Planning suitable pollination partners for apple trees should bear fruit

Flowering bulbs often indicate the start of the new season. As we see their first splash of colour we speculate the glimmering promise of the year to come and the arrival of spring. Bulbs however, being tulips or daffodils, can have a fairly wide flowering period and can be heavily influenced by the weather. For me, the true symbol of spring is blossoming apples.

As well as signifying spring, apple blossom denotes the promise of an abundant apple harvest; a true British favourite with ingrained traditional values.

In order to produce apples, apple trees need to be pollinated. In nature, pollination occurs by insects which crawl into the flower. Grains of pollen stick to the insect from the anther - the male reproductive part of the flower - and are deposited on the stigma - the female part. In the case of apples, this process is done mainly by honey bees. Most apple trees, however, are self-sterile, meaning they cannot fertilise themselves with their own pollen; pollen from a different apple variety is required in order for the tree to be fertilized.

Although this may pose a problem if you only have only one apple tree, the great thing about honey bees is that they can travel several hundred metres every day. 90% of apple trees in the UK can be pollinated by apple trees growing in nearby gardens or even by crab apples growing in the wild. If you are concerned that your tree will not get pollinated ensure you grow more than one apple variety.

Some apple trees are self-fertile, meaning they can fertilise themselves with their own pollen and do not need a pollinating partner, although they will bear better fruit in the presence of another apple variety.

Most apple trees are diploid, meaning they have two chromosomes and can be self-fertile or self- sterile; others are triploid, meaning they have three chromosomes. Triploid apple trees are always treated as self-sterile and need another apple variety nearby to pollinate them. They’re rather selfish, however, as they cannot return the favour of pollinating other apple trees!

If the pollination partner for the triploid tree is self-sterile, that apple tree will also need a pollination partner because it cannot be pollinated by the triploid apple tree. If, however, the pollination partner is self-fertile then it will not only pollinate the triploid apple tree but also itself. It is a common misunderstanding that triploid apple trees need two suitable pollination partners but this is not the case; they only need one, but the more pollination partners present, increases the likelihood of fruit set.

Another very important factor to consider is apple flowering times. Different apple varieties have different flowering periods and in order for the bees to do their work, flowers on different apple trees need to be open at the same time. There are two systems currently used to determine, more or less, when certain apple varieties will flower. One is a numbering system 1 – 6 where 1 is the earliest flowering and 6 the latest. Similarly the other system uses letters A – F and follows the same principle where A is the earliest. When purchasing an apple tree, make sure you look out for these flowering period indicators to help choose your apple varieties.

Depending on where you are in the country, apple blossom starts from late April - mid May and lasts for about 1-2 weeks. There are only a few days between each flowering group so pollination partners can overlap with their flowering periods. For instance, the blossom on an apple variety of pollination group 2 will last 1-2 weeks, making it suitable to be grown with a variety in groups 1 or 3 as the start of the blossom time will only be a few days between them.

Come see our apple blossom at RHS Garden Harlow Carr and find out more from our expert staff.

Jobs for the Week

• Watch out for late frosts; protect tender plants

• Earth up potatoes, and promptly plant any still remaining

• Regularly hoe off weeds

• Thin out direct-sown vegetables such as spinach, carrot and lettuce seedlings

• Harden off outdoor tomatoes, courgettes and pumpkins for planting early next month

• Plant out brassicas and leeks to their final positions.

• Surround strawberries with straw to protect fruit. Net them to keep birds off the fruit.

With thanks to Francesco Ponziani, Horticulturist at RHS Garden Harlow Carr

DIARY DATES

1 – 30 May: Bath House Gallery – Ceramics & Glass Showcase

Raku, slab and thrown pottery work is on show throughout May with a wide range of glass items. Practical and decorative work will make this a must-see event. Normal garden admission.

Tuesdays in May, 11am: Harlow Carr Garden Tours

Find out more about the most northerly RHS garden on a tour with the Friends of RHS Harlow Carr every Tuesday. A donation of £2 is suggested.

Saturday 26 & Sunday 27 May: Children’s Gardening Weekend

See Mr Bloom from CBBC perform live on Saturday to launch this new weekend event. Kids big and small can take part in a range of activities designed to inspire the gardeners of the future to grow from 11am to 3pm. Make your own Thumbelina-style rock garden, learn about bees with the Harrogate & Ripon Beekeepers, enjoy a creative writing workshop, pot up your own sweet peas and decorate an ‘In the Night Garden’ pot to take home. Normal garden admission.

26 May - 3 June: ‘Get, Set, Grow’ May Half Term Family Fun

Youngsters are being encouraged to get, set, grow at Harlow Carr during half term. Enjoy a daily garden trail, storytelling with the Garden Detectives, indoor crafts and each day a chance to theme your own pot and plant up a pumpkin seed. Normal garden admission.

As the UK’s leading gardening charity, the proceeds taken from events and tickets sales at all RHS gardens help to fund the many activities undertaken by the RHS to promote horticulture and help gardeners. For further information on all the above events please call 01423 565418.

RHS Garden Harlow Carr, Crag Lane (off the B6162 Otley Road), Beckwithshaw, Harrogate HG3 1QB (if using Sat Nav use postcode HG3 1UE). Gardens open every day of the year, except Christmas Day, from 9.30am until 6pm (or 4pm Nov-Feb inclusive). Last entry 1 hour before closing. RHS Members (+ 1 Family guest) Free; Prices (excluding Gift Aid): Adult: £11.50; Child 5-16: £5.750, Under 5s: Free; Family: £29. Groups (10+): £9.50 Gardens: 01423 565418. Shop and Plant Centre: 01423 724666. Bettys Café Tea Rooms 01423 505604.

RHS Membership

Join the RHS at Harlow Carr and you’ll receive many exclusive benefits including: a monthly copy of ‘The Garden’ magazine; free entry (with a family guest) to RHS Gardens: Harlow Carr, Wisley, Rosemoor and Hyde Hall; free access to over 130 RHS recommended gardens throughout the UK at selected periods; free gardening advice; privileged tickets to world famous flower shows and much more. Call for more information.