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Tips from the City's Horticulturist


Park Scene Red FlowersDriving around St. Peters, you’re welcomed by beautiful plantings on City property, in parks, and along some roadways. St. Peters’ professional horticultural staff is charged with maintaining this aesthetic beauty of our City.

Depending on the time of year, your yard requires specific maintenance to keep the lawn and plants healthy. St. Peters’ professional horticulturist offers these tips to help you in maintaining your yard:

Tips for the Month of March

March is a wonderful month. Spring arrives, and signs are everywhere that the “big thaw” is underway. The promise of warmer weather makes us anxious to get outside and prepare our yards for the upcoming growing season. Here are a few tips to help you get your lawn in tip-top shape.

March is an excellent month to plant trees. There are just a few things to remember to ensure the success of your new tree.

  • Always dig the hole extra wide, but never deep.
  • Before you place the tree in the hole, make sure there is a visible root flare at the top surface of the rootball or container. The flare appears as a distinct widening where the tree trunk meets the ground. If there’s too much soil piled over this flare, remove the top few inches of soil to get the tree placed with the flare at the surface.
  • Once the tree is planted, be sure to water it well, thoroughly saturating the planting hole. This allows the soil to settle around the rootball. Then check the tree every week and water it only when the soil is dry.

March is a great time to clean up the remnants of last year’s plants from your landscape beds. Removing old vegetation not only tidies up the landscape, but it reduces the success of overwintering pests. Be careful not to injure the new growth tips of your plants in the cleaning process.

Apply crabgrass preventative on your lawn before the end of March IF your lawn had crabgrass weeds last year.

If you did not apply a crabgrass preventer, you can plant grass seed in late March all the way through April. Early fall is actually the best time to sow grass seed, but spring sowing can be successful.

Aerate your lawn. A vigorously growing, healthy turf will have fewer weeds. You may be able to reduce the need for herbicides if you aerate your lawn at least once a year, overseed annually, and fertilize in the late spring and fall.

Don’t fertilize in March. Your lawn should have plenty of stored nutrients to start spring with, so fertilizing should be put off until May for cool season grasses and June for warm season grasses. Fertilizing too early just makes you have to mow more often!

Don't work the soil if it’s too wet. Wait until a ball of soil squeezed in your hand will crumble apart easily before trying to till. If you till while the soil is too wet you could end up with large clods of soil that are nearly impossible to break up when they dry.

Don’t plant annual flowers yet. Don’t let the sale ads talk you into planting your annual flowers too early. Occasional killing frosts in March and April are not uncommon in St. Peters, so planting annuals should wait until May.

Wait to prune your spring-blooming shrubs. Don’t prune your spring-blooming shrubs until after they’ve flowered or you’ll be cutting off the flower buds and reducing the number of blooms.

Don’t remove that daffodil or tulip foliage until it dies back. The foliage is hard at work creating the energy source for next year’s flowers, a process that usually takes 6 to 8 weeks. If you don’t allow this growth to happen, you won’t get flowers next year. Waiting until the leaves are completely brown to remove them will insure the plant was able to maximize its flowering potential for the next year.


Tips for the Month of April

Get out to the nursery to check out fresh inventory. Your favorite local nursery will be busy stocking their lots with trees, shrubs and perennials. April is a great month for planting so start shopping early and you will be rewarded with a large inventory to choose from.

Spring planning. Now is the time to study your landscape for gaps that could be nicely filled next year with spring blooming bulbs. Mark these spots and make a note to order bulbs in August.

Watch for weeds. Keep your hoe sharp! Don't allow weeds to get an early start in your garden.

Monitor garden precipitation. Mount a rain gauge on a post near the garden to keep track of precipitation so you can tell when your landscape needs water. Most gardens need about 1 inch of rain per week between April and September. Make sure your irrigation system is equipped with a rain sensor to prevent unnecessary watering. Water your landscape in the morning when evaporation is at a minimum. Soaker hoses and drip irrigation help conserve water.


