Elymus is a genus of grasses in the family Poaceae. Its most readily observed trait is a defined flowering period from June to August. Flowering heads appear in that window and are the key stage for seed production and identification. Gardeners often note the flowering period when planning maintenance or seed collection.

Elymus is a genus of grasses in the Poaceae family that flowers from June to August.

Elymus

Elymus (Poaceae) | Grass flowering June-August

Elymus arenarius is a grass adapted to sandy coastal sites and used for stabilising dunes. It prefers full sun on sandy, well‑drained ground and tolerates dry to moderate soil moisture and exposed, windy conditions. Flowering occurs June to August, and plants are most often deployed where sand movement must be controlled.

Sand ryegrass (Elymus arenarius) thrives on sandy coasts, preferring full sun and well‑drained, dry to moderate soils.

https://en.wikipedia.org/wiki/Leymus_arenarius

Leymus is a genus of plants in the grass family Poaceae (Gramineae). It is widespread across Europe, Asia, and the Americas.Leymus aemulans - Xinjiang, Central Asia Leymus ajanensis - Siberia, Russian Far East, Alaska Leymus akmolinensis - Siberia, Kazakhstan, European Russia Leymus alaicus - Central Asia Leymus altus - Xinjiang Leymus ambiguus - mountains of western US Leymus angustus - Altai wild rye - China, Mongolia, Siberia, Central Asia Leymus arenarius - lyme grass - Europe Leymus aristiglumus - Qinghai Leymus × buriaticus - Siberia Leymus cappadocicus - Turkey, Afghanistan Leymus chinensis - China, Korea, Mongolia, Amur, Siberia Leymus cinereus - basin wild rye - western North America Leymus condensatus - giant wild rye - California, Baja California, Coahuila Leymus crassiusculus - Qinghai, Shanxi Leymus divaricatus - Kazakhstan Leymus duthiei - China, Korea, Japan, Nepal, northern India Leymus erianthus - Chile, Argentina Leymus × fedtschenkoi - Kyrgyzstan Leymus flavescens - Alberta, northwestern US Leymus flexilis - Kyrgyzstan, Kazakhstan Leymus flexus - Qinghai, Gansu, Shanxi Leymus innovatus - from Alaska and Northwest Territories to South Dakota and Ontario Leymus × jenisseiensis - Siberia Leymus karelinii - Xinjiang, Central Asia, European Russia Leymus komarovii - China, Mongolia, Korea, Russian Far East Leymus kopetdaghensis - Turkmenistan Leymus lanatus - Kyrgyzstan, Tajikistan, Afghanistan Leymus latiglumis - Uzbekistan Leymus leptostachyus - Qinghai, Xinjiang Leymus mollis - colder parts of Asia and North America Leymus multicaulis - European Russia, Central Asia, Xinjiang Leymus × multiflorus - California Leymus mundus - Tibet, Gansu Leymus nikitinii - Turkmenistan Leymus oblongolemmatus - Qinghai Leymus obvipodus - Qinghai Leymus ordensis - Siberia Leymus paboanus - Russia, China, Mongolia, Central Asia, Afghanistan Leymus pacificus - California Leymus paucispiculus - Qinghai, Gansu Leymus pendulus - Qinghai Leymus pishanicus - Xinjiang Leymus pluriflorus - Qinghai, Gansu Leymus pseudoracemosus - Qinghai Leymus pubinodis - Xinjiang Leymus racemosus - mammoth wild rye - Eurasia from Bulgaria to Mongolia Leymus × ramosoides - European Russia Leymus ramosus - Eurasia from Crimea to Mongolia Leymus ruoqiangensis - Xinjiang, Qinghai Leymus salina - western US Leymus secalinus - Siberia, Mongolia, China, Korea, Central Asia, Himalayas Leymus shanxiensis - Shanxi Leymus sibiricus - Russia from Altai Krai to Magadan Leymus × sphacelatus - Tuva Leymus spiniformis - Qinghai, Shanxi Leymus tianschanicus - Iran, Central Asia, Xinjiang, Inner Mongolia Leymus triticoides - creeping wild rye - British Columbia, western US, Baja California, Tamaulipas Leymus × tuvinicus - Siberia Leymus × vancouverensis - British Columbia, Washington, Oregon, California Leymus villosissimus - Yakutia, Magadan, Kamchatka, Alaska, Yukon, Northwest Territories, British Columbia Leymus yiunensis - Xinjiang

Elymus arenarius

Sand ryegrass, sea lyme grass, lyme grass | Elymus arenarius

Elymus canadensis var. glaucifolius is a grass in the genus Elymus that grows to about 0.8 m. It prefers full sun and accepts sandy, loamy or clay soils provided they are moist but well-drained. Originating from North America, it flowers in the UK from June to August. Plant where its mature height will not overshadow lower-growing neighbours.

Canada Wild Rye (Elymus canadensis var. glaucifolius) is a clump-forming grass for full sun and moist, well-drained soils, flowering June to August.

https://en.wikipedia.org/wiki/Elymus_canadensis

Elymus canadensis var. glaucifolius

Canada Wild Rye | Elymus canadensis var. glaucifolius

Elymus interruptus is a grass in the Poaceae family, native to Central Asia. It belongs to the genus Elymus and produces its flowering structures in the UK between June and August. Plants present the upright, grassy form typical of wild rye species rather than broad-leaved herbaceous growth. Observing a specimen through a season will show its habit and flowering window clearly.

Elymus interruptus is a Central Asian grass that flowers in the UK from June to August.