The Rock Garden Year
• Clean up and add freshif necessary.
• Removefrom carpets of Arenaria, Aubrietia, etc.
• Sprinkle lime over the soil except where heaths and other lime-haters are to be grown.
• Look carefully to see if rock plants have been lifted from the soil by frosts, or if the surface soil has been washed away from the crowns.
• Where necessary, top dress with gritty soil, and press back the lifted plants into the soil.
• Wood ashes strewn around patches of dwarf bulbs will act as fertilizer and also add warmth.
• Thecan be remade this month during open weather. Lift out all the plants and heel them in elsewhere while rebuilding.
• Do not make any part of the rockery under the drip of trees, if this can be avoided.
• Build to the desired shape with rough material first, and then commence to build stones and soil from the bottom, making the stones quite firm, and leaving large soil-pockets for the rock plants. Use plenty of lime in the soil, except in places where lime-haters are to be planted.
• Top dress the soil round rock plants with granite chippings to prevent them from becoming too damp, which is a frequent cause of failure in winter months.
• Slight protection should be given to rock plants which are coming into flower. Cloches are useful, but a few twigs and dried leaves over small plants will be appreciated.
• Plant or sow Californian Poppies, Campanulas, Cotulas, Dianthus, Gentians, Gilia diathoides (rock pink),, lithospermum, Saponaria, Thymes and Veronicas.
•that have been raised under glass can now be planted, but sites should be chosen according to each variety; some prefer partial shade, and some like full sun. Some must have moist conditions, and should be planted where there is running water.
• Anemones are useful in the rock garden, but varieties should be chosen according to the soil. Some should be in flower now.
• Search for slugs among rock plants. A zinc collar placed round each plant is recommended, and also a top dressing of stale soot, lime, sifted coal ash, or finely-broken granite as an extra precaution. Traps and applications of slug-killer can also be used.
• Apply a top dressing of sandy soil if heavy rains have washed roots bare.
• Sow a few hardyof dwarf kinds where bare patches occur on a new rockery. Nemophila, Limnanthes Douglasii, Candytuft, Alyssum, and Portulaca clothe the rock garden the first year after its construction, very quickly and effectively.
• Warm, showery days invite slugs to the rockery, and tender plants are soon destroyed or damaged. After dark or early in the morning search for the invaders and destroy them.
• Excellent traps are half oranges, from which the juice has been squeezed.
• Make miniature now. In the smallest gardens a charming piece of mountain scenery can be made in an earthenware trough. For ease in tending, raise the trough to table height on some kind of support. See that drainage is provided.
• Old sinks make good trough gardens, and have, of course, an outlet for surplus water.
• Put rough material such as mortar rubble, old broken bricks, broken crocks, or large stones at the bottom of the trough to assist drainage. Cover this with leaves, coarse manure, or some other material to prevent the soil from washing down through the stones and clogging the drainage holes. Add more soil in which plenty of lime and sharp sand are present. And build the miniature landscape with stones and this fine soil.
• Dead flowers should be cut away, unless seed is wanted. Any decaying leaves should be removed.
• Some rock plants bear ornamental fruits. The dead flowers in such cases must be left to develop.
• Primulas may need water this month if the weather is dry, and similar water-loving plants, save seeds from choice plants as many rock plants can be raised successfully this way. Sow immediately the seed is ripe, in pans of gritty soil, covering with the finest possible layer of sand.
•can be raised easily from seed sown now. Sow Alyssum, (yellow) Arabis, Aubrietia, Campanulas (various), Cerastium, Cheiranthus, Cotulas, Primulas and Silene.
• Seeds of Pinks can be sown this month in boxes of sandy soil in the cold frame. Cuttings of short side-shoots can also be inserted under glass.
• Rockery Pinks suitable for increase by seeds orduring June are: , D. chinensis, D. ccesius, D. heddewigii.
• In new gardens, where large spaces on the rockery have to be filled, increase your carpet plants this month.
