March is the perfect time for planting a summer flower garden. The soil is warm, days are long and pleasant for working outside and nurseries are bursting with young seedlings looking for a good home.
But before going to the nursery and loading up with all those tempting pot packs of petunias and impatiens, take a good look at the spot where they will be planted. If the soil is depleted, compacted, rocky or full of competing roots, it needs help.
Even if the soil is good, it will produce more flowers if spaded to a depth of at least 9 inches with 2 to 4 inches of organic amendments, such as redwood compost or Nitrohumus, worked into the top layer.
By the way, amendments are meant to improve water retention, aeration and soil texture; they do not add nutrients. To do that, mix fertilizer granules into the top three inches of the soil.
Biggest Not Always Best
Now, with the soil all fluffed up and so friable that you can easily sink your trowel down six inches, you can stroll down to the nursery and confidently select your seedlings. A word of advice here. With seedlings, it’s not always the biggest that’s the best. In fact, smaller seedlings, although they take a little longer to reach maturity, produce remarkably healthier plants in your garden with more total flowers than larger seedlings.
Why? Because the roots of developing plants don’t like to be stopped, and larger plants in small pots have no place to put their roots. Coiled roots indicate interrupted plant growth. A good rule of thumb is to avoid a seedling with top growth larger than its root ball. It’s better, too, if the seedling is not already blooming. And of course, you don’t want plants that are lanky, yellow or diseased looking.
When you get your seedlings home, keep them damp until you can transplant them. Water your garden a day or so before you’re ready to work in it. As you set out the seedlings, work with a small group at a time. Dig a hole slightly larger than the size of the root ball. If you didn’t add fertilizer to the entire flower bed earlier, work some in to the bottom of the hole now. Controlled-release pelleted granules, like Osmocote, can touch the roots; unpelleted fertilizer should go an inch below the roots.
It’s very important to put fertilizer in the root zone at planting time because research has shown that two of the three main elements in plant fertilizers, phosphorus and phosphate, do not travel downward in the soil; in other words, you can’t add fertilizer later and hope to water these elements down to the roots. They need to be placed in the root area at planting time.
Leave Watering Basin
The most important fertilizer element, especially here in Western alkaline soils, is nitrogen. It can easily be applied later because it migrates readily down through the soil--in fact, it moves too easily. Nitrogen quickly travels right past the roots and leaches out, so it’s a good idea to apply it every four to six weeks during the growing season.
Firm the soil around the newly planted seedling and leave a small watering basin. Water every group of six seedlings as soon as you plant them; don’t wait until you finish the entire job because they may wilt. The root area of each plant must be saturated thoroughly.
I like to use a diluted fertilizer in the water, although others prefer a solution of Vitamin B1. If a seedling’s roots were cut or seriously disturbed in planting, expect it to wilt at first. You can reduce wilting by making a newspaper tent or a temporary sun screen from an umbrella, plywood, canvas, or inverted milk carton.
In about two weeks, after the seedlings’ roots have begun to establish themselves, consider pinching out the plant’s growing tip. Nearly all annuals and many perennials benefit from such pinching because it forces the plant to branch and become compact instead of tall and skinny. Moreover, many of the newer hybrids are simply too eager to bloom. They were bred to show color quickly, thus captivating shoppers while the plants are on nursery shelves. However, these baby plants should be putting strength into leaves and roots instead of premature blooms. Pinching out the growing tip encourages the plant to make branches, leaves, and roots--all essential to long-lived, healthy plants capable of producing profuse blooms. Although it’s hard to do, sacrificing those early blossoms will mean more total flowers in the long run.