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Ask the Gardener: Tips for growing, caring for roses in organic gardens

Ask the Expert Gardening
David Austin’s ‘The Lady Gardener’ variety of rose is great for displaying in vases.
David Austin’s ‘The Lady Gardener’ variety of rose is great for displaying in vases. AP Photo/Sang Tan/file 2013

What to do this week: Always put on sunscreen and a hat before heading outdoors. Save money by letting your lawn go dormant in the summer, the way nature intended. It will revive in the fall. To discourage invasive plants, mow wildflower meadows once now and again in the fall. Fertilize vegetables, flowering annuals, and roses once a month.

Q. If you don’t want to spray, are roses worth growing? What kind of roses can I get plenty of blooms from in an organic garden? How?

ALISON VARDARO, Hingham

A. Spraying roses is becoming a thing of the past. Though most mid-20th-century roses, such as ‘Peace’ and other tea roses, required fungicides and insecticides, breeders have been producing roses with excellent disease resistance for at least two decades. Many of these hybrids have genes from the antique roses that people grew before the introduction of gardening chemicals. So-called landscape roses such as the Knock Out series don’t have the prettiest or most fragrant roses, but they do pump out blooms all season. If you want to grow something special enough for a close encounter in a vase, look to David Austin’s English roses, such as deep red ‘Munstead Wood.’ Also worth a look and a sniff are many so-called floribunda roses, such as yellow ‘Julia Child,’ a great new rose named after Cambridge’s iconic “French Chef.’’ Space the roses far enough apart for good air circulation, and water them deeply at the base (trying to keep the leaves dry) each week in July and August. Apply an organic fertilizer once a month. Bonide is a safe organic fungicide, but don’t use insecticides. Remove all dead leaves and stems in November, then prune for appearance after the leaves sprout in April.

 

Mulch lets in water for root growth but shuts out light so weed seeds cannot sprout. It is usually made from shredded fall leaves or chipped and ground trees. —Matthew Benoit/stock.adobe.com

Q. What is the difference between mulch, manure, and compost?

JEN BUCHWALD, West Roxbury

A. Mulch is loose material shoveled over soil to create a neat appearance and reduce weeding and watering. It lets in water for root growth but shuts out light so weed seeds cannot sprout. Mulch is usually made from shredded fall leaves or chipped and ground trees. I avoid shredded wood that has been dyed for fear the coloring will disguise demolished building materials possibly containing chemicals. I want to mulch with dead trees, not dead buildings. I’ve tried plastic mulches but don’t like them. But I do like spreading newspaper around plants as a first layer of protection. (Don’t worry about the dyes.) Then I wet it and shovel bark mulch on top, which lasts longer as a result. Don’t let mulch come in contact with plant trunks or stems. Because worms gradually turn organic mulch into soil, you need to top off your garden with another 3 inches every few years, preferably in the fall.

Manure is waste from animals often mixed with bedding like straw. You want manure from vegetarians such as chickens, cows, and horses. Sorry, but don’t use cat-box litter or dog messes. Manure is good for your soil but has to be aged for many months before you can add it — otherwise, it can burn roots. It is very rich and sometimes contains undigested weed seeds, which are reduced by aging. I mix it with garden soil in the bottom of planting holes, where it cannot sprout.

Aged manure can be a component in finished compost, which is the product of organic matter that has decomposed beyond recognition and looks like soil (but is 100 percent organic matter with the usual sand and clay). I recycle my considerable yard waste by piling everything (except weed seeds and branches) in 3-by-3-foot bins to compost slowly instead of bagging it for curb collection. It’s recycling, it’s free fertilizer, and it’s actually easier. This is called “cold’’ composting. It is simpler than managing a “hot’’ compost pile, which is ready in mere weeks and kills weed seeds but also requires moisture and aeration or turning. It helps the process to alternate twice as many “browns,’’ such as dried leaves and grasses, with “greens,’’ such as fresh leaves and grass clippings. Think of it as a recipe. You can also buy an animal-proof plastic composter. These are good to keep by the kitchen door for recycling scraps such as coffee grounds, eggshells, and old vegetables (but not meat or fat, which attracts animals).

Of course, it’s easier to buy finished compost by the bag or have it dumped by the yard, and I do this, too. You can rake it over your lawn any time of year a quarter inch deep, and it will increase the depth and richness of your top soil so you don’t need to fertilize or water. You can also use it as mulch in your garden. To be absolutely sure it is weed-free, put a handful in a pot, water, and see whether anything sprouts.

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