Gardening fundamentals

The USDA Plant Hardiness Zone map splits North America into 10°F bands based on average yearly low temperatures. It answers one question: how cold does it get here in a bad winter? That's what decides whether your fig, your artichoke crown, or your rosemary comes back in spring.

It doesn't tell you summer heat, humidity, day length, rainfall, frost dates, or soil. A zone 7 gardener in Seattle and a zone 7 gardener in Atlanta grow completely different gardens. Zone is for perennial survival. Frost dates run everything you plant each year.

The 2023 map bumped roughly half the country half a zone warmer. If your beds are older than the update, look yours up again — plants that were marginal for you may be reliable now.

Every planting date in every guide is backwards math from two numbers: your average last spring frost (LSF) and average first fall frost (FFF). The days between them are your season. Indoor starts, transplant dates, succession sowings, fall harvest — all offsets from those two dates.

Spring math for warm-season crops (tomato, pepper, eggplant): start seeds indoors 6–8 weeks before LSF. Harden off 7–10 days. Transplant 1–2 weeks after LSF, once soil at 4 inches hits 60°F. Cool-season crops (peas, lettuce, spinach, brassicas) go out as transplants 4–6 weeks before LSF, or direct-sown as soon as the soil is workable.

Fall math is the piece most gardeners miss. Take the packet's days-to-maturity, add 14 days for shorter fall daylight, add another 14 if the crop needs to size up before frost, then count that far back from your first fall frost. That's your last safe sow date. Miss it by a week and you're buying spinach in October.

One more habit: succession planting. Sow lettuce, radish, cilantro, and bush beans every 2–3 weeks instead of all at once. You eat steadily instead of drowning for two weeks and then nothing.

Most failed vegetable gardens start with a wildly generous sun estimate. "It gets pretty sunny out there" isn't a measurement. What counts is direct sun, in hours, on a clear day between the equinoxes.

The categories are strict. Full sun is 6+ hours, ideally 8. Partial sun is 4–6. Partial shade is 2–4 (dappled counts as half). Full shade is under 2. Fruiting crops — tomato, pepper, squash, melon, cucumber, bean, corn — need full sun. Leafy crops (lettuce, kale, chard, spinach) take partial sun and actually prefer some afternoon shade in summer. Roots want at least 5 hours.

Measure it: pick a clear day near an equinox (late March or late September). Note the shadows at 8, 10, noon, 2, 4, and 6. Anywhere in direct sun for 3 of those 6 checks is at least partial sun. A $12 sun-hours meter beats guessing every time.

Ask any twenty-season gardener what they'd change about their first five years. Every one of them says the same thing: spend more time on soil, sooner. Soil isn't just something to hold the plant up — it's a living crowd of bacteria, fungi, protozoa, and worms that turns organic matter into plant food. Feed the crowd and the plants feed themselves.

Three levers. Texture (the sand-silt-clay ratio) you shift slowly with organic matter. Never try to fix clay by adding sand — you'll make concrete. Organic matter (compost, aged manure, leaf mold, worm castings) is the fastest lever: 1–2 inches on top each spring is a measurable jump in one year. pH (6.2–6.8 for most vegetables) you adjust with garden lime to raise or elemental sulfur to lower. Test before you dose.

The full lesson lives on /learn/soil. The short version: mulch heavily, compost yearly, test every 2–3 years, and don't rototill an established bed. Every disturbance sets the soil food web back a season.

Roots follow water. Water shallowly every day and roots stay in the top inch — the first hot weekend cooks them. Water deeply and less often and roots dive 12–18 inches down, where the soil stays cool and moist through a heat wave. This is the one habit change that separates hobby beds from productive ones.

Target about an inch of water a week for most vegetables, delivered in 1–2 long soaks at the root zone. Double it in a hot dry stretch; halve it in cool spring or fall. Set a tuna can in the bed the next time you water — you'll be surprised how long a real inch takes.

Delivery matters as much as amount. Drip lines and soaker hoses put water on roots and leave leaves dry, which alone cuts early blight, powdery mildew, and downy mildew dramatically. Overhead sprinkling is the worst possible choice for a vegetable garden. If it's your only option, water at sunrise so leaves dry within an hour.

And mulch. Two or three inches of straw, shredded leaves, or wood chips cuts evaporation in half, evens out soil temperature, blocks most weeds, and feeds worms as it breaks down. The closest thing to free money in gardening.

Plant the same crop in the same bed year after year and two things happen. Soil-borne diseases specific to that family — late blight, clubroot, Fusarium wilt — build up. And overwintering pests (Colorado potato beetle, squash vine borer, cabbage root fly) come back to a buffet. Rotate by family and both collapse.

The five families that matter most for a home gardener: Solanaceae (tomato, pepper, potato, eggplant), Brassicaceae (cabbage, broccoli, kale, radish, turnip), Cucurbitaceae (squash, cucumber, melon, pumpkin), Fabaceae (bean, pea — the nitrogen fixers), and Alliaceae (onion, garlic, leek). Rule of thumb: don't plant the same family in the same bed within 3 years, and follow a heavy feeder with a nitrogen fixer, then a lighter feeder.

