Weather in the Denver area doesn’t look like it’s going to cooperate this weekend, but here are some things you can be doing in the garden when the sun shines again.
Landscape
With temperatures still in the 40s and low 50s at night, it is too cold for seeding or planting all but the hardiest , such as potatoes, onions, lettuce and broccoli and ornamental seeds such as larkspur, poppies and alyssum and plants including pansies, violas and snapdragons.
Cool-season direct seeded plants or transplants need soil temperatures to be consistently at 40 degrees or more.
Warm-season crops and transplants need 60-degree or warmer soil temperatures to germinate or grow as transplants. Warm-season veggies and herb crops include tomatoes, peppers, eggplant, basil, pumpkins, cucumbers and green beans. Ornamental warm-season plants include zinnias, celosia, cosmos and sunflowers.
Soil temperatures are generally 10 to 15 degrees cooler than air temperatures. To determine soil temperatures, consider using a soil thermometer.
Soil thermometers are easier to read and can be found in garden centers (it is OK to use a meat thermometer, but then dedicate it for outdoor use). Place 4 inches deep and measure around 8 a.m.
is a garden trick Mother Nature generally can’t restrict (tornadoes and extremes excepted).
Use black or clear plastic (4-mil is common) and lay it over bare soil planting areas (first remove all mulch and spent foliage). Anchor the plastic with boards, bricks or whatever is available to keep it from blowing away or allowing cold air to get underneath the plastic. Keep it in place for at least a week or more; longer is better. Some gardeners leave the plastic in place, slice holes and plant warm-season crops such as tomatoes and peppers.
After warming the beds, check soil temperatures and plant accordingly, but be ready with row covers, cloches, sheets or plastic over PVC pipes (tunnels) for cold nights or severe weather events.
Plant Division
Many perennials and herbs need to be divided because they’ve become too large or have simply overgrown their space. After a few years, ornamental grasses die out in the center, so they benefit from division.
The best part to dividing is sharing with others or replanting elsewhere in the garden (more free plants!).
Plants quickly respond with new growth and vigor after being divided.
Some plants prefer spring division; others like to be divided in the fall. Some, such as lavender and sages (being woody in growth habit), don’t like being divided.
The basic rule of thumb is to divide summer and fall bloomers in early spring, and spring bloomers in the fall. For a handy guide, refer to Garden Gate Magazine’s chart on when to divide perennials ( .
Water the plant a day or two before dividing. Cut back any top-dead growth from last season (compost the clippings). Move mulch away from the plant.
Choose a cloudy, cooler day if possible, and if it rains after you transplant, it’s your lucky day.
Dig the new planting hole first. Use the dug soil as backfill and mix in a little compost if the soil is very compacted (not too much, or the roots won’t leave the amended area). A wider hole is better than deeper for re-establishment.
Use a shovel or spading fork to carefully dig around all four sides, at least 6 or so inches away from the clump. Lift the entire clump with your shovel and carefully take it to its new home.
If the clump is too heavy to move with the shovel, carefully place it on a tarp or box and slide it to the new planting hole. This works for short distances, otherwise use a wheel barrow. The clump should be fine if it is moist; a dry root ball may crumble.
Some plants have spreading root systems, so they benefit from being spread apart by hand or cut with a knife or shears before being replanted. These include asters, bee balm, lambs ear, coneflower.
Daylilies, hostas, astilbes and ornamental grasses form clumping root systems. Divide the clump with a sharp knife, shovel or saw, for really large grasses. Many divisions can be made from the divided clumps and replanted or shared.
Plant at the same depth as the previous location and firm soil around the plant to fill any air pockets. Water well, then mulch.
More from Betty Cahill at gardenpunchlist.blogspot. com
Garden smart tip
When renewing or adding mulch in the spring, it often is difficult to see emerging plants or ones that were just divided and replanted. Avoid smashing tender plants with mulch by covering them temporarily with lightweight plastic nursery pots or boxes, anything that will cover the plants. Do this in sections so the plants aren’t covered for too long. Remove the covers and carefully tuck in mulch around and underneath the foliage of each plant.