Tips for the Month of May

Fertilize cool season grass now. Now is the time to fertilize your cool season turf such as bluegrass, fescue, and ryegrass. If you have warm-season grass like Zoysia and Bermuda, wait until June to fertilize.

Cut it high, let it lie. When mowing, don’t bag your grass clippings. Either mow before the grass gets too tall, or raise your cutting height, so the clippings will be smaller and won’t smother the turf.

Plant your annual flowers now.

  • We're past the annual average date of last frost so go ahead and plant those annual flowers. When selecting annuals choose compact, bushy plants with a well-developed root system. Avoid leggy or underdeveloped plants.
  • Don't plant annual flowers close to trees. Annual flowers need more moisture than a tree’s root system can sometimes handle. Planting annual flowers too close to a tree can cause a variety of moisture related stresses, resulting in decreased vigor, decline, or even death of the tree.

Pinch off faded rhododendron blossoms. This “deadheading” process prevents the plant from developing seeds thus encouraging more flowers next year.

Houseplants. If you bring your houseplants outside for the summer, wait until the night temperatures are consistently above 50 degrees. Also, don’t place your houseplants in direct sun or their leaves can be sunburned.

Planting a vegetable garden. If you haven’t already done so, May is a great time to plant vegetables such as tomatoes, peppers, eggplant, and corn.

Trees and shrubs. It’s still a great time to plant trees and shrubs. Just make sure to water them at planting time and monitor the soil moisture the first few seasons. Most trees and shrubs prefer a thorough soaking then a period of slightly drying out before the soil is thoroughly soaked again.

Mulching. Spreading mulch over bare landscape beds is a good practice, but don’t overdo it! A 2- to 3-inch layer of mulch, kept away from tree trunks, will benefit your landscape by conserving moisture and reducing weeds, but an excessive amount of mulch can be harmful.


Tips for the Month of June

Apply a balanced fertilizer to your roses after the first good bloom set.

Keep an eye out for bagworms. Usually control measures are most effective when they are implemented early and the bagworms are very small.

Raise your mowing height for cool season grasses. Mow no lower than 2 1/2 inches, but some experts recommend 3 inches or 3 1/2 inches.

Watering your lawn. Don’t start watering your lawn unless you intend to keep it up all summer. Not watering or watering sparingly allows your cool season grass to build up some drought tolerance early in the season.

Fertilize warm season grass now. June is a great time to fertilize warm season grasses like Zoysia and Bermuda.

Watering your plants.


  • Check your containerized plants and hanging baskets frequently. As the temperature climbs, they may need watered daily.
  • Don’t forget to also monitor the water needs of newly planted trees and shrubs. New trees and shrubs prefer a thorough soaking of the soil when they’ve gotten dry. Neither frequent nor light watering is good for many reasons. Never water a tree that’s already wet, but don’t let trees dry to the point where they are wilting before you water.
  • Annual flowers respond well to frequent watering and fertilizing. As long as you keep the soil moist (not saturated) you can fertilize your annual flowers weekly.

Pruning perennials. Prune old flowers from your perennial plants to keep the garden tidy looking and prevent the plant from wasting energy on seed development.

Time to think about Halloween pumpkins. If you haven’t planted pumpkin seeds yet, plant them soon so you’ll have pumpkins for Halloween.


Tips for the Month of July

Fertilize your flowers cautiously. Continue to fertilize your annual flowers, perennials, and roses this month, but use caution. Make sure the soil is moist before fertilizing because the high salt content in most fertilizers can cause leaf scorching. Also, never fertilize when the air temperature is excessively hot.

Bagworms. If you discover that your trees or shrubs have bagworms and you didn’t spray them last month, it’s too late to spray in July. The bagworm’s maturity prevents chemicals from being effective at this point. The only effective control measure at this point is to remove the bags from the tree.

Don’t cut your grass too short. Most experts recommend a minimum 3- to 3 1/2-inch mowing height for cool season grasses during the hot summer months.

