Taken from Diet for a Small Lake

Hand harvesting Principle Hand harvesting is the most common plant-management technique used to control nuisance weeds in New York State. It is the only strategy that generally requires no permits in most parts of the state, no significant expertise, and little risk of side effects. It is used first, before the harvester is overwhelmed by the work, or used last after permits cannot be secured or consensus can’t be reached for larger scale techniques. It is used as an interim measure until a consensus of tired arms and sore backs supports the use of large-scale techniques. 

It is perhaps most effective when used in concert with whole-lake control strategies, as a follow-up to prevent re-infestation or re-establishment of large beds of weeds. It is ineffective for plants with extensive root systems, such as water lilies. Anyone can hand harvest, although only the cautious can do it well. It is comparable to weeding a garden. 

The entire root system must be removed by grasping the plant material from under the roots of the plant as close as possible to the sediment layer. Digging into the sediment may be needed to grasp the root crown and free the intact plant from the sediment. Side-effects, such as fragmentation, turbidity and bottom disturbance, are reduced by pulling plants slowly, and harvesting while the plants are still robust. Plants and roots should be deposited away from the shore to minimize re-infestation of the lake.

Insider’s guide to hand harvesting weeds

So you wanna pick some weeds? How hard can that be? Well, if collecting a bouquet of picturesque aquatic plants, it may be very similar to gathering wildflowers from an endless meadow. If trying to prevent these pesky plants from returning or spreading, however, the process is not quite so simple. Here are some tricks of the trade that have proven successful in effectively controlling the propagation and re-growth of Eurasian watermilfoil and water chestnut, perhaps the two most heavily plucked plants. For Eurasian watermilfoil (Myriophyllum spicatum) (Martin and Stiles, 2005 and Eichler, 2005): • Each sediment type creates unique challenges for hand harvesters. Muckier sediments are easily disturbed, resulting in turbidity that can inhibit divers abilities to locate plants. Harder sediments can be rough on the divers hands. • Beds are generally best harvested by working in from the outside edge, usually moving from greater to lesser depth to minimize disturbance of milfoil beds by boats (assuming they migrate to the harvesting site from the open water.) • Plant stems should be removed by prying the root crown out of the sediments, rather than pulling or tugging on the stems. Divers should insert their fingers into the sediments around the root crown, which may be the size of a tennis ball for mature milfoil plants, and should exert a steady pull. It has been described as similar to pulling an onion out of the soil, although the milfoil plants have more fine roots. For Water Chestnut (Trapa natans) (Samuels, 2005) • Water chestnuts reproduce from the nutlets. The nutlets are very sharp so wear old shoes and gloves when harvesting. • The best window for removing water chestnuts is between mid-June and mid-August. • Plants should be flipped upside down once picked to prevent seeds from dropping. If nutlets are removed before they drop, the plants will be eliminated as a seed base for future growth. The nutlets can survive in sediments for up to 20 years so any dropped in previous years are likely to be viable. Do not remove the plants too early; new plants may crop up and produce seeds, unless re-harvested. If plants are removed later than August, some nutlets may drop off during the harvesting process since they are loosely attached to the plant by late summer. • Since infestations spread outward from the edge of the plant beds, start removing plants from the outside and work into the center of the beds. • Kayaks are effective for removing chestnuts due to their maneuverability through dense beds, but canoes carry more chestnut cargo. • Plastic laundry baskets work well for holding chestnuts in kayaks. Leaf tip (self-standing) bags work well for transporting plants out of canoes or pontoons. • Dispose of the plant in the trash or by composting on land away from shore (but watch out for the nutlets!) I