US Growing Seasons: Frost Dates and Feeding

Two dates run the grower's calendar: your average last frost in spring and your average first frost in fall. Both shift across the country, sometimes between neighboring towns, so this guide skips the date table. Look up your own dates and count from them. Below is how the seasons divide, what to do in spring and before the first frost, how to bring potted plants indoors, and whether feeding changes in winter.

How US Growing Seasons Divide

A country this size can't share one calendar, so frost dates are the better marker. The frost-free stretch between the last spring frost and the first fall frost is your growing season. It is short in the northern states and at high elevation, and close to year-round in the warmest parts of Florida, the Gulf Coast, south Texas and the low desert Southwest.

Crops fall into two groups.

Cool-season crops: lettuce, spinach, kale, collards, cabbage, broccoli and peas. Many handle a light frost and often go in weeks before the last spring frost. A hard freeze can still damage them.
Warm-season crops: tomatoes, peppers, cucumbers, squash, beans and basil. Frost damages or kills them, so plant after the last spring frost, once nights are reliably mild.

In the warmest regions the split follows heat instead. Cool-season crops run from fall to early spring, and summer heat stresses tomatoes.

Find your dates

Ask your county or state cooperative extension office for your frost dates. They are averages, so frost after the "last frost date" can still happen. For fall crops, count back from the first fall frost using the days to maturity on the seed packet, and allow extra time because growth slows as days shorten.

Hardiness zones measure something else

The USDA Plant Hardiness Zone Map groups places by average coldest winter temperature, in 10°F zones split into 5°F halves such as 10b. Zones tell you which perennials usually survive winter outdoors. They don't give you frost dates, so use them for perennials and use frost dates for everything you plant new each year.

Spring Checklist: What to Do

Know your average last-frost date, then plant by group. Cool-season crops go in first. Warm-season crops wait for the frost to pass and the nights to warm. Harden off indoor-started seedlings over a week or so.
Start Microbes on planting day. New bed, new pot or transplant: inoculate that day, before the first feeding. Don't wait for fresh mulch or compost to settle. Microbes are what break it down, so waiting only delays the work.
Start feeding once plants are actively growing. For perennials and plants that spent winter indoors, that means when new growth appears.
Mix in order: water, Microbes, then powder. Our product notes say to apply Microbes with a microbe food, and Veg and Bloom need Microbes to work as designed.

Doses from the Growganica feeding chart, per gallon of water:

Microbes: 1–3 ml (¼–¾ tsp), drenched at the base, monthly.
Kelp It Real: ¼ tsp, foliar or soil, every 2–3 weeks.

Before the First Frost: What to Do

Frost can form on a clear, calm night even when the forecast low is a few degrees above 32°F. A hard freeze kills far more plants. With a frost a few days out, work through this list in order.

Sort your plants. Tender potted plants you want to keep come inside. Tender plants in the ground get harvested. Hardy ones stay.
Harvest. Pick ripe and nearly ripe tomatoes, peppers, squash, cucumbers and basil. Green tomatoes can finish ripening indoors.
Hold feeding on tender plants. Feeding can push soft new growth, and soft growth is what cold hits first. Cool-season crops that are still growing can stay on their normal schedule.
Ease off watering. Cool, short days mean plants use less. Water when the top inch or two of soil is dry. Soggy soil in cold weather invites root problems.
Cover what stays out. Use frost cloth or a sheet held up on stakes, off the leaves, and remove it in the morning. This can help on a borderline night. A hard freeze can still win.

Kelp ahead of the cold, as an option

Our Kelp It Real notes list a foliar spray ahead of a stress event, such as a heat wave, drought or frost, as one of its uses. If you try it on plants that stay outside, use the chart dose of ¼ tsp per gallon and apply it ahead of time. It is not frost protection, and we don't claim it will carry a plant through a freeze. We don't publish a pre-frost rate, lead time or test results. Kelp is an additive, not a feed.

Bringing Plants Indoors

This covers potted tender plants: tropicals, citrus, peppers, herbs and houseplants that spent the summer outside.

Move early. Tropicals can be hurt by cold nights well above freezing. Short on time? Take the plants you can't replace and the most tender ones first.
Check for pests. Look over leaves, undersides, stems and soil for insects, webbing and slugs, and rinse the foliage. Keep new arrivals apart from your other houseplants for a couple of weeks.
Use your brightest spot. Indoor light is much weaker than outdoor light. Some leaf drop while a plant adjusts is common.
Water less. Lower light slows drying. Let the top of the soil dry first, and don't leave pots standing in water.
Hold feeding until new growth shows. Then the chart doses apply. For houseplants we recommend Kelp It Real. Microbes also works indoors at the same dose.

Does Feeding Change in Winter?

Feeding follows growth, not the calendar. We don't publish a separate winter dose for any product, so the chart dose stays the dose. What changes is whether to feed at all.

Outdoor beds in cold winters: nothing to feed. Plants are dormant or finished, and in most of the US soil biology slows as the soil cools. Pick up again in spring.
Mild-winter regions with cool-season crops: if the crop is growing, keep its normal schedule. Don't raise the dose to chase slower growth.
Indoor plants: with new growth, the normal chart doses apply. If the plant is resting, don't feed it just to keep a schedule.

Where Growganica Fits

Most of this guide needs no product. Two have a part in it.

Microbes is Step 1 of the program (Inoculate). Start it at planting each spring, or the day you set up a new bed or pot.
Kelp It Real is a soluble seaweed extract (Ascophyllum nodosum), grade 0-0-14, and the only OMRI Listed product in the line. It is an optional Step 3 add-on that complements your regular feed and doesn't replace it.

Nothing in the line is frost protection. For plant-by-plant schedules, see the feeding schedule.

Frequently Asked Questions

What do I do before the first frost?

Sort your plants, harvest what is ripe or nearly ripe, hold feeding on tender plants, ease off watering, and cover what stays out. Tender potted plants you want to keep come inside, and a sheet or frost cloth held up on stakes can help on a borderline night. A hard freeze can still win, and nothing we sell is frost protection.

When do I start feeding in spring?

Start Microbes the day you plant, whether that is a new bed, a new pot or a transplant. Start regular feeding once plants are actively growing. For perennials and plants that spent winter indoors, that means when new growth appears.

Does feeding change in winter?

Feeding follows growth, not the calendar. We don't publish a separate winter dose for any product, so the chart dose stays the dose. What changes is whether to feed at all: dormant or frozen beds need nothing, while a crop that is still growing keeps its normal schedule.

Which plants should I bring inside before a frost?

Tender potted plants you want to keep: tropicals, citrus, peppers, herbs and houseplants that spent the summer outside. Move the ones you can't replace and the most tender ones first, because tropicals can be hurt by cold nights well above freezing. Plants in the ground that can't take frost get harvested instead.