3 Quick Tips: Spring crop production

Quick Tip 1:

Check growing medium pH
Check the growing medium pH level of your geraniums. The plants may look just fine, but the medium pH can drop rapidly, raising the availability of iron and manganese to toxic levels. Geraniums are iron-efficient as are some marigolds, salvia, impatiens, gerbera, basil and tomatoes. They are able to acidify the medium around the roots. Toxicity symptoms appear as speckled brown foliage (similar to spider mite injury) and edge-burn and eventually the foliage turns yellow. Check the medium pH level at least weekly.

For zonal geraniums, the pH range for a soilless medium is 5.8-6.2 and for a soil-based medium it's 6.0-6.5. The optimal range for ivy and regal geraniums is slightly lower (5.5-6.2). If adjustments are needed, the medium pH can be raised with the use of flowable liquid limestone.

Quick Tip 2:

Prevent iron deficiency
Plants such as bacopa, calibrachoa, scaevola, snapdragons and petunia are susceptible to iron deficiency. Iron deficiency symptoms appear as an interveinal chlorosis or yellowing, normally starting at the shoot tips but can also occur throughout the entire plant. Sometimes the leaves of iron-deficient plants turn almost white.

Prevent iron deficiency by maintaining a low growing medium pH and using an iron chelate fertilizer or a complete fertilizer that contains extra iron. Before applying iron, check the health of the plant roots. Yellow foliage and stunted growth are common symptoms of plants with unhealthy roots that may be mistaken for iron deficiency.

The target pH range for crops susceptible to iron deficiency is fairly low, 5.5-5.8.

It is important not to use iron chelate or fertilizers with extra iron on plants that are sensitive to iron. Growers still struggle with some spring crops which are susceptible to iron toxicity rather than deficiency, including marigolds, zonal geraniums and seed geraniums.

Manage the nutrition for these plants by minimizing plant-available iron by maintaining the medium pH in a higher range and avoiding fertilizing with too much iron.

Quick Tip 3:

Adapting to changing weather
The weekend weather forecast may call for sunny days with temperatures in the mid to high 80s following a week of cool, cloudy weather. As a result, there is a strong possibility, spring crops will experience summer temperatures in greenhouses equipped with little or no shading. Even one or two days of bright light levels with temperatures in the high 80s can stress bedding plants and hanging baskets with rooting systems that are not fully developed. Delicate foliage of shade plants such as impatiens are susceptible to sunburn.

During very warm sunny days, greenhouses need to be well ventilated and the crops irrigated to avoid wilting and undue stress. Prior to moving any greenhouse-grown plants outdoors in the spring, gradually expose plants in the greenhouse to cool temperatures. Once plants reach the desired size, greenhouse temperatures can be lowered to 45°F-55°F for about a week to acclimate them. Plants placed outdoors that have not been acclimated may develop paper thin brown spots or new growth may wilt due to chilling injury.

Have a question? You can write Tina at tsmith@umext.umass.edu.