Tim's Tips: More musts for healthy plants: fertilizer and lime

Over the last two weeks, I have told you about things that can make or break the survival of the trees, shrubs, perennials and annuals that you may want to grow in the garden.

Let me fill you in on a couple of lesser things that your plants need to stay healthy and grow strong. These can also be make-or-break items.

In all the years that I had my garden center, a common question concerned plants that just weren’t growing the way people hoped that the plants would grow.

Once I knew what type of plant the customer had, I would start with questions concerning how much sun the plant gets and the quality of the soil. Often, those things are answered on the plus side. Then I would ask, “How often do you fertilize the plant?” In way too many instances, the answer is: “I water the plant.” I usually reply with: “Plants are a lot like people. They both like to eat!”

The vast majority of the plants we put into our gardens need some type of fertilizer to keep them growing. In some cases, you may need to fertilize the plants at the beginning of the season and then again later in the season.

As an example, if you have rhododendrons, they really need to be fertilized right after they are done flowering. Once they go dormant in the fall, they should be fertilized again.

Let’s go to the opposite end of the spectrum. If you are growing annual flowers or vegetable plants, they really need a lot of fertilizer. If you plant annual flowers in a container, the potting soil you use has a certain amount of fertilizer in it. The plant roots will grow and take up that fertilizer to give the top growth the nutrients the plant needs. At some point in time, the nutrients have all been taken out of the soil. It is up to you to set up a proper fertilizer schedule that allows the plants to grow and produce flowers.

In the case of annual flowers, you start feeding early in the season and you don’t stop until the frost kills the plant. Vegetable plants are very similar in their need for fertilizer. If you think about that tiny tomato plant that you plant in either the ground or a container, it will eventually grow up to 6 feet. A plant that big is going to need a lot of fertilizer all season long if you want to eventually get lots of red, ripe tomatoes.

Every plant has a certain requirement for the amount of fertilizer that it needs. The care tag that comes with the plant will usually give you the requirement for fertilizing. However, some of the needs will need to be tweaked if the plant is in a more active growing time. Some of this is learned by trial and error. A lot of this information can be found by talking to seasoned gardeners. Keeping your plants well fed can make all the difference in the world.

Probably one of the most neglected aspects of keeping plants happy is the application of lime to the soil. Many plants do not like an acidic soil. Acidic soil makes it harder for the plants to take up nutrients out of the soil.

Unfortunately, the soil in New England is very acidic. Acid rain, the natural breakdown of organic matter and even the fertilizer you use can make the soil more acidic.

You can buy a soil test kit that will tell you the pH of the soil. PH is a measure of the acidity or alkalinity of the soil. Different plants need different pH levels to grow properly. The soil test kit will tell you the pH, and most kits have a chart that tells you the pH range for certain plants.

Once you know the pH of the soil around the plants, you can adjust the pH by the addition of lime. You will rarely find that the soil is too alkaline in New England, but it can happen. If that is the case, you may need to add sulfur or some other acidifying agent to change the pH.

Lawns in our area grow best if the pH is around 6.5. If the pH falls to around 5.5 or below, the grass grows poorly and the weeds will love it. Applying lime after checking the pH will allow you to keep the pH in line. That, in turn, will allow the grass to force out the weeds if you keep the lawn fertilized at the correct times of the year.

Well, that’s all for this week. I’ll talk to you again next week.

Tim Lamprey has worked in the lawn and garden industry for 45 years.