• Arabis, Aubrietia and the Mossy Saxifrages all increase easily by means of cuttings. Shoots two or three inches long make good cuttings. Insert in sandy soil under a hand light, or in a frame or in any place where they can be kept moist a~id shaded.
• Take more cuttings of rock plants. As soon as the cuttings are rooted, transplant them into the pockets in the rock garden.
• Where colour is desired,cornuta is very useful in the new rock garden. Seeds sown now on any free patches in the rockery will make a mass of bloom next summer. Sow thinly in pockets of sandy loam.
• Young plants of Iceland Poppies seldom get killed off by frost, if seed is sown this month. They are fine for, and thrive as real perennials in pockets of warm, sandy loam.
• New rock gardens can be made now.
• Wait for a showery day, and lift out the plants with as much soil as possible attached. Replant each temporarily in one of the borders, then remake at your leisure.
• Take out all large stones, dig over the soil and, if needed, improve the drainage by adding large bricks and other rough material to the inside portion.
• Begin to rebuild from the bottom, slope the rocks inward, fill the pockets with light soil well mixed with sand. Add lime where lime-loving plants are to be grown.
• Reset the plants as you rebuild, pressing each firmly into place.
• Dwarf evergreens can be planted now; these add distinction to the rock garden. Pyramidand spreading Junipers, in gold and blue forms, are available and most effective in winter.
• Alpines should be lifted and divided. The soil of the pockets can be lightly forked, and an additional top dressing of gritty material given round established plants.
• Introduce colour: Pink, red and white, Dianlhus ccesius (the Cheddar Pink), Dianthus alpinus, Helianthemum “Sudbury Gem,” Lychnis alpina,amcena, yellow, blue and purple, “Gold Dust” Alyssum, Cheiranthus, Viola gracilis, Aubrietia “Dr. Mules,” Gentiana Lagodechiana, Veronica spicata “Royal Blue,” Lithospermum “Heavenly Blue,” and Campanula pusilla.
• The following bulbs are especially suited for ; planted now in small groups: Anemone, Crocus, Chionodoxa sardensis, Erythronium denscanis, Fritillaria meleagris, Muscari Heavenly Blue, Scilla bifolia, Winter Aconites, Atarcissus bulbocodium cilrinus, Narcissus cyclamineus, Narcissus minimus, Narcissus triandrus albus, Tulipa clusiana, Tulipa Greigii, Tulipa Kaujmanniana.
• This is a good month to clean up the rock garden. Go over each pocket and remove decayed leaves. Stir the soil surface between the plants and add a top dressing of fresh soil where needed. Plants that are overgrown should be lifted and divided. Replant the best pieces and discard the rest.
• Top dress the surface of the soil round Alpines with stone chippings, or if these are unobtainable use sharp sand.
• Put slug traps every few yards to protect the plants, and to prevent slugs becoming numerous. Shelter woolly-leaved plants by placing a small piece of glass over them, supported by wires or sticks. The rare alpines should be sheltered with cloches.
• Plant small bulbs in drifts where colour will be lacking in the spring garden. Those best suited to this purpose are Muscari, Crocus, Snowdrop, Narcissus, Chionodoxas and Scillas.
• Disturb rock plants as little as possible this month.
• Renew top dressings of stone chips, pebbles, or sand, if they are washed well by rain.
• Keep an eye for slugs; especially round the crowns of tender plants.
• Finely-sifted coal ashes piled up in little leaps over the tender crowns will protect from frost and slugs.
• Occasionally go over the rock garden, removing dead leaves. Otherwise these cause rare Alpines to damp off.
• Examine all protected plants, and wipe surplus moisture off the glass of cloches.
• Rock plants lifted out of the soil by frosts should be pressed back. Put a layer of stone chippings on the surface round the plants.
• If the weather is mild keep a look out for slugs. They will make for the tender plants. Zinc collars, slug traps and crystals o1/2 copper sulphate are useful in dealing with these pests.
• Horizontal sheets of glass raised a few inches above the plants will protect woolly-leaved plants.