How to Start Seedlings in a Cold Frame and Time Transplants For Spring

Cold frames can extend your growing season. A cold frame is a simple structure designed to trap heat and protect plants from frost; additionally, it’s great for gradually adapting seedlings started indoors to conditions outdoors.

Cold frames are simple structures made up of four walls designed to trap warmth inside, with an open transparent lid to let sunlight warm it up. Building one yourself requires little more than some leftover windows and salvaged lumber.

Start Seedlings Indoors

Starting seedlings indoors allows you to access a wider selection of plants than are offered at garden centers in fully grown form. By using recycled containers such as yogurt/cottage cheese containers, paper egg cartons or 3-4 inch wide plastic seed starting trays equipped with drainage holes at their bases, an affordable yet efficient system for starting seeds and small transplants can be created.

Before transplanting seedlings outdoors, they must first be hardened off. This process gradually exposes them to harsher outdoor environments and helps them better withstand transplant stress.

To harden off seedlings, set them outside for gradually longer periods – starting from half a day and increasing up to leaving them outside all day long. To simulate wind, gently ruffle the seedlings or place a fan nearby to provide active air flow – this helps reduce fungal diseases that could otherwise damage or kill seedlings.

Time Transplants for Spring

Cold frames are an easy, season-extending structure designed to trap sunlight and warmth for cool-season vegetables such as lettuce, radishes and carrots. Constructed out of wooden box topped by recycled windows or shower doors (or plastic covering), cold frames protect plants from frost damage while creating their own microclimate for maximum success.

Timing depends on the seedling variety; generally though, at least three or four true leaves must have emerged before being transplanted from its tray. A seedling with more leaves is likely to experience faster growth after planting than one with limited or no leaves at all.

Remembering to consider when transplanting perennials is key as transplanting requires considerable energy from both you and the plant itself to reestablish its root system. Therefore, transplanting shrubs and perennials when they’re dormant and without blooms on them is ideal; similarly spring is the optimal time to transplant heat-loving perennials such as lavender and cleome which have established strong root systems already.

Preparing Your Cold Frame

Cold frames are simple structures designed to preserve warmth, providing protection from wind and frost while gradually acclimating tender transplants to outdoor temperatures.

On hot, sunny days, frames may become overheated; to reduce moisture build-up and help ensure air circulates more freely, slightly opening the lid may help. On extremely cold nights however, insulation may be needed in form of blankets or straw bales around the frame for extra warmth.

Cold frames provide the ideal setting for cultivating vegetables such as lettuce, radishes and carrots that don’t do well when sowden directly in gardens or containers. Not only can these crops thrive over winter in cold frames but can be harvested long after regular planting seasons have concluded – some varieties like carrots can even become sweeter when exposed to light frost and gain additional flavor when exposed.

Building Your Cold Frame

Cold frames consist of four walls designed to trap heat, and a clear lid which admits light. They can be made out of plywood, concrete blocks or bales of hay; an old window makes an excellent lid; Plexiglas also does well as it doesn’t absorb light as readily as glass does. A simple structure should be easy for most people to build for either permanent use in their garden or winter gardening activities.

Keep the temperature inside your cold frame below 75 degrees Fahrenheit when growing summer plants, and 60 degrees when raising plants that typically flourish in spring and autumn. Do this by regularly lifting the lid.

Seedlings that have been moved directly from indoor trays into their vegetable gardens must undergo an adaptation period called hardening off, whereby they gradually adapt to outdoor temperatures, sunlight and wind conditions. This transforms tender transplants into tough plants capable of withstanding all aspects of gardening environments.