What plants are sensitive to magnesium treatments?
Written by
Liu Xiaohui
Reviewed by
Prof. Martin Thorne, Ph.D.Certain plants can become adversely sensitive to magnesium treatments, even though they actually need the nutrient. For example, legumes like beans and peas contain nitrogen-fixing bacteria that don't tolerate magnesium applications well. Flowers such as blueberries and azaleas can become damaged after applications of magnesium, or, at the very least, they can be affected by the pH that magnesium can change. Seedlings with fragile roots can easily become damaged by salt, even when it's in a form that utilizes magnesium, such as Epsom salts. I remember seeing wilted tomato plants after recent applications of Epsom salts.
Legume Family
- Includes beans, peas, lentils, and clover
- Magnesium disrupts nitrogen-fixing rhizobia bacteria
- Causes reduced nitrogen production and stunted growth
- Shows yellowing between veins within 72 hours
Acid-Loving Species
- Blueberries, azaleas, rhododendrons, camellias
- Magnesium raises soil pH making iron unavailable
- Triggers severe interveinal chlorosis in new growth
- Leaf margins turn brown and crisp quickly
Young Seedlings
- All plant varieties in early growth stages
- Underdeveloped roots suffer salt burn easily
- Shows wilting despite moist soil conditions
- Growth stalls completely after treatment
Before applying magnesium, it is important to identify sensitive plants. It might be helpful to check the soil pH, because a pH below 5.5 indicates the presence of acid-loving species. If possible, check the roots. Healthy, firm, possibly white roots will be more tolerant of any treatments. In my nursery, when I use this method, I avoid applying treatments to any plants showing signs of stress.
Use caution when using magnesium treatments on sensitive plants, as special delivery methods may be required. You can base legumes on foliar sprays applied at half strength, getting the messenger and applying them early in the morning. Acid-loving plants benefit from using magnesium chelates because they supply magnesium without altering the pH. For seedlings and other sensitive plants, use only a heavily diluted solution that is poured into the soil, never on the foliage. I generally will water the plants first, creating a protective buffer.
Observe treated plants closely for any signs of distress. For processed legumes, you will see reduced nodule formation from the disruption of the nitrogen-fixing symbionts. Acid-requiring plants will exhibit patterns of iron deficiency from the disruption of iron transfer to the plant. Seedlings may wilt or stop growing altogether. At the first indication of trouble, flush the soil with clean water. You have used careful observation to prevent serious injury to your valuable plants!
Read the full article: 7 Critical Signs of Magnesium Deficiency Plants
