How Often to Water Plants in an Open vs Closed Terrarium

Terrariums are miniature indoor gardens enclosed in glass containers. They allow you to create a tiny self-contained world right in your own home. Terrariums are available in both open and closed styles.

Open terrariums have an open top and allow some air exchange with the outside.
Closed terrariums are fully sealed and create a humid, tropical environment inside.

One key aspect of caring for any terrarium is knowing how often to water the plants inside. Watering frequency can vary quite a bit between open and closed terrariums. Understanding these differences is important for keeping your terrarium plants happy and healthy.

How Often to Water an Open Terrarium

Open terrariums allow air flow between the inside of the container and the surrounding room. This air exchange helps regulate humidity and prevents the buildup of stale air. However, it also means that moisture evaporates from an open terrarium much more quickly than a closed one. As a result, open terrariums usually require more frequent watering.

For most open terrariums, aim to water about once per week on average. Check the soil moisture before watering each time. If the top 1-2 inches of soil feel dry to the touch, it’s time to water. For smaller open containers, you may need to water a bit more frequently, such as every 5-6 days.

The specific watering schedule can also vary based on factors like:

The plants included: Succulents and cacti store water in their leaves and stems. They can go longer between waterings than delicate ferns or tropical plants.
Growing conditions: Terrariums kept in hot, dry, or sunny locations lose moisture faster and require more watering. Cool, shaded areas slow evaporation.
Soil composition: Soil mixes with sand or perlite drain quickly and dry out faster. Retentive soil blends with peat or coconut coir stay moist longer.
Size of the terrarium: Larger volumes of soil hold more moisture and take longer to dry out. Very small open terrariums may need water every 4-5 days.

Take some time to observe your open terrarium and get a feel for how rapidly the soil dries down. Adjust your watering routine until you find the right frequency for your individual setup and environment. The general range is 5-7 days for most open terrariums.

How Often to Water a Closed Terrarium

In a closed terrarium, the sealed environment creates high humidity and reduces evaporation. This means closed terrariums typically require much less frequent watering than open ones.

For closed terrariums, aim to water only every 2-6 months on average. The majority can easily go 3-4 months between waterings.

Unlike with open terrariums, you don’t want to base watering strictly on soil dryness. Instead, watch for these signs it’s time to water a closed terrarium:

Condensation decreases: The glass walls and lid of a closed terrarium should stay consistently covered in tiny water droplets. If the condensation noticeably decreases, add water.
Mold or fungus gnats appear: Excessively wet soil can cause mold or fungus gnat infestations. Let the soil dry out a bit before watering if this occurs.
Plants decline: Slow growing plants like orchids and bromeliads will eventually use up the existing moisture. Signs of drought stress signal a need for watering.
Soil pulls away from the glass: With very infrequent watering, soil may visibly shrink or detach from the sides over time as it dries and compacts.

When watering a closed terrarium, pour water slowly down one side until it just starts to accumulate at the bottom. Stop before more than 1/4 inch of standing water builds up. Excess watering can lead to root rot and oxygen starvation.

If your closed terrarium has remained properly humid between waterings, aim for intervals of 3-5 months. Very arid climates or poorly sealed lids can shorten this to 2-3 months.

Watering Newly Planted Terrariums

The watering guidelines above apply to established terrariums that have been set up for several months already. Immediately after first planting a new terrarium, both open and closed styles need more frequent watering.

For the first 2-3 weeks after setup, check moisture every 2-4 days for open terrariums and weekly for closed styles. Water whenever the top layer of soil becomes even slightly dry. This encourages new root growth and prevents plant stress before a stable microclimate develops inside.

Gradually extend watering intervals until you reach the normal routine. Especially monitor moisture-loving plants like ferns and mosses closely at first. Their shallow roots dry out fastest and are most vulnerable to drought damage during establishment.

Watering Old or Neglected Terrariums

Over time, even a well-sealed closed terrarium can gradually lose humidity as seals weaken. Older or long-neglected terrariums often need more watering than usual when brought back into care.

If the glass is no longer fogged with condensation, increase closed terrarium watering to every 1-2 months until humidity rebuilds. Allow any shrunken soil to rehydrate slowly to prevent root rot.

Cross-check for signs of new growth and if mosses regain their green color. This indicates moisture levels have stabilized. Then you can gradually scale back to a 3-6 month watering routine.

Reviving a severely dried out open terrarium also requires extra care. Water sparingly at first just to rewet the lower soil layers. Wait a week before fully saturating from the top down. This gradual rehydration gives plants time to readjust without shocking the root zone.

There will be some exceptions, like David Latimer’s 60+ year-old terrarium, but they are only a minority and usually have certain conditions.

