Daylilies are best cut back in autumn, once the leaves have had a full growing season on the plant. While there are some evergreen types of daylilies, most are herbaceous, meaning that the leaves die back in the wintertime and sprout anew in the early spring.
How To Prune For Winter/Spring/Fall/Summer. It isn't necessary to trim or shape the plant in any way; just cut back Daylilies to remove dead growth. Spent flowers can be removed throughout the growing season. All greenery can be cut back in the fall at the end of the season or early spring before new growth emerges.
Flower stalks may be cut back after all the buds have bloomed. Remove spent foliage in late fall. Cut back leaves to within a few inches from the ground, also in late fall. If you prefer, you may wait until spring to remove leaves, as soon as you see new growth emerging from the ground.
Overwintering. As perennials, daylilies do not need a lot of winter care. Growth dies back to the ground at the end of the season, so removing this will prepare them for the next growing season. Remove foliage and any remaining flowers after the first frost and cut stems to a few inches about the ground.
Daylilies can be divided in early spring (as new growth begins to emerge) or in late summer. Dig up the entire clump with a spade. Shake or wash off the soil.
Prune lilies in the fall or early spring to remove spent foliage. Wait until the foliage has completely turned brown and limp, and then cut all top growth to the ground. Pruning lilies too early before the foliage has a chance to die back can prevent the bulb from storing adequate energy for winter.
The best time to divide daylilies is either early spring, before the plants have begun to grow, or late fall, after the blooming season. Dividing daylilies is pretty straightforward. You'll need a shovel or spade, and a sharp dividing tool or pair of scissors.
The spent flowers quickly turn to a mushy bloom and then dry over undeveloped buds which can prevent them from opening. Removing the dead blooms keeps this from happening. Also, daylilies which have not been deadheaded will form seed pods.
You can do this in late fall or early spring, depending on when you want to put in the effort. If you choose to do the cleanup in the fall, you can wait until the first hard frost before cutting back leaves. In the spring, it's best to trim just before or as the new green growth is coming up from the ground.
Trim back foliage to about 6-8 inches and lift whole clump from the garden. You can choose to split the clump in half, thirds or many pieces depending on its original size. The smallest division you make should have at least four “fans” of foliage. If you want to make your divisions larger, that's OK, too.
When you leave sad looking Daylilies with spent flower heads and yellow foliage, it just takes the spark out of the garden in late summer. Try removing all the leaves once you see them yellowing and find out the difference it can make in your garden.
Also, do not cut back hardy perennials like garden mums (Chrysanthemum spp.), anise hyssop (Agastache foeniculum), red-hot poker (Kniphofia uvaria), and Montauk daisy (Nipponanthemum nipponicum). Leave the foliage. It's important to protect the root crowns over winter.
The general rule of thumb for planting spring bulbs is to plant two to three times as deep as the bulbs is tall. This means most large bulbs like our Bulb-Zilla lilies will be planted about 6 inches deep while smaller bulbs will be planted 3-4 inches deep.
Although lilies tend may seem like rather exotic plants, they are fairly hardy and will survive winters outdoors in many locations (through zones 5-9). However, gardeners in colder, wetter climates may prefer to lift their lily bulbs for overwintering in a less harsh environment.
Hemerocallis (Daylily)
While the lifespan of one single Daylily flower bloom is only a couple of days, the plant itself can live up to three years. Keep in mind, that in some states, the daylily is considered a weed due to its invasiveness and will need additional control to prevent daylilies from taking over.
Dig a hole two times as wide as the roots and a foot (30 cm.) or so deep. In the center of the hole, pile dirt up to make a mound and put the plant atop the mound with the foliage end up. Spread the roots out to the bottom of the hole and fill back in with soil so the crown of the plant is at the top of the hole.
Daylilies tend to spread quickly on their own, given the opportunity in the form of open space. To prevent them from taking over your garden, it's prudent to divide them regularly, as we describe above.
Daylilies were traditionally plants that stopped growing and became dormant through the winter. But today there are semi-evergreen and evergreen cultivars that have foliage or leaves that remain green over winter and that are hardy and will grow and bloom well in Minnesota.
Daylilies are strong performers in the garden.
If you deadhead them (cut off the old flower stalks at the base) you will get even more blossoms than if you leave the stalks up to form seed pods which over the summer will ripen and burst in the fall. While it isn't necessary, doing it will get you better performance.