Specialist in Daylilies for the Northern Gardener

Daylilies have the reputation for being tough, adaptable, vigorous plants that require less care than other perennials. Their reputation is well deserved. If you have been growing perennials successfully, there is no reason to read any further. Your new plants will grow and bloom for many years with no special care whatever. In fact, accomplished gardeners will recognize the cultural procedures given here apply generally to most perennials. However, if you are a daylily fanatic and want to see the best growth and bloom possible, pay additional attention to their cultural needs.

Daylilies have traditionally been known to have dormant, semi-evergreen or evergreen biologies. In the past, dormant meant hardy and evergreen meant tender. Many generations of breeding better plants has seriously compromised this rule of thumb. There are now hardy evergreens and non-hardy dormants and more are coming. Growing daylilies successfully in the north only requires starting with hardy cultivars and adopting cultural practices that accommodate our severe Midwestern winters.

Site. Daylilies can adapt to most sites provided they have at least seven to eight hours of direct sun every day. Very few cultivars will bloom with less than eight hours of sun. There are a few exceptions. The first is daylilies planted in moist soils under large red and white pine. The pine trees must be planted or pruned so they do not form a complete leaf canopy over the daylily beds. Large areas of blue sky must be showing. The second exception is identical cultivars planted in two locations. One is generally in full sun and the second in minimal shade. The plant in Shade will generally bloom later than the full sun plant. This prolongs the bloom season for your favorite cultivar about two or three weeks. Third, sometimes very dark red and purple cultivars are not sunfast. Some midday shade will prevent the flower from deteriorating or "greasing".

Daylilies generally do not perform well when planted close to trees. Maples especially, have shallow root systems and heavy requirements for water and will outcompete the daylilies for both nutrients and water. Daylilies also need a site that is not constantly soaked with water like a pond edge or very low spot in the landscape. Annuals and vegetables perform beautifully in raised beds. Unfortunately, raised beds are generally not a good idea for daylilies or other perennials in the northern states unless the beds are surrounded with at least six inches of wooden timbers or eight inches of stone retaining wall. Otherwise, raised beds allow too much thawing and refreezing when exposed to extremes in weather, even when covered with exceptional amounts of winter mulch.

Soil and Fertility. Daylilies will grow in a wide range of soil types from sand to heavy clay. The requirements for daylilies are the same as for most perennials. The easiest way to assess your soil fertility and condition is to have a soil test performed. Soil test results give the right recommendations for fertilizer, compost, mulch and PH adjustment. The Soil Test Laboratory (612-625-3101) at the University of Minnesota performs soil tests inexpensively. If help is needed interpreting the results, the name and number of the county extension agent is also given. Aside from the soil test recommendations, there are only a few special procedures daylilies need for your culture to be perfect. The PH or acidity of the soil should be adjusted to about 6.5 or at least be in the range of 6.2 to 6.8. Daylilies also need somewhat large amounts of organic matter in the soil. New daylily beds need about five inches of compost (of any source or kind) tilled into the top eight to ten inches. Horse manure does not need to be composted before rototilling. Other manures need to be fully composted. Heavy dense clay soils need compost to adequately aerate the soil. Large amounts of sand help but compost is the best source of aeration. Inadequate aeration usually sets daylilies and other perennials up for a soil born fungal infection during a cool wet spring or fall. After the first year, an inch and a half of manure and wood shavings or other compost or mulch applied every year as a summer mulch will be an adequate source of organic matter. Daylilies also need regular watering. An inch a week applied in two waterings is perfect.

Planting. Daylilies should be planted no closer than two and a half feet apart except for miniatures which can be planted as close as twelve to eighteen inches. Newly purchased daylily plants should be planted as soon as is reasonable. Soak them a few hours (or overnight) in a bucket of water with rooting hormone (or starter solution or biostimulant). This helps them develop new roots quickly and often helps spring plantings bloom the same year. After the soil is prepared, the soil should be mounded slightly about an inch. This is for rainwater drainage away from the crown. A hole large enough to accommodate the root mass should then be dug into the center of the mound. The crown of the plant (where the leaves and roots meet) should be planted no more than one inch below the soil surface. Cover the roots with soil and water the plant completely. Remember to keep the cultivar name with the plant. Common plastic labels with the cultivar name written with an indelible marker will last for years underground as long as the label is not exposed to the sun.

