Wednesday 24 January 2018

Are the crocuses on my allotment flowering earlier every year? - a scientific investigation (of sorts)

12 January 2018
This is a question I am asking myself for quite a while now as it feels like I am seeing the first crocus flowers earlier and earlier each year. To answer this question I went back to the photos I have taken each year of my allotment. As the first flowers are always eagerly anticipated I normally take photos of the first crocuses and snowdrops I can see each year so I have a pretty good photo record of these flowers from 2012 until now.


First crocus flowers seen on my allotment

As you can see in the graph above, in 2012, 2013 and 2015 I recorded the first crocus flowers in mid February. In 2014 the first crocus flowers were out at the beginning of February. In 2016 and 2017 the flowers opened towards the end of January and this year I have seen the first crocus flowers on the 12th of January!
Having the dates of first flowering for seven consecutive years, I was actually able to test the above question statistically, with a so-called Spearman rank correlation test. Using the one-sided version of this test, which specifically asked the question 'Has flowering begun increasingly earlier throughout the period  2012-2018?', I could confirm  this with a probability of 99.91%, corresponding to a P-value of 0.0009 in the statistical test, which is considered a highly significant result in statistical terms. To answer the question in the title, yes, crocuses tend to flower earlier every year on my allotment, even though 2015 appeared to represent a bit of a blip.

16 February 2013

2 February 2014
I am not the only one recording earlier flowering dates for plants. A study derived a 250-year index of first flowering dates for 405 plant species in the UK and found that British plants are flowering earlier now than at any time in the last 250 years. As there is a strong correlation between temperature and the date when flowers first open each year we can assume that our climate is getting warmer.

24 January 2016
22 January 2017

Thursday 18 January 2018

The 10 best plants for pollinators on my allotment

Every year I grow lots of different flowers on my allotment. Most of them attract at least some pollinators but others are so attractive that they are often covered in bees, butterflies, hoverflies and other pollinators on a sunny warm day. A few plants I grow attract very specific pollinators such as campanulas (especially Campanula rotundifolium and C. persicifolium) which attract the harebell carpenter bee (Chelostoma campanularum) and some of my herbaceous potentillas which seem to attract only social wasps, but this may be a topic for another blog post. Here I want to show some of the plants on my allotment which attract a wide range of different pollinators, all well-worth growing in your garden if you want to help pollinators.

1. Crocus

One of the best plants for early bees and flies in late winter/early spring are the various crocuses I grow. I have mainly Crocus crysanthus and Crocus tommasinianus which flower late January and in February. On a warm day newly emerged bumblebee queens seek out the flowers, I have also seen drone flies (Eristalis spp.), hairy-footed flower bees (Anthophora plumipes) and other early solitary bees such as mining bees (Andrena spp.).


 









2. Poached Egg Plant (Limnanthes douglasii)

Poached egg plants are annuals but you only have to sow them once and they will come back year after year as they self-sow prolifically but never get out of hand. They normally flower in May and provide a welcome splash of colour and a good food-source for bees, hoverflies, other flies and beetles. On warm sunny days in May I often lie in wait with my camera near a patch of flowers to take photos of visiting pollinators, I never have to wait long until something arrives.













3. Ornamental Alliums

I grow various different ornamental alliums, from early alliums such as Allium roseum and Allium `Purple Sensation` to later alliums such as Allium sphaerocephalum, A. moly and A. caeruleum. All are good for pollinators and are easy to accommodate as you only have to remember to plant the bulbs in autumn. They all like sunshine and most of them will come back year after year if planted in well-drained soil. The main flower visitors seem to be bumblebees but I have also seen solitary bees on some of the earlier alliums, especially Allium roseum.



















4. Cosmos

I grow Cosmos bipinnatus and C. sulphureus on my allotment. Both are annuals and have to be raised from seed every year. Both sometimes self-sow but I find that often the seedlings germinate too early and are killed off by late frosts. For this reason I always make sure I collect seeds in autumn and sow them under cover in April to plant out in mid-May. The plants grow in any good garden soil and like full sunshine. The flowers attract mainly bumblebees, solitary bees and butterflies.












5. Giant Hyssop (Agastache spp.)

Many agastache are border-line hardy or have to be treated as annuals but a few are winter-hardy in the UK. I grow Agastache foeniculum (also called anise hyssop) which is fully winter-hardy on my allotment. Raising the plants from seed is easy if you have a greenhouse, otherwise you can find plants in most nurseries or online. Agastache likes full sunshine and well-drained soil, wet feet in winter will most likely kill the plant. It flowers in summer and is very attractive to bumblebees; it is a joy to watch all the busy bees collecting pollen and nectar on a sunny day.










6. Viper`s bugloss (Echium spp.)

Most echiums are biennial plants, they grow a rosette in the first year and a tall flower spike in the second. This is certainly the case for our native purple viper`s bugloss, Echium vulgare. There are a few perennial echiums such as Echium amoenum which comes from the Caucasus, but it is difficult to keep the plants alive in our wet winters. There are a few very attractive border-line hardy echiums from the Canary Islands such as Echium wildpretii and E. pinninana but they only survive outdoors in very sheltered gardens. Apart from the native Echium vulgare I have also grown Echium wildpretii which I raised from seed. I  kept the plants in a greenhouse in the first year and planted them outside in mid-May in the second year. The flower was spectacular (see pictures on the right and below) but it really is a lot of effort. This year I am trying out Echium pinninana, also grown from seed. I currently have large plants in the greenhouse and will plant them out in May. The flowers can be up to 4m tall!
 

