Unfortunately, as much as we love our houseplants, it is possible to kill them with kindness. Overwatering is one of the leading causes of indoor plants plant problems (and even death). Wet indoor plant soil can cause root rot and fungal disease that stop moisture and nutrient absorption, ultimately killing the plant.
There are several reasons why indoor plant soil stays wet, from lack of drainage to environmental conditions. Depending on the cause, you may have to improve the drainage of the potting soil, adjust the indoor temperature and humidity levels, or move the plants to a brighter and airier spot.
To fix what’s keeping plant soil damp, you need to know the cause. Let’s look at 8 possible causes and how you can fix the problem to save your indoor plants from an early death.
1. The Soil Does Not Drain Well
Poorly-draining soil is a common cause of waterlogged conditions in indoor planters, leading to root rot and fungal diseases in plants.
Most store-bought potting mixes for plants are formulated to retain water for outdoor plants. But indoors, where evaporation is lower and plants are not in full sun, this moisture is often too much. Specialized houseplant mixes have amendments to improve drainage to combat this issue.
Occasionally, indoor gardeners will even add soil from their yards to their homemade potting mixes. But garden soil is usually heavy and holds onto too much water for indoor plants, especially when it comes to clay soils.
Watch out for the following signs of indoor plant soil not draining properly to determine if this is the problem:
- Water collects on the surface of the soil after watering.
- Water takes a long time to drain out of the holes at the bottom of the container, even after you have thoroughly soaked the soil.
- The soil is dry just beneath the surface. To test, insert your finger about 2 inches (5 cm) deep into the soil. If it feels dry to the touch and the surface is wet, water is not permeating the soil.
How to Fix Poorly Draining Soil
Here’s what you can do to fix poorly draining soil:
Improve Drainage With Amendments
The best way to fix poorly-draining soil is to add perlite or pumice to a store-bought potting mix. You can also add coarse sand to improve drainage. This works well for succulent plants, replicating the soil textures they are accustomed to in their native habitats.
Never Use Garden Soil
Never use garden soil in your homemade potting mix. Not only will this retain too much moisture, but garden soil can also carry weeds or pests and diseases to your indoor plants.
Limit Water-Retaining Ingredients
Also, avoid adding too many water-retaining ingredients into the potting mix when making amendments. For instance, sphagnum peat moss and coco coir hold onto water and serve a similar purpose, so you don’t need to use both at the same time.
Consider Repotting or Transplanting
If the soil in an existing container does not drain properly, the only way to fix the problem is to repot it using a fresh potting mix.
Before transplanting a waterlogged plant, check for root rot and fungal growth.
Prune mushy and rotten roots and snip away yellow leaves. Gently remove as much wet soil as you can without disturbing the roots too much to remove any infested soil. Repot into a fresh soil mix and wait for the roots to settle before watering again.
2. The Pot Has Insufficient Drainage Holes
Excess water cannot drain out of the planter if there are no drainage holes at the bottom. Always check for drainage holes before buying a planter or planting to avoid growth problems down the line.
How to Fix Lack of Drainage
If you’ve already grown a few plants in pots without drainage holes, you may still have time to repot them in appropriate pots to help them recover. Always choose pots with drainage holes.
It’s also best to choose pots made with porous materials, such as unglazed terracotta. The breathable walls of the pot will wick excess moisture away from the soil more quickly.
On the other hand, many DIY enthusiasts prefer making planters at home using ingredients like Portland cement. These pots are called hypertufa pots. If you’re going this route, ensure that you make drainage holes in these pots before you start planting.
This video by Kim’s Garden shows how to make drainage holes in hypertufa planters:
3. The Drainage Holes Are Blocked
The drainage holes at the bottom of a planter tend to get clogged with damp soil over time. This prevents excess water from draining out of the container, leading to waterlogging.
How to Prevent Blocked Holes
Here are some tips on how to prevent the drain holes at the bottom of a planter from getting blocked:
- Don’t line the bottom of the planter with terra cotta shards, rocks, pebbles, or gravel. Although this is commonly recommended to improve drainage, these additions often do more harm than good.
- Use coco coir discs, fine plastic mesh, landscape cloth, or woven weed barrier to line the bottom of the pot to stop soil from spilling out and compacting.
- Check drainage holes regularly for obstructions.
4. The Room Temperature Is Too Low
Most indoor plants thrive in temperatures around 75 °F (24 °C) during the day and 65 °F (18 °C) at night.
