Manipulating Growth Rates

So what causes new growth? There are obvious factors such as the amount of sun, water and fertilizer a plant receives, but for the most part, it is governed by a plant's genetic code. A plant's growth rate can vary enormously from just a few inches to a couple of feet a season.

New growth can also be affected--and to a large extent manipulated--by several things, many of which gardeners can control. If you have plants that require a rich humus soil, for example, but the soil in your garden is of just average quality, the plants may survive but not flourish. James suggests that you can use that to your advantage in the garden.

For instance, if a particular plant like mondo grass is invasive under ideal conditions, then it might be more tame under less than ideal conditions. By changing the conditions, you can enjoy the plant more without worrying about it taking over your garden.

Unfortunately, the reverse of that concept is seldom true. In other words, a plant that prefers to grow in average soil, such as many popular culinary herbs, may not grow well in rich soil. James recommends experimentation to figure out what does and doesn't work in your garden.

Another way to manipulate a plant's growth rate is by varying its exposure to the sun. If a particular crape myrtle can grow to 20 feet in full sun, it will probably stop short of that height if grown in partial shade. "This trick comes in mighty handy when you're trying to keep a plant within the confines of a certain area," explains James. So, if you're growing a plant that prefers full sun, especially a flowering plant, you can intentionally slow its growth rate by placing it in a location that receives only early- morning to mid-day sun.

A far less common but just as effective way of manipulating a plant's growth rate is to restrict the amount of water it receives. A plant grows at its optimum rate with one inch of water per week. By withholding the water supply, you can slow the growth rate. Surprisingly, many plants can get by with a lot less water than you might think.

"You need to be careful because, obviously, plants need a certain amount of water to survive," cautions James. "But nowhere is this trick more effective than on the lawn, which is typically the most water-guzzling portion of any landscape." James suggests experimenting with water application on your lawn to zero in on precisely how much water it needs to remain green and healthy. You'll likely be amazed at the money you'll save on your water bill and the time you'll save mowing less often.

Crowding plants is another sure way to slow down a plant's growth rate. With only so much water and nutrients to go around, plants that are packed closely together are forced to share, and as a result, they won't grow as quickly as if they were left all alone. Of course, this trick can backfire because if you crowd plants too much, there's always a chance that none of them will grow.

One method that is directly related to growth enhancement is fertilizing. Whether you use store-bought synthetic, organic, or even homemade compost fertilizers, when you fertilize heavily and often, plants respond by putting on lots of new growth. But James cautions that too much fertilizer, especially high nitrogen fertilizer, may lead to initial excessive foliage growth, but little to no increased production of flowers or fruit. One reason may be that a plant growing at such a rapid rate requires more water.

Fertilizing can also lead to more pest and disease problems. "After all, if you were a hungry bug, bacteria or fungal spore looking for a place to call home, which would you prefer--an old, tough growth or a young, tender, succulent growth?" asks James.

Basically, controlling the growth rates of plants is all about experimentation, and naturally, not all experiments turn out the way we hope. But when they do, the results can be especially gratifying.