Learn — Deno’s Garden

The basics of growing plants from seed, and the words the rest of the site uses.

This page is written by Deno’s Garden in general terms. It is not quoted from a source and is not a recipe for any one plant: for that, use the plant's own page, and see How the steps are done for each step in Deno's words.

How a seed works
Why seeds wait, and why stratification works
Kinds of dormancy
Kinds of seed
Plant words
Tips for a first sowing

How a seed works

A seed is a young plant packed for travel. Inside its coat is the embryo, a tiny root and shoot with one or more seed leaves, and a store of food for it to live on until its own leaves can make more.

To sprout, a seed needs water, air and a suitable temperature, and some need light or darkness as well. Taking up water comes first: the seed swells, wakes up and sends out its root. A seed that is kept dry stays asleep however long it waits.

The first leaves to open are the seed leaves, which often look nothing like the plant's later leaves. The leaves after them, the true leaves, are the plant's own shape. Grasses, lilies and their relatives have one seed leaf; most other flowering plants have two; pines and other conifers have several.

Why seeds wait, and why stratification works

If every seed sprouted the moment it fell, many would die. A seedling that comes up in autumn meets winter while it is still tiny, and one that comes up in a dry spell dries out. Dormancy is how a seed waits for a safer time. It is alive, but it will not sprout until it has had a sign that a good season has come.

For many plants from places with cold winters, that sign is winter itself. While a moist seed is chilled, the balance of hormones inside it slowly changes: the one holding it back fades and the ones that start growth build up. It then sprouts in spring, with a whole growing season ahead. Cold moist stratification gives seed that winter in a fridge, on a timetable you choose.

Moist matters. A seed only feels the cold once it has taken up water, so dry seed in the fridge is being stored, not stratified.

Warm moist stratification stands in for summer or autumn. Some seed is shed with an embryo too small to sprout, and the embryo grows only in warmth. Some needs a warm spell and then a winter, which is why some protocols have a warm step before a cold one; outdoors, seed like this often comes up in its second spring rather than its first.

Other signs some seeds wait for are a hard coat worn thin by soil and weather or by passing through an animal (scarification does that job quickly), light reaching a small seed that lies near the surface, and, for some plants of fire-prone places, smoke. Seed from different places or harvests can differ in how deeply it is dormant, which is one reason one plant can have several protocols.

Kinds of dormancy

Seed scientists Carol and Jerry Baskin sort dormancy into five kinds. Knowing which kind a seed has tells you what sort of step it needs.

Physiological: The most common kind. The embryo is fully formed but held back from inside. It is ended by cold or warm moist stratification, sometimes by GA-3, and in some seed by a spell of dry storage.
Physical: A hard, waterproof seed coat keeps water out, so the seed cannot even begin. It needs scarification. Common in the pea, mallow and morning glory families. A quick check: soak the seed overnight. One that swells has let water in; one that stays small and hard still needs its coat broken.
Morphological: The embryo is too small or not finished when the seed is shed. Kept moist and warm, it grows inside the seed until it is big enough to sprout, which takes time rather than any special treatment.
Morphophysiological: Both at once: a small embryo that also has to be released from inside. This seed often needs warm and then cold, sometimes more than once, and is common among woodland wildflowers. It is the seed most likely to take two years outdoors.
Combinational: A hard coat and an inner block together, so it needs scarifying and then stratifying.

Kinds of seed

Seed that keeps dry: Most garden and wildflower seed can be dried and stored for years if it is kept cool and dry. Seed scientists call it orthodox. It still loses vigour with age, so fresher seed sprouts better.
Seed that dies dry: Some seed, mostly large seed from damp places such as acorns, chestnuts and buckeyes, dies if it dries out. Called recalcitrant, it has to be sown fresh or kept cool and slightly damp until sowing. This is why some protocols warn against dry storage.
Dust-fine and small seed: Tiny seed carries little food, so it has to sprout near the light, and many need light to sprout at all. Press it onto the surface without covering it and water from below so it is not washed away.
Large seed: Big seed carries enough food to push up through soil. A common rule of thumb is to cover a seed to about two or three times its own thickness, unless its protocol says to sow on the surface.
Hard-coated seed: Seed with physical dormancy: it needs scarifying before it can take up water.
Seed from berries and fleshy fruit: The pulp around the seed often holds substances that stop it sprouting, and it invites mould. Clean the flesh off before sowing or storing; see Deno on washing seed.
Hybrid and open-pollinated seed: A packet marked F1 is a hybrid of two chosen parents. It grows true itself, but seed saved from it usually gives a mix of different plants. Seed from wild plants and open-pollinated varieties grows into plants much like its parents.

Plant words

The terms used on species pages, protocol cards and the planner, in plain words.

