Chapter 17: Pocket Forests—A Better Way to Plant Trees

Most trees in the sub/urban landscape are planted individually within a bed of mulch. The bed surrounding the tree must be cared for—this is called bed maintenance in the landscaping industry. Bed maintenance is a major expense and frustration for many homeowners, HOAs, and commercial sites. We spend a great deal of time and money on weed control, replenishing mulch, edging, removing leaves, and a variety of other tasks associated with bed maintenance.

Bed maintenance is also a hub for toxic chemicals since many homeowners and service providers continuously apply herbicides to control weeds in these spaces. Unlike with ecological restoration, this is an application that must be repeated in perpetuity and harms life without providing any benefits. Most who want to transition away from herbicides are unable to do so because of the effort required to pull weeds by hand.

This set of issues and frustrations surrounding bed maintenance is where my work with pocket forests began. By then I understood the benefits of working with communities of flowers and grasses to create meadows. I surmised that this approach could work with trees and shrubs too. Perhaps we could eliminate bed maintenance altogether by planting trees and shrubs together in communities instead of as individuals? Better yet, this would increase photosynthesis, soil formation, sequestered carbon, water availability, and outrageous diversity.

I returned to one of our guiding frameworks: when in doubt, look to ecosystems for guidance. Trees and shrubs naturally grow very close to each other in natural forests. When young trees take over old fields, they are often growing within a foot of each other. Even after three or four decades they are still within 3–6 feet of each other. Over time, the spacing between the largest trees increases—but that creates new gaps for all sorts of other species to enter and occupy middle and lower layers within the forest ecosystem. I observed the same thing within the Amazon. Plants want to fill every available open space; they naturally grow very close to one another and fill many vertical layers.

The only time I observed open forests with lots of spacing between trees and a lack of middle and lower layers were those under intensive management and with too many deer. Unfortunately, with wolves being extirpated from most of the US, deer are a major threat to the well-being of many American forest ecosystems, especially east of the Mississippi River. With no predators to hold them in balance, deer feed on the young trees and shrubs, thereby eliminating future generations of growth.

I began experimenting with planting many young saplings close to one another, to fill areas that would normally only be occupied by one or several trees. I found that it eliminates many maintenance tasks without an increase in installation costs and provides all of the outcomes we hope to achieve in this book. Here are some of the specific benefits of this approach.

The Benefits of Pocket Forests

We know from Chapter 10 that saplings are cheap and easy to plant. We can comfortably plant 20 saplings per hour, and more if we hustle. With approximately the same time and costs necessary to plant one traditional nursery tree in a 10-ft × 10-ft bed, we can fill this entire space with a variety of native trees and shrubs. The saplings do not need to be watered because even in dismal conditions we typically see no more than 30% mortality (this is based on Leaf & Limb experiments in Raleigh, NC). That leaves plenty of trees to continue.

The only maintenance required during the first several growing seasons is to remove other trees and shrubs that take root. For easy reference, a 10-ft × 10-ft area requires around 20 minutes of maintenance each growing season. That is it. Over time, the pocket forest will naturally shade out competing plants and sustain itself.

Compare this to the typical model of planting one traditional nursery tree in the same 10-ft × 10-ft space. We need to water it for several years. Since it is our only tree in that space, we do not want to lose it. Then we need to perform annual bed maintenance practices in perpetuity.

Over the ensuing years, a pocket forest has greater resilience and stability than a single tree. If one tree dies, or if one species is killed by an invasive pest, there are many others still present. From a safety standpoint it is always better to plant more trees versus fewer. Trees that grow together have interwoven root systems, which makes them all collectively more stable in the face of storms and hurricanes. Trees in groups are less likely to fall as compared to individual trees.

As pocket forests grow, some trees will survive and others will pass on, but the community as a whole will grow healthier because of the high density of roots below ground and layers of leaves above ground. More roots, more leaves, and more species of plants result in more photosynthesis, turn more dirt into soil, sequester more carbon, soak up more water when it rains, and produce more outrageous diversity as compared to single traditional nursery trees in managed beds.

