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Table of Contents

Compiled by Stan Barrett, Colorado State University Cooperative Extension master gardener, Denver County.

  1. Flowers: I just moved to Denver--new house, native soil. I would like to plant a flower garden. Do I need to do anything special to prepare the soil?
  2. Flowers: I find large colonies of aphids on my roses every year. How can I control them?
  3. Flowers: What kinds of perennial flowers would be suitable for a sunny "low-water" garden?
  4. Lawns: I have an old lawn which is quite thin, with some bare spots. Would it be feasible to renovate the lawn rather than replace it with a new lawn?
  5. Vegetables: What kind of lettuce can I grow in Colorado?
  6. Vegetables: How would I go about having my soil tested for a vegetable garden?

I just moved to Denver--new house, native soil. I would like to plant a flower garden. Do I need to do anything special to prepare the soil?

Denver soil is typically high in clay and silt and low in organic material. It would be a good idea to start off by having a soil test performed, to find out what needs to be added. As a minimum you probably need to amend the soil by adding compost or well-rotted manure. (Note that 3 cubic yards of compost will cover 1,000 square feet to a depth of 1 inch.) Ideally you should add up to 3 or 4 inches in depth and dig it into the top 10 inches or so, removing as many rocks and weeds as possible. The soil test report may also advise adding nitrogen before planting.

Do not add sand in an attempt to improve drainage. The soil would have to contain 85-90% sand before infiltration rates were improved, so it is not feasible to add enough sand to obtain any benefit.

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I find large colonies of aphids on my roses every year. How can I control them?

Aphids will feed on all visible parts of roses, but seem to concentrate on new growth and buds. Low populations cause little injury but large infestations occurring later in the season can kilo new growth and prevent successful flowering. Two kinds of aphids, very similar in form, may be found on roses. These are rose aphids, which spend their entire lives on roses and potato aphids, which use roses as an overwintering host plant then leave the plant in spring for their summer hosts, which include a wide variety of vegetables and weeds.

Aphids are attacked by several predators during the summer. The most important of these are lady beetles and syrphid flies. Unfortunately, the predators do not appear until the aphid population has become significantly large, by which time they may have caused intolerable damage. The gardener can take proactive measures by hosing the insects off the plant using a strong jet of water (being careful not to damage the buds), or by using an insecticidal soap, which will not harm the beneficial insects. Control may also be achieved by spraying wit an insecticide such as Orthene, diazinom or malathion. Disyston, which is a granular systemic insecticide, is also effective when applied to the soil around the rose bush and watered in and will not affect the predators.

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What kinds of perennial flowers would be suitable for a sunny "low-water" garden?

  • Low-growing plants: Turkish veronica (Veronica lewanensis), many varieties of sedum spurium, thyme, Yellow iceplant (Delosperma nubeginum), Purple iceplant (Delosperma cooperi), Poppy mallow (Callirhoe involucrata).
  • Medium height plants: Rocky Mountain penstemon (Penstemon strictus), Autumn Joy Sedum (Sedum spectible), Purple coneflower (Echinacea purpurea), Moonshine (Achillea filipendula), Jupiter's beard (Centranthus ruber).
  • Tall plants: Russian sage (Perovskia atriplicifolia), Gaura (Gaura lindheimeri), Blue mist spirea (Caryopteris clandonensis).

 

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I have an old lawn which is quite thin, with some bare spots. Would it be feasible to renovate the lawn rather than replace it with a new lawn?

When an existing lawn requires "rejuvenating" one should first consider why the lawn has declined to a condition that makes such action necessary. For example, is there a very heavy thatch layer? Is the underlying soil poor? Is the lawn diseased? Once these questions have been answered you can decide which approach will be most cost-effective: renovate or replace.

The process of renovating an old lawn generally involves introducing a blend of improved seed of the same type of grass, or seeding in a different type of grass that has similar color, texture and growth habits as the old lawn. The effectiveness of the process is somewhat limited by competition from the existing grass. The best approach is to first aerate the lawn using a machine with 1/2 inch diameter times, 3-inches long. Make enough passes to achieve an average spacing of about 2-inches between holes. Next, plant the seed, either by hand or, preferable, using slit-seeding or drill-seeding equipment. Finally, dress the lawn with a light covering of good quality finely ground compost. Water in accordance with the instructions on the seed package. The best time of the year to renovate is spring or early fall.

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What kind of lettuce can I grow in Colorado?

Butterhead, looseleaf and romaine types of lettuce grow well in Colorado, whereas, in trials at CSU, crisphead lettuce rarely set a hard head. Of the butterhead types, "Ermosa" with smooth light green leaves, "Dapple", a beautiful red oakleaf and "Pirate", with a red tinge to its leaves, have all proven to be Colorado adapted. Looseleaf varieties that do well here include "Green Ice" and "Red Sails". For romaine, try "Winter Density".

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How would I go about having my soil tested for a vegetable garden?

A soil test is a valuable first step in developing or improving a garden. It can save money, trouble and frustration by showing you just what the deficiencies are in your soil and what supplements can be added to correct them.  The test may be performed at a commercial lab or at the CSU Soil Testing Lab in Fort Collins. For the latter, first obtain an application form from your county Extension office. The form will advise you how to make a representative sample from your lot, what tools to use and how to submit the sample to the lab and will ask what crops you plan to grow. About three weeks after sending in the sample you will receive a report giving you the results, with suggestions on how to start your improvement program.

 

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Date last revised: 01/05/2010