When we look at a maple tree in its autumn glory, or smell an eye-catching rose, or profess admiration for a friend's lush philodendron, we are rarely as aware of the magnificent roots happening right below. "Out of sight, out of mind" is the hard truth for many gardeners, indoors or out, but the wonder of roots should not be overlooked!
What exactly is a root? We learn at a young age that the root is the part that grows down while the plant grows up and hopefully we learn that they absorb water and nutrients. We were possibly even in a school play demonstrating this! If we continue to make a study of roots we come across terms like lateral, fibrous, transport, feeder, radicle, tap, and more. It's not necessary for you to know the exact terminology of a root system to be a successful gardener but it is important to know where they are located and what they require to fully support your beautiful plants.
Did you know: Plant roots can grow under the soil, on top of the soil, in water, in air, and sometimes all of these at once!
Roots Under Your Feet!
Root systems need three things for health and survival:
2. Oxygen (yes, even underground)
3. Soil that is loose enough to allow root penetration. This means a very low level of soil compaction.
In undeveloped areas, the soil has enough space between particles (pore size) to allow roots to penetrate deeply. This is how the idea of deeply-rooted trees emerged. The reality of urban areas is that the soil below construction becomes so compacted that oxygen saturation stops at the point of compaction and thus roots do too. What's a root to do? Grow along the shallow path of least resistance! Surprisingly, the majority of the roots of trees and shrubs in your yard and local parks can be found within one inch to two feet of the soil's surface. This framework of roots can extend far beyond the reach of branches so remember this when fertilizing. Broadcast fertilizer over a wide area around trees rather than just at the base of the trunk. When planting, the reason we recommend digging a hole deeper and wider than the current root ball is to enhance the pore size/oxygen immediately available to your new plant.
Roots in Pots!
You've probably heard the term "root-bound" spoken with a hint of horror when it comes to houseplants. And while it's true that the roots of many tropical potted plants like room to wiggle and grow, some enjoy the close hug of container walls.
These plants prefer to be root bound (at least for a while): hoyas, peace lilies, spider plants, aloes, zz plants, asparagus ferns, and snake plants. This doesn't mean they don't love a re-pot with fresh nutritious soil every spring or two, but you can put them back in the same size pot.
Roots in the Air!
Aerial roots are roots that grow out of the stems or branches of plants above the soil level. These air roots can develop on both terrestrial plants, which are planted in the ground, and on epiphytes, which grow above the ground attached to objects like trees and rocks.
On such vines as philodendrons, ivy, pothos, and hoyas, air roots perform the multi-functional role of structural support as well as water absorption. Often these plants will only grow air roots in humid areas so don't worry if your tropical monstera doesn't grow air roots in your Colorado living room! It's doing just fine under the soil.
You might notice aerial roots growing out of your succulent stems. This can be a sign of your plant stretching towards more light and moisture. You can either ignore them since they aren't harmful, or you can plant the succulent deeper in the soil, burying the stem and its air roots.
Orchids are a fantastic example of plants with only air roots. Their roots provide structural stability, clinging to the trunks of trees and the sides of rocks, and also collect surrounding moisture and nutrients from humidity in the air to feed themselves. In their natural habitats there are enough nutrients in the water droplets suspended in the air to keep them healthy. Your house is a comparatively sterile environment and so your epiphytic plants depend on you to provide adequate food.
So the next time you are happily walking through your blooming garden or singing to your thriving potted peperomia, give a nod to the unseen underground heroes... roots!