Diseases and Pests. Daylilies do not generally have serious disease and pest problems in the north. The few diseases they do have can be easily controlled by proper culture. Always pull summer mulch away from the crown at least an inch in early spring and again in late fall to prevent bacterial and fungal infection of the crown when sudden freezes damage the daylily foliage and crown. Freezing plus soil born fungul and bacteria diseases cause "spring sickness" in daylilies and are difficult to treat effectively except by proper culture. If chemical treatment is necessary, use a soil drench fungicide labeled for ornamentals. It should be applied twice about ten days apart. Some serious growers use a soil drench fungicide applied in late fall as a preventative. Fungal diseases causing spots on the leaves can be (but do not generally need to be) treated with a fungicide labeled for ornamentals and leaf spot fungi. Watering your plants early in the day when it is humid will prevent leaf spot fungi. Pests include aphids, thrips and spider mites. They are rarely a problem in the north. If they are, chemical sprays labeled for the particular pest and ornamentals will control them. In all cases, follow the directions on the pesticide label.

Weed Control and Mulches. Any mulch used for perennials can also be used with daylilies. Mulch shades and cools the soil, helps prevent weeds from germinating and composts in place providing organic matter to the soil. Raw horse manure (with the biscuits broken up) and wood shavings make an excellent mulch since they do not cause a Nitrogen deficit in the soil. Remember to pull any mulch away from the crown of the plant at least an inch in early spring and again in the fall. Preemergent seed herbicides (Preen*, Surflan*, Treflan* and others) prevent weeds from growing in daylily beds. They perform best when applied in early fall at the "heavy" rate. Grass herbicides (Grass-be-gone*, Post*, or Fusilade*) can be used anytime the grass is actively growing to spray clumps of daylily foliage to kill invading grasses without harming the daylily.

Dividing and Transplanting. Daylily clumps should be dug out of the ground and divided every three to five years. Overgrown clumps do not bloom and grow well. Spring is the best time to dig and divide since survival will be better. However, replanting anytime up to the beginning of September is acceptable. Vigorous reblooming cultivars like Stella De Oro (and its many relatives) Quickly outgrow a site and need to be divided and replanted every two years. Clumps can be divided by washing all the soil from the roots and pulling two, three and four fan divisions off the clump. After washing, let the divisions dry in the shade for several hours or overnight. This lets cut surfaces heal and prevents fungal and bacterial infections. Replant the divisions as described above and always add two scoop shovels of compost for each replanted division. Remember to keep all divisions labeled with the correct cultivar name. Give the extra divisions to deserving friends.

Overwintering. Many, but not all, cultivars are as "hardy as a rock" and do not need winter mulch. However, even the "hardy as a rock" cultivars will grow and bloom better when given overwintering care. The first step in overwintering is to make sure all summer mulch is pulled away from the plant crowns at least an inch. This is advisable for all perennials. Do not remove the old dead daylily foliage in late fall unless you see 1/4" black fungal spots (called sclerotia). The black spots are the overwintering stages for leaf spot fungi. The old daylily foliage helps hold the winter mulch and snow in place for the remainder of winter. All daylilies and most perennials should be covered with six inches of straw, hay or hardwood leaves. Bags of dry leaves removed from the lawn also make good winter mulch. Since the leaves are in bags, they are easily removed and composted in the spring. Never use softwood leaves for winter mulch unless they are bagged. They will become wet and mat down on your perennials killing most of them. If you have ever seen evidence of mice or voles, poison mouse bait scattered under the winter mulch is advisable. Winter mulch should remain in place from the time the ground begins to freeze all through winter until the middle of April. Then the mulch and old daylily foliage can be removed. Because spring can be early or late from one year to the next, a good rule of thumb is to wait until the soft maples and elms are in bloom before removing winter mulch in the spring. If winter mulch is removed early and a severe cold snap freezes new foliage, wait until it thaws and remove the injured leaves with a scissors. Newly purchased and newly divided daylilies should be covered with ten to twelve inches of winter mulch their first winter. Winter mulch definitely helps perennials survive winter. This is due to four factors. First, extra organic matter is added to the soil. Second, the winter mulch insulates plants from extremely cold winter temperatures. Third, winter mulch insulates plants from a warm January thaw. January thaws can warm the soil enough for plants to come out of dormancy and begin to grow. They are severely damaged when cold temperatures return. This is what kills many otherwise hardy perennials in the Midwest. Mid-winter thaws can also heave new plants out of the ground. Fourth, there is some evidence that perennials continue to develop new roots between the time the foliage turns brown and the ground freezes solid. This is certainly true for daylilies. Winter mulch extends the time before a solid freeze.

Additional Information. Additional information can be found in the texts dedicated to daylilies and your local or state daylily society. Beware however, once you are exposed to the incredible world of modern daylilies, you will become obsessed with them. The place to start your obsession is the Hemerocallis Society of Minnesota, (c/o Mr. David Nordbye, 8818 James Ave. South, Bloomington, MN 55431) and The American Hemerocallis Society (c/o Elly Launius, Executive Secretary, 1454 Rebel Drive, Jackson, MS 39211). Both have a text, Daylilies. Everything You've Always Wanted to Know About Daylilies. A Beginner's Handbook., published by the American Hemerocallis Society.