Why do some seeds sprout in 3 days while others «sit» for weeks

Beginner gardeners, especially those planning to spend minimal time at the cottage or in the garden, often optimistically schedule their garden work like this: one weekend I’ll sow seeds of all crops, exactly a week later they will all sprout together, after another two to two and a half weeks I’ll already be able to prick out overcrowded seedlings, after three to four weeks I’ll apply a general feeding, and so on.



In reality, such beginners may face an unexpected surprise. Yes, you can sow all seeds “in bulk” at the same time, but while seedlings of some plants really appear in just a few days, others may take twice as long to germinate, and some may need several weeks or even more than a month. Then you will have to urgently shift your seemingly perfectly planned schedule and divide picking, transplanting, feeding, and other work for different crops into several stages, which can seriously disrupt your plans.

To avoid this, let’s figure out in advance why different seeds behave so differently at the very first stage of development — so the speed of their germination does not become a surprise for you and you can plan your gardening work more successfully in the future.

Let us immediately determine that the reasons for differences in seed germination time (from several days to several weeks) can be divided into two groups — agrotechnical and biological.
 

Among the main factors affecting seed germination speed are the biological characteristics of plants and the quality of the seed material. Which characteristics influence the process and how?

Seed size. Small seeds, as a rule (but not always!), germinate faster than large ones. This is because they absorb moisture faster, which is the main signal for the germination process to begin, require fewer nutrients for germination, and reach the light faster since they are usually sown more shallowly.

Seed coat thickness. Seeds with a thick and hard coat (for example parsley, dill, legumes, coriander, lupine, sweet pea) absorb moisture slowly. Until water penetrates inside and softens the coat, the germination process will not begin.



Presence of germination inhibitors in the seed coat. Some plants (celery, dill, parsley, carrot, etc.) contain so-called growth inhibitors in their seed coats, which prevent seeds from germinating under unfavorable conditions such as cold or excessively dry soil. Such seeds need a long time and suitable conditions (moisture, temperature, etc.) for these substances to be washed out before they can leave the dormant state. Most often these inhibitors are essential oils, hormones, and similar compounds.

Seed germination energy. Seeds can условно be divided into slow-germinating (for example carrot, parsley, onion) and fast-germinating (radish, lettuce). Germination energy usually refers to the force with which the sprout “pushes” outward. The higher this energy, the faster and more uniformly seedlings appear — and this is simply a physical characteristic determined by nature itself. Sometimes it is indicated as a percentage for certain seeds (for example, peas average 85–95%, while parsnip and carrot are only around 40–70%).

Seeds of many crops also require a mandatory dormant period before germination, corresponding to their overwintering in cold soil in nature — without this condition they may not sprout at all. This applies to most perennial flowers (aquilegia, aconite, delphinium, lavender, primrose, phlox, gentian, peony, rudbeckia, clematis, euphorbia, lupine, poppy, calendula, heuchera, veronica, iberis, catnip, buddleia, baptisia, milkweed, helianthemum, heliopsis, ornamental onion, St. John’s wort), conifers (spruce, pine, juniper), medicinal and aromatic plants (lavender, mint, thyme, lemon balm)…



Seed freshness. Most crops have specific seed storage periods, after which they lose their germination ability. Such old seeds partially or completely lose their original germination energy, sprout unevenly, or fail to sprout at all. Keep in mind that storage life differs greatly between crops and deteriorates at different rates — for example pumpkin, zucchini, bean, cabbage, and many cucumber and tomato seeds can still germinate in the fifth or sixth year after harvest, while freshly harvested seeds of parsnip, celery, scorzonera, asters, gazanias, delphiniums, and phloxes should be sown no later than the following season, otherwise you may not get any seedlings at all.

Proper storage conditions are also extremely important for seed germination — if not observed, seeds will “spoil” earlier and fail to produce normal seedlings.

Seed pelleting. Finally, some manufacturers pellet seeds before sale to increase their size for more precise sowing, speed up germination, protect them from diseases and pests, and reduce fertilizer costs. Pelleting means covering seeds with an artificial nutrient and/or protective coating, which should never be soaked before sowing — it must dissolve on its own already in moist soil to perform its function.

