I have read articles that indicate specific soil temperatures are required before planting certain plants in the spring. How do I determine what the soil temperature is? Are there actual soil thermometers to use?

The uptake of water and nutrients is greatly affected by soil temperature. Seed germination is also affected by temperature. Planting before the soil is sufficiently warm can delay or prevent the establishment of many plants.

As you might imagine, not all plants are the same. Cool season crops like peas, cabbage, lettuce and onions can be planted and will establish when soil temperatures are still quite cool (45 degrees Fahrenheit). Tomatoes and peppers, however, will not grow well until soil temperatures reach 59 degrees or more. Melons and cucumbers need temperatures in the middle 60’s to take off. Most flower and herb seeds require a minimum temperature of 62 degrees, but will germinate faster if warmer.

Soil thermometers are available at many garden centers. Expect to pay between $10 and $20 for a good thermometer or a good deal more if you want something fancy. Insert the thermometer 4 to 6 inches in the ground for your reading. Remember that not all areas of your yard will warm up at the same time. Soil type, sun exposure and adjacent structures all influence the rate of warming. Your soil thermometer can take the guesswork out of the equation and allow you to get the earliest possible start.

I frequently read tips that recommend the ideal time to prune a plant is when it is “dormant.” How do I know when a plant has gone dormant?

Dormancy usually refers to the time that the leaves drop off and lasts until the plant leafs out in the spring. For many plants, the best time to do any major pruning would be in early spring before it starts leafing out.

Trees such as birch and maple are usually better pruned in late spring when the plant has fully leafed out. Otherwise they have a tendency to “bleed” sap at the points where they were cut. Evergreen trees are best pruned in late spring just before the “candles” of new growth harden off. As you can see, it is more important to know what kind of plant that you need to prune, and not to just prune anything just because it is dormant, because many plants will break that “rule.”

Last year, I planted healthy Purple Wave petunia plants in a container, but they hardly grew and hardly bloomed. I’ve seen great Purple Wave plants everywhere in the past. What did I do wrong last season?

Without knowing your exact environmental conditions last year, we will try to give some possible reasons things could have gone wrong. Any petunia will require at least 6 hours of sun a day. Any less than that will cause low bud counts and stringy-looking plants.

Using improper soil for a container-grown plant could be another reason. Stay away from topsoil, which is too heavy, holds too much moisture, and restricts root growth. Use a light, “soilless” mix with peat and perlite.

Fertilize every other week with a 20-20-20 fertilizer. “Wave” petunias are rapid growers and heavy feeders. Use a container large enough to let those Wave petunias grow. A pot no smaller than 12 inches would be best.