June garden tips

03 June 2021

Find out what needs doing in the garden in June, including what seeds to sow and what maintenance need doing.



What to plant in June

Flower seeds to sow in June

Sow seeds of annual flowers to fill gaps. Mix the seeds into sand or cover seeds with a mix of potting compost and sand so you can easily spot which areas you have sown and don’t enthusiastically hoe or pull up seedlings by mistake. Remember to keep the soil moist until they have germinated and the seedlings have grown into their space.

Vegetable seeds to sow in June

Keep sowing salad leaves and lettuces. If you find them too fiddly try using seed tape – seeds set into paper tape. A very clever way of ensuring you don’t sow too thickly. Plus it ensures straight rows. They are a bit more expensive but satisfying.

Sow spinach and kale. Both are useful crops that are easy to grow and good to eat. Sow F1 varieties for reliable performance. Use thinnings for salads.

June is the last time to sow green beans.

Give your garden a makeover and save money at the same time with a special Thompson and Morgan offer of 10% off.

Garden jobs for June

Pinch out dahlias

Pinch out the growing tips of dahlias and other perennials to create bushy plants. Stake dahlias and other plants that are going to grow tall and flop.

Watch out for mildew

Watch for outbreaks of mildew that follows dry weather and affects stressed plants. Remove any affected foliage as soon as you spot it before the problem spreads. Mildew looks like soft grey dusty mould.

Cut down spent stems

Cut down spent flowering stems of red hot pokers and foxgloves which make the plants look better and encourages new stems and shoots.

Keep up with weeding and tidying

Keep pulling weeds. Little and often works best. Five minutes here and there aiming to pull them before they flower and set seed.

Watch out for thugs and bullies that may be swamping better behaved plants and either cut back some foliage or pull out unwanted seedlings allowing light and air to reach all plants.

Weeding and sweeping paths and patios makes the garden look neat and loved, even if the borders are a bit out of hand. You can hoe weeds out of fine gravel, or use an L-shaped patio tool to remove any weeds in the crevices of paths and patios. Use a yard broom to sweep the paths afterwards.

Improve your edging 

It's a good time to turn your attention to the lawn edges as long as the ground is moist. Use a half-moon lawn tool and pick up any fallen pieces of turf left in the gully. If it's a straight edge, use a line made rom two sticks and string to create a super-neat look. When edging the trick is stand over the edge and hold the tool against your body, whether using a pair of lawn edging shears or a half moon tool. This ensures that the edges are completely vertical.

Start a herb garden

The great plus about herbs is that most require little looking after. Just choose the right plants for your spot and don’t give them too much TLC. Mediterranean herbs need sun and dry free-draining ground so plant in poor ground with plenty of grit and backfill with the same. Mints like rich soil but are invasive so either plant in pots or seal off their roots from surrounding soil. Parsley can be difficult to get off but once up and running keeps going through most that winter throws its way.

Deadhead and feed roses

After the first flush of flowers deadhead repeat flowering roses, just nip off the faded flowers right underneath. Don't be tempted to remove a lot of stem under each fading flower. Simply cut straight under the spent flower, or pinch it off with your fingers. Deadheading this way helps your roses to rebloom quickly. Feed them with a high potash pelleted food such as Vitax Q4. This will produce more flower and the potash will toughen up the foliage and help it to resist diseases.

Roses that flower only once should be left because many produce attractive hips that add winter interest.

Divide bearded irises

Divide bearded irises a couple of weeks after they have finished flowering. Lift plants, break off the older parts of the rhizome and keep the firm plump pieces. Trim the leaves to just above the fan as this reduces stress, and replant facing the sun, with the top of the rhizome just visible as they need to soak up the sun.

Trim and preserve herbs

Trim herbs to help the plants keep their shape and grow better. Herbs can be dried by popping them in the oven on the fan only setting (i.e. no heat), or freeze them in small quantities - little plastic snack bags are perfect for this.

Protect tender plants from slugs

Look out for slugs and snails hiding in nooks and crannies. They’ll be out in force after all those tender young shoots coming up this month. Hunts are best done in early morning and evening when cool damp air brings them into the open. Depending on how much of a problem they are in the garden you can try various control methods. Nematodes (microscopic organisms that predate on slugs and snails) are organic and safe with pets and children but require careful application. Nematodes can be ordered online

Also try non-toxic and eco-friendly Slug Defence granules. These make crossing them unpleasant for slugs and snails and offer good protection. They’re made from sepiolite clay, a natural material that is dry and sharp which can be used with edibles. There are also organic pellets available to buy. If, however, you have a really serious problem you may need to resort to old school slug pellets. As these are toxic keep their use to a minimum, just a very few pellets should do the trick.

Protect the growing tips of beans from slug damage. They don’t recover. Push some new beans into the ground as replacements if needed.

Try to site pots up and out of reach of slugs who will eat the heads of violas in double quick time.

Find out more about controlling slugs and snails

Feed plants

Liquid tomato feed can be used as a supplement on ornamental as well as productive plants. Anything potted into compost and containerised, such as summer bedding, will benefit from a fortnightly feed of tomato feed because the nutrients in the compost run out after 3 to 4 weeks. If you find the watering can too heavy, invest in a smaller one. They're really useful.

Feed all greenhouse crops such as cucumbers and tomatoes and continue to apply a fortnightly feed until the beginning of September. Agapanthus, often said to thrive on a poor diet, respond really well to being fed with tomato food. You’ll get far more flowers.

Make comfrey tea

Cut down comfrey and add to the compost bin as it helps the decomposition process. Also make some liquid plant feed by covering a bunch of leaves with water in a bucket, weighted down with a stone or brick, and leave for a couple of weeks until the resulting liquid turns nicely brown and smelly. Dilute with water to use.

Find out more about making and using comfrey tea

Stop cutting asparagus

Stop cutting asparagus in mid to late June. This allows plants to gather strength in order to give a good crop next year. Help the process by giving the beds a hoe to remove weeds, feed with blood fish and bone and mulch with some organic matter.

Plug gaps in the border

There are lots of things that you can bed into the border to add more flower power later in the year. Look out for healthy looking penstemons, but avoid any that look woody and ragged. Scabious also work well and their nectar-rich flowers attract hoverflies. Their maggot-like larvae will help keep greenfly down. ‘Butterfly Blue’ is a sterile scabious that flowers for at least three months. Or you could add some dark-leaved sedums, such ‘Purple Emperor’, to extend the season. Try to buy in threes or fives, to avoid the pincushion effect.

This is also the best time of year to plant hardier salvias and fuchsias. They’ll have plenty of time to put down roots, before winter arrives.

Pot on tomatoes

Tomatoes – with luck young plants will still be on sale, if you haven't grown your own from seed - can be potted on as their roots become visible at the bottom of the pot.

Find out more about growing tomatoes here

Harvest elderflower 

Pick some elderflowers to make cordial. Pick young, newly opened heads for greater flavour and pick in dull weather or early morning for freshness. Also avoid picking after rain. Try our elderflower cordial recipe here.

Keep harvesting salad leaves

Keep cutting cut and come again salad leaves and make sure the soil doesn’t dry out to prevent them bolting.

Read more tips for the summer garden, including expert tips for watering wisely and plants for the June gap

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