Watering your plants.


  • Check your containerized plants and hanging baskets frequently. As the temperature climbs, they may need watered daily.
  • Don’t forget about those newly planted trees and shrubs. Monitor them for water needs. Never water a tree that is already wet, but don’t let trees dry to the point where they are wilting before you water.

Pruning perennials. Prune old flowers from your perennial plants to keep the garden tidy looking and prevent the plant from wasting energy on seed development.


Tips for the Month of August

Watering. Frequently water any trees, shrubs, and plants that were newly planted over the last few seasons. Of course, you should use water wisely. Check the soil around the plant before watering and don't apply any water if the soil’s already moist. Well-established plants can make it through a mild drought just by shedding some leaves or going dormant.

Weed control. Don’t allow weeds to mature and produce seeds or you’ll be battling a much larger population of weeds in the future.

Webworm. This time of year, webworm becomes visible in the forest and in some yard trees. Though this pest looks unsightly, it is rarely a significant threat. The trees are almost finished with their leaves for this year so unless the population is extremely high, the caterpillars don’t usually cause any great harm.

Dividing Irises. Now is a good time to divide bearded iris if they’re crowded. Iris are one of the few perennials that benefit from summer division.

Grubs. If you think you have grub damage in your turf, check to see how dense the grub population is before randomly treating with pesticides. A healthy lawn can handle a few grubs per square foot.

Fertilize and overseed warm-season tur
f. Apply the last application of fertilizer to warm season grasses this month and begin overseeding turf and performing any lawn renovations toward the end of the month. You’ll get the greatest success with new grass seed if it’s sown by Labor Day.

Pruning spring blooming shrubs. Be careful when pruning your spring blooming shrubs. Azaleas, Rhododendrons, Forsythia, and other early spring bloomers are setting next years flowers now. Pruning in late summer will reduce your spring flower display.

Plant fall and winter vegetables this month.

Discontinue fertilizing woody plants this month. Trees and shrubs are slowing down for the season and will begin hardening off for winter. Pushing a lot of vegetative growth now will disrupt this process.


Tips for the Month of September

Fertilize and overseed cool-season turf.

  • Cool season turf grasses are storing energy for next year right now, as opposed to sending out a lot of top growth like they do in spring. Fertilizing in September helps this storage process and encourages a thick, healthy turf.
  • Overseed your cool season turf this month if you didn’t do it at the end of August. Do this as early as possible to allow the grass more time to establish before winter.
  • The most successful procedure for overseeding is: core-aerate first, broadcast the seed second, and rake or power rake third. This methods creates a healthier environment and insures proper seed to soil contact. Keep the newly seeded area moist to encourage maximum seed germination and establishment.

Weed control. If turf seeding is done early enough you will still be able to spray broadleaf weeds in October. Fall control of perennial broadleaf weeds (e.g. dandelions) is much more effective than spring control.

Continue watering. Make sure and water if it doesn’t rain. Trees, shrubs, perennials and turf may all need supplemental watering.

Fall flowers. The annual flowers are winding down so you may want to evaluate how much effort to invest in them. If you want that seasonal burst of color that annuals provide, try planting pansies or ornamental cabbage now for several months of cool season color.

Plant perennials this month. Planting new perennial plants or dividing old plants now will allow ample time for establishment before the ground freezes. You’ll be rewarded in the spring, as the fall planted perennials take off.

Exception: If you plant mums in the fall, think of them as annuals because they may not make it through winter unless they are very established. Mums should be planted in spring to ensure establishment and provide greater winter survival.

September is a great time to plant evergreens.
Evergreens lose a considerable amount of moisture through the winter so early establishment increases their chance for survival through the desiccating winter.

Don’t worry if the inner needles of your White Pine turn brown and drop off the tree. This annual shedding of the oldest needles is a natural occurrence.


Tips for the Month of October

Time to clean out your flower beds. If you haven't done it yet, it’s probably time to pull out those tired old annual flowers. Clean the beds really well to reduce the populations of insects or disease organisms that over-winter on old plant debris.

