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Ask the Master Gardener: The best practices when it comes to lawn fertilizer

Asiatic lilies grown in the Brainerd area. Photo by Jennifer Knutson

Dear Master Gardener: What should I be doing for lawn fertilization this spring? Do you recommend a weed-and-feed product?

Answer: If you need crabgrass control, you should apply a preemergent herbicide before fertilizing your lawn and before crabgrass comes out of the ground. So, don't buy a product that contains both crabgrass control and fertilizer—applying them separately is the best approach. A good rule of thumb is to apply a crabgrass preventer when the lilacs are blooming.

Although it is OK to fertilize in May through the end of June, the best time to apply lawn fertilizer is the end of August to mid-October. If you fertilized last fall you probably do not need to do it again this spring. If you do want to fertilize again, it is important not to apply it too early because rains may wash it all away before the grass is growing well enough to use it. There are both natural and synthetic fertilizers. A natural fertilizer will release its nutrients slowly, and is usually made from various waste products. Some options include Milorganite, Sustane, manure, and grass clippings.

According to the University of Minnesota Extension, the disadvantages to weed-and-feed products include the following:

• For weed control to be effective, herbicides should be used at specific times during the year depending on which weed species is being targeted. Weeds must be visible and growing at the time of application to be most effective.

• The time of herbicide application to kill a specific weed may not be the ideal time for fertilizer application.

• Fertilizer-herbicide products should never be used when the herbicide would be ineffective or unnecessary.

• For maximum effectiveness and to reduce the chance of damaging the lawn, fertilizers need to be watered in. On the other hand, many herbicides need to remain on the plant leaves for effective weed control. Therefore, weed-and-feed products often compromise the effectiveness of the fertilizer, herbicide or both during application.

• Fertilizer-herbicide combination products often apply much more herbicide than is needed to kill the target weeds.

Where there are only scattered weeds throughout the yard, it may be best to just spot treat those individual weeds or small areas of weeds rather than applying a weed-and-feed product over the entire lawn.

Dear Master Gardener: I've seen lily bulbs for sale recently and thought they had to be planted in the fall. Can lily bulbs be planted in the spring?

Answer: Lily bulbs may be planted in fall or spring. When buying them locally, choose firm, plump bulbs with the roots attached. Whether you purchase them locally or by mail order, plant the bulbs as soon as possible and choose lilies that are hardy to USDA zone 3. Asiatic and LA Hybrid (Longiflorum Asiatic) lilies are the most popular and easiest to grow in northern gardens.

Plant them in full sun (6-8 hours of sunlight) in well-drained soil. We tend to have light, sandy soil in this area, so add organic matter to help hold onto nutrients and prevent them from becoming too dry. For the best effect, plant lilies of the same cultivar in groups of three or five bulbs, spacing them 8-12 inches apart. Plant small lily bulbs 2-4 inches deep and large bulbs 4-6 inches deep, measuring from the top of the bulb. Fertilize your lilies each spring with a 5-10-10 formula or a slow-release fertilizer, following the instructions on the label. Deadhead flowers as they fade, but do not remove stems or foliage as they provide nourishment to the bulb for next season's blooms.

May Gardening Tips

• Put plant supports in place for peonies, balloon flower, delphinium and other tall, floppy plants before they get too tall.

• Prune spring-flowering shrubs right after they are done blooming so they have time to set flower buds for next spring.

• Attract butterflies to your yard by planting nectar-producing flowers such as Asclepias (butterfly weed), Monarda (beebalm), Nepeta (catmint), Echinacea (coneflowers), Liatris, Russian sage and zinnias. Protect bees and butterflies by avoiding the use of pesticides in the garden. Don't bother putting up a butterfly house because butterflies will never inhabit them. They sleep high up in trees, nestled in the safety of leaves.

• Time to get your hummingbird feeders out. Ruby-throated hummingbirds arrive around the first week in May.

• Be on the lookout for signs of fourlined plant bugs — they become active in May. Their feeding causes dark, round sunken spots about 1/16 - 1/8-inch-wide on leaves. They are found on many plants, but most commonly on mint, basil, Liatris, azalea, dogwood, forsythia, viburnum and amur maple. They won't kill the plant, but can make it look unsightly. Pick them off and crush them or drop them into a bucket of soapy water.

• Peas, leaf lettuce, spinach and radish seeds can be sown directly into the garden the second or third week in May. Transplant onions and members of the cabbage family (cabbage, cauliflower, broccoli) while soils are still cool. Wait until the beginning of June when both air and soil temperatures are warm before planting tomatoes, peppers and eggplants.

• Harden off plants started indoors or in a greenhouse before planting them outdoors by setting them in a shaded, protected area during the day and bringing them indoors at night. Avoid direct sunlight until plants are outdoors full-time.

• When the soil warms up, you can begin planting gladiola corms, and canna and dahlia rhizomes. Wait until late May or early June to plant caladium corms, begonia tubers and transplants of tender bulbs outdoors.

• May is a good time to plant grass seed. For good results, rough up the soil first. Unfortunately, this will expose crabgrass and other weed seeds that will also sprout up. Right after seeding apply a specially formulated version of pre-emergent herbicide that clearly states it is meant for newly seeded lawns, so it doesn't kill your desired grass seeds, too.

• Children may enjoy planting sunflower seeds and watching the cheery, fast-growing plants grow throughout the summer. At the end of the summer the seeds can be harvested and roasted for a tasty treat. Read the book The Sunflower House by Eve Bunting with your children or grandchildren and they may be inspired to create their own sunflower playhouse.

University of Minnesota Extension Master Gardeners are trained and certified volunteers for the University of Minnesota Extension. All information given in this column is based on university research. To ask a question, call the Master Gardener Help Line at 218-454-GROW (4769) and leave a recorded message. A Master Gardener will return your call.

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