Many -even annoying- weeds are edible. You do not need to sow them, and still find them in abundance.
Make stew, use them in salads, soups, pesto, omelets, quiche, pizza, etc.
Some weeds as nettle and dandelion is widely known to be suitable for consumption. Others are often surprising discoveries.

Edible does not necessarily mean good. But tastes differ. Are chicory, syringes, spinach, radishes ... a delicacy, or rather bweuk ....? Great, here is some stuff ...

Basically, you can eat the stinging nettle (Urtica dioica) and small nettle (Urtica urens) also raw if you roll up the leaves frequently to break the fire hairs. A risky and time consuming task. So rather (use gloves) put them briefly in boiling water. Use the terminal bud and the (four) upper leaves. The other leaves are also edible, but some older and tougher. And you will find there is more than enough. Fits well in pesto, cheese and bread.
Nettle seeds contain 10% oil. They can be dryed and pressed. Fibers are useful for muslin.
The leaves and flowers of all kinds are edible. Including non stinging Deadnettles (Lamium) and purple (Lamium purpureum), white (album L.), spotted (L. maculatum) and the yellow archangel (L. galeobdolon).

Japanese knotweed (Fallopia japonica, synonym: Polygonum cuspidatum) is an invasive species that is now rampant here. Goats, cattle and pigs feast of it. And for us it is edible. They taste like rhubarb, a vegetable from the same plant family. And you can also prepare so. Harvest shoots between 15 and 25 centimeters. The slightly thicker you better peel first.

Ground ivy (Glechoma hederacea) is a strong, rampant groundcover, with beautiful round leaves and purple flowers. If you find one, you will find many. Little bitter, but good on a cheese sandwich. Formerly used instead of hops to brew beer. (Like gale.)

Hairy (Galinsoga quadriradiata) and bald galinsoga (G. parviflora) can be found almost everywhere, especially in the garden. Young leaves and stems (before flowering) taste well in soups, stew, salad and as spinach.

Sorrel (Rumex, multiple species, most of which are edible) has large, oblong leaves, like spinach to use in salads, quiche, soups and sauces. A famous dish made with sorrel (Rumex acetosa) is eel in green sauce.

Bulrush or cattail (Typha latifolia L.) grows along the waterfront, recognizable by the reed cigars. Young shoots of bulrush have inside a white stem that is even raw edible. The rhizomes (underwater) are very nutritious. Harvest only in clean water. Wash and heat the roots (due to possible bacteria). The starchy inside you can eat after cooking or baking.
Young buds of the bulrush, you can eat like asparagus. The pollen of the flower is used as flour.
Seeds can also be eaten (burn off the fluffy part , dry or roast the seeds).

The young shoots of the cleavers (Galium aparine), you can eat after a short dip in boiling water to remove the adhesive strength of the leaves.  With the roasted seeds you can make coffee. And tea from the leaves and stems. (Also useful as a cheese starter and to clean.)

The Romans used to eat common mallow (Malva sylvestris and M. neglecta, now a common roadside plant) as a vegetable: braising or steaming. Seeds, seed pods and flowers are also edible.
Of silverweed (Potentilla anserina) you can dig out the roots and eat them.

Plantain (Plantago media ruige-, narrower P. lanceolata and larger P. major) is raw edible and contains many vitamins. It can be used in stead of lettuce or spinach. The seeds may be ground into powder and added to flour in order to serve as a flour.

Angelica (Angelica archangelica) has sweet stems and leaves. The stem is used as candied fruit (also in cakes, puddings, jam and liqueur ..). Fresh leaf and stem may be harvested in the spring and summer before flowering. You can also dry them. Just like the seeds.
If the plant is cultivated for the roots you can cut away flowering stems so the nutrients go as much as possible to the root system. Harvesting the roots is done in the autumn of the second year.
Sweet essential oil is extracted by steam distillation from the roots or from the fruits and seeds as the basis for perfume and liqueur (Vermouth).

Edible as spinach or lettuce: the goosefoot family (Chenopodium) lambsquarters (Ch. album) and Good King Henry (Ch. bonus henricus.) (Even (flour  of) the seeds). Also saltbush (Atriplex): orache (A. hortenis).

Chickweed (Stellaria media) is an excellent edible ground cover.
Elder: see edible ornamental plants.
Shepherd's purse (Capsella bursa-pastoris) has edible leaves, flowers, seeds and roots.
Bindweed (Calystegia sepium) and field bindweed (C. arvensis) have edible leaf, flower, seed and root (washing and steaming).
Sow thistle (Sonchus) use the young leaves, the yellow flowers of gorse.
Evening primrose (Oenothera Biennis) has edible roots, leaves, seeds and flowers.
Young leaves of tansy (Tanacetum vulgare) are traditionally in Diest baked in pancakes.
Of redshank (Persicaria maculosa) the leaves are used like spinach, or in quiche.

Dandelion (Taraxacum officinalis): roast the root for coffee and eat young leaves as lettuce (possibly bleaching). Flowers are used to make (before seed production) marmalade. The stem is toxic.
Ripe rowan (Sorbus aucuparia L.) is edible. Also suitable for coffee.
Coltsfoot (Tussilago farfara) is coming soon after the winter. Young leaves and flower buds are usable.
(Butterbur (Petasites hybridus) is toxic.)
From common hogweed (Heracleum sphondylium) the cooked roots would be edible. The young leaves and shoots are edible. Not to be confused with giant hogweed (Heracleum mantegazzianum), which can cause burning blisters! (The young shoots and leaves are still harmless.)

Lots of seeds of berries and fruit are poisonous. Degradability and accumulation of the poison are important, and the dose. This also applies to the toxic potatoes and tomatoes we eat a lot and often. Cooking helps.
You can best due to parasites first heat all plant parts from the water before you eat them.

Just pick which you are sure that it is edible. Otherwise, prefer yaking a photograph of a plant for determination. Learn to identify (and read) well. Use reliable and recent sources. Base your knollage never just a photo. Nor on one single source on the web (anyone can publish anything on it.)

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