Best Practices for Watering Open and Closed Terrariums

When watering both open and closed terrariums, follow these general guidelines for the healthiest plants:

Always use room temperature, non-calcareous water if possible. Cold or hot tap water can shock plant roots.
Pour slowly and gently to avoid washing away soil, especially around delicate shallow roots.
Completely saturate the soil with each watering, but avoid excessive puddling.
Allow excess drainage to flow out through open terrariums before replacing the cover.
Wipe salt deposits or hard water stains from glass walls using a soft cloth after watering closed styles.
Add a bit of fresh charcoal to absorbs odors if closed terrariums develop musty smells.
Turn or tilt the container occasionally to promote even moisture distribution.
Add pebbles or gravel beneath the soil to improve drainage and aerate plant roots if needed.

With attentive care, both open and closed terrariums can thrive for many years. Adjusting your watering routine for the type of terrarium and needs of the specific plants inside is key to maintaining their health and vibrancy. Observe closely, keep written notes if needed, and find the ideal schedule for your individual setup.

Choosing the Right Plants Based on Watering Needs

Selecting plants that are well-suited to the moisture levels in open vs closed terrariums is an important factor for success. Here are some top choices for each style:

Open Terrarium Plants

Succulents: Hen and chicks (Echeveria), burro’s tail (Sedum morganianum), aloes, jade plant.
Air plants: Tillandsia species.
Cacti: Red or blue candle cactus (Myrtillocactus geometrizans), pincushion cactus (Mammillaria species).
Orchids: Moth orchids (Phalaenopsis), lady slipper orchids (Paphiopedilum).

Closed Terrarium Plants

Tropical ferns: Bird’s nest fern (Asplenium nidus), rabbits foot fern (Davallia fejeensis), button fern (Pellaea rotundifolia).
Creeping fig (Ficus pumila)
Nerve plant (Fittonia verschaffeltii)
Pilea and Peperomia species
Mosses: Sheet moss (Hypnum sp.), cushion moss (Leucobryum sp.), mood moss (Dicranum scoparium).
Bromeliads: Cryptanthus, Neoregelia, Guzmania, Vriesea.

How Light and Temperature Impact Watering Frequency

Light exposure and temperature both influence evaporation rates and plant growth inside terrariums. Adjusting your watering practices based on these factors can help maintain optimal conditions.

Light

Increased light drives faster plant growth and water uptake. Supplemental lighting shortens watering intervals for the most active plant growth.
Direct sunlight on closed terrariums causes extreme interior heat and humidity. Water more frequently if unavoidable to compensate for rapid drying.
Low light reduces evapotranspiration. Lengthen intervals for shade-loving plants in darker locations.

Temperature

Heating vents and warm spots deplete moisture quicker in open terrariums. Keep an eye on soil in hot zones.
Colder climates and rooms under 70°F slow plant growth and water needs. Stretch watering frequency.
Closed terrariums seal in heat. Avoid direct sun and provide ventilation if interior overheats.
Monitor enclosed tropical species closely if temperatures regularly drop much below 60°F. Lower vigor increases drought risk.

With a little adjustment, both open and closed terrariums can thrive in a wide range of light and temperature conditions. Observe your plants and tweak your watering routine as needed.

Identifying Under or Overwatering

It takes some practice to find the optimal watering cadence for your terrarium. Watch for these signs of under or overwatering and adjust your schedule accordingly:

Underwatering

Open Terrarium

Soil pulls away from container sides
Plants are wilted or shriveled
Leaves turn brown or drop
Growth slows down

Closed Terrarium

Condensation fades
Plants decline or stop growing
Leaves yellow, dry at tips
Elasticity of mosses decreases

Overwatering

Open Terrarium

Excess water pools in bottom
Mushy black roots
Soft stems
Leaf drop
White fungal growth

Closed Terrarium

Water accumulates at bottom
Presence of gnats or mold
Rotting wood
Yellow, swollen lower leaves

Don’t hesitate to amend your watering practices. Both too much and too little moisture causes harm. With attentive care, you’ll find the right routine.

Caring for Terrariums While Away

Vacations and business trips can disrupt your normal terrarium watering schedule. With some preparation though, both open and closed styles can be left for 1-3 weeks. Here are some tips for terrarium care while away:

Water heavily right before leaving and allow excess drainage. This maximizes soil moisture reserves.
Group multiple open terrariums together. Shared evaporation humidifies the air and slows drying.
Move terrariums away from heating/AC vents which accelerate water loss.
Consider an automatic drip irrigation system on a timer for extended absences.
Have a friend or neighbor water open terrariums if gone longer than 10-14 days.
Remove any rotting plant matter and wipe glass clean just before leaving to minimize unattended issues.

With proper planning, most established terrariums will still thrive despite occasional extended dry periods. Adjust watering to account for duration before and after travelling.

