Plant Spacing

To grow optimally, most plants need plenty of room for roots to grow down, stalks to grow up, and stems to grow side-to-side. Being planted too close to a wall, fence, or other plants can reduce airflow and sun exposure and increase rubbing damage, insect spread, and disease transfer.

Spacing plants properly is one of the easiest ways to ensure maximum growth and delicious harvests while reducing pest and disease problems. Too many plants growing too closely together makes it difficult for any of them to grow properly. It ranks right up there with seed planting depth when it comes to plant health.​

How much space does my plant need?

How much space is needed depends on the type of plant. Pole bean seeds can be planted a hand’s distance apart and thrive as long as they have something to climb. If your cabbages are crammed too close together, you may never get decent heads. Seed packets are a great place to start for information on plant spacing, but there’s more to it than what meets the eye.

What about the roots?

It’s easy to see how big a mature plant is when you look at it, but what about the root system? How big is it? How much room does it need? How close can it be to its neighbors? You may already know that some root systems spread out while others have taproots that tend to go straight down, but the answers may surprise you.

UPDATE: Thanks to information from Jim on pepper growing research, I have learned that peppers can actually be grown 10-12" apart, rather than the 18" listed above.

Putting several shallow-rooted plants close to each other can reduce plant health and productivity. Mixing shallow-rooted plants with deeper-rooted plants makes the most of a space.


Intensive plantings have their place

Intensive planting is also known as square foot, postage stamp, and biodynamic gardening. It refers to the following set of principles:

• Using raised beds
• Improving the soil before planting
• Installing plants so that their leaves just touch their neighbors at maturity
• Not stepping on planting beds
• Succession planting to keep the beds productive
• Employing crop rotation

These guidelines are all good, and they do work. Problems occur when gardeners pick and choose which aspects of the intensive gardening program they actually use. In many cases, plants are installed too close together and gardeners still step on the beds.

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Intercropping

Intercropping, the science-based version of companion planting, also puts plants closer together than is recommended on seed packets, but with good reason. Intercropping takes advantage of the benefits offered by different plants to make the most of garden space. The Three Sisters Method of growing corn, beans, and squash together is a good example of intercropping. Corn grows tall, pole beans climb the corn and provide nitrogen, and the broad, bristled leaves of squash plants shade the ground. You can replace the corn and squash with sunflowers and lettuces for similar results. You get the idea. Intercropping also puts trap crops, chemical warfare, and biodiversity to work for you, but that’s a different post.


The art of thinning

As seedlings grow, you may need to thin them out. Rather than pulling unwanted seedlings (or weeds) out, use scissors to snip them off at the soil level. This leaves the remaining plants with their roots undisturbed. It also protects the millions of beneficial soil microbes attached to the root systems. Those microbes will migrate to the remaining plants and help them grow.


Bottom line, if you want to get the most from your garden, plant seeds at the proper depth and transplant them with mature sizes in mind.