Spring gardening

[May 10, 2011]  While 60- to 70-degree temperatures get us used to warmer weather, we may be jumping the gun on planting warm-season garden items. Witness the 30-degree temperature drop of the last week. Many annual flowers, tomato plants and other warm-season plants should not be set out until after May 10. When we look at our average frost-free date, we see that it is April 25. About half the time in the last 30 years, the average last killing frost of spring has occurred by then. This also means that about half the time it hasn't.

Those selling transplants love those of us who like to buy these plants in early to mid-April. More years than not, they get to sell us at least two sets of transplants. Of course, all bets are off if you use protective covers, such as milk jugs, row covers or wall-of-water types of protection. Usually it is just as easy to wait until the recommended date, and that would be after the range of April 25-May 10 for green beans, sweet corn and tomatoes. These are all considered "tender vegetables."

Melons, peppers, pumpkin and squash are considered "warm-loving" and should be planted in the range of May 10-June 1. Pumpkins planted for Halloween jack-o'-lanterns should be planted about Father's Day. These pumpkins will get ripe too quickly for use in late October if planted the normal time. Pumpkins for pies can be planted in the May 10-June 1 period.

Any time now when soil conditions permit, it is time to plant things such as asparagus crowns, leaf lettuce, onions, peas, potatoes, radishes, rhubarb plants, spinach and turnips. Give it another week or two and it is time to plant such things as broccoli, cabbage and cauliflower. As with most things, a little bit of planning goes a long way in preventing problems later on.

Questions abound regarding fertilizing the garden. Without soil test information, the rule-of-thumb rate for fertilizing flower or vegetable gardens is about 15 pounds of 10-10-10 per 1,000 square feet of area. If you are using 12-12-12 or 13-13-13 fertilizer, use about 12 pounds per 1,000 square feet.

Soil pH may need to be adjusted due to the addition of lime and sulfur, which are acidifying. Generally, about 4.25 pounds of lime neutralizes the acidity from 1 pound of nitrogen or sulfur. Beware of pH requirements for different plants before you go out to apply lime. Surrounding plants are also affected. Examples would be blueberries, rhododendron, azalea, pin oaks and many evergreens.

Reminders

• If you haven't applied crabgrass preventer, you have a very short window, as forsythia has already bloomed (sort of), but don't apply if you seeded your lawn. You can use a post-emergent product if germination occurred and immature crabgrass is present.

• It is about time to mow already. Remove no more than one-third of the leaf blade at a time to prevent raking or catching clippings.

• Cut back butterfly bushes to live material, with a 10-inch maximum height.

• Cut back mums, but leave 2 inches of dead material since much stored food is located there.

• Cut back ornamental grasses to a height of 4 inches or so.

[By JOHN FULTON, University of Illinois Extension]