When to divide daylilies
In the North, we usually begin dividing daylilies in May and continue through August. Divide daylilies to obtain more plants for your own garden or to share. Most daylilies do not require frequent division, but if you see diminished bloom, division may re-invigorate the plant.
We test soil temperatures in the spring and wait to divide until soil temperatures reach 55° F, at which point daylilies begin vigorous growth. Other growers have reported success when digging earlier, but it will depend upon the season and your growing conditions.
Another good opportunity to dig and divide a daylily is after the daylily has finished its bloom cycle. It is risky to dig daylilies during extremely hot weather, so if there is a heat wave, wait for cooler temperatures. In most seasons, this would be around mid-August in our Minnesota location, but gardeners in areas farther south would wait until September or so.
The conventional wisdom is to divide and re-plant daylilies at least six weeks before the ground freezes. In the North, it is advised to mulch new plants for winter protection in case there is little or no snow cover. If winter temperatures plunge below 0°F with no snow cover, loss of even hardy perennials is likely. You should follow recommended practices for winter protection of perennials for your area.
Set up a work area
Before you start, set up a work area and gather tools, supplies etc. A workbench will help save your back if you have a number of plants to divide. Our current workbench has a plastic mesh surface with a drainage system beneath to carry away excess water. You could consider creating a temporary work surface using sawhorses and planks, etc. Set up the work area with water drainage in mind so you don't end up working in a huge puddle!
Tools and more
To dig and divide large clumps, use two spading forks and a long-handled shovel. For smaller clumps, a spading fork or a small transplant shovel may do the job. A water supply, a hose, and a spray nozzle are essential. Use plastic tubs and dishpans for soaking clumps to loosen garden soil.
At the workbench, use a long sturdy screwdriver and/or kitchen knife to make divisions. In addition, a smaller knife, a hand fork, pruning shears (to cut back scapes), and scissors (to cut foliage) come in handy. Sterilize tools with rubbing alcohol or a 10% chlorine bleach/water solution between cuts. (Wear protective gloves when using any chemicals such as bleach.) We use mesh nursery trays to hold divisions. You could also use dishpans or other flat containers. If the weather is cold, wear insulated rubber gloves.
Plan your labels ahead and have the necessary materials ready. Use pre-printed labels (from your laser printer -- do not use an ink jet printer for labels unless laminated!), or make temporary tags, using a permanent marker on surveyor tape or on nursery tags.
Tips for digging
Dividing a small daylily plant is a fairly simple task, but a large clump can require a bit of elbow grease!
It is usually best to dig (or “lift”) an entire clump to work on it. Some growers cut back the foliage before digging, but we prefer to keep most of the foliage intact until after cleaning. You may use a long-handled shovel, a smaller transplanting spade (for small clumps), a sturdy spading fork, or a combination. You may want to start with a spading fork to preserve more roots and switch to a shovel if you need extra leverage for a large clump.
We start by loosening the soil in a circle around the clump with a spading fork, rocking it back and forth to free the plant. This is often all that is needed in lighter soil to lift the clump. For large well-established clumps in heavy soil, switch to a long-handled shovel for extra leverage to complete the task of lifting.
IMPORTANT: Lift the plant from beneath the crown to avoid damaging the plant!
Shake off as much garden soil as possible after lifting. Top soil is valuable, so always try to keep it in the garden! Removing excess soil also means there is less weight to carry and makes clean up easier. If you are transplanting the daylily to another garden, removing the soil thoroughly helps prevent the spread of unwanted soil organisms to the new location.
Label it immediately to avoid that dreaded variety: "Unknown"
Label the clump, especially if you are working on more than one variety at a time. One safeguard against mixing up plants is to use a permanent marker and write the name directly on a scape or leaf. Another is to write the name on a strip of plastic surveyor tape and tie it around the clump. Pre-printed labels can be a time saver. Make your own long-lasting labels using a laser printer or label maker (we use a Brother label maker). The print on ink jet labels will run when wet unless laminated, so avoid them unless you take this extra precaution.
Be prepared to get wet and muddy!
The next phase involves lots of water! Here is the part where warm weather is appreciated. For cold weather, invest in some insulated rubber gloves to keep your hands warm. Wear an outfit that can get wet and muddy!
Move the clump to an area for hosing off as much soil as possible. It is often helpful to place the clump in a tub of water to soak. Slosh it around to wash off the soil and replace the water as needed. We use large plastic tubs and plastic garden carts to soak clumps. Lift clumps out of the tub and use a hose-end spray nozzle to wash away the soil.
For large clumps, begin division while on the ground. Insert two spading forks placed back to back in the middle of the clump and push the handles toward each other (i.e., toward the center of the clump). The leverage should split the clump in half. Repeat division with the two spading forks until the pieces are in manageable sizes. Continue to wash away the soil as you go. Once the pieces are easy enough to manage, move them to a workbench to complete the job.
Cut the foliage to about one foot for ease in handling. Be sure to keep track of the name if you wrote it on the plant itself per the prior suggestion. You can always cut the foliage shorter at a later point.
Finishing up
At the workbench, continue to divide until you have the desired number of divisions. Most daylilies do not form rhizomes (there are some that do, some of the species in particular), so your goal is to end up with divisions that include roots, a piece of the crown (the whitish portion between roots and foliage) and foliage. A piece of crown is essential for any non-rhizomatous daylily; a true root or a daylily leaf without a piece of crown will not grow into a new plant.
Daylily foliage grows into natural divisions called fans; each fan has a pair of leaves emerging from the crown. We recommend a minimum of two fans per division. The larger the division, the faster the daylily will re-establish. Some daylilies make small fans which easily fall apart upon division, so you might not always be able to keep two fans together.
Many growers like to use a long, sturdy screwdriver to wiggle divisions apart. Some cultivars do not form divisions that split apart easily, so for these you may need to cut through the crown with a kitchen knife. Clean cuts are always best. Keep tools sterile by wiping them down with rubbing alcohol or a 10% bleach/water solution.
Important: Always handle plants from beneath the crown! Pulling or tugging on the foliage will lead to crown damage and the likely loss of viable plant material.
After you have finished dividing, cut the roots and foliage so they balance one another. We usually trim both to 6-8". Some growers trim more severely, but we find that transplants do better in our climate with more plant material to begin with, especially toward the end of the season. Daylilies need a healthy piece of crown and a good supply of roots at transplanting time.
Let the plants dry for an hour or so out of direct sunlight before re-planting. This allows the plant to form a callous over cut surfaces and helps prevent pathogens from entering the wounds.
Finally, clean tools and tubs. Wear protective gloves. Wipe cutting tools with rubbing alcohol or a 10% bleach/water solution. Rinse soaking containers with a 10% bleach/water solution.
For planting instructions, see How to Plant.