Clumber Gardener June 2016

Chris Margrave Head Gardener

As we move into the summer months, there's plenty to be doing in your gardens. We caught up with our Head Gardener to find out what you need to be doing in your gardens in June.

Californian Lilacs

Ceanothus or the “Californian lilacs” as they are commonly called, produce some of the most vivid blue flowers of any shrub which can be grown outdoors.  The evergreen varieties flower in late spring and early summer and are generally pest and disease free and need little pruning.  The clue to growing them well, as with any other plant, is in their origins, so give them Californian conditions, or conditions as close to California as we can get in the north Midlands.   This means a site sheltered from cold winds, a soil that is well drained, and a spot which receives lots of sunshine.  A south facing wall, where they will get a proper baking, is perfect ceanothus territory.   When suited, they will reward you with a spectacular display over 6 or 7 weeks.

Californian lilac
Californian lilac at Clumber
Californian lilac

So, lots of pluses, but there are a couple of drawbacks .  Ceanothus are not the longest lived of shrubs.   After six years or so, they will go into decline and in really cold winters they will suffer, both from repeated frosts and from heavy snow.    The main cause of damage is often the weight of heavy snow breaking branches. 

The choice of varieties is enormous.  In May and early June the free-flowering ‘Puget Blue’, will be covered in vibrant powder blue flowers.  Height and spread are around 3m/10ft.  ‘Blue Mound’ at 1.5m/5ft is much shorter and bears dark blue flowers.   More compact still is ‘El Dorado’, which has the bonus of attractive variegated leaves with a deep green centre and a yellow edge.  Flowers are fragrant.  Ultimate height and spread are round 1.2m (4ft). 

My personal favourite is ‘Concha’; its red buds open to reveal intense blue flowers.  It is one of the hardier ceanothus.   I have grown it in a cold, exposed North Yorkshire garden on heavy clay and it easily out-performed other varieties.  It reaches a height of about 2.4m/8ft.  We grow it in more favourable, sheltered conditions in Clumber’s Walled Kitchen Garden and in our Garden Tea House garden, where we have three ‘Concha’ plants.  The colour palette here is restricted to blues, purples, pinks and pale yellows.  The pink flowered Polygonum bistortum ‘Superbum’ and ornamental strawberry Fragaria ‘Pink Panda’ and the yellow daisy Anthemis ‘Sauce Hollandaise’ all flower at the same time as ‘Concha’ and make effective partners.   A golden leaved dwarf hop ‘Golden Tassles’ and a silver grey foliage cardoon also provide excellent foils.  If you’re after other blues which flower at the same time as ceanothus, hardy geraniums, catmints (nepeta) and the pale blue Veronica gentianoides would all be worth considering.

Jobs for the Month – June

If you haven’t already planted out tender bedding, perennials and vegetables, plant these out early in the month after the danger of frost is over.  Sweet corn, runner beans, marrows and courgettes can be planted into prepared ground, along with half hardy annuals for summer bedding schemes such as marigolds and salvias. 

If soil is dry and the weather hot and sunny, water newly planted shrubs and perennials.  Use a mulch, such as bark chippings, to conserve soil moisture and help keep weeds in check.  This should be spread about an inch (2.5cm) thick.

Shade and ventilate your greenhouse in hot weather.  On hot, sunny days water the floor of the greenhouse, a process known as “damping down”, to keep the air moist.  This will help reduce problems with red spider mite which thrive in dry air.

Harvest first early varieties of potato.  Continue harvesting rhubarb and asparagus, early peas and salad leaves.  Strawberries are usually a target for squirrels and blackbirds.  Cover ripening fruits with netting.  Put down straw around the plants to prevent fruits bring splashed with soil.

Watch out for pests and diseases.  The mild winter and recent rains will no doubt see lots of slug and snail activity on young vegetable seedlings such as lettuces and brassicas.

Biennials such as forget-me-nots and wallflowers can be sown outside.  Dig or fork over the soil, rake it level and firm.  Take out a seed drill with the corner of a rake, water the base of the drill, sow the seed and backfill.  Germination usually takes about a fortnight.

Herbaceous perennials are growing apace and need staking, otherwise shoots will be damaged and fall over onto neighbouring plants.