Having proper drainage is crucial for growing healthy plants in any container, but especially large planters. Without adequate drainage, roots will sit in water and rot leading to dead or diseased plants. There are several effective options to ensure your large planters have sufficient drainage so plants can thrive.
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Why Drainage is Important
When watering plants in containers, it’s easy for excess water to accumulate at the bottom. Without drainage holes for the water to escape, roots are left sitting in soggy conditions. This leads to a number of problems:
- Root rot – Wet soil lacks oxygen which causes roots to rot. This damages the root system and stunts plant growth.
- Fungal diseases – Excess moisture promotes fungal growth leading to issues like root rot, stem rot and blights.
- Nutrient deficiencies – Saturated soil makes it difficult for plants to take up nutrients effectively.
- Pests – Some insects and bugs thrive in moist environments.
Essentially, poor drainage suffocates plant roots and creates an environment ideal for diseases. Drainage holes allow excess water to drain out the bottom of planters leaving the soil moist but not soaked. This allows space for oxygen to reach roots and prevents oversaturated conditions.
Drainage Options for Large Planters
There are a number of effective options to provide drainage for large planters:
Drill holes in the bottom
Drilling several holes in the bottom of a planter provides an easy drainage solution. This can be done with a power drill and drill bit. The holes should be approximately 1/4″ to 1/2″ wide and spaced a few inches apart for adequate drainage. Just be sure the planter is propped up on feet or bricks so water can easily flow out the holes. This is an easy DIY solution for any type of planter material – plastic, ceramic, wood, etc.
Install a drainage plug
Special drainage plugs can be inserted into a hole drilled in the bottom of a planter. These plugs typically have weep holes or slots that allow water through while keeping the soil in. They can be found at most hardware stores or gardening centers. Drainage plugs come in various sizes to fit different planter holes. Make sure to get one wide enough to allow sufficient water flow.
Add gravel or stones
A 2-4 inch layer of gravel or stones at the bottom of a planter can aid drainage. Small pebbles work well as they leave air pockets for water to drain down through. Avoid very small stones like sand which can compact over time. Be sure to also place landscape fabric over the gravel layer to prevent soil from filtering through. The gravel provides a reservoir for excess water to collect and drain out the planter holes.
Include drainage channels
Some planters come with vertical ridges or channels in the interior sides to facilitate drainage. These channels give water a direct path down to the drainage holes. If your planter doesn’t have built in channels, you can add them by adhering a corrugated plastic sheet vertically along the interior walls. The ridges act to catch water and direct it downwards.
Use free-draining potting soil
Using a fast draining potting mix will help water flow through the soil rather than accumulating. Avoid regular garden soil which can become compacted. Opt for a commercial potting mix blended specifically for containers. Or make your own by combining a quality potting soil with perlite or vermiculite to improve drainage. The potting soil should be light and fluffy allowing oxygen to easily permeate.
Elevate the planter
Elevating a planter off the ground improves drainage by allowing gravity to pull water out the bottom. Place pots on feet, bricks, blocks or other sturdy materials a few inches high. You can also set planters on wire racks or grids to promote air flow under the planter. Just be sure the surface allows water to freely drain away.
Include an overflow drain
In addition to bottom drainage holes, adding an overflow drain near the top rim creates another exit point for excess water. Drill a hole around 2 inches down from the upper rim. Make sure it is not so low that soil would spill out. This overflow drain will prevent waterlogging if the lower holes get clogged or the volume of watering is too great. It provides extra insurance against wet conditions.
Best Drainage Solutions for Specific Planters
Certain drainage options work better with specific types of planters:
| Planter Type | Recommended Drainage Solutions |
|---|---|
| Plastic nursery pots | Built-in drainage holes, gravel layer |
| Ceramic or terra cotta | Drainage plugs, gravel layer, overflow drain |
| Wood | Drill holes, gravel layer, drainage channels |
| Concrete | Gravel layer, drainage plug, overflow drain |
| Metal | Drill holes, drainage plugs, overflow drain |
| Self-watering | Gravel layer, soil mix, overflow drain |
The drainage method will depend on the planter construction and your DIY skills. Focus on creating multiple exit points for excess water – through the bottom, sides and top rim. Combining several drainage techniques provides the best insurance against wet soggy soil.
Conclusion
Proper drainage is one of the most critical elements for successfully growing plants in containers. For large planters that hold a lot of soil and water, having adequate drainage is especially important. Installing various holes, channels, reservoirs and vents provides key exit routes for excess moisture to prevent the root rot and other issues wet soil causes. With smart drainage tactics, your large planters can support thriving plants all season long.