Plant spring blooming bulbs this month. In our area it is best to wait until October to plant the spring blooming bulbs like tulips and daffodils. Watch the weather trends; the goal is to get plants re-established before the ground freezes. Doing this work in the fall will give next year’s garden a more established and vigorous appearance than if you wait until spring to do it.

Bring houseplants inside. Watch the temperature in case it gets too cold for your houseplants to be outside. Clean them thoroughly before bringing them inside.

Transplant perennials this month. October is a great month to divide or transplant most perennials.

Weed control. October is a great time to spray your turf to eliminate broadleaf weeds (like dandelions, clover, and thistle). Herbicides are rapidly transferred to the roots this time of year, so fall applications are very effective.

Fertilizing and overseeding cool-season turf.


  • If you want a lush green cool season lawn next spring, fertilize in fall. Mid- to late-October is the perfect time for your final turf fertilizer application. The grass will go into winter with more reserves and will reward you with great green color in spring.
  • We’re past the absolute best time to sow grass seed, but If we're experiencing warm days and there’s adequate moisture you can still have considerable success with over-seeding your cool season lawn. Temperature and moisture are the most critical factors in grass seed germination.

Continue watering. Make sure to water new trees, shrubs, and perennials if we don't get good soaking rains. Pay especially close attention to newly transplanted items and evergreens. They are the most susceptible to the desiccating effects of winter.


Tips for the Month of November

Test your soil. November is the time to have your soil tested to determine pH and nutritional levels. That way you’ll have time to add any necessary amendments before the next growing season. A great resource for testing your soil is the University of Missouri Extension Office located on Brown Road right here in St. Peters. You can reach the Extension Office at 636-970-3000.

Planting new trees and shrubs.


  • November is an ideal time to plant trees and shrubs. Before digging the hole, prepare the site by loosening the soil well beyond the drip line of each plant. Plant shrubs at the depth they grew in the nursery and no deeper. For trees, make sure the flare (the swelling right above the roots) is not buried. Remove all wires, ropes and non-biodegradable materials from roots before back filling. Apply a 2- to 3-inch mulch layer, staying several inches away from the trunk. Always water immediately after planting.
  • Protect the trunks of newly planted trees, especially fruit trees, from mice and rabbits with a cylinder of 1/4-inch mesh hardware cloth. Place the cloth a few inches below the soil line to protect against burrowing mice. Remove the cylinder in the spring.

Continue watering. Continue to thoroughly water trees, shrubs, lawns and planting beds until the ground freezes. Evergreens especially need extra water because their leaves or needles transpire all winter.

Don’t let leaves pile up on your lawn. To prevent injury to turf grasses, keep leaves raked up or try mulching leaves with the lawn mower. A fairly thick layer of leaves can be reduced to almost nothing by mowing them. Remember, some amount of leaf mulching is healthy for the turf because it cycles nutrients back into the soil. Just don’t let the mulched-up leaves form a thick layer over the turf.

Clean up vegetable garden. Be sure to clean up dead plants from the vegetable garden. Old plants can harbor insects and diseases over the winter.

Mulching. Mulch around new plants to protect them as the ground freezes. Avoid covering roses too early. Wait until most of the leaves have dropped and night temperatures have fallen into the teens a few times. Remove old rose leaves to reduce the over-wintering of insects and disease.

Houseplants need light. Give houseplants as much light as possible as lower light days begin. Decrease the frequency of fertilizing indoor plants until spring. Begin to increase the length of time between watering, but don't cut back on the amount of water given at any individual watering.




5200 Mexico Road
St. Peters, MO 63376


(Archery Range, Dog Park, RV Park, Fishing, Boating, etc.)
1000 Lakeside Park Drive
St. Peters, MO 63376
636-387-LAKE (5253)


at City Hall
1 St. Peters Centre Blvd.
St. Peters, MO 63376
636-397-6903, ext. 1624

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