Wintertime

IMPORTANT: CACTUSES IN THE WINTERTIME

In the winter cactuses require a period of rest, when physiological activities are minimized, which is an evolutionary response to their extreme environment; this dramatic behaviour, in fact, allows them to survive the harsh climate of their natural habitats and therefore it is something we should know about and respect. During this kind of dormancy they should be kept in a cool place with very low humidity levels and not receive any water, though there are exceptions to this general rule as explained further below. In the spring we can resume the routine horticultural practices since the plants will have started growing again and with any luck they will prepare to flower.
Placing dormant cactuses indoors, on a window-sill for example, is not a wise choice. Instead it’s recommendable to move them to an unheated room such as a garage, attic or basement as well as a stairwell that need not be very bright as the plants are not growing. When this is impossible they might as well be overwintered on a balcony under some makeshift shelter from the cold and rain. On the contrary, if brought into a heated place they will not be allowed to go dormant and the new growth is likely to be unhealthily thin due to lack of light (etiolation). Moreover, if water is not applied the plants will wither and die as a consequence of the high transpiration. Many cactuses can withstand frost if given the protection of a conservatory where the temperature can rise significantly on sunny days; there’s also a group of plants, the so called “cold-hardy cacti”, comprising Austrocactus, Echinocereus, Escobaria, Opuntia, Pediocactus, Sclerocactus, Thephrocactus, Toumeya, Uthaia and a few others that can even survive harsh winters covered in snow as long as they’re not exposed to rain and humidity.

Preparations for the winter: September is the last month to apply insecticides or fertilizers. Watering should be suspended when the outside mean night temperature goes down to about 8°C (46°F). It is recommendable to install a ventilator in your glasshouse or conservatory to improve air circulation and keep humidity levels low thus preventing the proliferation of mildew and fungal diseases. It is also important to keep the room clean and disinfected, taking care to remove dead leaves, spent flower heads and ripe fruits. In addition, the place should not be crammed with pots if you want to avoid the spread of pests and diseases. Be also careful not to damage plants since pathogens are able to invade them through the wounds.

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Plants can be roughly divided into four categories according to the environmental conditions that best suit them:
         A – Very warm place - like a heated house - (= /above 57°F)
         B – Cool to warm place (from 45/to 54°F),
         C – Cool, unheated place (from28/to 43°F),
         D – Cold or outdoor place sheltered from the wet (=/ 27°F or lower).

The list comprises the most commonly cultivated species of cacti and other succulents. The temperatures shown must be regarded as approximate values since the tolerance of plants to cold conditions depends on a number of factors usually linked to one another, such as atmospheric humidity (the greater the humidity level, the higher the temperature required), the duration of exposure to the cold (many cacti can endure light, occasional frosts but not severe or prolonged ones), the health of the plant and its acclimatization to the local weather conditions and so on. When in doubt as to the ideal temperature, it’s better to keep it a few degrees higher than lower, especially for non-cactaceous succulents.

WINTER MINIMUMS

TEMPERATURE group A

Adansonia digitata	C°+18	F° 64
Aloe deltoideodonta var. brevifolia	+15	59
Didierea madagascariensis	+15	59
Euphorbia alfredii	+18	64
Euphorbia bongolavensis	+15	59
Euphorbia bulbispina	+15	59
Euphorbia capsaintemariensis	+15	59
Euphorbia croizatii	+15	59
Euphorbia francoisii	+15	59
Euphorbia genoudiana	+15	59
Euphorbia hofstaetteri	+15	59
Euphorbia lophogona var. tenuicaulis	+15	59
Euphorbia milii fa Zombitsy	+15	59
Euphorbia milii var. tulearensis	+15	59
Euphorbia millotii	+15	59
Euphorbia neohumbertii f.ma rubrifolia	+15	59
Euphorbia pachypodioides	+20	68
Euphorbia pedilanthoides	+18	64
Euphorbia perrieri var. elongata	+15	59
Euphorbia rossii	+15	59
Euphorbia umbraculiformis	+15	59
Euphorbia viguieri var. capuroniana	+15	59
Laportea perrieri	+15	59
Operculicaria decaryi	+14	57
Othonna retrofracta	+14	57
Pachypodium baronii	+14	57
Pachypodium bicolor	+18	64
Pachypodium namaquanum	+14	57
Pelargonium alternans	+14	57
Uncarina decaryi	+15	59
Uncarina grandidieri	+15	59
Uncarina leptocarpa	+15	59
Uncarina platycarpa	+15	59
Uncarina stellulifera	+15	59

