Adenium
Adenium is a genus of flowering plants in the Apocynum family, Apocynaceae, first described as a genus in 1819.
 It is native to Africa and the Arabian Peninsula.
Witch-hazel
Witch-hazels ("Hamamelis," ) are a genus of flowering plants in the family Hamamelidaceae, with four species in North America ("H. mexicana", "H. ovalis", "H. virginiana", and "H. vernalis"), and one each in Japan ("H. japonica") and China ("H. mollis").
 The North American species are occasionally called winterbloom.
Witch-hazel cone gall aphid
The witch-hazel cone gall aphid ("Hormaphis hamamelidis") is a minuscule insect, a member of the aphid superfamily, whose presence on a witch-hazel plant is easily recognizable by a red conical gall structure.
 This gall, rich in nutrients, provides both food and shelter for the female aphid.
Gall
Galls or cecidia are a kind of swelling growth on the external tissues of plants or animals.
 Plant galls are abnormal outgrowths of plant tissues, similar to benign tumors or warts in animals.
 They can be caused by various parasites, from fungi and bacteria, to insects and mites. Plant galls are often highly organized structures and because of this the cause of the gall can often be determined without the actual agent being identified.
 This applies particularly to some insect and mite plant galls.
 The study of plant galls is known as cecidology.
Adenium obesum
Adenium obesum is a species of flowering plant in the dogbane family, Apocynaceae, that is native to the Sahel regions, south of the Sahara (from Mauritania and Senegal to Sudan), and tropical and subtropical eastern and southern Africa and Arabia.
 Common names include Sabi star, kudu, mock azalea, impala lily and desert rose.
Adenium oleifolium
Adenium oleifolium is a species of flowering plant in the dogbane family.
Thames Water Desalination Plant
The Thames Water Desalination Plant or Beckton Desalination Plant is a water desalination plant in Beckton, London, United Kingdom.
 The first of its kind in the UK, it was constructed for Thames Water by a consortium of Interserve, Atkins Water and Acciona Agua.
 The plant was officially opened by Prince Philip, Duke of Edinburgh on 2 June 2010.
 The plant provides up to 150 million litres of drinking water each day – enough for nearly one million people.
Adenium swazicum
Adenium swazicum is a species of flowering plant in the dogbane family, Apocynaceae, that is native to the lowveld of Swaziland and the Mpumalanga province of South Africa.
Melon
A melon is any of various plants of the family Cucurbitaceae with sweet edible, fleshy fruit.
 The word "melon" can refer to either the plant or specifically to the fruit.
 Botanically, a melon is a kind of berry, specifically a "pepo".
 The word "melon" derives from Latin "melopepo ", which is the latinization of the Greek μηλοπέπων ("mēlopepōn"), meaning "melon", itself a compound of μῆλον ("mēlon"), "apple, treefruit ("of any kind")" and πέπων ("pepōn"), amongst others "a kind of gourd or melon".
 Many different cultivars have been produced, particularly of cantaloupes.
Adenium arabicum
Adenium arabicum is a species of plant commonly used for bonsai and cultivated for its leaves, growth form and flowering characteristics.

Question: Adenium and Witch-hazel are both what kind of plant?
Answer: flowering plants