All plants

Corn

Zea mays subsp. mays

Poaceae · grass family

Matures
65–100 days
Harvest
Once · Annual
Sun
6–8+ hrs
Spacing
12 in
Botanical engraving of Corn

Planting window

When to sow, by microclimate — foggier blocks run a different calendar than sunnier ones.

JanFebMarAprMayJun
Foggy●●●
Sunny◐●●
JulAugSepOctNovDec
Foggy◐
Sunny●
Well-suitedMarginalNot suited

Sunlight

How well it does at each level of direct sun per day.

<2 hrsNot suited
2–4 hrsNot suited
4–6 hrsMarginal
6–8 hrsWell-suited
8+ hrsWell-suited
Well-suitedMarginalNot suited

Soil depth

Root room it needs — useful for sizing raised beds and containers.

6–10"Not suited
10–15"Not suited
15–18"Marginal
18–24"Well-suited
Well-suitedMarginalNot suited

Spacing

Room each plant needs — along the row and between rows — for sizing beds.

In-row
12 in
Between rows
36 in

Growth habit

The shape it makes in the bed and how tall it gets — what tells you whether to give it a trellis, a stake, or just room.

Habit
Upright
Mature height
5–8 ft

Stands on its own; the tallest types appreciate a stake in wind.

How to start it

Sow it where it grows, or raise it under cover and set it out — and how far ahead to start the seedlings if it's the latter.

Usually
Direct-sow
Direct-sowWell-suited
TransplantMarginal

Sown straight into the bed it will grow in.

Well-suitedMarginalNot suited

Getting started

How it goes in the ground — how deep to sow or set it, and the soil temperature it needs to wake up. The cold-soil floor is the real limiter for direct-sowing in a foggy SF spring.

Started from
From seed
Ideal soil temp
65–95°F
Sow depth
1–1.5 in
Time to emerge
3–12 days

Germinates between 50–105°F; happiest around 65–95°F.

30°F110°F
IdealWorkable

Pests & diseases

What tends to trouble this crop — what it is, what you'll see, and what to do about it, least-toxic first.

Corn earworm is managed differently on corn than on other crops: consider not treating at all and simply cutting the damaged ends off the ears at harvest, or apply a few drops of mineral oil to the silks just inside each ear 3 to 5 days after the silks first appear.