TEMPERATURE group B

Adenia spinosa	C° +10	F° 50
Adenium obesum	+7	45
Agave potatorum var. verschaffeltii	+7	45
Alluaudia adscendens	+10	50
Aloe parallelifolia	+8	46
Aloe thraskii	+10	50
Aloe trachyticola	+8	46
Anacampseros alstonii (Avonia quinaria)	+10	50
Arrojadoa penicillata	+8	46
Asclepiadaceae (equatoriali ed africane)	+10/+12	50-54
Bromeliacee (Dyckia, Hechtia, Puya)	+10/+12	50-54
Bulbine margarethae	+8	46
Caralluma hesperidum	+7	45
Caudiciformi (mediamente)	+12 o >	54or>
Cissus (mediamente)	+12 o >	54or>
Conophytum uvaeforme	+8	46
Dioscorea (Testudinaria) elephantipes	+10	50
Discocactus horstii	+8	46
Discocactus zehntneri var. araneispinus	+7	45
Dracaena draco	+8	46
Euphorbia abdelkuri	+8	46
Euphorbia aeruginosa	+10	50
Euphorbia bourgaeana	+10	50
Euphorbia broussonetii	+8	46
Euphorbia bupleurifolia	+8	46
Euphorbia canariensis	+8	46
Euphorbia filiflora	+7	45
Euphorbia gymnocalicioides	+9	48
Euphorbia inermis	+8	46
Euphorbia isaloensis	+12	54
Euphorbia kibwezensis	+10	50
Euphorbia milii Drake	+10	50
Euphorbia milii f.ma Brieville	+8	46
Euphorbia milii var. vulcanii	+8	46
Euphorbia obesa	+7	45
Euphorbia perrieri var. perrieri	+12	54
Euphorbia piscidermis	+10	50
Euphorbia sakarahensis	+12	54
Euphorbia stellaspina	+10	50
Euphorbia tescorum	+10	50
Ferocactus flavovirens	+8	46
Ferocactus fordii	+8	46
Ferocactus johnstonianus	+8	46
Fouquieria splendens	+12	54
Gymnocalycium hypthiacanthum	+8	46
Gymnocalycium mihanovichii	+8	46
Gymnocalycium paediophilum	+8	46
Hatiora salicornioides	+8	46
Hoodia macrantha	+8	46
Huernia hystrix	+8	46
Huernia macrocarpa var. penzigii	+8	46
Jatropha podagrica	+8	46
Lophocereus schottii fa mostruosa	+7	45
Monadenium magnificum	+10	50
Monadenium stapelioides	+10	50
Myrtillocactus geometrizans	+7	45
Nopalxochia phyllanthoides	+7	45
Othonna cacalioides	+10	50
Pachycormus discolor	+10	50
Pachypodium brevicaule	+10	50
Pachypodium densiflorum	+12	54
Pachypodium eburneum	+10	50
Pachypodium lamerei	+7	45
Pelargonium crithmifolium	+12	54
Pseudolithos migiurtinus	+12	54
Rhipsalidopsis gaertneri	+8	46
Stapelia grandiflora	+8	46
Stapelianthus pilosus	+10	50
Tavaresia angolensis	+10	50
Tavaresia grandiflora	+8	46
Tricocaulon cactiforme	+10	50
Tylecodon luteosquamata	+10	50
Tylecodon paniculata	+10	50
Tylecodon reticulata	+9	48
Tylecodon rubrovenosus	+7	45
Tylecodon scandens	+8	46
Uebelmannia pectinifera	+8	46
Umbilicus (mediamente)	+10	50
Uncarina grandidieri	+15	59
Uncarina perrieri	+12	54
Uncarina röesliana	+12	54
Uncarina sp. nova	+10	50