A working four-bed rotation. Year 1: Bed A gets tomatoes (heavy feeders — they empty the nitrogen). Year 2: beans or peas (they restock it). Year 3: brassicas (moderate feeders using the restocked N). Year 4: roots or alliums (light feeders that finish clean). Move every family clockwise through your beds each year.

There's a lot of noise here. The classic companion-planting charts recycle unverified claims (marigolds under everything, borage cures all). What actually holds up in the research is narrower and more useful.

Three mechanisms work. Confusion: aromatic plants (basil, dill, cilantro, alliums) mask the scent of the host crop so pests can't find it. Attraction: flowering herbs (alyssum, dill, fennel, yarrow, calendula) feed the lacewings, hoverflies, and parasitic wasps that eat aphids, whiteflies, and caterpillars. Trap crops: nasturtiums pull aphids off cucurbits, and blue Hubbard squash pulls squash bugs off zucchini.

Pairings that hold up: basil with tomato (both grow better and share water); alliums (onion, chive, garlic) with brassicas (repels cabbage moth); nasturtium along any squash, cucumber, or melon bed; French marigolds ('Nemagold') for nematode suppression, but only after a full season in the soil. Overrated: the Three Sisters as a home-garden productivity trick — beautiful culturally, usually less productive per square foot than separate beds.

Small does not mean unserious. A well-run 40 sq ft of containers on a south balcony can out-produce a neglected 400 sq ft backyard. The rules just get stricter — every square foot, every hour of sun, every gallon of soil has to earn its keep.

Best practices, in order of impact. (1) Chase the sun: measure your actual direct-sun hours (see Lesson 03) and put fruiting crops in the sunniest 6+ hour spots; give leafy crops the 4-hour corners. (2) Go up, not out: trellises, tomato cages, obelisks, and railing planters triple your usable square footage. (3) Size the container to the crop — undersized pots stunt everything: 3–5 gal for peppers, herbs, and bush beans; 7–10 gal for tomatoes, eggplant, and summer squash; 12+ gal for potatoes; a 6 in windowbox is plenty for lettuce and radish. (4) Use real potting mix, never garden soil — it compacts, suffocates roots, and drags in pathogens. (5) Water and feed on a shorter clock: containers dry 2–4× faster than beds and nutrients wash out with every watering; check daily in summer and feed with diluted fish emulsion or compost tea every 2 weeks.

Best crops for small spaces. Compact by design: cherry and patio tomatoes ('Tumbling Tom', 'Patio Choice', 'Bush Early Girl'), bush cucumbers ('Spacemaster', 'Bush Champion'), bush beans, hot and sweet peppers, dwarf eggplant ('Patio Baby'), determinate zucchini ('Astia', 'Bush Baby'). Cut-and-come-again greens: leaf lettuce, arugula, spinach, mustard, kale, chard — one shallow container feeds a household for weeks. High-value herbs that earn their pot: basil, parsley, cilantro, chives, mint (in its own pot — mint invades), thyme, oregano, rosemary. Root crops that fit: radish, baby carrots ('Paris Market', 'Little Finger'), scallions, baby beets. Vertical stars: pole beans, sugar snap peas, malabar spinach, small-fruited melons on a strong trellis. Skip or delay in true small space: sweet corn, standard sprawling watermelon, pumpkins, artichokes, asparagus — they need real ground and elbow room.

Pest avoidance is easier in small spaces if you use the geometry. Isolation helps: containers on a balcony 3 stories up rarely see cabbage moths, squash bugs, or vine borers. Screening helps more: cover new brassica and cucurbit seedlings with lightweight row cover (Agribon 15) until they flower — physical exclusion beats every spray. Keep it clean: no piles of debris, no standing water in saucers (mosquitoes), no dropped fruit rotting between pots (fungus gnats and slugs). Inspect weekly, top-of-leaf and underside; catch aphid colonies at 5 bugs, not 500. Rinse infested plants with a strong hose spray — this alone controls aphids, spider mites, and whitefly for most home growers. Companion plant tight: one basil per tomato pot, alyssum or calendula in an 8 in dish in the middle of the balcony to pull in hoverflies and lacewings. And rotate what you can — move nightshades and cucurbits to different containers each year and refresh at least the top 3 in of potting mix between seasons.

Microgreens are seedlings harvested when the first true leaves appear — typically 8 to 14 days after seeding. Nothing exotic: broccoli, radish, pea, sunflower, kale, arugula, kohlrabi, mustard, beet, cilantro, basil. They deliver 4–40× the vitamin content of the mature plant per ounce (Yale/Maryland research) and cost about $2/oz to grow versus $4–$5/oz at a grocer.

The whole setup is small. You need shallow 10×20 in trays (nursery '1020' flats are the standard — get some with holes and some without, so a solid tray sits under a mesh one for bottom-watering), a bag of seed-starting mix or coco coir, a spray bottle, and a bright window or a $25 clip-on LED grow light. That's it. No fertilizer, no transplanting, no season.

