Magnesium for Plants

Magnesium for Plants is a supplement rather than a complete fertilizer, so it goes alongside your regular feed, not in place of it. In spring and summer, apply once weekly at 1–2 teaspoons per gallon from a watering can, or use the 2 teaspoon setting on a hose-end sprayer. In fall and winter, cut back to every 4–8 weeks. Start when you see yellowing between the veins on older leaves, and keep going while the new growth greens up over the following weeks.

The classic sign is yellowing between the veins on older, lower leaves while the veins themselves stay green, sometimes with the edges curling or turning reddish. It shows on old growth first because your plant moves magnesium to its newest leaves when supplies run short. The pattern matters: yellowing on new growth points to iron instead, and whole leaves yellowing evenly points to nitrogen. Magnesium for Plants is made for that specific interveinal pattern on older foliage, so match the symptom before treating.

Closely related. The magnesium in Magnesium for Plants comes from magnesium sulfate, which is what Epsom salt is, so it does the same core job of supplying magnesium and sulfur. The difference is that this is formulated as a plant supplement: 5% magnesium at a consistent, measured concentration, with sea kelp added to aid uptake, and rates worked out for watering cans, hose-end sprayers and foliar misting. Either way, it helps only when a magnesium shortfall is the actual problem.

Containers lose magnesium quickly. Frequent watering leaches it out of a limited volume of soil, and many potting mixes start low in it. Heavy feeding makes it worse, especially with high-potassium fertilizers, because potassium competes with magnesium for uptake. The same is true of sandy or acidic soils, which hold magnesium poorly. That’s why potted plants show interveinal yellowing more often than plants in rich garden beds, and it’s the gap Magnesium for Plants is made to fill, used alongside a complete fertilizer.

New growth greens up over a couple of weeks once magnesium is available, since it goes straight into chlorophyll production. A foliar misting of Magnesium for Plants at 1 teaspoon per quart can speed the visible change. Leaves that have already yellowed between the veins may partly recover but often won’t fully re-green, so the improvement shows mainly on the growth that follows. Where the tendency is ongoing, as in containers or sandy soil, steady use through the season keeps it from recurring.