The appearance of spring bulbs is one of the first signs winter is over. Early bloomers like tulips, daffodils and crocus can bring a colorful sight, welcoming spring to your garden. Proper care, like learning how and when to divide bulbs, ensures that these perennial favorites return to grace your flower beds year after year.
The Benefits of Dividing Bulbs
Typically, early blooming spring bulbs will return each year without much work, which makes them a great addition to any garden. Over time, however, the bulbs can multiply, with smaller bulbs growing as offshoots from the main bulb. These smaller bulbs can lead to overcrowding, making it difficult for bulbs to grow correctly. Dividing your bulbs gives them more room to grow, leading to a healthier, more abundant bloom. Cannas, irises and other rhizomes are types of bulbs. Like a potato tuber, they're actually underground stems that grow horizontally. They're long and firm, with multiple growing points or buds along the sides. These grow upward and out of the ground as new stems. As the years go by, the number of rhizomes and their size increase, producing a mass of rhizomes that needs dividing.
When to Divide Bulbs
While you may not need to divide bulbs every year, the best time to do so is when you notice the plant isn't providing as many blooms as it has in the past growing season. Bulbs will likely require dividing every three to five years.
The best time to divide bulbs is after the bloom has ended and the foliage starts to die back. Don't pull them out before the leaves die, or the bulb won't take in enough nutrients to survive until the following spring.
How to Divide Bulbs
Dividing spring bulbs is simple. Once the leaves die, carefully dig up the bulbs from the soil. Dig a few inches out from the plant using a small garden fork or a hand trowel to prevent damage. Dig under the bulb to lift it out from beneath. Using your hands, gently pull the smaller baby bulbs apart from the main bulb. Discard any diseased, soft or pest-damaged bulbs, keeping only those that feel firm and look healthy.
With larger groups, the rhizomes will fall apart when you dig them up, making that first division for you, but you may require a gardening knife to help break apart smaller groups of rhizomes. Gently move the roots apart and identify the growth points, just as you can see eyes on potato tubers. With both cannas and irises, you can see the growth points easily, and there should be multiple"eyes" on each rhizome. Select rhizomes that have both a stem and roots attached, bypassing any that don't have any eyes or buds.
Before you start, rinse away any soil and inspect the rhizomes, removing any soft or decaying areas. Be gentle when handling the rhizomes to avoid damaging them. After rinsing, dunk the rhizomes in a disinfecting bath of 1 part bleach to 9 parts water. Using disinfected clippers, prune back the roots.
Irises are particularly prone to disease, so it's essential to disinfect the blades of your cutting tools both before you start dividing the group, as well as before working on another group of irises. A solution of 1 tablespoon of bleach in a gallon of water should be strong enough to cleanse the blade. Rinse the bleach off the clippers before cutting the rhizome.
Crocus flowers are technically corms and not bulbs. The difference between bulbs and corms is that although they're both enlarged underground stems, a corm's storage tissue is the stem itself rather than the leaf tissue. Instead of featuring layers of leaves, a corm is a solid, almost tuber-like structure covered by an outer protective layer called a tunic. The base structure features nodes that can grow into new corms.
Similar to true bulbs, like tulips and daffodils, when a crocus starts blooming less, it's likely becoming overcrowded by smaller offshoots in need of dividing. Wait until the foliage dies back in late summer and dig them up gently. Pull the smaller corms off by hand.
Storing and Planting Divided Bulbs
Depending on when you dig up your bulbs for division, you may need to store them until it's time to replant in the fall. Prep your bulbs for storage by removing all the soil and drying them out. Place them in a shaded space out of the sun to air dry for a few days. Put the cleaned, dry bulbs in a mesh bag, leaving out any damaged or diseased bulbs. Store the bulbs in a cool, dark space away from any produce for the summer. Check on them periodically to make sure they stay cool and dry until fall. If you have multiple varieties, store them in separate labeled bags.
In the fall, plant your divided bulbs spaced apart so they have plenty of room to grow. Keep in mind that new smaller bulbs may need to mature before they'll produce flowers and may skip a season before you see any blooms from them. Instead of planting them directly into your garden bed, you can plant them in a temporary spot and then transplant them when they're mature.
Not only does dividing spring bulbs help them flourish, but it also saves you money in the long run since you can simply plant divided bulbs instead of buying new ones. With a little bit of time and effort, you'll enjoy plenty of colorful blooms welcoming each spring season.
To learn more about caring for crocus, check out Burpee's crocus growing tips and common issues.
Hardy bulbs, like irises and cannas, will produce flowers year after year when planted in the right growing zones. However, as bulbs grow, they can get overcrowded and need to be divided to protect the plants and keep them blooming. Keep reading to learn more about when to divide bulbs and how to do it.