Minnesotans consider Memorial Day weekend the perfect time to plant flowers. But life sometimes gets in the way. You get busy with something else and all of a sudden July 4th is staring you in the face.
If you haven't planted yet, it's not too late. Garden centers and farmers markets have plenty of colorful flowering annuals that can be planted now and enjoyed for the rest of the summer. In addition to standard four-or six-packs, some annuals are sold in 4-inch containers or in jumbo cell packs. These larger plants will give you instant color the moment you transplant them into your garden or assemble them in a patio container.
You'll also find well-developed potted perennials -- some at reduced prices -- as well as pots of garden lilies, just beginning to bloom. As long as you find them in good-sized containers, perennials should transplant easily. And, if you plant now, there's plenty of time for their roots to become established before the soil freezes in the fall.
Best bets in annuals
• Bypass the "cool" ones. While most annuals produce flowers all summer, some (pansies, Johnny jump-ups, stocks and calendulas) grow better in spring, when temperatures are cooler. So pass them by.
• Size matters. Look for annuals that appear proportional to their pots, rather than way too large. Tall, floppy tops and masses of roots escaping through the container's drain holes are a sure giveaway that the plants have been confined too long.
• Root out the problem. If possible, choose annuals that have been planted in divided cell packs (similar to ice cube trays) as opposed to large, undivided packs. Plants that have been growing together in an undivided container will have roots that are hopelessly entwined. To minimize root damage, use a knife to separate plants rather than pulling them apart.
• Prune and pinch. Some annuals that have grown too tall before planting may be pruned. Pinching back lanky petunias may seem cruel because it removes the flowers. But within a week or two you'll be rewarded not only with more flowers, but with lots of side shoots that will also bloom. Similarly, the tall central blooming stalks of salvias and celosias can be pinched back.
• Be selective. Choose plants that are full and relatively symmetrical, rather than tall and spindly. Avoid the runts, plants that are smaller and noticeably less developed than others of the same variety.
• Fixate on foliage. Look for plants with healthy foliage rather than an abundance or flowers or flower buds. Leaves should be a good green color, top to bottom. A couple yellow leaves at the base of an otherwise healthy-looking perennial usually aren't a problem, but don't buy a plant that has lots of yellow foliage.
• Beyond the bloom. Some perennials will have bloomed already, but that's no reason to reject them. Simply cut off the flower stalks before you plant them. Some perennials bloom again this summer, but most will become established in your garden, then bloom next year.
Prep for plants
Soil preparation is important before transplanting flowers, especially perennials. Once plants are in, it's difficult to improve the site. So work the soil, incorporating organic matter (good compost or bagged peat moss) along with a little slow-release fertilizer.
Because sunlight is intense this time of year, plant on a cloudy day or in the evening, then water the soil thoroughly. If the new flowers are in a sunny site, protect them for several days by placing a cardboard screen or baffle adjacent to the side that gets the most sun.
Continue to water deeply to encourage good root development. Add a layer of mulch to help conserve moisture. Pull the annuals once they're frost-damaged, but leave perennial foliage in place to trap snow. Then add more mulch over your perennials some time in November, when soil begins to freeze.
Deb Brown is a horticulturist with the University of Minnesota Extension Service Yard and Garden Line. For help with garden, plant and insect questions, call the Extension service at 612-624-4771.