When you plant, do you always add plant food? Do you double-dig to enrich the soil as much as possible? Do you carefully avoid harming a plant’s root ball in any way?
Do you recognize these time-honored gardening rules? If you follow them, you are devoting a great deal of effort for very little return—in fact, you’re doing more harm than good. These rules, and many others that everyone knows about caring for plants, are based on folk wisdom rather than scientific knowledge, and following them will waste your time, money, and energy. In this column I’ll give you a new set of rules, rules based on scientific knowledge about how plants grow. You’d be surprised to know how much botanists and molecular scientists are still finding out. I’ll explain how you can break all the rules and wind up with a healthy and beautiful garden.
First, some basic information about plants. Green plants manufacture their own food through a complicated process called photosynthesis: they use the carbon dioxide in the air, plus water molecules and the sun’s energy, to produce carbohydrates. This process is the basis of all life on earth and has been going on much, much longer than people have been caring for plants. Plants can take care of themselves as long as they’re planted correctly in the first place.
Different plants have adapted over long periods of time to specific environments: wet or dry, sunny or shady, cool or hot, acid or alkaline soil. Plants have a complicated relationship with the microbes present in soil, and we’re just beginning to understand that. So it makes sense to put a plant in a place where it’s well adapted to thrive and to disturb the soil as little as possible.
Based on this very brief summary of what we know, here are some simple things you can do to ensure the health of a plant:
Pick the right plant for your site. Ask if the plant needs shade or sun, a wet or dry site. Read the plant label. Do some research, or consult a professional horticulturist. No plant will grow anywhere; so if the saleperson tell you it will, go somewhere else. But there are great plants for any kind of site, so you can find one for yours. If you choose carefully, your plants are more likely to survive.
Buy the youngest plant you can. If you have a choice between a perennial in a 3-inch pot and one in a two-gallon pot, pick the small one. It will be cheaper and easier to plant as well as healthier. A young plant will adjust more quickly to its new environment and is likely to catch up with the larger plant in a single growing season.
Ensure that the plant does not remain pot bound. Your goal when planting is to encourage the roots to grow into the soil: if a plant is handled incorrectly, its roots can actually remain potbound in the area of soil originally contained in the pot or burlap sack. To encourage the roots to grow, you need to rough them up a bit. If the tree is bound and burlapped, remove the burlap and wire cage around the roots (or insist that the workers do this). If the plant is in a pot, loosen the roots, especially if they are winding around inside the pot. Tease the roots out with a hand rake or slash then with a sharp knife. Remove some of the roots if you see very little soil (with a sharp knife, slice off the bottom inch or so of the root ball). Gently shake off most of the growing medium, especially if you see particles of fertilizer or vermiculite. Don’t dig the hole until you see the final size of the root ball (see #5 below).
Do not amend or improve the soil in any way. This is extremely important. You want the plant to adapt to the soil it will grow in and to grow a large root system. If you amend the soil, the plant is likely to keep winding its roots around the small zone of enriched soil, effectively remaining potbound.
Dig a hole that’s only slightly larger than the root ball. Save your back! The hole you dig should be a couple of inches wider and no deeper than the root ball that remains after step #3 above.
Plant at the same level the plant was before or slightly higher. Never plant a tree lower than it was before. The fine roots that take in oxygen grow close to the surface. If you bury them too deep, you smother the tree.
Tamp the soil down firmly around the roots. Fill in the soil around the roots in layers. Add a few inches of soil all around, then press down with your hands or with your heel all around. Repeated until the plant is solidly in place, with the soil at the correct level. Tamp down gently all around to make sure the plant cannot shift in the soil. Do not leave large air pockets.
Immediately after planting, water very thoroughly. Provide at least an inch of water all around the root ball and beyond. How do you know when you’ve given an inch of water? Place a small container on the ground. When an inch accumulates in the container, stop watering.
Never mound soil or mulch around the base of a plant. When you plant a tree, create a donut-shaped mound of soil just beyond the root ball to help direct water to the entire root system. If you mulch, spread the mulch no more than an inch or two thick, and don’t let it touch the trunk. Those volcano-shaped mounds of mulch that many people use accomplish only two things: they smother the feeder roots and encourage fungus infections.
Water correctly. Provide at least an inch of water per week during dry periods for at least a year after planting (whenever the air temperature is above freezing). Water deeply once a week as needed, and make sure the water goes out beyond the root ball. Trees with trunk diameters of more than one inch require even a longer period of supplemental watering—the rule of thumb is one year per inch of trunk diameter. The main reason that new plants fail is lack of adequate water.
This “Backyard Environmentalist” column appeared in the Glen Rock Gazette and northjersey.com website on August 26, 2016.