to plant them in the ground they store easily in dry, cool locations. Just open the box they came in, and make sure the packages have some air and the bulbs or roots will stay in good condition for several weeks.  If you do get your items in advance of when you want to plant them, you can as mentioned above start them indoors; this can really be helpful in having fuller plants with more blooms through the summer.

You may also have plans to plant bare root perennials this spring for growth and blooms not only this summer but for many seasons to come! Typically bare root perennials are not sensitive to frost and below freezing temperatures. However, they can be a bit sensitive to cold and damp soils that can occur in spring. Therefore, you may not need to wait as long to plant your bare root perennials as you do your summer blooming bulbs, but be aware if the ground seems very moist and cold from snowmelt and increased rains you will want to wait until the soil warms up a bit. When I plant bare root perennials I always start them in old nursery pots, as I can control the soil temperature and moisture which is critical to starting new transplants. Even in May and June when it is safe for me to plant bare root perennials directly in the ground I prefer to start them in pots; if you are able to do this with your bare root perennials it will be worth the extra effort!

It may be cold and snowy where you are, or it may be warm and sunny! Either way, Spring isn’t too far off and if you want a yard full of beautiful flowers this year, there is no better time than now to start planning and ordering your summer blooming bulbs!