Fixing 5 common gardening mistakes

With a new season under way, this is a great time to review your successes and failures from last year, correct any mistakes, and clear up any misunderstandings you may have to ensure that everything goes smoothly this time around. I'm going to provide a little guidance on the most common questions and fixes for the most common mistakes.

1 Pruning hydrangeas

To know when to prune your hydrangea, you first must know which species you have (if you aren't sure, these identifying photos will help). Here's a handy guide:

Hydrangea macrophylla: Prune in late summer, as soon as the flowers fade, but never after September. Remove weaker stems from the base of the plant, being careful to retain several stems of old wood, which will produce buds for next year's flowers.

Hydrangea arborescens Grandiflora: Cut to the ground in late winter or early spring.

Hydrangea paniculata Grandiflora (Peegee): Simply remove spent flowers and thin or cut back last year's growth in late winter or early spring.

Hydrangea quercifolia (oakleaf hydrangea): Remove dead wood at the base of the plant in early spring.

SEE PHOTOSWhich hydrangea is yours?

Hydrangea anomala petiolaris (climbing hydrangea): Unruly vines can be shortened in summer. Otherwise, pruning is seldom necessary.

2 Fertilizing the lawn

Apply 1 pound of nitrogen -- not 1 pound of fertilizer -- per 1,000 square feet of lawn. To determine how much nitrogen is in a bag of fertilizer, look at the three numbers on the package, typically represented as 5-10-5, 10-10-10, etc. The first number indicates the percentage of nitrogen present (the second number corresponds to phosphorus; the third, potassium). So if you have a 10-pound bag of 20-3-10, nitrogen comprises 20 percent of its contents, which means there are 2 pounds of nitrogen in the package.

Using this calculation, one-half of the bag contains 1 pound of nitrogen, which would cover 1,000 square feet. Applications on well-established, healthy lawns should be timed to coincide with Memorial Day and Labor Day. If the lawn is in sorry shape, one-third can be applied around July 4. Opt for slow-release fertilizers over quick-release ones.

3 Preventing blossom-end rot on tomatoes

Blossom-end rot manifests as dark, mushy spots on the bottom of tomatoes. To prevent the disease, which is caused by a calcium deficiency, incorporate about 2 cups of dolomitic lime for each plant, working it 8 to 12 inches into the soil before planting. If you have done this in the past two years, you should have your soil's pH tested before amending with lime and apply at the rate indicated by test results. Uneven irrigation also interferes with calcium uptake so be sure plants get 1 to 11/2 inches of water -- both supplemental and from rainfall -- per week. If tomatoes show signs of the disease, spray liquid calcium on leaves for a quick fix.

4 Controlling squash vine borers

These pests lay their tiny eggs along the lower portions of squash stalks and stems, and then morph into inch-long thick white caterpillars with brown heads that bore into stalks and kill the plant while chewing their way out. They cocoon in the soil, where they survive over the winter and re-emerge in late spring as orange-and-black moths ready to repeat the carnage. Sometimes, there's even a second generation in August.

What to do: Keep a close eye out for the red flattened-oval eggs and pick them off as soon as you find them. You'll need to be vigilant and hunt at least once a week to avoid damage. Telltale signs of attack are small puncture holes in the bottom portion of the stalk and stems, where you'll also find frass, or caterpillar excrement, which resembles sawdust. Slit punctured stems open lengthwise near holes using a razor blade, and pick out the borers. Then, raise the soil level at the base of the plant to cover the injured portion of the stem. This will encourage new roots to grow. If all else fails, use a product labeled for use against squash borers, such as all-natural Btk, and be sure to follow directions precisely.

5 Don't jump the gun!

One of the costliest mistakes you can make during spring is planting too early.

It happens every year: We have a few unseasonably warm days in a row, and gardeners get excited, buying up flats of annuals and vegetables and planting them outdoors. Then wham! An overnight frost hits and your plants are dead.

Avoid this by waiting until the end of May to plant. Be sure to harden off vegetable seedlings before planting to acclimate them to direct sunlight exposure and outdoor temperatures. Do this by setting them in a shady spot for an hour and then bringing them back indoors. The next day, place them outdoors in shade for two hours. Repeat daily, increasing outdoor exposure by an hour each day. Plant them in their permanent homes at the end of the week.