TEMPERATURE group C

Adromiscus antidorcatum	C° +5	F° 41
Adromiscus clavifolius	+5	41
Adromiscus festivus	+5	41
Adromiscus herrei	+5	41
Adromiscus maculatus	+5	41
Aeonium arboreum var. atropurpureum	+5	41
Aeonium ciliatum	-2	28
Aeonium decorum	+5	41
Aeonium lindleyi	+5	41
Aeonium sedifolium	+5	41
Aeonium tabulaeforme	+5	41
Aeonium undulatum	+5	41
Agave bracteosa	+2	36
Agave ferdinandi-regis	+5	41
Agave ghiesbreghtii	+6	43
Agave macrocantha	+5	41
Agave purpusorum	-2	28
Agave roezliana	-2	28
Agave titanota	+5	41
Aloe arborescens	+5	41
Aloe barbadensis (vera)	+5	41
Aloe compressa var. rugosquamosa	+6	43
Aloe descoingsii	+5	41
Aloe dichotoma	+5	41
Aloe erinacea	+6	43
Aloe erythrophylla	+6	43
Aloe haworthioides	+5	41
Aloe humilis	+5	41
Aloe humilis	+4	39
Aloe juvenna	+5	41
Aloe longistyla	+6	43
Aloe parvula	+6	43
Aloe plicatilis	-2	28
Aloe rauhii	0	32
Aloe somaliensis	+5	41
Aloe suprafoliata	+6	43
Aloe vaombe	+5	41
Aloe variegata	0	32
Anacampseros crinita	+5	41
Anacampseros papyracea	+5	41
Arequipa leucotricha	+3	37
Arequipa rettigii	+3	37
Ariocarpus agavoides	+5	41
Ariocarpus bravoanus	+5	41
Ariocarpus fissuratus “intermedius”	+5	41
Ariocarpus fissuratus var. hintonii	+5	41
Ariocarpus intermedius	+2	36
Ariocarpus kotschoubeyanus var. elephandidens	+5	41
Ariocarpus kotschoubeyanus var. macdowellii	+5	41
Ariocarpus retusus	+5	41
Ariocarpus scapharostris	+5	41
Ariocarpus trigonus (and its varieties)	+5	41
Astrophytum capricorne var. aureum	+5	41
Avonia quinaria ss. alstonii	+6	43
Avonia quinaria ss. quinaria	+6	43
Aztekium hintonii	+5	41
Aztekium ritteri	+6	43
Beaucarnea recurvata	+5	41
Bijlia cana	-2	28
Blossfeldia liliputana	+3	37
Borzicactus roseiflorus (Akersia)	-2	28
Brachystelma decipiens	+6	43
Browningia (Azureocereus) hertlingiana	-2	28
Bursera fagaroides	+5	41
Calibanus hookeri	+5	41
Calymanthium substerile	0	32
Caralluma hesperidum	-2	28
Cephalocereus palmeri	+5	41
Ceraria namaquensis	+6	43
Cereus forbesii fa. spiraliforme	+5	41
Ceropegia dichotoma	+5	41
Ceropegia fusca	+6	43
Ceropegia hians	+6	43
Ceropegia stapeliformis	-2	28
Ceropegia woodii	+5	41
Chorisia speciosa	+5	41
Cleistocactus flavispinus	-2	28
Cleistocactus ianthinus	-2	28
Cochemiea halei (Mammillaria)	-2	28
Cochemiea poselgeri	0	32
Cochiseia robbinsorum	+3	37
Conophytum bilobum	+5	41
Conophytum pearsonii	+5	41
Copiapoa cinerea	+5	41
Copiapoa cinerea var. eremophila	+4	39
Copiapoa coquimbana	+5	41
Copiapoa grandiflora	+5	41
Copiapoa humilis var.longispina	+5	41
Copiapoa hypogea	+5	41
Copiapoa krainziana	+5	41
Copiapoa laui	+5	41
Copiapoa megarhiza	+5	41
Copiapoa pseudocoquimbana	+5	41
Copiapoa tenuissima	+5	41
Copiapoa dealbata	+3	37
Coryphantha asterias	-1	30
Coryphantha bergeriana	-2	28
Coryphantha bumamma	+5	41
Coryphantha erecta	+5	41
Coryphantha greenwoodi	+2	36
Coryphantha macromeris	+3	37
Coryphantha pallida	-2	28
Coryphantha poselgeriana var.valida	+5