Anise

A soil-borne fungus (*Sclerotium rolfsii*) that attacks plant stems right at the soil line during hot weather. It hits over 500 different plant species. Two telltale signs to look for: white fan-shaped fungal growth on the lower stem, mulch, and soil surface, and tan-brown spherical sclerotia (they look like mustard seeds) on infected tissue. Most active during sustained heat with humid conditions.

Triggers: Optimal at 86°F (30°C) soil and air temperature with humid conditions. Inactive below 70°F. Most damaging during sustained mid- to late-summer heat waves. It extends further north in warmer-than-normal seasons.

Risk fades when: Sustained cooler weather — highs below 80°F and overnight lows below 70°F for 5+ days — reduces fungal activity. The sclerotia (resting bodies) persist in soil for years, so resolution is seasonal, not curative.

A seedling killer caused by several different fungi working together. It hits vegetables, flowers, herbs, microgreens, and cover-crop seedlings the same way — seeds rot before they emerge, or young seedlings collapse right at the soil line. Wet seed-starting mix and poor airflow in seedling trays are the classic conditions.

Triggers: Wet soil or starting mix, poor drainage, seedlings packed too tightly, contaminated trays or media, and stagnant air all favor damping-off.

Risk fades when: Drying the soil surface and improving airflow slows new spread. Collapsed seedlings don't recover, but the rest of the tray can be saved.

A water mold (not a true fungus) that attacks roots and crowns in waterlogged soil. It's most dangerous in heavy, poorly drained soil after extended rain — basically any time water sits around plant roots for days.

Triggers: Pythium infects from 50-95°F as long as the soil stays saturated. Phytophthora capsici is most active at 75-85°F. What matters most is how long the soil stays waterlogged, not just whether it rained.

Risk fades when: Risk fades when soil returns to field capacity (normal drained moisture). How long that takes depends on your soil — sand drains in hours, clay can take days.

Aphids are soft-bodied sap-sucking insects that cluster on tender new growth. Most established plants tolerate moderate populations and will outgrow damage on their own, but aphids are the most important plant virus vectors in the garden, transmitting more than 100 plant viruses including potato leafroll, cucumber mosaic, and turnip mosaic. Honeydew excreted while feeding supports sooty mold growth and attracts ants that protect aphids from natural enemies.

Triggers: Optimal development at ~75°F (green peach aphid) per UC IPM Floriculture; melon aphid develops fastest above 75°F. Many species heat-intolerant above 90°F and crash in mid-summer. Soft new growth and over-fertilization with high N favor population buildup. Females give live birth parthenogenetically most of growing season — one generation in ~1 week under optimal conditions.

Risk fades when: Per UC IPM and Clemson HGIC, populations crash in mid-summer heat (>90°F) for many species, return in cooler conditions

Flopping happens when stem strength can't support the plant's mass — usually because the plant grew too fast, didn't get enough sun to build strong stems, or got too much nitrogen which pushes soft leafy growth at the expense of structural strength. Rain and wind compound the problem by weighing down soft tissue. Some plants are inherently floppy — peony, dahlia, delphinium, large mum, tall sunflower — and need staking from the start. Others normally hold themselves up but flop when grown in shade or overfed. Stake early (in spring before plants have grown into their support) rather than late (when stems are already bent and a stake just preserves the deformity). Pruning or pinching tall plants when young encourages branching and reduces flop risk.

Triggers: Per MSU Extension: full sun produces sturdy self-supporting plants; shade or over-fertilization produces soft top-heavy growth. Rain and wind accelerate flop. Plants with naturally heavy blooms (peony, dahlia, large lily, hollyhock) need staking from start.

Risk fades when: Stake early in spring before too much growth. Late staking just preserves the bend. Pinch tall plants when young to encourage branching. Reduce nitrogen feeding if plants are floppy and overgrown.

Covers parsley, dill, cilantro, lovage, and angelica leaf-spot pressure from host-family fungi — especially Septoria on parsley and cilantro. Causes small tan to brown leaf spots, yellowing, and defoliation during wet, humid, splashy weather.

Triggers: Wind-driven rain, dew drips, overhead irrigation, tools, handling wet plants, infected debris, and seedborne inoculum all drive spread.

