Time to re-pot houseplants, start some seeds for your Colorado garden

March ushers in the countdown to spring and the outdoor gardening season. While waiting, spiff up the indoor plants, direct-seed cool crops and annuals under lights and finish outdoor pruning before things green up.

Indoor houseplants are putting on new growth as the days get longer, so it’s time to give them your full attention. If roots are growing out of the bottom drainage hole or plants need more frequent watering, it is time to re-pot.

How to re-pot houseplants

Carefully remove the root ball. Loosen (called teasing) tight roots by gently massaging the root mass or score them with scissors or a knife if they are tightly wound. Re-pot using a slightly larger, clean container with sterile potting soil.

Place a piece of nylon or a coffee filter over the bottom hole instead of pebbles or broken clay pieces, which take up space for roots to grow. Place some new soil on the bottom of the container and then around the sides once the plant is in the container. Water well and don’t fertilize for at least a month. Cacti and succulents can be watered a couple of days after re-potting.

Top dress large potted indoor plants that can’t easily be re-potted by removing the top 3 inches of soil and replacing it with new soil.

Dusty plant leaves block sunlight and stress the plant, so clean leaves gently with a room temperature moist cloth. Or place plants in a sink or shower and use lukewarm water for a thorough rinse. Avoid getting water on fuzzy leafed plants like African violets and Streptocarpus.

Some plants prefer to be in tight quarters including, peace lily, spider plants, ficus, African violets, jade plants, aloe, asparagus ferns and Christmas cactus. Being root-bound allows the plant to focus on blooming or direct energy to growing more side shoots.

Houseplant pests

Pest insects may not be easy to spot, but damage or plant decline from them is unmistakable. The usual culprits are mealy bugs, soft brown scale, spider mites and fungus gnats.

Spider-mite damage appears as a mottled leaf on an Anthurium.
(Betty Cahill, Special to The Denver Post)

Spider-mite damage appears as a mottled leaf on an Anthurium.

Mealy bugs are white, waxy, soft-bodied scale insects that suck plant juices and leave sticky honeydew on leaves. Leaves turn yellow, then drop. They are usually found where leaves and stems join and are commonly found on coleus, poinsettias, jade and citrus. Carefully dab each insect with rubbing alcohol or try insecticidal soaps.

Scale insects, mainly the soft brown scale, can be problems on ficus, ivies and ferns. In small numbers, try to rub or peel them away. Treating them for their entire life cycle from crawlers to hard-bodied scales (which takes two to four months) is most effective with soil-applied systemic insecticides.

Two-spotted spider mites attack several different indoor plants, causing leaves to look stippled or mottled. Washing plants regularly with a good jet of spray helps control both spider mites and eggs.

Adult fungus gnats, small fruit-fly-sized pests, are easy to spot. They prefer wet, organic-rich soils. High numbers can damage plant roots. Attract adults with yellow sticky traps. Toss a thick potato slice on the soil surface to attract the larvae (then toss) or use the non-toxic biological product Bt Israelensis strain in pellet or liquid form.

Isolate new plants brought in to the house for at least three weeks and consider treating with sticky traps, horticultural oils or insecticidal soaps as prevention for hitchhiking pest insects.

Humidity levels are low in the winter, so consider placing plants close together to create more moisture. Also try placing them on top of a watered pebble tray — but not sitting in the water.

Always read product label instructions and use products safely and wisely. Additional indoor plant pest information can be found at http://extension.colostate.edu/topic-areas/insects/managing-houseplant-pests-5-595/

Tagawa Gardens' Garden Advisor Linda Larsen uses a cut straw to carefully pick individual Crimson Cushion Beefsteak tomato seeds to place in small trays to begin the cultivation process of growing them for your garden on February 6, 2017 in Centennial, Colorado. Larsen, who is also a master gardener and bee keeper, goes through a step by step process on how to begin the process of cultivating seeds to plants for your summer garden.
Helen H. Richardson, The Denver Post

Tagawa Gardens’ Garden Advisor Linda Larsen uses a cut straw to carefully pick individual Crimson Cushion Beefsteak tomato seeds to place in small trays to begin the cultivation process of growing them for your garden on February 6, 2017 in Centennial, Colorado. Larsen, who is also a master gardener and bee keeper, goes through a step by step process on how to begin the process of cultivating seeds to plants for your summer garden.

Indoor seed-starting

Start seeds of cool-season broccoli, Brussels sprouts, cabbage, cauliflower, parsley, cilantro and leeks indoors for transplanting outside in April to mid-May — or earlier if soils are warmed and plants are protected in cold frames or tunnels.

Annuals that need plenty of time to develop to a good transplant size for planting outside in the spring include ageratum, calendula, lobelia, salvia, ornamental pepper, snapdragons, pansies, impatiens and fibrous begonias.

Late-winter tree and shrub pruning

Finish dormant shrub and tree pruning this month.

Prune or remove damaged, diseased or dead wood. Reduce tree canopy size if trees are touching houses or interfering with pedestrian or automobile traffic. Pruning thin wooded trees like silver maples may prevent limbs from splitting or damage from late spring snow storms

Prune fruit trees in late winter (now) before bud break. After pruning consider applying a dormant oil to suffocate overwintering pest adult insects and their eggs. A dormant spray is a good preventer for pest issues during the growing season.

Check the stems of ash, aspen, dogwood, lilac, willow and privet for oystershell scale. These ⅛-inch-long brown scales that look like small oyster shells are winter-protected insect eggs. Eggs hatch in the spring, and then start feeding by sucking plant sap. The damage can kill limbs, even leading to tree death.

For small infestations on small trees or shrubs, scrub off the scales with a plastic scrub pad (careful not to overdo it on thin-barked trees). If they are limited to a single limb, prune off the limb. For ongoing management, dormant oils can be applied in winter.

Keep a close eye on infested trees for emergence of the eggs to the crawler stage. Consider insecticides when they emerge, around mid-May (could be earlier or later). Read more at http://extension.colostate.edu/topic-areas/insects/oystershell-scale-5-513/

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