How to Plant & Maintain a Pocket Forest

Pocket forests can be planted almost anywhere in the sub/urban space. Most any size will do, though I typically recommend an area that is at least as large as a parking space for a vehicle. We plant pocket forests using saplings for all the reasons we learned in Chapter 10. What comes next builds on that chapter, so please reread it if necessary.

Like many things in this book, what follows are not strict rules. There is plenty of room to experiment and build on these ideas. Here is the process in a nutshell:

1. Prepare the site.
2. Buy native trees and shrub saplings.
3. Plant the saplings.
4. Perform maintenance.

Before I begin, I want to make note that I’m attempting to teach the easiest way to plant a pocket forest. For a more challenging approach we can grow our own saplings using the Project Pando model outlined in Section 5 of this book. We can also create our own “recipe” of specific species to plant. This is beyond the scope of this book, but here is an example of a pocket forest recipe for those interested:

A pocket forest recipe

Before we begin, here are the tools and supplies we need:

• Some way to measure the planting area (measuring tape, measuring wheel, etc.).
• Enough cardboard to cover the planting area, preferably reused from packages. Avoid cardboard treated with wax or other preservatives—we want the cardboard to rot.
• Optional: enough leaf mold to cover the area in a 2-inch layer.
• Enough arborist wood chips to cover the area in a 6-inch layer (if no leaf mold) or a 4-inch layer (if using in conjunction with leaf mold).
• A sapling planting tool.
• A sufficient number of durable markers to indicate the location of each plant. I recommend driveway markers. Landscape flags are also an option, but not as good since the plastic flags tend to fall off during the first or second growing season.
• A variety of native tree and shrub saplings.

Here is a video showing the installation process:

Step 1: Prepare the Site

To begin, we measure the available planting space. Once we have the total space, divide by 4. This tells us how many saplings we will need to buy to plant them approximately 2 feet from each other, which is our ideal target.

Example: We have a 4,000-ft2 area where we want to plant a pocket forest. 4,000 divided by 4 is 1,000 total plants.

This spacing is not strict. We can increase the distance to 3 feet, or even to 4 feet if we must. However, spacing modifications will change the math. If we use a 3-foot spacing, divide the total area by 9. This results in a total of 445 plants in the previous example. If we use a 4-foot spacing, divide by 16. This results in a total of 250 plants. Or we could change our approach and use 20 plants per 100 square feet, which is a tad more than a 2-foot spacing, but not quite 3 feet. Using the prior example, this would require 800 trees instead of 1,000.

Please keep in mind that changes in spacing affect the time necessary for maintenance, both in terms of duration for each maintenance session and the number of seasons for which maintenance will be necessary. More open space means there will be more competing plants to remove, and it will take more time for the pocket forest to shade the gaps. Using the previous example, a change from 1,000 to 800 plants would result in a minor increase in maintenance. But a change to 250 plants would result in a substantial increase in maintenance.

Next, we need to kill competing herbaceous plants. This work should begin during the middle of the growing season and is very important—inadequate control over existing weeds can stunt a pocket forest and add substantial maintenance time. Please note that the instructions outlined next will not suffice for sites where there are invasive trees, shrubs, and vines. If they exist, eliminate them using targeted strategies before proceeding.

Invasives aside, start by laying down 1–2 layers of cardboard across the entire area, then add 2 inches of leaf mold followed by 4 inches of arborist wood chips on top. The leaf mold is not critical; it simply enhances the health of the planting bed. We can substitute the leaf mold with an additional 2 inches of arborist wood chips instead, for a total of 6 inches of arborist wood chips. Do not exceed 8 inches of depth, since doing so can make planting more challenging. These layers will rot, control competing herbaceous weeds, and create the perfect environment in which to plant our saplings during the dormant season.

If in doubt about whether these measures will suffice, particularly on sites with aggressive weeds such as abandoned farmland, make one herbicide application per the instructions in the previous chapter about meadows before laying the cardboard.

Step 2: Buy Native Tree & Shrub Saplings

We need a variety of species, including large shade trees (e.g., oaks), small- to medium-sized trees, and shrubs. We want a range of sizes at maturity so that the end result has many vertical layers of leaves from near the ground to high above. I recommend using at least 25 different native species, but more is better. In some pocket forests I have used close to 90, which is excessive (but fun!). Using around 50 species should be more than sufficient.