Risk fades when: Spread depends on wet foliage, splash, dew, and wet-plant handling. A dry period lowers immediate new infection risk.

Lodging is the permanent displacement of a plant from vertical, and it comes in two distinct forms that call for different fixes. In stem lodging the stalk buckles or snaps low down, and the culprit is a stem too tall, too soft and too weak for its own head - the classic product of excess nitrogen, crowding, or shade. In root lodging the stem stays intact and the whole plant tips over because the soil-root anchorage let go. That second one is a weather event as much as a growing error: rain softens the ground around the base, then wind supplies the leverage, and once the bending force at the base exceeds what the roots can hold, over it goes. Wet, sandy or recently irrigated soil makes root lodging far more likely, which is why overhead sprinkling before a storm is such a bad idea - it wets the anchorage and drives stem elongation at the same time. NDSU Extension takes lodging seriously enough to cap their nitrogen recommendations for sunflower because of it. The window of greatest danger is late: tall plants carrying heavy heads or full seed, in the weeks before harvest. Neither form recovers. A lodged plant may curve back upward at the tip, but the stem stays down.

Triggers: Two mechanisms. Root lodging is the permanent displacement of the plant from vertical due to failure of the soil-root system, without stem failure (Pinthus 1973); it is usually associated with rain, which weakens anchorage near the stem base, combined with wind acting on the upper plant to produce a bending moment that exceeds the root failure moment. Stem lodging is when the stalk breaks at or below the head- or ear-bearing node. On moist or sandy soils the chance of root lodging exceeds that of stem lodging, because soil shear strength is reduced; sprinkler irrigation has been shown to promote lodging by elongating stems, weakening anchorage when water is retained in the topsoil, and thickening the canopy. NDSU Extension: excessive wind resulting in sunflower root lodging or stalk breakage does not happen every year, but lodging is a concern of most sunflower growers, and the upper values of nitrogen rate recommendations were reduced specifically to limit lodging loss. Clemson and UGA Extension list lodging in sweet corn as a result of too much nitrogen and wind damage. Crowding and shade weaken the basal stem by reducing light reaching the lower canopy. Wheat is most prone to lodge in the two to three months preceding harvest; sunflower is most prone from early head development onward.

On Anise: Rich soil or exposed windy sites can topple the slender stems.

Prevention: Avoid excess nitrogen and plant in a sheltered bed.

Risk fades when: Lodging is by definition permanent - a lodged stem will not stand back up, though the growing tip often curves upward again, leaving a bent plant. Stake or support what you can while the soil is still soft, tying loosely to a stake driven clear of the root plate. Prevention is mostly restraint with the fertiliser can: excess nitrogen produces tall, soft, weak stems and is the single most controllable cause. Grow tall plants in full sun rather than shade, thin or space them so light reaches the lower stem and thickens it, and avoid overhead watering when wind is forecast, since wet soil combined with wind is the classic root-lodging setup. Shelter exposed beds. Choose shorter or dwarf cultivars where wind is a regular problem. A lodged crop can usually still be harvested, but expect losses and disease where stems and heads lie on wet ground.

A plant will trade away its seed crop to stay alive. The reproductive stage is far more sensitive to drought than the vegetative stage, and the damage is done in a narrow window - during flowering and while seed is filling. Peer-reviewed work describes the sequence: drought reduces the amount of viable pollen, hinders pollen tube growth so fertilisation fails, makes flowers less attractive to pollinators, and reduces nectar. Fewer flowers are set, and those that set are aborted. Iowa State Extension quantifies the field consequence in beans - drought can reduce pod number by up to twenty percent through flower and pod abortion, and seeds per pod and seed size fall too, though less sharply than pod number. Drought also shortens the fill period by forcing earlier maturity, so seeds finish small and light. Legumes take a second hit that is easy to miss: in dry soil the root nodules stop fixing nitrogen, because they lack both moisture and carbohydrate from the plant. If the dry spell is brief, fixation resumes. So the plant that looks merely thirsty in July is quietly deciding how many seeds you will harvest in September.