Creating Transition Zones to Balance Moisture

One watering challenge with open terrariums is balancing the needs of plants with different requirements growing side by side. Creating transition moisture zones allows you to accommodate both.

For example, incorporate succulents that prefer dry conditions on one side of the container. Then place tropical mosses that need constant moisture at the opposite end. Zone the space in between for plants with intermediate preferences.

When watering, only saturate the moist end fully. Allow the other areas to get just light overflow. This prevents overwatering arid species while helping deliver enough hydration to humidity-loving plants.

Also vary soil composition and depth across the terrarium to reinforce moisture zones. Use shallow, fast-draining mixes on the dry end and retain moisture better on the wet end with added peat moss.

With this type of planned layout and watering approach, even finicky plants can coexist successfully within a single open terrarium.

Improving Drainage and Aeration

Stagnant moisture and poor aeration quickly leads to decline in enclosed terrariums. Ensure healthy drainage and air penetration into the root zone with these tips:

Include lighter, coarser components in soil, such as perlite, pumice, or gravel.
Place a layer of activated charcoal or pebbles at the bottom before adding soil.
Elevate plants above water accumulation zones, using pebbles or wood.
Choose plants with naturally airy, spreading root structures. Avoid taproots.
Water slowly along the edges rather than pouring straight into the center.
Allow excess water to drain out through open terrariums after each watering.
Trim back dense groundcover plants to prevent matting and improve subsurface air circulation.

Proper drainage prevents waterlogging. And a steady air supply nourishes soil organisms and plant roots cut off from outside wind and weather.

Humidity vs. Soil Moisture in Closed Terrariums

It’s important to understand that humidity and soil moisture are two separate factors within closed terrariums. Heavy condensation inside the walls does not directly indicate wet soil. Resist overwatering an already soggy root zone just to elevate interior humidity levels.

Instead, do the following to safely increase humidity without overwatering:

Use distilled water to prevent mineral deposits clouding the glass.
Introduce pebbles and water features that expose more surface area to evaporate.
Add more plants overall: leaves transpire moisture into the air.
Remove dead foliage immediately to eliminate decaying matter.
Make sure the lid fits tightly to seal in evaporated water.
Switch out part of the soil for moisture-retentive coco coir or peat.

With thoughtful design and plant selection, you can achieve the high humidity closed terrariums require without jeopardizing their roots.

Transitioning a Closed Terrarium to an Open Style

Over time, as plants grow, some closed terrariums struggle to maintain the right balance of moisture and humidity. Transitioning a overly wet closed system to an open-style can improve growing conditions.

To convert to an open terrarium:

Move the container to brighter light to help plants adapt and increase airflow.
Remove the lid entirely and replace with wire mesh or an open glass pane.
Transplant waterlogged plants into fresh, better-draining soil mix. Trim off any rotten roots.
Prune back overgrown vegetation to reduce transpiration surface area and lower humidity.
Water more frequently, but avoid soaking the soil completely. Allow the root zone to dry out partially between waterings.
Monitor for signs of stress and adjust conditions gradually.

With attentive care during transition, converting a failing closed terrarium into an open-style one can give struggling plants a fresh start.

Troubleshooting Overwatering Issues

Despite your best efforts, closed terrariums sometimes get waterlogged. Root rot, mold, and foul odors signal overly wet conditions. Here are some troubleshooting tips:

Remove plants and repot any still viable to let root balls dry out.
Mix fresh activated charcoal into the soil to control odors before replacing plants.
Discard and replace any soil or moss that doesn’t dry out after removing it.
Wipe down the glass walls well to eliminate algae growth.
Increase ventilation by propping the lid ajar. Gradually close over several weeks once improved.
Water very sparingly over the next 4-6 months to slowly normalize moisture levels.

Be prepared to transition to an open style permanently if problems reappear quickly after correcting overwatering. Some closed terrariums never achieve the right balance.

Maximizing Enjoyment of Both Terrarium Types

Following the right watering practices maximizes the unique beauty and enjoyment of both open and closed terrariums:

Open Terrariums

Allow for visual access and light penetration from all sides.
Select a mix of colorful succulents and flowering plants.
Incorporate hardy air plants mounted on ornamental wood or stone.
Use transparent glass containers and decorative natural gravel or sand.

Closed Terrariums

Choose low-light tropical plants with colorful foliage.
Introduce striking mosses and lichens on wood or stone.
Layer variants of greenery with diverse textures and form.
Add miniature waterfalls, pools, and rainforest-themed decor.

There are endless possibilities for customizing both types into living works of art. Mastering watering techniques helps ensure their health and maintain their beauty.

Conclusion

Watering appropriately for the enclosure style is essential for nurturing thriving terrarium gardens. Open and closed systems have very different needs in terms of frequency, moisture zones, and drainage. Carefully observing plant health, humidity, and soil moisture levels allows you to adjust your watering