Foliar Spray vs Soil Drench: Which to Use

Drench the soil to feed the plant. Spray the leaves for a small, quick top-up or to get ahead of stress. A spray does not replace feeding the soil. This is the practical how-to for deciding which one you need, which of our products suit a sprayer, and how to keep nozzles clear and leaves unburned.

The Short Version

Kelp It Real, Vitamin Sea and Phishy can be sprayed or drenched.
Veg works either way, but a drench is the primary method.
Bloom is a soil feed. Spray it only when leaves show a phosphorus or potassium shortfall, and watch for tip burn.
Microbes is a drench at the base of the plant.
King Krustacean and Incredible Bulk: we don't publish a foliar rate for either, so we don't recommend spraying them. Use them as the feeding chart directs.

Spray early in the day or in the evening, not in hot sun. Foliar can show a response sooner than a drench, but it delivers less.

Foliar vs Drench: What Each One Does

In general, leaves can take up only small amounts, quickly, while roots take up the bulk, steadily. The two methods do different jobs, and growers get into trouble when they ask one to do the other's work.

Foliar spray

Speed and staying power: can show a response sooner, usually for less time.
How much it delivers: small amounts.
Best for: quick top-ups, trace-mineral gaps, getting ahead of stress.
Main risks: leaf burn in strong sun, clogged nozzles, wet foliage.

Soil drench

Speed and staying power: usually slower to show, usually lasts longer.
How much it delivers: the main way to feed.
Best for: regular feeding on a schedule.
Main risks: over-applying, pouring onto dry or waterlogged soil.

Our product notes agree on speed. The Kelp It Real notes say foliar shows the fastest response, within 24 to 48 hours on stressed plants. Plants vary, so treat that as a guide. The Vitamin Sea notes say foliar gives the fastest visible response. Faster does not mean stronger.

Product-by-Product Guidance

We don't publish a separate per-gallon dose for foliar use. The figures below are the feeding chart's per-gallon doses. Treat them as a ceiling for a spray and start at the low end of any range.

Kelp It Real: spray yes, fastest on stressed plants; drench yes. Chart dose ¼ tsp per gallon. Use it every 2 to 3 weeks. It is a soluble extract. It is also hygroscopic, so keep it airtight or it clumps.
Vitamin Sea: spray yes; drench yes. Chart dose 1 tsp (5 ml) per gallon. Use it every 3 to 4 weeks. It is a seawater-derived mineral concentrate, so dilute it. Never mix it with synthetic fertilizers, pesticides or herbicides. Apply it alone, a few days apart.
Phishy (formerly SeaPhood): spray yes; drench yes. Chart dose 1–5 ml (¼–1 tsp) per gallon. Our notes describe both a soil drench and a foliar feed. It smells like fish. That is manageable outdoors, and for indoor use our notes point to Vitamin Sea or Kelp It Real. Oil separation is normal, so shake or stir before you measure. Do not mix it with other mineral fertilizers.
Veg: spray yes, secondary; drench yes, primary. Chart dose ¼–½ Tbsp per gallon. It is a wettable powder made to feed soil microbes as well as the plant, and it needs Microbes to work as designed.
Bloom: spray only for a phosphorus or potassium leaf shortfall; drench yes, the normal route. Chart dose ¼–½ Tbsp per gallon. Tip burn is the thing to watch on a foliar pass. It also needs Microbes.

Powders in a sprayer

Our dry products are fine powders. Bloom clears 100-mesh, about 149 microns. We have not independently confirmed Veg's finished mesh, and we don't publish a figure for Kelp It Real. A fine powder can still block a nozzle if it has not dissolved. As general practice, dissolve or disperse the powder fully in a bucket, strain it, and shake the sprayer as you work, because fine particles settle. We don't publish sprayer or filter specifications.

What to Do

When to spray

Time of day. Early morning or evening, when it is cooler and the sun is low. Indoors, avoid spraying right under hot lights.
Weather. Calm days with no rain due soon.
Plant timing. Kelp It Real ahead of a heat wave, drought or frost, to help plants cope. Vitamin Sea when leaves show signs of a micronutrient shortage, such as yellowing between the veins, which can also have other causes. Bloom only when leaves show a phosphorus or potassium shortfall. These are the cases our product notes name.

To spray

Measure up to the chart dose for one gallon into a bucket of water. Shake Phishy before you measure.
Stir until no clumps or dry pockets remain, then pour the mix through a fine strainer or cloth into the sprayer.
Test first. Spray a few leaves and wait a day or two. If they look normal, spray the rest.
Spray until the leaves are wet, tops and undersides, and stop before the mix runs off in streams. Keep it off open flowers and dense flower clusters, where wet blooms can invite mold.
Rinse the sprayer afterward, and use one that has only ever held plant food or water.

To drench

Water first if the soil is dry. Moist soil usually takes a drench more evenly.
If the mix includes Microbes and a powder, add them in this order: water, Microbes, then the powder. That is the order we use for Veg.
Pour around the base of the plant over the root zone, not over the leaves.
Follow your plant's schedule for how often on the feeding schedule.

Mistakes That Burn Leaves and Waste Product

Spraying in hot sun. The spray can burn leaves as it dries, and it dries before the leaf can take much up.
Treating the spray as the whole feed. Leaves can only take up so much. The Kelp It Real notes say it complements other feeds, and the plant still needs the soil feed underneath.
Mixing it stronger. A stronger mix makes leaf burn and tip burn more likely. Stay at the chart dose or below.
Re-spraying the same symptom. If yellowing keeps returning, check watering, drainage and roots first.
Tank-mixing by habit. Vitamin Sea goes on alone, and Phishy stays away from other mineral fertilizers.
Leaving out Microbes. Veg and Bloom need Microbes to work as designed. No spray makes up for that.

Where Growganica Fits

Kelp It Real is the clearest fit for a sprayer. It is a soluble extract, our notes name foliar use, and it is the one we point to for houseplants. Vitamin Sea is the product our notes single out when leaves show signs of a micronutrient gap. Phishy sprays too, but the smell suits outdoor use better. Veg and Bloom are soil feeds first, and both need Microbes underneath them.

If your plants look healthy and you feed the soil on schedule, you may not need to spray at all. If the trouble on the leaves is a pest or a disease, a nutrient spray is not the answer, and none of our products is sold as a treatment for either. For the bigger picture on feeding the soil first, see the 3-step living soil system.

Frequently Asked Questions

Which Growganica products can go in a sprayer?

Kelp It Real, Vitamin Sea and Phishy can be sprayed or drenched. Veg works either way, with a drench as the primary method. Bloom is a soil feed, sprayed only for a phosphorus or potassium leaf shortfall. Microbes is a drench at the base of the plant. We don't publish a foliar rate for King Krustacean or Incredible Bulk, so we don't recommend spraying them.

When should I spray?

Early in the day or in the evening, on a calm day with no rain due soon, and not in hot sun. Indoors, avoid spraying right under hot lights. Test a few leaves first and wait a day or two before spraying the rest.

Does foliar feeding work faster than a soil drench?

It can show a response sooner. The Kelp It Real notes say foliar shows the fastest response, within 24 to 48 hours on stressed plants, and plants vary. Faster does not mean stronger: leaves take up small amounts, and the drench is still the main way to feed.