We can contact our local native nursery, an online native nursery, and/or the state forest service to ask them for a list of what they have available. Ask them for their favorite recommendations, pick 25–50 species at random, or make informed decisions based on research. So long as these species are native to our area and generally appropriate for the site (revisit Chapter 10 for guidance), it is hard to make a bad decision.

Buy enough saplings to fill the area based on the math in Step 1.

Step 3: Plant the Saplings

We start by subdividing the area into 1,000-ft2 sections. If the area is less than 1,000-ft2, we can skip this step. Next, we divide each species by the number of 1,000-ft2 sections. We should create a collection of all the saplings we will plant in each 1,000-ft2 section.

Example: We have a 4,000-ft2 area. This yields four 1,000-ft2 sections. We already know we need 1,000 total plants. Assume we are using 50 different species. 1,000 total plants divided by 50 species = 20 of each species. 20 plants of each species divided by four 1,000-ft2 sections = 5 of each species per 1,000-ft2 section. The end result should be 4 collections of 200 saplings, each containing 5 saplings of each of the 50 species.

Once we have our collection of saplings for each 1,000-ft2 section, we plant the saplings in that space. When planting, we should follow three broad guidelines:

• We should generally attempt to be random. We must not create a planting plan or neat rows—this defeats the purpose. Natural ecosystems are not planned and they do not occur in neat rows.
• Attempt to meet the targeted space between plants. But do not be exact—approximations are encouraged.
• This last one is optional: avoid planting species of the same type near each other. Spread them out across the space.

If there are structures and sidewalks nearby, we can plant as close or far away as we please. I have pocket forests planted right next to the sides of buildings and others where I left 6 feet of space so I can maintain a gap through pruning. Some only have shrubs near the sidewalks. Others have oaks near the sidewalks. There is no right or wrong decision.

It is crucial that we add a marker next to each plant. This will make maintenance very easy later since we will know which saplings we planted and which we did not—this can become confusing as the plants age. Four-foot driveway markers are ideal but there are many options we can choose from, including landscape flags.

Final options to consider—but do note that none are necessary.

• If we have access to compost or compost tea, per Chapter 14, we can spread it around these saplings or spray it directly onto the plants.
• If deer or rabbits are abundant in our area, we may need protection. See the sidebar for more information.
• Add a sign with a QR code to engage and educate passersby.
• Add labels on or near plants indicating their species names.

Now comes the best part: watching these plants grow over the coming years!

Step 4: Perform Maintenance

Our primary maintenance objective is to keep other trees and shrubs from taking over our pocket forest. Seeds will enter our pocket forest via bird poop, wind, and squirrels. It does not matter whether these saplings are native, non-native, or invasive—we want none of them. Sometimes we may have to keep aggressive vines out as well, such as English ivy. We can ignore herbaceous plants, since the trees will eventually outcompete these plants. But for the perfectionists among us (myself included) it does not hurt to remove these if we desire to do so. It simply requires a little extra time.

We should allocate three to five maintenance sessions per growing season spaced one to two months apart. Time for each maintenance session varies, but is typically in the range of 5 minutes per 100-ft2.

Example: The 4,000-ft2 area from the prior example would require around 3 ⅓ hours per session × 4 sessions per growing season = 13 hours per growing season for three growing seasons. This assumes that we (A) controlled competing vegetation in advance, (B) clearly marked each tree, and (C) planted saplings approximately 2 feet apart. Without these, maintenance time can easily balloon well beyond this figure.

Continue this practice for two to four growing seasons, to the point at which the pocket forest has fully shaded the ground below and other plants are not able to easily gain a foothold in this ecosystem. More time may be necessary, especially if we planted trees further than 2 feet apart.

Here is a video providing some additional thoughts, tips, and insights regarding maintenance.

Watering is unnecessary. Yes, some plants will die. That is ok. We should expect to see death in the range of 5–30% in the early years. Sites with ideal conditions often have mortality around 5%. Sites with especially harsh conditions might be closer to 30% mortality. This assumes adequate control over weeds and other competing vegetation. Without this control, we could see mortality approach 80%, especially on sites with very aggressive weeds (e.g., old farmland). If a sapling dies, leave it—they often make a comeback the next growing season. Saplings are impressively tough.

