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Greenhouse Beds

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This is part 3 of 4 in the series Greenhouses in Alberta

Once you’ve chosen the structure and materials for your Alberta Zone 3 greenhouse, the next step is deciding how best to set up your planting areas or beds. The choice between in-ground beds, raised beds, and container gardening can have a big impact on plant health, ease of maintenance, and your overall success. This post explores the pros and cons of each approach—and ends with guidance on how to select the right bed style for your unique situation.


In-Ground Growing

In-ground growing means that instead of using beds, you plant directly into the soil beneath your greenhouse structure, that there’s no artificial barrier under the dirt, like the bottom of a planter box. This is the most traditional method of gardening and can be an especially good option if your greenhouse is built over fertile, well-draining ground.

Benefits

  1. Natural Soil Biology
    • You get the advantage of the existing ecosystem—microbes, worms, and other organisms that help break down organic matter and provide nutrients to your plants.
    • Over time, soil fertility can improve naturally, especially if you regularly incorporate compost or organic matter.
  2. Improved Root Depth
    • Because plants aren’t confined by the walls of a bed or container, they can send their roots deeper into the ground.
    • This can lead to stronger, more resilient plants that can access water and nutrients stored deeper in the soil.
  3. Cost Savings
    • You won’t need to purchase materials for building beds or buy large amounts of potting mix.
    • Maintenance costs can be lower, aside from occasional soil amendments if needed.

Drawbacks

  1. Weed Control
    • Weeds already present in your native soil will also thrive in your greenhouse environment, potentially competing with your plants.
    • You may need more frequent weeding compared to raised beds or containers.
  2. Soil Amendments
    • Depending on your soil quality, you might have to add compost, manure, or other amendments regularly to maintain optimal fertility and soil structure.
    • Heavy clay or sandy soils require ongoing improvement efforts.
  3. Potential Drainage Issues
    • If your greenhouse is on poorly draining land, water could pool around plant roots, promoting rot and fungal diseases.
    • Proper site preparation (e.g., installing drainage channels or using raised walkways) may be necessary.

Raised Beds

Raised beds are constructed plots (usually wooden or metal-framed) filled with a customized soil mix. These are immensely popular in greenhouse settings because they allow for better control over soil quality, moisture, and temperature.

Key Advantages

  1. Temperature Control
    • The soil in raised beds warms up faster in spring, giving you a head start on your growing season—an essential factor in Alberta’s short summers.
    • Warmer soil also helps seeds germinate more quickly.
  2. Easier Weed Control and Better Drainage
    • Elevated soil levels make it simpler to spot and remove weeds before they become a problem.
    • Raised beds naturally improve drainage, preventing waterlogging and root rot.
  3. Flexible Soil Composition and Height
    • You have full control over what goes into the bed—perfect if you need specific pH levels or nutrient profiles for certain crops.
    • The ability to build beds at different heights is beneficial for accessibility, especially for those with mobility issues or back problems.

Potential Considerations

  • Initial Cost: Purchasing lumber or other materials for frames, plus quality soil mixes, can be more expensive than in-ground options.
  • Irrigation Needs: Because raised beds dry out faster than in-ground beds, consistent watering is vital.
  • Space Planning: Ensure you leave enough room between raised beds for comfortable walkways and easy access to all plants.

an inside view of a greenhouse by owlcreek.caContainer Beds Gardening 

Container gardening includes pots, grow bags, planter boxes, and even self-watering systems. In a greenhouse, it’s common to see a range of container sizes, from small herb pots to large tubs for tomatoes or cucumbers.

  1. Pots: Clay or plastic pots are portable and come in various shapes and sizes.
  2. Grow Bags: Fabric bags that offer excellent root aeration and drainage; they’re easy to store when not in use.
  3. Self-Watering Planters: Ideal for busy gardeners, these containers have built-in reservoirs that supply water as needed.

Benefits

  1. Portability
    • You can move containers to chase the best light, group plants with similar watering needs, or free up space as necessary.
  2. Targeted Soil Amendments
    • Each container can have a specific mix tailored to the plant’s requirements, such as more acidic soil for blueberries or a moisture-retentive mix for lettuce.
  3. Pest and Disease Management
    • Planting in isolated containers can limit the spread of pests or diseases—if one container becomes infested, it’s easier to quarantine.

Challenges

  1. Potential for Root Constriction
    • Large plants, like tomatoes or peppers, may become root-bound if their containers are too small.
    • You’ll need to choose adequately sized containers and possibly transplant as the plant grows.
  2. More Frequent Watering
    • Container soil tends to dry out faster, especially in warm greenhouse conditions.
    • Having a clear watering schedule or a drip irrigation system can help avoid underwatering or overwatering.
  3. Expense
    • While single containers are relatively inexpensive, the costs can add up if you need many large or specialized ones.
    • Quality potting mix also needs regular replenishment or refreshing to keep nutrients available for plants.

Choosing the Right Beds Style

Selecting the best growing approach for your greenhouse depends on a few key factors:

  1. Space Considerations
    • If your greenhouse is large with decent native soil, in-ground or raised beds might make the most sense.
    • Smaller greenhouses may benefit from container gardening to maximize flexibility and rearrange as needed.
  2. Time and Budget
    • In-Ground is generally the least expensive to set up but can require more labor in weeding or soil amendments.
    • Raised Beds demand an up-front investment in materials but often reduce long-term maintenance issues.
    • Containers can be economical if you already have pots, but large-scale container gardening can quickly become costly.
  3. Desired Plant Types
    • Large, Deep-Rooted vegetables (e.g., tomatoes, squash) often do best in raised beds or in-ground settings with plenty of root space.
    • Specialty Crops with unique soil requirements (e.g., blueberries needing acidic conditions) may be best grown in containers.
    • Greens and Herbs thrive in any setup, but containers allow you to move them around to optimize light conditions or humidity.

Your greenhouse bed choice has a major influence on plant growth, maintenance needs, and overall productivity. In-ground beds harness native soil life while keeping costs lower, though they may require more attention to weeds and drainage. Raised beds offer superior temperature control, weed management, and customization—especially valuable in a short-season climate like Alberta’s. Finally, containers give you the freedom to move and fine-tune your growing conditions, at the price of potentially more frequent watering and higher setup costs if you need many large planters.

Ultimately, the right choice depends on your space, budget, time, and crop preferences. You may even mix and match approaches—using raised beds for staple crops, containers for specialty plants, and a small in-ground area for anything well-suited to your native soil. By selecting the best method (or combination) for your situation, you’ll create a greenhouse environment that supports healthy, abundant harvests all season long.

Amy
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