If you don`t have a greenhouse and/or the time for the border-line hardy echiums it is easiest to grow our native Echium vulgare. You can sow the seeds directly outside, best in summer to give the plants time to establish before they flower in the next year. All echiums are great for bumblebees.


7. Poppies (Papaver spp.)

Poppies are easy to grow, cheerful early summer flowers, most are annual or short-lived perennials but a few, such as oriental poppies (Papaver orientale), are long-lived perennials. I grow a selection of poppies, from annual corn poppy (Papaver rhoeas), to short-lived arctic poppy (Papaver nudicaule) and long-lived oriental poppy (Papaver orientale). It is quite interesting that poppy flowers do not provide any nectar for pollinators but the flowers are nevertheless very attractive as the pollen is very protein-rich and produced in such abundance that especially bees cannot resist. Bumblebees have a special trick to collect the pollen which is called buzz pollination. As soon as the bees land in a poppy flower they start to vibrate their flight muscles very rapidly to dislodge the pollen from the anthers. You can hear this if you stand close to a poppy flower with a bumblebee inside as a high-pitched buzzing sound.
 












8. Wild marjoram (Origanum vulgare)

Probably one of the best plants for pollinators, wild marjoram is easy to grow in any good, well-drained garden soil in full sunshine. The tiny flowers produce a large amount of nectar which is highly attractive to all sorts of pollinators. Solitary bees, bumblebees, hoverflies, other flies, wasps, moths and butterflies all visit the flowers, and often they are so occupied with drinking nectar that I can get quite close to them to take photos.













9. Thistles (e.g. Cirsium spp., Carduus spp.)

Thistles are often seen as a weed and some can certainly be a nuisance but there are many very pretty and well-behaved thistles which are worth growing in a garden. I have to admit that I have a soft spot for thistles and have grown quite a lot now on my allotment. The thistles I have tried out but which I have not continued growing for various reasons are milk thistle (Silybum marianum) which was too prickly, nodding thistle (Carduus nutans) which is pretty but grew too large, woolly thistle (Cirsium eriophorum) which was too large and died after flowering, and purple milk thistle (Galactitis tomentosa) which is pretty but not winter-hardy here in UK so has to be grown from seed every year. The thistles I am still growing and can wholeheartedly recommend are our rare native tuberous thistle (Cirsium tuberosum) and Cirsium rivulare `Atropurpureum`. I am trying out a new thistle this year, Cirsium nipponicum from Japan, hopefully a good one.
All thistles are great plants for pollinators, especially bumblebees and butterflies seem to like the flowers but I have also seen solitary bees, beetles and hoverflies visiting.












10. Asters

Asters (also called michaelmas daisies) are one of the main stars of the autumn garden. There are a few spring-flowering asters such as Aster tongolensis but most asters flower from late summer until the first frosts. I grow many different asters such as Aster amellus, Aster x frikartii, Aster `Little Carlow`, New York aster (Symphyotrichum novi-belgii), New England aster (S. novi-angliae) and fragrant aster (S. oblongifolius). All asters are good pollinator plants, some are more attractive to pollinators than others but you cannot really go wrong if you stick to the asters with the more simple flowers. I mainly see late bumblebees such as common carder bumblebees (Bombus pascuorum) and late butterflies such as the admiral visiting the flowers.




Thursday 11 January 2018

The Sussex Prairie Garden

As there is not a lot happening on the allotment at the moment I thought I show you some pictures from one of my recent garden visits.

The visit to Sussex Prairie Garden in September last year was certainly a highlight. It is a relatively new garden and has only opened to the public in 2009. Grasses and perennials are planted on a large scale, very colourful and all mixed together in a naturalistic style. There are small paths everywhere in the large borders leading you right in between the often towering plants which I liked a lot. In many gardens you can see a border just from one side but here you can immerse yourself between the plants. You can read more about the garden here.
 
Below are some pictures I took during my visit.

Grasses like Miscanthus and Panicum mix with perennials such as Sanguisorba, Echinacea and Salvia (below).


Here I have discovered the largest Dahlia flower I have ever seen (below).


Silphium terebinthinaceum and Actaea simplex (below)


There are many different asters in the garden, here you can see a purple Symphyotrichum novae-angliae with Eupatorium purpureum in the background (below).


Geranium 'Rozanne' with Deschampsia caespitosa (below)


Persicaria amplexicaulis (below)


Colourful annuals planted in-between the perennial plants such as Rudbeckia fulgida (below).


Rudbeckia triloba, a very pretty short-lived perennial plant, on my allotment unfortunately only annual (below).


Sanguisorba and Miscanthus (below). I tried growing Sanguisorba on my allotment but I think the soil is drying out too much in summer.


A very pretty perennial sunflower (Helianthus sp.), also very attractive to pollinators (below).


Rudbeckia fulgida and Echinacea purpurea, a colourful combination (below).


Autumn-flowering anemone with Rudbeckia fulgida (below).


Miscanthus with Helianthus 'Lemon Queen' (below)


I think the blue flower is  Strobilanthes wallichii, here growing with Persicaria (below).


Geranium 'Rozanne' growing with Nassella tenuissima and a pretty aster (below).


Purple Geranium and yellow Rudbeckia look pretty growing together (below).


Eryngium with Miscanthus and Echinacea purpurea (below)


Drone fly (Eristalis sp.) visiting Symphyotrichum novae-angliae (below).


Interesting work of art is scattered across the garden (below).


 A sea of Rudbeckia fulgida


My next blog post will hopefully feature some snowdrops and other spring flowers. The leaves are pushing through the soil already so it will soon look a bit more colourful on my allotment.


New Wildlife Allotment blog

 I have started a new monthly blog about my wildlife allotment a few years ago for the Hardy Plant Society. I you are interested you can rea...

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