The best part? No bed maintenance required! We do not need to add any arborist wood chips, compost tea, or treatments of any kind. We certainly can—compost tea especially can be a helpful addition. But none of this is necessary. We also no longer need to worry about pest control services since this is a healthy ecosystem. There are exceptions, of course, especially in regard to invasive pests. For example, we may need to protect ash trees against the emerald ash borer.

As the installation matures, we should perform structural pruning on all the trees growing at the edges of the pocket forest since these tend to grow lopsided as they reach for available sunlight. We may also need to prune branches away from houses, buildings, and other structures using proper pruning cuts. This is ongoing for many years but is not unique to pocket forests. All trees in the sub/urban landscape need ongoing structural pruning.

Pending specific site conditions, we may also need to prevent aggressive vines and invasive plants from entering into the outer edges of our pocket forests.

Other Applications of This Process

We can use this pocket forest process for other applications. Here are some of my favorites:

Thickets

Native thickets are collections of shrubs and small tree species growing close to one another. They form an important ecosystem and often serve as transition zones between grasslands and forests and provide food and shelter for all sorts of insects and birds. Thickets were once far more abundant than they are now. But due to hundreds of years of agriculture and development in general, these ecosystems have declined.

We can use the process for pocket forests to plant thickets. They are perfect for establishing borders and privacy screens between properties. Even with most of these plants being deciduous, they still provide privacy during the dormant season due to being planted so closely together; the plants become closely entwined. They work well under powerlines where height is a concern. We can also use thickets to provide fast and effective erosion control on hills and buffers along streets and streams.

The process is the exact same as for a pocket forest, with one modification: we only use shrubs and small tree species. Do not choose anything that grows taller than around 15 feet. I recommend that the thicket have a minimum width of 10 feet to create sufficient density.

For fun, we can also include edible species. I like to include native blueberries, native plums (Chickasaw plum is my favorite!), and sumac that I use to make sumac lemonade, a delicious and refreshing summer treat. We can invite neighbors to enjoy this food and create a social gathering place.

Filling in Shady & Wooded Areas

Many wooded areas in the sub/urban landscape have little to no understory plants as a result of over-management and predation from deer. To increase life while simultaneously decreasing the need to maintain these spaces, we can plant an understory of shade-loving shrubs and small trees that thrive in these conditions. One of my favorites is the native paw-paw! Its fruit tastes like mango mixed with marshmallows and orange creamsicles.

When we dig, we need to minimize harm to existing trees, particularly their large roots. Luckily installing saplings requires minimal digging, so this is an easy issue to avoid.

Reforestation Efforts

The future of reforestation is still being written. Many methods are currently being used and tested—we have drones that drop seeds, robotic machines that plant saplings, humans planting thousands of saplings per day by hand, and many more.

The pocket forest process can also play a role. The idea is to plant islands of native pocket forests and thickets, then let those islands naturally spread out. The fancy name for this approach is applied nucleation. The new installations may require some form of deer protection in many areas of the United States. But once established and of a certain height, the fence can be removed and reused. The advantage of applied nucleation is that it is roughly as effective as a traditional tree-planting approach, but it requires fewer resources.

Replacing Invasive Trees & Shrubs

It is important to remove and eradicate invasive trees, shrubs, and vines for all the reasons we know. But we cannot leave that space vacant. Something will grow—presumably more invasive plants. We can use the planting methodology from this chapter to load that space with native saplings of our choosing. By densely filling this space with these plants, we reduce the likelihood that the invasive plants will return.

Combine Pocket Forest & Meadows to Create an Entire Landscape

All the methods from this chapter and the previous one combine beautifully. These systems form the colors on our canvas—we can blend them together in many ways to overhaul and blanket entire properties. For example, on one property we can:

• Plant pocket forests in the back.
• Install thickets for screening along the sides.
• Fill the understory of existing stands of trees with native saplings.
• Plant meadows from seed in the front.

Once in place, the maintenance requirements are as described in this and the previous chapter, with one minor addition: we must perform a bit of extra maintenance in the borders between the systems. For example, we may need to keep the pocket forests from advancing into the meadows and vice versa. The borders of these systems tend to be the most vulnerable to intrusion, especially when it comes to invasive species.