The ideal temperature for a specific indoor plant depends on factors like the species of the plant, season, time of the day, and indoor humidity levels. However, most houseplants are from the tropics and can’t handle temperature dips below 50 °F (10 °C).
Along with leaf damage, low temperatures can also cause indoor plant soil to remain wet.
- Low temperatures decrease the evaporation of water from the soil.
- Low temperatures decrease the rate of transpiration from the leaves of the plant, so plants use less water.
- Plants grow slowly in cold weather, so they take up less water from the soil.
- Cold temperatures can damage a plant and send it into shock, stunting growth.
How to Prevent Cold Shock
Cold temperatures and wet soil can be lethal for plants.
Follow these tips to prevent cold temperatures from keeping indoor plant soil wet:
Monitor Temperatures With a Thermometer
Some digital thermometers record maximum and minimum temperatures along with the real-time temperature. These values help you gauge if there are wide fluctuations in temperature throughout the day.
Place Plants Away From Cold Drafts
Move the plants away from windows or doors where cold drafts enter the house. Also, do not keep the plants in corridors that tend to be cold and drafty.
Keep Plants Away From Cooling Appliances & Crank up the Heat
Cold drafts from the vents of cooling appliances can cause drastic temperature swings. Consider setting the room heater to a higher temperature (after accounting for the comfort levels of the inhabitants).
Move Planters to a Sunnier or Warmer Site
Move the planters near a south- or west-facing window or porch where the sun will warm the soil and keep it dry. Make sure they remain out of the path of direct sun to avoid scorching the leaves.
Do Not Overwater
Wait for the top few inches of the soil to dry out before watering most houseplants, especially in fall and winter.
5. The Humidity Level Is Too High
When the indoor humidity levels are high and the air is saturated with moisture, evaporation of water from the soil and transpiration from the leaves reduce, leaving the soil moist for longer.
High humidity also attracts fungus, mold, and pest attacks that damage the plant and stunt its growth. As a result, the plant cannot use the water in the soil.
How to Limit Indoor Humidity
High humidity levels are beneficial for most houseplants.
But if they are so high they are causing damage, here’s how you can bring down the humidity level around your indoor plants:
- Tweak the controls of the humidifier.
- Move plants farther apart.
- Trim the leaves on the lower branches. This will expose the soil to the air and help it dry quickly.
- Do not let water stagnate in the drainage saucer. Stagnant water keeps the soil near the plant’s root zone wet.
It’s vital to strike a balance between keeping the air humid enough for your plants and dry enough to allow the soil to dry out sufficiently. Do some experiments with different spots in your home until you get it right.
6. The Light Is Too Low
Most indoor plants thrive in brightly-lit spaces. Although there are some that survive low-light conditions for short periods, lack of sun negatively impacts growth.
With lower light comes lower evaporation, leaving the soil wet for longer. A plant that isn’t growing well also doesn’t use up as much moisture, compounding the problem.
How to Fix Low Lighting
Luckily, it is not difficult to fix low-light issues. Simply move the plants to a brighter location but still out of the path of direct sun. Make adjustments slowly, especially for plants previously in very low light areas, to avoid scorching the leaves.
7. There Is Poor Ventilation in the Room
Poor ventilation slows down the rate of evaporation from the soil and transpiration from the leaves, keeping the soil moist. Lack of airflow can also attract fungal diseases and pests that can damage the plant, especially when the leaves are also moist from overhead watering.
How to Fix Subpar Ventilation
To improve ventilation around your plants, ensure there is enough space between pots and keep a few windows open (as long as there aren’t strong or chilly winds). You can also prune areas of dense leaf growth or use a gentle fan placed far away from the plants for a subtle breeze.
8. The Pot Is Too Large
Plants must be repotted and moved to a larger pot when they outgrow their present containers. So, many growers tend to use much larger pots when repotting to save on time and effort.
However, large pots hold more soil. More soil retains more water and takes longer to dry out after watering. This means your plant sits in a pool of water until the root system is big enough to use up the remaining moisture.
How to Prevent Pot Size Issues
When repotting, only choose a container around one or two sizes up. This gives your plant space to grow, but not so much that growth is negatively impacted.
Once you’ve identified the cause of waterlogged soil, the issue is usually easy to fix. It may require a repotting session or some experimentation with environmental conditions, but your plants will appreciate it in the end.