Planting a cactus in a glass jar can be done, but it requires some special considerations to help the cactus thrive. Glass jars provide less air circulation and drainage compared to regular planters, so steps need to be taken to prevent overwatering and rotting of the cactus roots. With the right soil mix, watering technique, and jar set up, glass jars can make for beautiful and unique cactus planters.
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Choosing the Right Cactus
Not all cacti are well-suited to growing in glass jars. Small, slow growing cacti varieties with shallow root systems tend to do best. Some good options include:
- Fishhook barrel cactus
- Pincushion cactus
- Hedgehog cactus
- Dragon fruit cactus
- Moon cactus
- Old lady cactus
Larger, fast growing cacti like saguaro or prickly pear are not recommended, as they require more space for their extensive root systems. Cacti that grow in the desert may also not adapt well to the higher humidity environment in a closed glass jar.
Using a Fast Draining Soil
Creating a very porous, fast draining soil mix is key to growing cacti in glass jars. This will prevent water logging and allow oxygen to reach the roots. A good soil mix contains:
- 1 part potting soil
- 1 part coarse sand
- 1 part perlite or pumice
The sand and perlite provide excellent drainage. Avoid using normal garden soil, as this retains too much moisture.Always start with a potting mix formulated for cacti and succulents, then amend it with extra perlite as needed. The soil should feel lightweight and airy in your hand.
Choosing the Right Glass Jar
Pick a glass jar with an opening wide enough to easily plant your cactus and provide proper air circulation. Look for ones with the following features:
- A wide mouth – at least 2 inches across
- Smooth, sloped shoulders
- A relatively cylindrical shape
Jars with very narrow openings or those that bulge out restrict air flow. Make sure to thoroughly clean and sanitize used food jars before planting.
The size of the jar should fit the size of your cactus. Choose a jar that is a few inches wider and taller than the plant. This allows room for growth and insertion of your tools to water. For most small cacti, a 1/2 gallon wide mouth mason jar works well.
Drainage Options
One downside of glass jars is they lack drainage holes. You have a few options to provide drainage:
- Gravel layer – Add 1-2 inches of gravel at the bottom of the jar. Position soil above this.
- Fabric over holes – Carefully drill 2-4 holes in the bottom of the jar. Cover holes with mesh or fabric to prevent soil leaking out.
- Self-watering insert – Purchase a plastic self-watering insert with a reservoir and drip tray that fits inside the jar.
A layer of decorative pebbles, stones, or sand on top of the soil also helps prevent surface moisture buildup.
Watering your Cactus
The biggest challenge with glass jar planters is getting the watering right. Some tips for watering success:
- Water thoroughly, until it drains from the bottom drainage holes or from the self-watering reservoir.
- Wait until the soil is completely dry before watering again. Test with a finger or moisture probe.
- During the winter growing period, only water every 2-3 weeks as growth slows.
- If the jar lacks drainage, water even less – small sips once a month.
- Avoid misting the cactus directly – moisture on the tissue can cause rot.
Proper soil mix and drainage will help prevent overwatering issues. Adjust your schedule based on the particular size and needs of your cactus variety.
Acclimating the Cactus
When first planting into the glass jar, pay close attention to acclimating the cactus. Follow these tips:
- Gradually increase light exposure over 2-3 weeks to avoid sunburn.
- Maintain warm temperatures around 70-80°F.
- Allow at least 1 week without watering to prevent transplant shock.
- Monitor for signs of stress like wilting and adjust care as needed.
- Consider starting with a small, nursery-grown cactus that is already acclimated to indoor conditions.
Ideal Growing Conditions
Once settled into the glass jar, most cacti require the following care:
- Light – Bright but indirect light. South or west facing windows are ideal. Avoid direct summer sunlight.
- Temperature – Prefers consistent warmth around 70°F. Can tolerate short drops to 50°F at night.
- Humidity – Tolerates low humidity, around 40-60% RH.
Monitor your cactus for signs it is thriving like new growth emerging from the center. Adjust conditions as needed if you notice decline.
Potential Problems
Growing cacti in glass jars comes with some potential challenges. Here are some common issues and how to fix them:
| Problem | Cause | Solution |
|---|---|---|
| Rotting at base | Overwatering | Use fast draining soil, water less frequently |
| White crusty deposits on soil | Mineral deposits from tap water | Water with filtered or distilled water |
| Sparse growth | Insufficient sunlight | Provide brighter filtered light |
| Wilting, drooping | Under watering | Increase watering frequency |
| Leggy growth | Not enough light | Supplement with grow light |
Tips for Success
Follow these tips to help ensure your cactus thrives inside a glass jar:
- Choose slow growing, compact cactus varieties adapted to containers.
- Use a porous potting mix and add drainage like stones or gravel.
- Water thoroughly but infrequently based on your cactus’s needs.
- Provide bright, indirect light from a south or west window.
- Fertilize monthly during the spring and summer with a balanced fertilizer.
- Monitor moisture and humidity inside the jar to prevent issues.
Conclusion
With the right techniques, many small cactus species can grow quite well inside glass jars. The key steps are using an appropriate potting mix for drainage, watering correctly, and giving the cactus adequate sunlight. Glass containers provide less insulation than ceramic pots, so environment factors like humidity need to be monitored. Overall, glass jars allow for creative and visually striking displays of ornamental cacti.