Triggers: Iowa State Extension: drought can reduce pod number by up to 20 percent as a result of flower and pod abortion; seeds per pod and seed size are also affected but to a lesser extent than pod number; drought stress often results in earlier maturity, shortening the grain-filling period and resulting in lower seed weights and yields. In dry conditions legume nodules cease nitrogen fixation because of lack of soil moisture and lack of carbohydrate supply from the plant; if water deficits are short-lived, nodule nitrogen fixation can resume. Peer-reviewed literature: the reproductive stage of growth is more sensitive to drought than the vegetative stage, resulting in fewer flowers and poor pod or fruit set, which decreases seed numbers; drought stress negatively affects pollination by decreasing the amount of viable pollen grain, decreasing pollen germination, hindering pollen tube growth to impair fertilisation, increasing the unattractiveness of flowers to pollinators, and decreasing nectar production. Flowering and seed-filling stages are among the most disrupted by drought. Reported yield reductions of 39 to 45 percent from four days of visible moisture stress during the second to fourth week of seed fill in soybean. NOTE ON EVIDENCE: the quantitative figures come from soybean and common bean research; anise is included as a seed crop subject to the same flowering-and-fill drought sensitivity, without a species-specific source.

On Anise: Drought during flowering and fill shrinks the seed crop.

Prevention: Keep moisture even through bloom and seed development.

Risk fades when: Aborted flowers and shed pods do not come back, and a seed that filled short stays short. What matters is where you spend the water. If irrigation is limited, prioritise the flowering and seed-fill window over every other stage - the vegetative plant tolerates drought far better than the flowering one does. Water deeply and evenly rather than lightly and often, so the root zone never swings from wet to dry. Mulch to buffer the swing. Where heat and drought coincide, as they usually do, expect the effects to compound. For beans and other legumes, remember the dry soil also shuts down nitrogen fixation in the nodules, so a drought-stressed crop is short of nitrogen as well as water; a short deficit is recoverable and fixation resumes.

Seed-spice crops like cumin, caraway, anise, and coriander are grown for the dried seed, and the last stage of the season - when the flower umbels finish ripening and dry down - decides the harvest. When that window turns humid or wet, the seed cannot dry properly on the plant: it stays green and soft, molds or discolors in the head, sprouts in place during a warm damp spell, or shatters and drops before it can be gathered. These crops evolved in hot, dry summer climates, so a wet late summer is the single biggest threat to a clean seed crop. The plant itself often looks healthy; the loss is entirely in the seed, which finishes low in aromatic oil, poor in germination, and prone to going musty in storage. The fix is cultural and about timing: grow in full sun with good airflow, and cut the whole umbel as soon as it begins to turn brown and dry rather than waiting for every seed, finishing the drying under cover.

Triggers: Seed-spice umbellifers (cumin, caraway, anise, coriander) are warm-season crops that ripen seed best in hot, dry weather. Humid or wet conditions during the ripening-and-dry-down window prevent the seed from curing on the plant, leading to molding, discoloration, pre-harvest sprouting, or shattering. Cumin in particular needs a long frost-free season with dry weather during ripening. NOTE ON EVIDENCE: scoped to the apiaceae seed-spice crops that share this warm-dry ripening requirement; the mechanism is the general seed-maturation-in-wet-weather failure common to dry-seed crops, without a species-specific quantitative source.

Risk fades when: Seed that has already molded, sprouted, or shattered does not recover. The practical control is harvest timing: cut whole umbels as soon as they begin to brown rather than waiting for every last seed to dry on the plant, then finish drying them in a warm, airy, protected spot. Growing in full sun with generous spacing for airflow lowers the humidity around the ripening heads in the first place.

A powdery mildew of carrot-family herbs such as dill, parsley, fennel, and cilantro. It coats leaves and stems with a white-to-gray powdery growth, and heavy infection yellows and weakens foliage and taints flavor. Unlike most leaf diseases it spreads in warm, dry weather with high humidity, and does not need leaf wetness.

Triggers: Powdery mildew thrives in warm, humid conditions and, unlike most fungi, does not require leaf wetness; rain actually suppresses it. Shade and crowding raise risk.

Risk fades when: Sustained heat above about 90°F slows powdery mildew. Two such days reduces active pressure; existing colonies remain on infected leaves.