June Tips & Advice
Harvest salad onions, salad leaves, beetroot and radishes as they mature.
Harvest indoor cucumbers and other 'fruiting' crops regularly to encourage more fruit to set.
Early peas may be ready for harvest. Once all the pods are harvested, cut off the tops of the plants, leaving the roots in the ground to conserve valuable nutrients to the soil. Peas and other legumes can ‘fix’ nitrogen from the air.
Overwintered Japanese onions can be harvested when the tops start to fall over. Leave the bulbs to dry in a sunny spot outside, or in a airy shed if rain is forecast. This will allow the skins to harden, and the bulbs to store better.
Early potatoes may start to be ready for harvesting; many are ready when the plants come into flower. Take care when digging them up to insert your fork some distance away and to lift the soil carefully. Otherwise you may pierce and damage the tubers.
If you have started off crops early under cover, and live in a mild part of the UK, you could be harvesting early crops of courgettes, small summer squashes, sweetcorn, calabrese, pak choi, kohl rabi, French and broad beans and carrots. Spring or early summer cabbages and cauliflowers planted last year will also be ready for cutting.
Continue with successional sowing of salad crops, beetroot, Chinese cabbage, pak choi and radish, to ensure an even supply over the season. In hot weather, leafy salad crops may do better when sown in partially shady sites. Hot dry weather can lead to bitter tasting leaves.
Sow French, broad and runner beans, peas, squash, sweetcorn, and outdoor cucumbers directly into prepared beds outside. French beans are best sown in traditional rows, 45cm (18in) apart, at 15-22cm (6-9in) spacing. Sweetcorn works best planted in blocks, at 45cm (18in) spacing, with two seeds per hole. The strongest seedling can be selected later, and you will have the safety of knowing there is a fall-back in case of slug damage. Any seeds sown earlier under cover can now be planted out into the same block pattern.
Runner beans benefit from well-prepared ground with lots of well-rotted manure and organic matter dug in. They need to be planted alongside suitable supports (often a frame or wigwam of bamboo canes tied together with twine) for the shoots to twine around and grow upwards.
Courgettes, marrows and pumpkins can still be sown outdoors in early June. Encourage good fruit set by hand pollinating. Push the male flowers (distinguished by the lack of swollen stem/young fruit behind the petals) lightly into the female flowers.
Witloof chicory can be sown this month, to be ready for forcing next winter (when other salads are scarce). Sow in drills directly outside.
Although most winter brassicas need to be sown earlier in the season, you can still sow turnips now for an autumn crop, as they are best lifted while still young and sweet. Sow them in drills 15cm (6in) apart, and thin them as soon as they are large enough to handle, to leave one plant every 10cm (4in).
Continue to earth up potatoes not ready for harvest (unless planted through black plastic). Potatoes can also be grown in containers.
Plant out tomatoes if this has not already been done. Train them up canes or string, and remove sideshoots from cordon tomatoes. These sideshoots develop in the leaf axils (i.e. between the stem and leaf), and if allowed to develop will sap the energy of the plant and reduce the quality of the yield. Small sideshoots can easily be pulled off with a thumb and forefinger, and can be easily rooted to obtain more plants. When four flower trusses have formed, pinch out the growing point just above the highest truss.
Celeriac and self-blanching celery can be planted out this month. A well-prepared site with lots of organic matter dug in is essential. Planting celery in blocks aids the blanching process, as does placing a strip of plastic around the edge of the block to exclude some light and further improve the pale colour and sweetness of the blanched stems.
Outdoor ridge cucumbers can be planted out this month. They benefit from a site that has been enriched with lots of organic matter to help retain water. Pinch out the tip of the plant when it has made six pairs of leaves, to encourage sideshoot and cucumber formation. Feed regularly with a liquid tomato feed, following the instructions on the packet.
Strings stretched along the sides of broad bean plants will support them and prevent them flopping once pods develop.
Peas need staking with pea sticks, netting, or pruned twigs from the garden.
Plant out other vegetables sown indoors earlier in the season, including winter brassicas and sweet peppers. Peppers can only be planted out when all risk of frost has passed. The gaps between winter brassica plants can be used for quick-maturing catch crops, perhaps radishes or gem lettuces, as brassicas take time to grow into their eventual spacing.
Plant out artichokes that were previously sown under cover. They are tall handsome plants, and the steamed unopened flower buds are considered a delicacy. They can be grown as perennials (in which case they need 90cm spacing), or as biennials (45cm spacing is sufficient).
Harvest asparagus spears from established plants for six to eight weeks from May into the early summer. Do not harvest spears from crowns less than two years old. After harvest and flowering, it is a good idea to feed them so that they have sufficient energy for next year’s crop.
Control weeds to prevent them competing for moisture and nutrients. Hoe regularly between rows on hot days to make sure the weeds dry up and die without re-rooting. Weedkiller is usually inappropriate as there is a high risk of it killing or damaging your crops as well as killing the weeds.
material courtesy of www.rhs.org.uk