Bottom watering is a popular and effective way to water houseplants and garden plants. It allows the roots to pull up only the amount of water they need, reducing the risk of overwatering. But can you still overwater with bottom watering? Here’s a look at how bottom watering works and whether it’s possible to use too much water.
What is bottom watering?
Bottom watering, also called sub-irrigation, is the process of placing the pot in a tray or basin of water and allowing the soil to wick up moisture from below. The water is absorbed through holes in the bottom of the pot. Bottom watering provides moisture directly to plant roots and helps prevent dry, hydrophobic soil on top.
There are a few key benefits to bottom watering:
- Only the root zone gets wet, leaving the topsoil dry. This mimics how plants get water in nature.
- It encourages deep root growth since roots grow towards moisture.
- Less risk of diseases like powdery mildew that thrive in damp leaves.
- Minimizes water loss through evaporation.
- Reduces the risk of overwatering since the plant only takes up what it needs.
Can you overwater with bottom watering?
Yes, it is possible to overwater plants even when bottom watering. The key is to not leave the pot sitting in water for too long. The soil can only absorb so much moisture at a time. If the plant is small or the soil is slow-draining, even 30 minutes may be too long.
Signs you may be overwatering with bottom watering include:
- Water pooling in the drainage tray – the soil cannot absorb it fast enough
- Moisture reaching the top layers of soil
- Lower leaves feeling mushy, swollen or turning yellow
- Mold or fungus gnats due to excessive moisture
- Slow growth or no new growth
To avoid overwatering, pay attention to these factors:
Soil mix
Choose a fast-draining potting mix, or amend dense soil with perlite, sand or vermiculite. This allows excess water to drain away.
Watering duration
Start with 10-30 minutes of bottom watering depending on factors like pot size and plant needs. Remove the pot once the top 1-2 inches of soil are moist.
Plant size
Small, young plants need less water than large, mature plants. Adjust bottom watering time accordingly.
Climate conditions
Bottom water less frequently in cool or humid conditions where soil dries slower. In hot, dry weather, plants need more bottom watering.
Pot material
Plastic pots retain moisture longer than porous clay or terra cotta. Factor this in when deciding bottom watering duration.
Water quality
Tap water and hard water may need less time to moisten soil than filtered or distilled water. Very pure water is absorbed faster.
How often to bottom water
Frequency of bottom watering depends on the plant variety, pot size, climate conditions and your soil mix. As a general guideline:
Succulents: Every 2-3 weeks
Cacti: Every 2-4 weeks
Orchids: 1-2 times per week
Pothos: 1-2 times per week
Peace lily: 2-3 times per week
Chinese evergreen: 1-2 times per week
Check the moisture level of the soil before bottom watering again. Allow the top inch to dry out before re-wetting.
Bottom watering tips
Here are some best practices when bottom watering houseplants and garden plants:
- Always water in the morning to allow excess moisture to evaporate through the day.
- Remove any drained water from the outer pot right away.
- Bottom water in the sink or tub to contain drained water.
- Lift the pot to check its weight – a light pot needs water.
- Group plants with similar watering needs for efficiency.
- Keep an eye on young seedlings that need less water.
- Water less in winter when plants grow slower.
- Allow extra bottom watering time for plants in terra cotta pots.
Bottom watering indoor plants
Bottom watering is an excellent technique for houseplants. Here are some tips for success:
- Use pots with drainage holes so excess water can escape.
- Place pebbles or peanuts in the drainage tray to elevate the pot.
- Pick a watering container like a tray, bucket or basin that fits your pots.
- Group houseplants with similar water needs together on watering day.
- Remove pots after 10-30 minutes once water reaches soil surface.
- Pour out any remaining water in the outer cache pot or decorative pot.
Some great indoor plants for bottom watering include:
| Indoor Plant | Bottom Watering Frequency |
|---|---|
| Pothos | 1-2 times per week |
| Chinese Evergreen | 1-2 times per week |
| Peace Lily | 2-3 times per week |
| Parlor Palm | 1-2 times per week |
| Snake Plant | Every 2-3 weeks |
| Philodendron | 1-2 times per week |
Bottom watering succulents
Succulents prefer less frequent watering. Here are tips for bottom watering succulents and cacti:
- Use a very well-draining soil mix, like half potting soil and half perlite.
- Allow the soil to fully dry out between bottom waterings.
- Only bottom water every 2-4 weeks depending on climate and container size.
- Soak the pot for 10-20 minutes and don’t allow it sit in water.
- Rely more on signs the plant needs water like wrinkling vs. a set schedule.
Bottom watering outdoor plants
Bottom watering works well for container gardens and raised garden beds. Tips include:
- Use cans, buckets or trays that fit your container sizes.
- Group containers together on pavement or soil to water efficiently.
- Lift pots to judge their water needs before bottom watering.
- Add water until it drains from the bottom of the container.
- Keep potted plants elevated with “pot feet” for drainage.
Vegetables well suited to bottom watering:
- Tomatoes
- Peppers
- Lettuce
- Broccoli
- Cucumbers
- Beans
- Carrots
Herbs that appreciate bottom watering:
- Basil
- Oregano
- Thyme
- Rosemary
- Parsley
- Cilantro
- Mint
Bottom watering in raised garden beds
For raised beds, use soaker hoses or irrigation tubing laid in a grid pattern on the soil. This allows water to seep gradually upwards to plant roots from below. Deeply soak the bed 1-2 times per week depending on weather and plant needs.
Pros and cons of bottom watering
Bottom watering has many advantages but also some potential drawbacks to be aware of:
Pros:
- Avoids dry, hardened topsoil
- Encourages deep roots
- Less disease risk
- Minimizes water loss to evaporation
- Harder to overwater
- Good for vacation watering
Cons:
- Must remember to empty drainage tray
- Need saucers or trays for each pot
- Not good for muddy outdoor conditions
- May get salt buildup in soil over time
- Can still overwater certain plants
Bottom watering FAQ
What are the signs of overwatering with bottom watering?
Signs of overwatering include soggy soil, standing water in the outer pot, swollen lower leaves, slow growth, mold or fungus gnats. Your plants may signal they are getting too much water.
How long should I bottom water my plants?
Most plants only need 10-30 minutes of bottom watering. Remove pots once the top few inches of soil are moist. Less time is needed for small pots and quick-draining mixes.
Is bottom watering good for all plants?
Most plants can be bottom watered but some do not appreciate too much moisture around their roots. African violets, philos, and calatheas do better with occasional top watering.
Do you need drainage holes to bottom water?
Yes, drainage holes are essential for bottom watering. The excess water needs an escape route to avoid root rot from soggy soil. Drill extra holes if needed.
What are the best containers for bottom watering?
Terra cotta, plastic, glazed ceramic, and wood containers all work well for bottom watering. Avoid decorative pots without drainage holes on the bottom.
Conclusion
Bottom watering is an excellent technique that helps prevent both under and over-watering issues. But it is still possible to over-saturate your soil if plants are left sitting in water for too long. Avoid root rot by using well-draining soil, following recommended watering schedules, and checking that your pots fully dry out between bottom waterings. Pay close attention to signs of overwatering and cut back if needed to keep your plants thriving.
