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Tool Time


If you grow vegetables, one of the most valuable tools around is a soil thermometer. That’s because many vegetable seeds germinate and grow even when the soil is only 45 degrees. On April 6, I took my trusty soil thermometer and discovered that the top three inches of soil where I grow annual herbs was still only 41 degrees. I waited two weeks and it gradually warmed up so I could sow spinach, lettuce, onions and Swiss chard without having the seeds rot in the cold, wet soil.

Here are soil temperature ranges for seedling development. Sowing seeds of some warm-loving vegetables (like beans) before the soil is adequately warmed, is sure to make them rot before they get a chance to sprout. And warm-loving veggies (marked with an asterisk below) should not be sown outdoors before May 15—the average last day when a spring frost could settle in the Chicago area). Otherwise, the seeds may sprout, but the tender green growth is vulnerable to a cold snap and the plant won’t survive. You can start planting these edibles once the soil reaches these temperature ranges:

Snap beans* 65-80 Beets 50-80 Cabbage 50-80
Lima beans* 75-80 Squash 70-85 Turnip 70-85
Parsley* 60-85 Peas 50-80 Radish 50-70
Lettuce 45-70 Chard 50-80 Spinach 45-65
Pumpkin* 70-85 Onion 45-75

You don’t need an expensive digital thermometer. You can get one for about $15 and it will last a long time. Check your local garden center or visit Johnny’s Seeds catalog for a complete description of the optimal soil temperatures for sowing vegetable seeds outdoors. Happy Sowing…

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questions

I purchased some pre-chilled hyacinths and tulips for forcing but there were no directions with them. Does this mean I don’t have to chill them in the refrigerator, and will they just bloom in the house any time during the winter? The last batch of bulbs became moldy in the refrigerator.

I have a nicely sheltered, rounded 7-foot tall Japanese red maple on the southeast corner of my backyard. Half of the tree has lost its leaves, the formerly red bark is turning gray, and a good-sized square of bark has been stripped off on the side that faces the yard. I sprayed the exposed bark with black pruning spray to close any entry for insects. I have not cut off any of the branches.

Does the winter have any effect on the tree? Should I look for some insect infestation? What should I do now?

My split-leaf Japanese maple tree is 15 to 20 years old, about 7 feet high and about 10 feet wide. It is overtaking the corner of the yard. Can I trim it, and at what time of the year?

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