Garden Diary 2019

Many visitors stop in their tracks when entering the garden and seem astonished to find such a colourful scene.

Garden Projects

At the start of the season, the Friday Group decided to undertake a Compost Trial. Barbara reported on an article about the use of Sylvagrow, a relatively new organic product, tested and recommended by a number of large and small horticultural businesses and available at a local Nursery. Hardy’s Cottage Garden Plants in Hampshire owned by Rosy Hardy, multiple Gold Medal winner at Chelsea and well known for the quality and variety of plants, has switched to using this product throughout the Nursery.

Each time supplies of compost need replenishing at the Botanic Garden we select the best product preferred and then source any offers. Most brands have been tried over the years invariably giving mixed results; the early formulas of peat-free and coir-based compost proved unsuitable, quickly drying out and impossible to wet again. Now, with a need to steer away from peat-based composts, selecting the best mix can be a trial in itself, especially when products change in content and consistency from one batch to the next.

The trial commenced in early March using Sylvagrow, New Horizon Peat Free Compost and our usual compost as a control. Plant divisions were split into six, planting two in Sylvagrow, two in New Horizon and two in our usual compost. The labelled pots were placed in crates, positioned in an enclosed area and checked weekly for condition, watering requirements and growth rates. By late spring the plants had produced substantial new growth and, with the exception of two, all appeared healthy. Commercial nurseries have the facilities to monitor and water plants on a daily basis, but, as the bulk of our plants grew well on the minimum of attention, the trial was completed after a few weeks. By this time, Sylvagrow was not supplied by the local Nursery so New Horizon Peat Free will be the first choice, it is available at most Garden Centres. The RHS now use Sylvagrow for propagation of all plants, and we will use it again, if available locally, in future.

Jed acquired a second Dutch Trolley late last year. He finished working on it during Spring enclosing the trolley in a wooden frame with mesh sides and doors giving shade and keeping out marauding squirrels. Ultimately intended to store plants reserved for planting in the garden or for other reasons, this provided an ideal place to house the plants for the period of the compost trial.

To avoid plants inadvertently being sold too early following propagation, the plunge bed by the Potting Shed is now reserved for newly potted plants. A ‘Plants not ready for Sale’ sign has been added to the area where plants are left to settle and grow new roots before moving to the sales tables.

Many visitors ask how we keep the hostas looking so good. This year, we used ‘SlugGone’ wool pellets around the crowns just as they emerged and the plants remained pest-free until late July. Snails hide amongst the dense foliage of Clematis armandii on the wall behind the hosta bed, then they descend after dark to feed on leaves turning them into lace by late summer. SlugGone doesn't deter snails, but we will continue to use it next season despite the lack of evidence of efficacy in the gardening press. In December last year, a ban on the use of slug pellets containing metaldehyde was announced, coming into force in June 2019. The ban was overturned at the beginning of August after a challenge on its legality by Chiltern Farm Chemicals one of the biggest manufacturers.

Iris and Erika finished renovating the peony bed. With the exception of two peonies and three members of the Acanthus family, the rest of the plants were removed, divided and replanted in different positions within the bed. Peony obovata and Peony mlokosewitschii (Molly the Witch) benefitted from their new-found space becoming much healthier and with more flowers. The bed had become very congested but now has significant empty spaces, left deliberately for a year or so to enable us to remove any japanese anemone shoots which appear as the roots are difficult to eradicate. Sure enough, they keep popping up throughout the bed accompanied by aquilegia seedlings. The RHS reported in May that japanese anemones have been added to the invasive plant list. The RHS website www.rhs.org.uk/ includes pages on Garden Thugs. Some of those listed are well recognised; it is worth a read. Alchemilla mollis is not listed although considered invasive being a prolific seeder. Walking in Derbyshire recently, we came across an area above Cromford where large tracts of Alchemilla mollis were growing in a clearing in woodland. Crocosmia (Montbretia) is listed under Schedule 9 to the Wildlife & Countryside Act 1981 with respect to England & Wales. As such, it is an offence to plant or otherwise allow this species to grow in the wild. We should not sell Crocosmia pottsii x aurea (Montbretia) or pass them on to others to grow and certainly not dispose of them in compost collection schemes or into the environment. Although they spread rapidly by corms they rarely spread by seed. According to the Non-Native Species website www.nonnativespecies.org other Crocosmias are rarely found outside the landscaped environment and rarely behave in an invasive manner. Crocosmia species in the wild are likely to be montbretia.

All the new irises planted last year survived the winter although allium seedlings (another invasive species) are still popping up but much reduced in number. Constant removal by a dedicated few has produced the desired result but vigilance is needed. The tall bearded iris were fed with bonemeal at the recommendation of Simon Dodsworth the owner of English Irises. To minimise damage by foxes, chicken wire was erected around the plants with a net over the top preventing any disturbance to the rhizomes. Although they have grown well, no flower spikes appeared but Simon didn’t expect them to flower this year. He also recommended using a seaweed feed in future to avoid the fox problem.

The other new irises, the Californian hybrids, all produced a lovely display of flowers and most have since produced good clumps of foliage. A few of the original iris cultivars known for their good constitution have been returned to the bed.

Further along the Sundial border, the old woody salvia plants were removed. New plants, purchased from Avondale Nursery: Salvia ‘Dyson’s Joy’ AGM, S. greggii ‘Emperor’, S. ‘Royal Bumble’ AGM, S. ‘Silas Dyson’ and S. verticillata ‘Purple Rain’ plus S. microphylla ‘Cerro Potosi’ from another source are all establishing well.

A number of plants in the alpine troughs failed to thrive as a result of conditions last year and the troughs by the bottom sheds were invaded with purple leaved Oxalis corniculata.

Two of the troughs have been emptied, jet-washed and left to dry before being lifted off the brick plinths and weeds and debris cleared from underneath. Erica and Ray Cobb visited Fir Croft Alpine Nursery at Calver, Derbyshire to purchase a small selection and eight alpines have now been planted in one trough. Further work on the troughs will continue.

In addition to the new salvias and alpines, 34 other new plants have been purchased or donated to the garden so far this year. Three are from the Hardy Plant Society Conservation Scheme; two Phlox and one Geranium. Our phlox plants have not performed well for some time, so a mulch of manure was applied and, a short time later, the phlox gave their best display in recent years benefitting from sunshine and regular rainfall providing ideal growing conditions. In the same family as phlox, long established varieties of polemonium, normally with a long flowering season, sadly died over winter, probably due to previous summer drought.