Plant Care Basics: Soil
The purpose of soil is to support the roots of a plant and to provide it with nutrients. The purpose of a plant’s root system is to provide structure and anchorage to the plant, but also to absorb air, water, and nutrients. We must manage the health of the soil in order to manage the health of the roots. This is done by attending to the moisture level and structure of the soil.
Types of Soil
There are many different types of soil and soil amendments on the market. The growing media that you choose for your plant should depend on the level of water retention and drainage your plant needs. Some plants, like ferns for example, are adapted to a soil that has less space between soil particles. This soil holds more water and has less oxygen in the soil. Other plants, like most aroids, are adapted to a soil that has more space between soil particles, allowing for more oxygen to reach the roots.
When choosing a growing medium for a plant (that is soil based), it is usually a good idea to start with an all-purpose bag of soil that can be found at any garden center. If the goal is to achieve a growing medium that is light/ airy/ chunky, perhaps for an aroid or hoya, it is a good idea to add amendments to this all-purpose soil. Most soils are made mainly of peat moss or coconut coir which have good water retention qualities. From there, you may want to add perlite, vermiculite, and/or bark chips to aid in drainage. The all-purpose bag may already have some amendments in it, but usually it’s a good idea to add more. Play around with your ratios to see what you prefer and know that this may also have to do with your personal watering habits. Many house plant enthusiasts have very involved recipes for their soil mixtures. You may find that mixing soils is something you really care about and want to get fancy with! Or you may find that just adding a bit of perlite to your bag of soil will also do the trick just fine.
Soil Health
It is important to keep up the structure and nutrients of the soil.
Aeration: In nature, plants in the ground have soil that is naturally getting aerated. We need to do this for our plants so that the soil does not get compacted. When the soil is compacted, water cannot evenly saturate the soil, meaning there will be some pockets of roots that are not receiving water. Usually, you can tell that the soil of a plant is heavily compacted if, at the time of watering, the water runs right over the soil and out the drainage hole. The soil seems to be hydrophobic (repels water) and does not get fully saturated. Looks like it’s time to aerate!
To aerate the soil grab a chopstick (or something akin to a chopstick), and gently interest into the soil an inch or two. Create a few different holes just like this around the surface of the soil. If met with any resistance, stop inserting the chopstick, you’ve hit a root. It’s a good idea to do this a couple of times a month before watering your plants.
Fertilization: Your plant needs certain macro and micronutrients in order to grow. The three main elements used by plants are nitrogen (N), phosphorus (P), and potassium (K). Over time, these nutrients get depleted from the soil and need to be replenished by fertilizer. Nitrogen, phosphorus, and potassium will be the main makeup of your fertilizer, but it is also a good idea to choose a fertilizer that provides other micronutrients as well. Look to the back of the fertilizer container to see all of the nutrients that it provides.
Tips for Fertilizing Houseplants:
Tip 1: Fertilize your tropical houseplants during the growing season (spring, summer, fall). If a house plant is growing during the winter, you may continue to fertilize.
Tip 2: There are many different types of fertilizer on the market: organic, synthetic, liquid, granular, etc. All are great options, just find the one that works best for you!
Tip 3: It’s a good idea to dilute the suggested dosage so as to not risk root burn.
Tip 4: You can either fertilize once a month at a slightly higher concentration (but still diluted from the instructions on the bottle!) or you can fertilize “weakly weekly.” This means that you fertilize almost every time that you water your plant in the growing season but at a highly diluted concentration.
Tip 5: It is important to note that fertilizer is not a fix-all for an unhealthy plant. If a plant is suffering from stress due to environmental issues, pests, disease, etc., fertilizer will not solve the problem. The use of fertilizer is to maintain the proper levels of nutrients in the soil. Fertilizer is equivalent to a human taking a multivitamin. It does not replace going to the doctor or living a healthy lifestyle (i.e. for a plant having proper light conditions, watering routine, etc.). Instead, it is a necessary step in maintaining the overall health of the plant.
Repotting
Knowing how and when to repot a plant is an important skill for any house plant enthusiast.
When to Repot a Plant:
There is a debate amongst the houseplant community about whether to repot immediately after bringing a plant home from the nursery or ordering a plant online. One school of thought is that you should let the plant acclimate to its new environment before causing further stress by repotting it. The other school of thought is that usually a plant is pretty rootbound in its original nursery pot, and it may be in need of a larger pot size. Here’s our take on this: we recommend that you let your plant acclimate for at least a few weeks before potentially repotting it. If the plant is rootbound, it will be fine surviving a few more weeks in its pot. As you grow in experience as a houseplant parent though, you may find that you have success in immediately repotting.
Repotting should be done in the growing season. When repotting a plant you are creating new space for root growth. If the plant is not growing when you repot it, there will be large pockets of soil that do not have roots. This soil will hold on to water and potentially cause root rot.
Signs the plant needs to be repotted:
A. If roots are coming out of the drainage holes, it's time to repot.
B. It may be a sign that a plant is rootbound and needs to be repotted if the plant is not absorbing water when you water it. Investigate the situation by gently placing a chopstick or finger in the soil to see if there is any wiggle room. If you seem to be hitting mostly roots, and the problem isn’t that your soil is compacted due to underwatering, it may be a sign that your plant is rootbound.
You may also choose to repot a plant without increasing its pot size. If a plant has been sitting in a particular pot for a few growing seasons, its soil’s nutrients will be depleted. If this plant does not show signs of needing to be up-potted, it may just be time for some fresh soil rather than a larger pot.
**When in doubt do not repot! A pot that is too large can lead to issues of root rot. Pockets of soil that do not contain roots will have too much moisture retention and could create an environment of root rot or soil pathogens.
How to Repot:
It’s a good idea to repot a plant whenever it is ready to be watered.
Choose a pot that is 1-2 inches larger than the current pot. Make sure it has drainage holes. Careful: a pot size that is too big can cause root rot!
Place soil at the bottom of the new pot, about a fourth to a third of the way up.
Take the plant out of its current container and gently massage the root ball. If the roots are forming a circular pattern at the bottom, make sure to disrupt this. It’s okay to break a few roots, but do be gentle! If the plant has fine, delicate roots, be sure that your massaging is very gentle/ minimal.
This is also a good time to check on the health of the roots. Trim back any roots that are brown and mushy. These roots have rotted. Depending on the plant, the signs of healthy roots are ones that are thick, fleshy, firm, and white. **Some plants that have more delicate root systems tend to have darker colored roots. That’s okay! To determine the health of darker-colored roots look for roots that are firm to the touch.
Place the root ball into the new container, and add more soil. Pack down the soil enough so that the roots are covered and the plant is secure. It’s important to not pack the roots down too densely, because oxygen needs to be able to reach the roots.
Pack the soil about an inch or two from the rim of the pot and give your plant a good watering. (If you notice that after watering a lot of the soil has been sucked down, you may have packed your soil too loosely. Just add some more soil to the top. In fact, it’s a good idea to check that the soil hasn’t done this the next few times you water.)