Weather Planting Caution

Protect Your Plants from Cold Stress!

As spring arrives and the first warm days tempt us to start planting, it’s important to proceed with caution. Greenhouse-grown plants, while vibrant and healthy, are highly sensitive to outdoor conditions and require proper hardening off before they can thrive in your garden. Without this gradual transition, sudden exposure to cool temperatures, strong winds, or direct sunlight can shock plants, leading to stunted growth, leaf damage, or even plant loss.

Understanding the Importance of Hardening Off

Hardening off is the process of slowly acclimating greenhouse plants to outdoor conditions. Since these plants have been cultivated in a controlled environment with consistent warmth, humidity, and filtered sunlight, they are not immediately equipped to handle Michigan’s unpredictable spring weather. A proper hardening-off period typically takes 7–10 days and involves gradually exposing plants to outdoor elements, increasing their tolerance to temperature fluctuations, wind, and direct sunlight.

Frost Risks & Temperature Guidelines

Spring weather in Michigan can be deceiving—mild, sunny days are often followed by chilly nights. Nighttime temperatures frequently drop below 50°F in early spring, which is too cold for many tender plants. Additionally, frost remains a significant threat throughout May, and even a light frost can severely damage or kill non-hardy plants.

To protect your investment and ensure healthy plant growth:

• Wait to plant tender annuals and vegetables until nighttime temperatures consistently remain above 50°F.
• Tropical plants, such as hibiscus, mandevilla, and palms, require nighttime temperatures of at least 60°F before they can be placed outdoors permanently. These plants originate from warm climates like Florida and cannot tolerate Michigan’s cooler nights.
• Perennials, cold-hardy vegetables, and early spring flowers like pansies, snapdragons, and lettuce are more tolerant but still benefit from gradual exposure.

A good rule of thumb is to wait until after Memorial Day to plant summer annuals and tropicals, ensuring they have the best chance of success.

Tips for Early Plant Purchases

If you’re eager to get a head start on your garden, you can purchase your plants early, but they will need special care:

• Keep plants in a bright, warm location indoors until the weather stabilizes.
• On mild days (above 50°F), place plants outside in a sheltered area for a few hours to help them adjust. Avoid placing them in direct midday sun or strong wind, which can cause stress or dehydration.
• Bring plants indoors at night or if temperatures dip below the recommended levels.

Monitor Weather & Watering

We want you to have a thriving, beautiful garden, and nothing is more disappointing than losing plants due to unexpected weather changes. Keep an eye on the forecast, especially nighttime lows, and check your plants daily for water needs. A well-hydrated plant is more resilient to temperature fluctuations, but overwatering can also be harmful—ensure proper drainage to prevent root rot.

At Diegel’s Greenhouse, we appreciate your business and want you to have the best gardening experience possible. Taking the time to properly acclimate your plants now will lead to a lush, healthy garden all season long!