If you choose seeds with the fastest germination for your beds, remember that different crops differ not only in seed germination speed but also in the speed of subsequent seedling growth. For example, green onion, cress, radish, dill, spinach, and leafy lettuces usually develop the fastest, while celery, lavender, eustoma, petunia, and others develop slowly.
 

In addition to biological reasons for different germination speeds, germination is of course influenced by agrotechnical factors.

Any seed germinates only when adequately supplied with moisture and oxygen under suitable temperature and light conditions. At the same time, different crops require these conditions within their own ranges, and if conditions are violated, seeds germinate much more slowly than normal or may fail to germinate at all.

Simply put, small seeds should not be deeply buried during sowing — their sprouts simply won’t have enough strength to reach the soil surface. Seeds that germinate in the light also cannot tolerate deep “burying.” Soil that is too dense or waterlogged blocks oxygen access, causing seeds to “suffocate” and rot. If the soil is too dry, the seed coat will not swell and dissolve in time for the sprout to break through it, even if metabolic processes inside the seed have already started. Keeping heat-loving plants cold already at the seed germination stage is also not a good idea, because low temperatures reduce water absorption and activation of metabolic processes. And so on — we hope the idea is clear.



The good news is that some of the above-mentioned factors (both biological and agrotechnical) can be influenced if you want seeds to sprout faster.

For example, you can speed up germination of seeds with thick and hard coats through scarification (scratching, nicking, rubbing seeds with sand or abrasive particles), alternating treatment with cold and hot water, or acid treatment followed by thorough rinsing. Seeds that require a long cold period before germination can be “tricked” by stratification — keeping them in a moist substrate (sand, peat, vermiculite) at temperatures of 0–5°C (for example on the lower shelf of a refrigerator) for several weeks or months depending on the crop. Bubbling helps quickly saturate slow-germinating seeds with oxygen and deactivate germination inhibitors — treatment in water at 20–25°C intensively saturated with oxygen or air (for example using an aquarium compressor) for 12–24 hours. And finally, almost all types of seeds benefit from pre-sowing soaking in warm water (or even better — water with growth stimulators) for several days, which helps soften the coat, wash out growth inhibitors, saturate seeds with moisture, and increase germination energy.
 

Approximate timeframes for planting different crops – when to expect the first sprouts (of course, with proper seed quality/freshness and under optimal germination conditions).

Radish, arugula, mustard, cress, dill, leaf lettuce, and turnip produce seedlings 3–5 days after sowing.

Cucumbers, zucchini, cabbage, beetroot, radish, beans, peas, corn, spinach, chard, and borage usually germinate in 5–7 days.

Pepper, tomatoes, eggplants, pumpkin, sorrel, bulb onion, garlic, Welsh onion, and chives require more time — from 7 to 14 days.

Celery, parsley, strawberry, rhubarb, monarda, mint, rosemary, thyme, fennel, tarragon, marjoram, coriander, chervil, oregano, anise, and hyssop appear in 14–21 days.

Carrot and parsnip have the longest period — from 20 to 30 days before seedlings appear.



Marigold, zinnia, stock, sweet alyssum, matthiola, iberis, and amaranth produce seedlings in 5–7 days.

Sunflower, aster, calendula, Drummond’s phlox, rudbeckia, oxeye daisy, dimorphotheca, sweet pea, annual dahlia, Shabo and Chinese carnations, as well as gaillardia germinate in 7–10 days.

Ageratum, cornflower, balsam, godetia, delphinium, morning glory, clarkia, cosmos, pelargonium, petunia, echinacea, and flowering tobacco appear in 10–14 days.

Eschscholzia, nasturtium, snapdragon, and balsam require 14–16 days before seedlings appear.

Lavender, verbena, lavatera, salvia, hollyhock, hellebore, globeflower, gentian, and aquilegia have a longer period — 15–20 days.

Seed germination times are approximate and averaged. If you carry out various types of pre-sowing preparation in advance (soaking, scarification, bubbling, sprouting, stratification, warming, treatment with biostimulants, etc.), these periods may shift — sometimes almost by half.

Also remember that almost all crops have early and late varieties, which can also greatly affect the germination speed of their seeds.

Fast-germinating seeds are not “worse” or “better” than those that sprout slowly. Before sowing any seeds, simply make sure of their freshness and quality, and strictly follow the germination algorithm, which can vary greatly between different crops — and then all your seedlings will appear evenly and on time.