Pests11

Aphids
What it is
Aphids have soft pear-shaped bodies with long legs and antennae and may be green, yellow, brown, red, or black depending on the species and the plants they feed on. A few species appear waxy or woolly due to the secretion of a waxy white or gray substance over their body surface.
What you'll see
Low to moderate numbers of leaf-feeding aphids aren't usually damaging in gardens or on trees. However, large populations can turn leaves yellow and stunt shoots; aphids can also produce large quantities of a sticky exudate known as honeydew, which often turns black with the growth of a sooty mold fungus.
What to do
Before planting vegetables, check surrounding areas for sources of aphids and remove these sources. On the other hand, these aphid-infested weeds can sometimes provide an early source of aphid natural enemies.
Source
Armyworms
What it is
Armyworm larvae feed in groups, which distinguishes them from other vegetable pests such as corn earworms and loopers. Markings on newly hatched armyworms are usually hard to distinguish from those of other caterpillars; older larvae have distinct lengthwise stripes.
What you'll see
Armyworms may feed on the crowns of seedlings. On larger plants, armyworm caterpillars skeletonize leaves.
What to do
Handpick. Virus diseases, parasites (Hyposoter and Trichogramma), and general predators may be effective on caterpillars.
Source
Corn Earworm or Tomato Fruitworm
What it is
The corn earworm or tomato fruitworm is a common caterpillar pest of many vegetables and flowers. Newly hatched larvae have several rows of dark bristles on their backs.
What you'll see
Earworms feed on leaves, buds, and flowers of many vegetable crops. They destroy seedlings, bore into lettuce heads and bean pods, make deep watery cavities in fruit, and leave frass.
What to do
Handpick, and avoid spraying with insecticides. Bacillus thuringiensis may kill 40 to 60% of the population but must be applied just after eggs hatch and before caterpillars enter fruit.
Source
Cucumber Beetles
What it is
Adult beetles are shiny with black heads, long antennae, and about 1/4 inch long. Adults may be striped or spotted, depending upon species.
What you'll see
Adults feed on the leaves of many vegetables as well as on soft fruit. Shoots and blossoms may also be consumed.
What to do
Management of cucumber beetles is difficult. The best strategy for most vegetable gardens may be to place protective cloth over emerging plants and remove it when plants are old enough to tolerate damage.
Source
Cutworms
What it is
Cutworms are dull brown caterpillars ranging in length from 1 to 2 inches when fully grown. They curl into a C-shape when disturbed.
What you'll see
Cutworms feed on blossoms and leaves of many ornamental plants and attack most garden crops. They clip off seedling stems near or just below the soil level.
What to do
Cutworms are pests mainly in the spring. Destroy crop residues; keep garden weed-free in winter.
Source
Earwigs
What it is
The adult earwig is readily identified by a pair of prominent appendages that resemble forceps at the tail end of its body. Used for defense, the forceps are somewhat curved in the male but straighter in the female.
What you'll see
European earwigs feed on a variety of dead and living organisms, including insects, mites, and growing shoots of plants. They are voracious feeders on soft-bodied insects such as aphids and insect eggs and can exert significant biological control under some circumstances.
What to do
Management of earwigs requires an integrated program that takes advantage of their habitat preferences. Initiate a regular trapping program.
Source
Flea Beetles
What it is
Their small size, enlarged back legs, characteristic shot-hole damage, and habit of jumping when disturbed make flea beetles easy to identify. There are numerous flea beetle species.
What you'll see
Adults feed mostly on leaves, leaving tiny pits or small holes at their feeding sites. Flea beetles feeding together can cover leaves with bleached, pitted areas or ragged holes.
What to do
Remove debris in the fall to remove any overwintering beetles. Reflective mulches applied very soon after planting and before plants become infected can be helpful.
Source
Seedcorn Maggot
What it is
Seedcorn maggot larvae are small, legless, white maggots usually less than 0.33 inch when full grown; the head end is pointed and the rear is blunt. Adults are dark gray flies about half the size of the common housefly.
What you'll see
Maggots kill germinating seeds and very small seedlings. Once the stand is established and seedlings have developed a few leaves, maggots are unlikely to cause economic damage.
What to do
Cool, wet weather promotes seedcorn maggot infestations. Avoid overfertilization with manure; maggots prefer to lay eggs in rich soil.
Source
Spider Mites
What it is
To the naked eye, spider mites look like tiny, moving dots; however, you can see them easily with a 10X hand lens. Adult females, the largest forms, are less than 1/20 inch long.
What you'll see
Mites cause damage by sucking cell contents from leaves. A small number of mites usually isn’t reason for concern, but very high populations—levels high enough to show visible damage to leaves—can damage plants, especially herbaceous ones.
What to do
Cultural practices can have a significant impact on spider mites. Mid­season washing of trees and vines with water to remove dust may help prevent serious late-season mite infestations.
Source
Thrips
What it is
Most adult thrips are elongate, slender, minute (less than 1/20 inch long), and have long fringes on the margins of both pairs of their long, narrow wings. Immatures (called larvae or nymphs) are oblong or slender and elongate and lack wings.
What you'll see
Thrips feeding on plants can damage fruit, leaves, and shoots and very noticeably affect plants’ cosmetic appearance. However, thrips rarely kill or threaten the survival of trees and shrubs.
What to do
Thrips species that feed on many different plant species often move into gardens and landscapes when plants in weedy areas or grasslands begin to dry in spring or summer. Avoid planting susceptible plants next to these areas, and control nearby weeds that are alternate hosts of pest thrips.
Source
Vegetable Leafminers
What it is
Adult leafminers are small, active, black flies often with a prominent yellow triangle between the bases of the wings. The head behind the eyes is mostly black.
What you'll see
Leafminers attack many different vegetable and flower hosts, including cole crops, cucurbits, tomatoes, peas, beans, aster, begonia, dahlia, impatiens, lily, marigold, petunia, and verbena. Adult female leafminers puncture leaves and sometimes petals to feed on exuding sap.
What to do
Leafminers rarely require treatment in gardens. Clip off and remove older infested leaves.
Source

Diseases4

Bacterial Soft Rot of Corn
What you'll see
Bacterial soft rot first appears as rapid desiccation of the youngest leaves. A soft, watery rot of leaf tissue occurs inside the leaf whorl.
What to do
The disease is most commonly encountered in sprinkler-irrigated gardens or when unseasonal rains occur. If soft rot develops, avoid overhead sprinklers.
Source
Common Rust on Corn
What you'll see
Common rust causes pustules that may appear on any aboveground part of the corn plant but they are most abundant on leaves. The pustules, which may erupt and become powdery, occur nearly simultaneously on both leaf surfaces.
What to do
Common rust is favored by cool temperatures and high humidity or overhead sprinklers. Some resistant varieties may be available.
Source
Common Smut of Corn
What it is
Head smut may be confused with common smut. However, the vascular bundles within the galls of head smut readily differentiate head smut from common smut.
What you'll see
Common smut is easily recognized by the tumorlike galls that form on any aboveground plant part. Galls at first are a glistening, greenish white to silvery white.
What to do
Remove and destroy tumorlike growths as soon as noticed; keep the black powder in galls from getting into the soil. Plant early as common smut becomes more prevalent in later harvests.
Source
Head Smut of Corn
What it is
Head smut may be confused with common smut. However, the vascular bundles within the galls of head smut readily differentiate head smut from common smut.
What you'll see
Head smut is characterized by large smut galls that replace ears or tassels. The galls are first covered by fragile, creamy white membranes that eventually rupture to release masses of dark brown spores.
What to do
Spores from the head smut fungus survive in the soil for long periods. Resistant varieties may be available.
Source

Sources

Every figure above is backed by these.