Seeds and sprouting

Germination: A seed coming to life and sprouting: first a root, then the first leaves. "90% in 10–14 days" means 9 seeds in 10 sprouted, taking 10 to 14 days.
Protocol: One recipe for germinating a seed: a list of steps, each saying how long and at what temperature, and the result the source got. Why a plant can have several.
Dormancy: A seed that is alive but will not sprout until something it is waiting for has happened, such as a winter's cold, a summer's warmth or its hard coat wearing thin. Most steps are there to end dormancy. Why seeds wait.
Viability: Whether a seed is still alive and able to sprout. It falls as seed ages, faster if it is kept warm or damp.
Seed leaves (cotyledons): The first leaves a seedling opens, part of the seed itself. The true leaves come next.
Seedling: A young plant just grown from seed.

Steps on a card

Stratification: Keeping seed moist at a set temperature for weeks or months, to stand in for a season. Cold moist is about 40°F, in a fridge, like winter. Warm moist is about 70°F, at room temperature, like summer. Why it works.
Scarification: Breaking through a hard seed coat so water can get in: nicking or sanding it, hot water, or acid.
GA-3: Gibberellic acid, a natural plant hormone. Soaking some seed in it can do the work of a cold spell.
Dry storage: Keeping seed dry for a while before sowing. Some seed needs this, and for some it is fatal; the protocol says which.
Sow on the surface: Some seed needs light to sprout, so it is pressed onto the soil, not covered.

How the steps are done has Deno's own instructions for each.

Dates

Last frost date: The day in spring after which nights in your area usually stop dropping to freezing (32°F). Tender seedlings go outside after it. The planner gives the median date, when frost has ended in half of years, and a later 1-in-10 date, after which frost comes only one year in ten.
Plant out: Move seedlings from their pots into the garden, after the last frost.

Raising seedlings

Prick out: Move seedlings from the pot they sprouted in into pots of their own, usually once they have true leaves.
Damping off: Seedlings that suddenly collapse, rotted at soil level by a fungus. Clean pots, fresh seed-starting mix, moving air and not overwatering all help prevent it.
Harden off: Get indoor seedlings used to sun and wind before planting out, by setting them outside for a few hours at first and a little longer each day, over about a week.

Kinds of plant

Annual: Grows, flowers, sets seed and dies in one year.
Biennial: Takes two years: leaves in the first, flowers and seed in the second, then dies.
Perennial: Lives for three years or more. A herbaceous perennial dies down to the ground each winter and comes back in spring; a woody one (a shrub or tree) keeps its stems.
Forb: A soft-stemmed flowering plant that is not a grass. Grass-like plants are graminoids.
Subshrub: A low plant that is woody at the base and soft above.
Bulb: A plant that stores food underground in a swollen bud, like a tulip or onion. Many are slow from seed: years from sowing to the first flower.
Geophyte: Kew's word for a plant that dies back to an underground part and waits there through winter or drought. A bulbous geophyte grows from a bulb, a tuberousone from a tuber or corm, and a rhizomatous one from a creeping underground stem.
Helophyte: A marsh plant, rooted in wet ground or shallow water with its leaves in the air.
Liana, climber: A plant that climbs: a liana is a woody climber, a climber any plant that climbs.
Epiphyte, lithophyte: A plant that grows on another plant (epiphyte) or on bare rock (lithophyte) rather than in soil.
Monocarpic: Flowers once and then dies, even if it took several years to get there.

On a species page

Hardiness zones: USDA zones, numbered 1 to 13 by how cold the coldest winter night usually gets; 1 is the coldest. "Zones 3–9" means the plant survives winters in those zones.
Native range: Where the plant grows wild.
Genus and species: The two-part Latin name. The first word, the genus, is a group of close relatives, like Quercus for the oaks; the second picks out one of them, as in Quercus alba, white oak. A synonym is another Latin name that has been used for the same plant.

Tips for a first sowing

Start with good seed. Fresh seed from a reliable supplier, or from your own plants, sprouts best. Keep spare seed sealed, cool and dry; a jar in the fridge works.
Label everything with the plant's name and the date you sowed it. You will not remember.
Use clean pots and a fine seed-starting mix, not garden soil, which packs down and carries the fungi that cause damping off.
Moist, not wet. The mix should feel like a wrung-out sponge. Seed sitting in water rots.
Stratify in the fridge or outdoors. Seed can be stratified in a sealed, labelled bag or pot in the fridge (Deno's paper-towel method is on How the steps are done). Or sow pots in autumn or winter and leave them outside, where the weather does the stratifying; cover them against mice and heavy rain. Check fridge seed often and sow any that has started to sprout.
Give seedlings plenty of light as soon as they are up. On a dim windowsill they stretch, lean and flop; a grow light a few inches above them keeps them short and sturdy.
Be patient. Some seed sprouts over months, and some not until its second spring. Do not throw out a pot that shows nothing yet: keep it moist and give it another season.
Sow more than you need. Not every seed sprouts, and not every seedling survives.