Want sweeter grapes? Summer fertilization is the key to strong vines and rich flavor

Grapevines need specific care during summer to produce sweet, healthy fruit. And fertilizing correctly at this stage is crucial for strong roots, balanced growth and better yields.

According to horticulture experts, grapevines in fruiting phase benefit most from a balanced mix of phosphorus, potassium and micronutrients — but timing is everything.

Best nutrients for summer

• Phosphorus (P): supports root strength and fruit set;
• Potassium (K): helps build sweetness and disease resistance;
• Magnesium and boron: maintain leaf health and support grape development.

How and when to fertilize

• Apply fertilizer once the vines have fully leafed out and are growing;
• Use diluted liquid fertilizer for faster absorption;
• Water first, and fertilize during cool hours — morning or evening.

Mistakes to avoid

• Too much nitrogen: causes leafy growth with poor fruit;
• Chlorine-based fertilizers: may harm roots by salinizing soil;
• Late feeding: affects grape flavor and delays ripening.

By the way, sweeter grapes don’t start on the vine — they start in the soil. Feed smart, and harvest better.