The workflow, one tray at a time. (1) Fill the mesh tray with 1–1.5 in of pre-moistened seed-starting mix and level it — do not press hard. (2) Sprinkle seed heavily and evenly across the surface — much denser than for a garden, roughly 1 oz for a 10×20 tray of small seed like broccoli or kale, more like 1.5 oz for larger seed like pea or sunflower. Do not bury; just press seeds into contact. (3) Cover with a second inverted tray for 3–4 days of 'blackout' — the darkness and pressure force the seedlings to root deeply and stretch tall. Mist under the cover once a day. (4) Uncover, move to light (window, LED, or shop light 4–6 in above), and bottom-water once a day by setting the mesh tray briefly into the solid tray with a half-inch of water — never overhead water, that invites damping-off. (5) Harvest with sharp scissors just above the soil line when the first true leaves show and the tray looks like a lawn — usually day 8 to 14 depending on the crop. Rinse, dry gently, refrigerate in a ventilated container. Good for 5–7 days.

Cleanliness is 90% of the game. Damping-off (a soil fungus that flops seedlings) and mold are the only real failures, and both come from wet leaves plus stagnant air. Fixes: soak seeds 4–8 hours before sowing (rinse well), bottom-water only, keep a small fan on low nearby for airflow, and give trays a hydrogen peroxide rinse (1 tbsp per quart) between rounds. Never reuse soil for a second microgreen crop — compost it and start fresh.

Best crops to start with, ranked by ease and flavor: broccoli (mild, fast, cheap seed), pea shoots (sweet, big, forgiving — pre-soak 8 hours), radish (peppery, ready in 7 days), sunflower (nutty, dense, pre-soak 8 hours and remove hulls day 4), kale, arugula, kohlrabi. Skip until later: mucilaginous seeds like basil, chia, and cress — they gel up and need a specialty method.

The Three Sisters — corn (elder sister), climbing beans (middle sister), and squash (youngest sister) — is the most thoroughly documented Indigenous cropping system in the Americas, refined by Haudenosaunee, Anishinaabe, Cherokee, Wampanoag, Muscogee, Hopi, and many other nations across a wide range of climates. Not a myth, not a garnish. It is a working companion-planting system with real numbers behind it.

The mechanism: corn provides a living pole so beans can climb without a trellis. Beans host nitrogen-fixing rhizobia on their roots, restocking the soil that heavy-feeding corn depletes — a mature bean planting can add roughly 40–70 lb of nitrogen per acre. Sprawling squash covers the ground, its broad leaves shading out weeds and cutting soil evaporation, and its prickly stems deterring raccoons, deer, and some rodents from the corn.

Real-world data, not folklore. Cornell's Iroquois White Corn Project and multiple peer-reviewed studies (Postma & Lynch 2012 on complementary rooting; Zhang et al. 2014 on intercropping yield; Mt. Pleasant 2016 on Indigenous polyculture productivity) have shown that a properly grown Three Sisters plot returns more total calories and more balanced nutrition per acre than the same land in corn monoculture — often 10–30% more biomass and dramatically higher protein and vitamin A per acre because the three crops share light, water, and nutrients on different timelines and root depths. It is one of the best-documented cases of over-yielding polyculture in the temperate world.

How to plant it, home-garden scale. Build a low mound (a 'hill') about 18 inches across and 6 inches tall, spaced 4 ft apart in both directions. Warm the soil to at least 60°F. Plant 4–5 corn kernels in the center of each mound, about 1 in deep. When the corn is 4–6 in tall (usually 2–3 weeks later), plant 3–4 pole beans in a ring around the corn, 6 in out from the stalks. A week or two after that, plant 2–3 winter or summer squash seeds around the outer edge of the mound. That staged sowing matters — beans planted with corn out-race and strangle it, and squash planted first shades out the corn.

Variety choices are what make or break it in a modern garden. Use a strong-stalked flour, flint, or dent corn ('Iroquois White', 'Bear Island Chippewa Flint', 'Cherokee White Eagle', 'Hopi Blue') — modern sweet corn is too short and too weak-stalked to hold beans. Pair it with a true pole bean, not a bush bean ('Cherokee Trail of Tears', 'Genuine Cornfield', 'Rio Zape'). For the third sister use a heirloom winter squash or pumpkin with running vines ('Seminole', 'Cushaw', 'Hidatsa Shield Figure', 'Long Pie'). Plant at least a 10 ft × 10 ft block — corn is wind-pollinated and needs multiple rows to set seed.

Respect where this comes from. The Three Sisters is a gift from Indigenous farmers who bred these specific cultivars over thousands of years and share the practice today through seed keepers like Rowen White (Sierra Seeds), the Indigenous Seed Keepers Network, and Braiding Sweetgrass author Robin Wall Kimmerer. When you can, buy seed from Indigenous-owned seed companies (Ute Mountain Ute Farm & Ranch Enterprises, Native Seeds/SEARCH, Onondaga Nation) and name the origin when you teach it.